Contributions of the Prion Protein Sequence, Strain, and Environment to the Species Barrier.

Amyloid propagation requires high levels of sequence specificity so that only molecules with very high sequence identity can form cross-ß-sheet structures of sufficient stringency for incorporation into the amyloid fibril. This sequence specificity presents a barrier to the transmission of prions between two species with divergent sequences, termed a species barrier. Here we study the relative effects of protein sequence, seed conformation, and environment on the species barrier strength and specificity for the yeast prion protein Sup35p from three closely related species of the Saccharomyces sensu stricto group; namely, Saccharomyces cerevisiae, Saccharomyces bayanus, and Saccharomyces paradoxus. Through in vivo plasmid shuffle experiments, we show that the major characteristics of the transmission barrier and conformational fidelity are determined by the protein sequence rather than by the cellular environment. In vitro data confirm that the kinetics and structural preferences of aggregation of the S. paradoxus and S. bayanus proteins are influenced by anions in accordance with their positions in the Hofmeister series, as observed previously for S. cerevisiae. However, the specificity of the species barrier is primarily affected by the sequence and the type of anion present during the formation of the initial seed, whereas anions present during the seeded aggregation process typically influence kinetics rather than the specificity of prion conversion. Therefore, our work shows that the protein sequence and the conformation variant (strain) of the prion seed are the primary determinants of cross-species prion specificity both in vivo and in vitro.

Ion-specific effects on prion nucleation and strain formation.

Ordered, fibrous, self-seeding aggregates of misfolded proteins known as amyloids are associated with important diseases in mammals and control phenotypic traits in fungi. A given protein may adopt multiple amyloid conformations, known as variants or strains, each of which leads to a distinct disease pattern or phenotype. Here, we study the effect of Hofmeister ions on amyloid nucleation and strain generation by the prion domain-containing fragment (Sup35NM) of a yeast protein Sup35p. Strongly hydrated anions (kosmotropes) initiate nucleation quickly and cause rapid fiber elongation, whereas poorly hydrated anions (chaotropes) delay nucleation and mildly affect the elongation rate. For the first time, we demonstrate that kosmotropes favor formation of amyloid strains that are characterized by lower thermostability and higher frangibility in vitro and stronger phenotypic and proliferation patterns effectively in vivo as compared with amyloids formed in chaotropes. These phenomena point to inherent differences in the biochemistry of Hofmeister ions. Our work shows that the ionic composition of a solution not only influences the kinetics of amyloid nucleation but also determines the amyloid strain that is preferentially formed.

Sequence specificity and fidelity of prion transmission in yeast.

Amyloid formation is a widespread feature of various proteins. It is associated with both important diseases (including infectious mammalian prions) and biologically positive functions, and provides a basis for structural "templating" and protein-based epigenetic inheritance (for example, in the case of yeast prions). Amyloid templating is characterized by a high level of sequence specificity and conformational fidelity. Even slight variations in sequence may produce a strong barrier for prion transmission. Yeast models provide useful insight into a mechanism of amyloid specificity and fidelity. Accumulating evidence indicates that cross-species prion transmission is controlled by the identity of short sequences (specificity stretches) rather than by the overall level of sequence identity. Location of the specificity stretches determines the location and/or size of the cross-ß amyloid region that controls patterns of prion variants. In some cases of cross-species prion transmission, fidelity of variant reproduction is impaired, leading to the formation of new structural variants. We propose that such a variant switch may occur due to choice of the alternatively located secondary specificity stretches, when interaction between the primary stretches is impaired due to sequence divergence.

Incidence, risk factors, and outcome of pneumatosis intestinalis in pediatric stem cell transplant recipients.

BACKGROUND: Pneumatosis Intestinalis (PI) is a rare complication following hematopoietic stem cell transplant (HSCT). We sought to assess the incidence, risk factors, and outcome associated with PI. PROCEDURE: We retrospectively reviewed the incidence of PI among 178 patients who underwent allogeneic HSCT between September 1999 and February 2010. RESULTS: Eighteen of 178 children (10.1%) who received allogeneic HSCT developed PI at a median of 94 days (range, 11-1169) after transplant. All patients presented with either abdominal pain or distention, and half of the patients had free air on radiographs. Patients who developed PI had a significantly higher proportion of acute (83% vs. 44%, P = 0.002) and chronic graft versus host disease (GVHD; 56% vs. 18%, P < 0.001). Only 39% of patients with PI had GVHD involving the gasterointestinal track. All patients were managed conservatively without surgery. Transplant related mortality (TRM) was significantly higher in patients who developed PI compared to those who did not (OR 4.3, 95% CI: 1.3-13.1; P = 0.007), but no deaths were attributable to PI. CONCLUSIONS: We conclude that PI is a common complication associated with treatment of GVHD after HSCT, and patients who develop PI experience higher TRM. Patients who develop PI should be managed medically.

Comparison of pre-cryopreserved and post-thaw-and-wash-nucleated cell count on major outcomes following unrelated cord blood transplant in children.

Engraftment and OS after umbilical CBT is highly dependent on the TNC. The contribution of the wash step to cell loss and ultimately the dose of cells available for transplant is not well described. To investigate the amount of cell loss after washing and its impact on major outcomes compared to pre-cryopreserved TNC, we analyzed data from patients prospectively enrolled on a National Heart, Lung and Blood Institute sponsored cord blood transplant study between 1999 and 2003. There were 310 patients ≤18 yr of age with malignant (N = 218) or non-malignant (N = 92) disease enrolled on this trial. Only single CBU were used. All CBU were thawed and washed using an identical process. The median TNC after thawing and washing (PTW) was 5.43 × 10(7) /kg (79% recovery of cells). The cumulative incidence of neutrophil engraftment was significantly higher in patients receiving a PTW TNC ≥2.5 × 10(7) /kg (p = 0.01). The cumulative incidence of TRM was higher among patients receiving post-thaw-and-wash TNC <2.5 × 10(7) /kg (p = 0.039). In conclusion, receiving a PTW TNC of <2.5 × 10(7) /kg resulted in worse neutrophil engraftment and increased transplant-related mortality compared to a PTW TNC of ≥2.5 × 10(7) /kg.

Genetic and epigenetic control of the efficiency and fidelity of cross-species prion transmission.

Self-perpetuating amyloid-based protein isoforms (prions) transmit neurodegenerative diseases in mammals and phenotypic traits in yeast. Although mechanisms that control species specificity of prion transmission are poorly understood, studies of closely related orthologues of yeast prion protein Sup35 demonstrate that cross-species prion transmission is modulated by both genetic (specific sequence elements) and epigenetic (prion variants, or 'strains') factors. Depending on the prion variant, the species barrier could be controlled at the level of either heterologous co-aggregation or conversion of the aggregate-associated heterologous protein into a prion polymer. Sequence divergence influences cross-species transmission of different prion variants in opposing ways. The ability of a heterologous prion domain to either faithfully reproduce or irreversibly switch the variant-specific prion patterns depends on both sequence divergence and the prion variant. Sequence variations within different modules of prion domains contribute to transmission barriers in different cross-species combinations. Individual amino acid substitutions within short amyloidogenic stretches drastically alter patterns of cross-species prion conversion, implicating these stretches as major determinants of species specificity.

A Systematic Review of Parenting Interventions to Support Siblings of Children with a Chronic Health Condition.

This systematic review summarises the parenting intervention literature for parents of children who have a sibling with a chronic health condition, and evaluates intervention efficacy for improving parent (parenting skills, parenting efficacy) and child (emotional and behavioural adjustment, condition knowledge, quality of life) outcomes. Electronic databases were searched to identify relevant papers published in English from inception until May 2020. Reference lists of eligible papers were further searched for relevant articles. Six papers (two controlled trials, four uncontrolled trials) evaluating four separate intervention programs met inclusion criteria. All included parent- and child-focused intervention components. Results showed an overall trend for pre- to post-intervention improvement in children's behavioural and emotional adjustment and health condition knowledge. Few studies examined effects on parent outcomes, and there was no evidence of change on these measures. Overall, results suggest that parenting interventions may help to improve siblings' emotional and behavioural adjustment and condition knowledge; however, all of the interventions combined parent- and child-directed intervention components, making it difficult to determine which intervention elements drive change. Further research is needed to test mechanisms by which parenting interventions may improve outcomes for siblings of children with chronic health conditions, and to establish the efficacy of this approach.

The aftermath of violence: children, disaster, and posttraumatic stress disorder.

Terrorist attacks, situations of armed conflict, and all forms of catastrophe tax our abilities to cope, understand, and respond. Because of their developmental status, children are even more emotionally vulnerable to the devastating effects of a disaster. When tragedy strikes a family, community, or the nation, helping children cope and regain a sense of safety is critical. A child with posttraumatic stress disorder (PTSD) develops symptoms such as intense fear, disorganized and agitated behavior, emotional numbness, anxiety, or depression after being directly exposed to or witnessing an extreme traumatic situation involving threatened death or serious injury. Victims of repeated abuse or children who live in violent neighborhoods or war zones, or who have witnessed extensive media coverage of violent events, may experience PTSD.

Validity of a screening tool for detecting subtle cognitive impairment in the middle-aged and elderly.

The present study tested 121 middle-aged and elderly community-dwelling individuals on the computer-based Subtle Cognitive Impairment Test (SCIT) and compared their performance with that on several neuropsychological tests. The SCIT had excellent internal consistency, as demonstrated by a high split-half reliability measure (0.88-0.93). Performance on the SCIT was unaffected by the confounding factors of sex, education level, and mood state. Many participants demonstrated impaired performance on one or more of the neuropsychological tests (Controlled Oral Word Association Task, Rey Auditory and Verbal Learning Task, Grooved Pegboard [GP], Complex Figures). Performance on SCIT subtests correlated significantly with performance on many of the neuropsychological subtests, and the best and worst performing quartiles on the SCIT subtest discriminated between good and poor performers on other subtests, collectively indicating concurrent validity of the SCIT. Principal components analysis indicated that SCIT performance does not cluster with performance on most of the other cognitive tests, and instead is associated with decision-making efficacy, and processing speed and efficiency. Thus, the SCIT is responsive to the processes that underpin multiple cognitive domains, rather than being specific for a single domain. Since the SCIT is quick and easy to administer, and is well tolerated by the elderly, it may have utility as a screening tool for detecting cognitive impairment in middle-aged and elderly populations.

Effects on cognition of conventional and robotically assisted cardiac valve operation.

BACKGROUND: The effect of valve surgical procedures on cognition was investigated in patients undergoing conventional or robotically assisted techniques. The confounding factors of surgical procedure, mood state, preexisting cognitive impairment, and repeated experience with cognitive tests were controlled for. METHODS: Patients undergoing conventional valve procedures (n = 15), robotically assisted valve procedures (n = 15), and thoracic surgical procedures (n = 15), along with a nonsurgical control group (n = 15) were tested preoperatively, 1 week after operation, and 8 weeks after operation by use of a battery of cognitive tests and a mood state assessment. Surgical group data were normalized against data from the nonsurgical control group before statistical analysis. RESULTS: Patients undergoing conventional valve procedures performed worse than those undergoing robotically assisted valve procedures on every subtest before operation, and this disadvantage persisted after operation. Age and premorbid intelligence quotient were significantly associated with performance on several cognitive subtests. Anxiety, depression, and stress were not associated with impaired cognitive performance in the surgical groups after operation. A week after operation, patients undergoing conventional valve procedures performed worse on the cognitive tests that had a motor component, which may reflect discomfort caused by the sternotomy. Patients undergoing robotically assisted valve procedures were significantly less impaired on information processing tasks 1 week after operation when compared with those undergoing conventional valve procedures. The majority of patients who were impaired 1 week after operation recovered to preoperation levels within 8 weeks. CONCLUSIONS: The robotically assisted valve surgical procedure results in more rapid recovery of performance on cognitive tests. However, regardless of the type of surgical intervention, the prospect of a recovery of cognitive performance to preoperative levels is high.

Recovery of cognitive function after coronary artery bypass graft operations.

BACKGROUND: The effect of coronary artery bypass grafting (CABG) operations on cognition was examined after controlling for the operation, emotional state, preexisting cognitive impairment, and repeated experience with cognitive tests. METHODS: On-pump CABG patients (n=16), thoracic surgical patients (n=15), and a nonsurgical control group (n=15) were tested preoperatively, and at 1 and 8 weeks postoperatively, using a battery of cognitive tests and an emotional state assessment. Patient groups were similar in age, sex, level of education, and premorbid intelligence quotient score. Surgical group data were normalized against data from the nonsurgical control group before statistical analysis. RESULTS: CABG patients performed worse on every subtest before the operation, and this disadvantage persisted after the operation. Anxiety, depression, and stress were associated with impaired cognitive performance in the surgical groups 1 week after the operation: 44% of CABG patients and 33% of surgical control patients were significantly impaired; yet, by 8 weeks, nearly all patients had recovered to preoperative levels, with 25% of CABG and 13% of surgical control patients improving beyond their preoperative performance. CONCLUSIONS: Stress, anxiety, and depression impair cognitive performance in association with CABG and thoracic operations. Most patients recover to, or exceed, preoperative levels of cognition within 8 weeks. Thus, after controlling for nonsurgical factors, the prospects of a tangible improvement in cognition after CABG are high.