Characterization of the flanking region of the Shiga toxin operon in Stx2a bacteriophages reveals a diversity of the NanS-p sialate O-acetylesterase gene

Shiga toxin-producing E. coli (STEC) are diarrheagenic strains that can cause bloody diarrhea and hemolytic-uremic syndrome. Their main virulence factor, the Shiga toxin (Stx), is encoded by phages integrated into the bacterial chromosome. Stx phages are widely diverse and carry many genes with limited or unknown function. As the toxin subtype Stx2a is associated with highly pathogenic strains, this study was mainly focused on the characterization of the stx flanking region of Stx2a phages. Of particular interest was a sialate O-acetylesterase (NanS-p), which has been described previously to be encoded downstream stx in some phage genomes and may confer a growth advantage for STEC. Complete DNA sequences of Stx2a phages and prophages were retrieved from the GenBank database, and the genomic regions from anti-terminator Q to holin S genes were bioinformatically analyzed. Predicted NanSp sequences from phages encoding other Stx subtypes were also studied. Additionally, expression of nanS-p was quantified by qPCR in strains selected from our laboratory collection. The analysis of Stx2a phage genomes showed that all carried the Q, stx2a, nanS-p and S genes, but with allele diversity and other sequence differences. In particular, sequence differences were detected in each of the three domains of NanS-p esterases encoded by Stx2a phages and other Stx phages; however, nanS-p was not identified in the Stx2e, Stx2f and Stx2g phages analyzed. The expression of nanS-p increased in most stx2a-positive strains under phage inducing conditions, as was previously shown for stx2a. As the present work showed diversity at the Q-S region among Stx phages, and particularly in the encoded NanS-p enzyme, future studies will be necessary to evaluate if NanS-p variants differ in their activity and to assess the impact of the absence of nanS-p in certain Stx phages.

Population replacement of benzimidazole-resistant Haemonchus contortus with susceptible strains: evidence of changes in the resistance status

The spread of anthelmintic resistance (AR) in nematode populations threatens the viability of sheep production systems worldwide, and warrants the adoption of sensitive, practical, and standardized tests to detect AR. The aim of this study was to characterize the replacement of an Haemonchus contortus population resistant to benzimidazoles (BZDs) by a susceptible one, by means of both phenotypic and genotypic techniques. Phenotypic methods to assess BZD resistance included in vivo tests, such as the fecal egg count reduction test (FECRT), and in vitro tests, such as the egg hatch assay (EHA). Additionally, genotypification of polymorphisms associated with BZD resistance by sequencing a fragment of the isotype 1 β-tubulin gene was carried out. The initial, BZD-resistant population (initial Balcarce population) exhibited an egg count reduction (ECR) of 59.3%. Following refugium replacement, the final population (final Balcarce population) exhibited an ECR of 95.2%. For the initial Balcarce population, the median effective dose (ED₅₀) for the EHA was 0.607 μg thiabendazole (TBZ)/mL, with a rate of eclosion at a discriminating dose (E_DD) of 0.1 μg TBZ/mL of 76.73%. For the final Balcarce population, ED₅₀ was 0.02 μg TBZ/mL, and E_DD was 1.97%. In the initial population, 93% of the analyzed individuals exhibited genotypic combinations associated with BZD resistance (53% Phe/Phe₁₆₇-Tyr/Tyr₂₀₀, 37% Phe/Tyr₁₆₇-Phe/Tyr₂₀₀, and 3% Phe/Tyr₁₆₇-Glu/Leu₁₉₈). Conversely, no combination associated with resistance was found in individuals from the final population. All of the tests were useful for detecting AR to BZDs. The results from the genetic and phenotypical studies were consistent, and the resulting information greatly aided in interpreting the outcomes of the population replacement and the potential impact of this strategy on management of AR.

Deamidation drives molecular aging of the SARS-CoV-2 spike protein receptor-binding motif

The spike protein is the main protein component of the SARS-CoV-2 virion surface. The spike receptor-binding motif mediates recognition of the human angiotensin-converting enzyme 2 receptor, a critical step in infection, and is the preferential target for spike-neutralizing antibodies. Posttranslational modifications of the spike receptor-binding motif have been shown to modulate viral infectivity and host immune response, but these modifications are still being explored. Here we studied asparagine deamidation of the spike protein, a spontaneous event that leads to the appearance of aspartic and isoaspartic residues, which affect both the protein backbone and its charge. We used computational prediction and biochemical experiments to identify five deamidation hotspots in the SARS-CoV-2 spike protein. Asparagine residues 481 and 501 in the receptor-binding motif deamidate with a half-life of 16.5 and 123 days at 37 °C, respectively. Deamidation is significantly slowed at 4 °C, indicating a strong dependence of spike protein molecular aging on environmental conditions. Deamidation of the spike receptor-binding motif decreases the equilibrium constant for binding to the human angiotensin-converting enzyme 2 receptor more than 3.5-fold, yet its high conservation pattern suggests some positive effect on viral fitness. We propose a model for deamidation of the full SARS-CoV-2 virion illustrating how deamidation of the spike receptor-binding motif could lead to the accumulation on the virion surface of a nonnegligible chemically diverse spike population in a timescale of days. Our findings provide a potential mechanism for molecular aging of the spike protein with significant consequences for understanding virus infectivity and vaccine development.

Combining single-cell RNA-sequencing with a molecular atlas unveils new markers for Caenorhabditis elegans neuron classes

Single-cell RNA-sequencing (scRNA-seq) of the Caenorhabditis elegans nervous system offers the unique opportunity to obtain a partial expression profile for each neuron within a known connectome. Building on recent scRNA-seq data and on a molecular atlas describing the expression pattern of ∼800 genes at the single cell resolution, we designed an iterative clustering analysis aiming to match each cell-cluster to the ∼100 anatomically defined neuron classes of C. elegans. This heuristic approach successfully assigned 97 of the 118 neuron classes to a cluster. Sixty two clusters were assigned to a single neuron class and 15 clusters grouped neuron classes sharing close molecular signatures. Pseudotime analysis revealed a maturation process occurring in some neurons (e.g. PDA) during the L2 stage. Based on the molecular profiles of all identified neurons, we predicted cell fate regulators and experimentally validated unc-86 for the normal differentiation of RMG neurons. Furthermore, we observed that different classes of genes functionally diversify sensory neurons, interneurons and motorneurons. Finally, we designed 15 new neuron class-specific promoters validated in vivo. Amongst them, 10 represent the only specific promoter reported to this day, expanding the list of neurons amenable to genetic manipulations.

First clinical symptom as a prognostic factor in systemic sclerosis: results of a retrospective nationwide cohort study

The objective of the study is to determine the importance of the mode of onset as prognostic factor in systemic sclerosis (SSc). Data were collected from the Spanish Scleroderma Registry (RESCLE), a nationwide retrospective multicenter database created in 2006. As first symptom, we included Raynaud's phenomenon (RP), cutaneous sclerosis, arthralgia/arthritis, puffy hands, interstitial lung disease (ILD), pulmonary arterial hypertension (PAH), and digestive hypomotility. A total of 1625 patients were recruited. One thousand three hundred forty-two patients (83%) presented with RP as first symptom and 283 patients (17%) did not. Survival from first symptom in those patients with RP mode of onset was higher at any time than those with onset as non-Raynaud's phenomenon: 97 vs. 90% at 5 years, 93 vs. 82% at 10 years, 83 vs. 62% at 20 years, and 71 vs. 50% at 30 years (p < 0.001). In multivariate analysis, factors related to mortality were older age at onset, male gender, dcSSc subset, ILD, PAH, scleroderma renal crisis (SRC), heart involvement, and the mode of onset with non-Raynaud's phenomenon, especially in the form of puffy hands or pulmonary involvement. The mode of onset should be considered an independent prognostic factor in systemic sclerosis and, in particular, patients who initially present with non-Raynaud's phenomenon may be considered of poor prognosis.

Oral Cerebrolysin enhances brain alpha activity and improves cognitive performance in elderly control subjects

Cerebrolysin is a porcine brain derived peptide preparation with potential neurotrophic activity. The effects of a single oral dose of the Cerebrolysin solution (30 ml) on brain bioelectrical activity and on cognitive performance were investigated in healthy elderly people. A single oral dose of Cerebrolysin induced a progressive increase in relative alpha activity power from 1 to 6 hours after treatment in almost all the brain electrodes in elderly control subjects. As compared with baseline alpha power (45.8+/-9.5%), the increase in relative alpha activity in the left occipital electrode (O1) reached significant values at 1 hour (57.2+/-8.5%; p < 0.05), 3 hours (59.4+/-7.6%; p < 0.05) and 6 hours (63.4+/-9.8%; p < 0.05) after Cerebrolysin administration. Enhancement in relative alpha power was accompanied by a generalized decrease in slow delta activity that was maximum at 6 hours after Cerebrolysin intake. A significant improvement in memory performance, evaluated with items of the ADAS cog, was also found in elderly people taken a single dose of oral Cerebrolysin (6.9+/-1.0 errors at baseline versus 4.9+/-1.0 errors after treatment; p < 0.01). This memory improvement was more evident in recognition (2.8+/-0.6 errors vs. 1.5+/-0.7 errors; p < 0.05) than in recall tasks (4.1+/-0.5 errors versus 3.4+/-0.5 errors; ns). These data indicate that Cerebrolysin potentiates brain alpha activity, reduces slow EEG delta frequencies and improves memory performance in healthy elderly humans, suggesting that this compound activates cerebral mechanisms related to attention and memory processes. According to the present results, it seems that oral Cerebrolysin might be useful for the treatment of memory impairment and brain damage in eldely subjects with or without neurodegenerative disorders.

Rhabdoid tumors of the kidney in children: CT findings

OBJECTIVE

The purpose of this study was to identify CT characteristics of rhabdoid tumor of the kidney, a rare, aggressive, malignant neoplasm of unknown origin that occurs mainly in infants and young children.

MATERIALS AND METHODS

CT scans of eight children (newborn to 13 years old; mode, 4 months old; six boys and two girls) with histopathologic diagnosis of rhabdoid tumor of the kidney were evaluated retrospectively by two of the authors, who were not blinded to the diagnosis. All eight CT scans were performed with intravenous and oral contrast, and noncontrast intravenous CT scans were available in four cases. The following CT characteristics were evaluated: location of tumor within the kidney; presence of calcification, subcapsular hematoma, multiple tumor lobules, enlarged vessels, vascular invasion, or central tumor necrosis or hemorrhage; visibility of tumor margin; distant metastasis; and primary tumor size.

RESULTS

All eight primary tumors (five on the left, one of which had contralateral renal nodules) were central in location and involved the hilum. Calcification outlining the tumor lobule was present in two of the four tumors on noncontrast CT scans. Subcapsular hematoma was seen in five children. Tumor necrosis and hemorrhage were seen in seven children. Tumors were well defined from the renal cortex in four children. Lobules of tumor were seen in seven children.

CONCLUSION

CT findings of calcification, subcapsular hematoma, and lobular appearance in a large, centrally located, and heterogeneous renal mass in a child suggest a rhabdoid tumor of the kidney.

Results of a clinical multicentric randomized phase-ii study of nonsmall cell lung-cancer treated with vinorelbine Cisplatin versus vinorelbine alone

From July 1992 to December 1993, 62 patients with non-small cell lung cancer (NSCLC) were admitted to a multicentric randomized study. The patients were treated with vinorelbine (V) alone at a dose of 25 mg/m(2)/i.v. weekly or with V at a dose of 25 mg/m(2)/i.v. on day 1 and 8 plus cisplatin at a dose of 80 mg/m(2)/i.v. on day 1 every 3-4 weeks (VP). An objective response was observed in 42% of patients treated with VP versus 12.5% of those treated with vinorelbine alone (p=0.038). There was no significant difference in the median survival duration between the two groups (38 versus 30 weeks for VP and V, respectively). Toxicity was tolerable but more severe in the VP regimen. These data suggest that V is an active agent in NSCLC and that the VP regimen may yield results comparable to other cisplatin combinations for treatment of these tumors.

Use of antithrombin III in critical patients

OBJECTIVE

To evaluate the effect of the AT III concentrates upon the clinical evolution and hemostatic parameters.

DESIGN

Prospective, open, randomized trial.

PATIENTS AND PARTICIPANTS

Septic and multiple trauma patients admitted to our Intensive Care Unit.

SETTING

Levels of AT III below 70% were used as criteria to choose 36 patients, 20 of whom received treatment with AT III and 16 did not.

INTERVENTIONS

AT III concentrates were administered at an initial dose of 60 U/kg followed by 10 U/kg every six hours.

RESULTS

The administration of AT III neither contributes to alterations in haemostasis, nor the clinical evolution (evaluated according to Apache II score).

CONCLUSIONS

The results suggest that the administration of AT III concentrates to critical patients with acquired low levels, but without manifest DIC, may not be justified; although further studies on a larger population are required to establish definite conclusions.

Tetralogy of Fallot associated with complete atrioventricular canal

A 6-year-old girl had the clinical appearance of tetralogy of Fallot but was found at cardiac catheterization to have tetralogy of Fallot associated with complete atrioventricular canal. She underwent repair, and at recatherterization two years later, the hemodynamic result was excellent. Proper angiography is necessary to diagnose this combination, and correct preoperative diagnosis is necessary to plan a rational operative approach.