Ancient habitat shifts and organismal diversification are decoupled in the African viper genus Bitis (Serpentes: Viperidae)

Aim: The expansion of open habitats during the mid-Miocene has been hypothesized as a driver of allopatric speciation for many African taxa. This habitat-dependent mode of diversification has been implicated in the shift from C3 (e.g. forest/woodland) to C4 dominated systems (i.e. open savanna, grasslands) in a number of African squamates. We examined this hypothesis using a genus of African viperid snakes (Bitis) with both open habitat and forest-dwelling representatives. Location: Africa. Methods: A comprehensive multilocus dataset was used to generate a calibrated species tree using a multispecies coalescent model. Individual gene trees and patterns of nuclear allele sharing were used to assess species monophyly and isolation. To test the habitat-dependent evolution hypothesis, we generated an ancestral character state reconstruction for open and closed habitats using the dated phylogeny. This was related to the timing of open habitat expansion and forest/woodland contraction in Africa. Results: The genus Bitis originated in the Oligocene, with species level diversification in the late Miocene/Pliocene. Four well-supported clades correspond to the recognized subgenera Bitis, Keniabitis, Macrocerastes and Calechidna. Several previously unrecognized lineages potentially represent cryptic species. Main conclusions Habitat-dependent evolution does not appear to have been a main driver for generic level viperine diversification: the ancestral state for Bitis was open habitat and at least one clade moved into forest in the Miocene, long after forest had contracted and fragmented. Forest-dependent species diversified only in the late Miocene, presumably as forest became further reduced in extent, fitting an allopatric model of speciation. Although our results do not favour a general pattern of habitat-dependent diversification in Bitis, cladogenesis within the subgenus Calechidna for “arenicolous” species (Bitis caudalis complex) and “rupicolous” species (B. Atropos-cornuta complex), corresponds to the aridification of southwest Africa. This suggests there are subtleties not captured in the broad open habitat category, which are relevant for understanding the role of habitat-dependent evolution

ATN classification and clinical progression in subjective cognitive decline

Objective: To investigate the relationship between the ATN classification system (amyloid, tau, neurodegeneration) and risk of dementia and cognitive decline in individuals with subjective cognitive decline (SCD). / Methods: We classified 693 participants with SCD (60 ± 9 years, 41% women, Mini-Mental State Examination score 28 ± 2) from the Amsterdam Dementia Cohort and Subjective Cognitive Impairment Cohort (SCIENCe) project according to the ATN model, as determined by amyloid PET or CSF β-amyloid (A), CSF p-tau (T), and MRI-based medial temporal lobe atrophy (N). All underwent extensive neuropsychological assessment. For 342 participants, follow-up was available (3 ± 2 years). As a control population, we included 124 participants without SCD. / Results: Fifty-six (n = 385) participants had normal Alzheimer disease (AD) biomarkers (A–T–N–), 27% (n = 186) had non-AD pathologic change (A–T–N+, A–T+N–, A–T+N+), 18% (n = 122) fell within the Alzheimer continuum (A+T–N–, A+T–N+, A+T+N–, A+T+N+). ATN profiles were unevenly distributed, with A–T+N+, A+T–N+, and A+T+N+ containing very few participants. Cox regression showed that compared to A–T–N–, participants in A+ profiles had a higher risk of dementia with a dose–response pattern for number of biomarkers affected. Linear mixed models showed participants in A+ profiles showed a steeper decline on tests addressing memory, attention, language, and executive functions. In the control group, there was no association between ATN and cognition. / Conclusions: Among individuals presenting with SCD at a memory clinic, those with a biomarker profile A–T+N+, A+T–N–, A+T+N–, and A+T+N+ were at increased risk of dementia, and showed steeper cognitive decline compared to A–T–N– individuals. These results suggest a future where biomarker results could be used for individualized risk profiling in cognitively normal individuals presenting at a memory clinic

Subjective Cognitive Impairment Cohort (SCIENCe): study design and first results

BACKGROUND: We aimed to describe the Subjective Cognitive Impairment Cohort (SCIENCe) study design, to crosssectionally describe participant characteristics, and to evaluate the SCD-plus criteria. METHODS: The SCIENCe is a prospective cohort study of subjective cognitive decline (SCD) patients. Participants undergo extensive assessment, including cerebrospinal fluid collection and optional amyloid positron emission tomography scan, with annual follow-up. The primary outcome measure is clinical progression. RESULTS: Cross-sectional evaluation of the first 151 participants (age 64 ± 8, 44% female, Mini-Mental State Examination 29 ± 2) showed that 28 (25%) had preclinical Alzheimer’s disease (AD) (amyloid status available n = 114 (75%)), 58 (38%) had subthreshold psychiatry, and 65 (43%) had neither. More severe subjective complaints were associated with worse objective performance. The SCD-plus criteria age ≥ 60 (OR 7.7 (95% CI 1.7–38.9)) and apolipoprotein E (genotype) e4 (OR 4.8 (95% CI 1.6–15.0)) were associated with preclinical AD. CONCLUSIONS: The SCIENCe study confirms that SCD is a heterogeneous group, with preclinical AD and subthreshold psychiatric features. We found a number of SCD-plus criteria to be associated with preclinical AD. Further inclusion and follow-up will address important questions related to SCD

Toward a theory‐based specification of non‐pharmacological treatments in aging and dementia: Focused reviews and methodological recommendations

INTRODUCTION: Non-pharmacological treatments (NPTs) have the potential to improve meaningful outcomes for older people at risk of, or living with dementia, but research often lacks methodological rigor and continues to produce mixed results. METHODS: In the current position paper, experts in NPT research have specified treatment targets, aims, and ingredients using an umbrella framework, the Rehabilitation Treatment Specification System. RESULTS: Experts provided a snapshot and an authoritative summary of the evidence for different NPTs based on the best synthesis efforts, identified main gaps in knowledge and relevant barriers, and provided directions for future research. Experts in trial methodology provide best practice principles and recommendations for those working in this area, underscoring the importance of prespecified protocols. DISCUSSION: We conclude that the evidence strongly supports various NPTs in relation to their primary targets, and discuss opportunities and challenges associated with a unifying theoretical framework to guide future efforts in this area

A comparison of responses to raised extracellular potassium and endothelium-derived hyperpolarizing factor (EDHF) in rat pressurised mesenteric arteries

The present study examined the hypothesis that potassium ions act as an endothelium-derived hyperpolarizing factor (EDHF) released in response to ACh in small mesenteric arteries displaying myogenic tone. Small mesenteric arteries isolated from rats were set up in a pressure myograph at either 60 or 90 mmHg. After developing myogenic tone, responses to raising extracellular potassium were compared to those obtained with ACh (in the presence of nitric oxide synthase and cyclo- oxygenase inhibitors). The effects of barium and ouabain, or capsaicin, on responses to raised extracellular potassium or ACh were also determined. The effects of raised extracellular potassium levels and ACh on membrane potential, were measured using sharp microelectrodes in pressurised arteries. Rat small mesenteric arteries developed myogenic tone when pressurised. On the background of vascular tone set by a physiological stimulus (i.e pressure), ACh fully dilated the small arteries in a concentration-dependent manner. This response was relatively insensitive to the combination of barium and ouabain, and insensitive to capsaicin. Raising extracellular potassium produced a more inconsistent and modest vasodilator response in pressurised small mesenteric arteries. Responses to raising extracellular potassium were sensitive to capsaicin, and the combination of barium and ouabain. ACh caused a substantial hyperpolarisation in pressurized arteries, while raising extracellular potassium did not. These data indicate that K+ is not the EDHF released in response to ACh in myogenically active rat mesenteric small arteries. Since the hyperpolarization produced by ACh was sensitive to carbenoxolone, gap junctions are the likely mediator of EDH responses under physiological conditions

Vascular smooth muscle cells remodel collagen matrices by long-distance action and anisotropic interaction

While matrix remodeling plays a key role in vascular physiology and pathology, the underlying mechanisms have remained incompletely understood. We studied the remodeling of collagen matrices by individual vascular smooth muscle cells (SMCs), clusters and monolayers. In addition, we focused on the contribution of transglutaminase 2 (TG2), which plays an important role in the remodeling of small arteries. Single SMCs displaced fibers in collagen matrices at distances up to at least 300 μm in the course of 8–12 h. This process involved both ‘hauling up’ of matrix by the cells and local matrix compaction at a distance from the cells, up to 200 μm. This exceeded the distance over which cellular protrusions were active, implicating the involvement of secreted enzymes such as TG2. SMC isolated from TG2 KO mice still showed compaction, with changed dynamics and relaxation. The TG active site inhibitor L682777 blocked local compaction by wild type cells, strongly reducing the displacement of matrix towards the cells. At increasing cell density, cells cooperated to establish compaction. In a ring-shaped collagen matrix, this resulted in preferential displacement in the radial direction, perpendicular to the cellular long axis. This process was unaffected by inhibition of TG2 cross-linking. These results show that SMCs are capable of matrix remodeling by prolonged, gradual compaction along their short axis. This process could add to the 3D organization and remodeling of blood vessels based on the orientation and contraction of SMCs

The Redox State of Transglutaminase 2 Controls Arterial Remodeling

While inward remodeling of small arteries in response to low blood flow, hypertension, and chronic vasoconstriction depends on type 2 transglutaminase (TG2), the mechanisms of action have remained unresolved. We studied the regulation of TG2 activity, its (sub) cellular localization, substrates, and its specific mode of action during small artery inward remodeling. We found that inward remodeling of isolated mouse mesenteric arteries by exogenous TG2 required the presence of a reducing agent. The effect of TG2 depended on its cross-linking activity, as indicated by the lack of effect of mutant TG2. The cell-permeable reducing agent DTT, but not the cell-impermeable reducing agent TCEP, induced translocation of endogenous TG2 and high membrane-bound transglutaminase activity. This coincided with inward remodeling, characterized by a stiffening of the artery. The remodeling could be inhibited by a TG2 inhibitor and by the nitric oxide donor, SNAP. Using a pull-down assay and mass spectrometry, 21 proteins were identified as TG2 cross-linking substrates, including fibronectin, collagen and nidogen. Inward remodeling induced by low blood flow was associated with the upregulation of several anti-oxidant proteins, notably glutathione-S-transferase, and selenoprotein P. In conclusion, these results show that a reduced state induces smooth muscle membrane-bound TG2 activity. Inward remodeling results from the cross-linking of vicinal matrix proteins, causing a stiffening of the arterial wall

Prevalence of abnormal Alzheimer’s disease biomarkers in patients with subjective cognitive decline: cross-sectional comparison of three European memory clinic samples

Introduction: Subjective cognitive decline (SCD) in cognitively unimpaired older individuals has been recognized as an early clinical at-risk state for Alzheimer's disease (AD) dementia and as a target population for future dementia prevention trials. Currently, however, SCD is heterogeneously defined across studies, potentially leading to variations in the prevalence of AD pathology. Here, we compared the prevalence and identified common determinants of abnormal AD biomarkers in SCD across three European memory clinics participating in the European initiative on harmonization of SCD in preclinical AD (Euro-SCD). Methods: We included three memory clinic SCD samples with available cerebrospinal fluid (CSF) biomaterial (IDIBAPS, Barcelona, Spain, n = 44; Amsterdam Dementia Cohort (ADC), The Netherlands, n = 50; DELCODE multicenter study, Germany, n = 42). CSF biomarkers (amyloid beta (Aβ)42, tau, and phosphorylated tau (ptau181)) were centrally analyzed in Amsterdam using prespecified cutoffs to define prevalence of pathological biomarker concentrations. We used logistic regression analysis in the combined sample across the three centers to investigate center effects with regard to likelihood of biomarker abnormality while taking potential common predictors (e.g., age, sex, apolipoprotein E (APOE) status, subtle cognitive deficits, depressive symptoms) into account. Results: The prevalence of abnormal Aβ42, but not tau or ptau181, levels was different across centers (64% DELCODE, 57% IDIBAPS, 22% ADC; p < 0.001). Logistic regression analysis revealed that the likelihood of abnormal Aβ42 (and also abnormal tau or ptau181) levels was predicted by age and APOE status. For Aβ42 abnormality, we additionally observed a center effect, indicating between-center heterogeneity not explained by age, APOE, or the other included covariates. Conclusions: While heterogeneous frequency of abnormal Aβ42 was partly explained by between-sample differences in age range and APOE status, the additional observation of center effects indicates between-center heterogeneity that may be attributed to different recruitment procedures. These findings highlight the need for the development of harmonized recruitment protocols for SCD case definition in multinational studies to achieve similar enrichment rates of preclinical AD

Perspectives on ethnic and racial disparities in Alzheimer\u27s disease and related dementias: Update and areas of immediate need

Alzheimer\u27s disease and related dementias (ADRDs) are a global crisis facing the aging population and society as a whole. With the numbers of people with ADRDs predicted to rise dramatically across the world, the scientific community can no longer neglect the need for research focusing on ADRDs among underrepresented ethnoracial diverse groups. The Alzheimer\u27s Association International Society to Advance Alzheimer\u27s Research and Treatment (ISTAART; alz.org/ISTAART) comprises a number of professional interest areas (PIAs), each focusing on a major scientific area associated with ADRDs. We leverage the expertise of the existing international cadre of ISTAART scientists and experts to synthesize a cross-PIA white paper that provides both a concise “state-of-the-science” report of ethnoracial factors across PIA foci and updated recommendations to address immediate needs to advance ADRD science across ethnoracial populations. © 2018 The Author

Thrombospondin-1 in Early Flow-Related Remodeling of Mesenteric Arteries from Young Normotensive and Spontaneously Hypertensive Rats

We tested the hypotheses that TSP-1 participates in the initiation of remodeling of small muscular arteries in response to altered blood flow and that the N-terminal domain of TSP-1 (hepI) can reverse the pathological inward remodeling of resistance arteries from SHR