Sex differences in relationships between habitat use and reproductive performance in Soay sheep (Ovis aries)

The role of habitat use in generating individual variation in fitness has rarely been examined empirically in natural populations of long‐lived mammals, particularly for both sexes simultaneously. This is the case despite the increase in studies attempting to understand evolutionary change in such populations. Using data from the St. Kilda Soay sheep population, we quantified the association between lifetime reproductive performance (lifetime breeding and reproductive success) and the proportion of the home range covered by a key grass species, H. lanatus, for 490 females and 304 males. Increased H. lanatus cover was associated only with increased female lifetime reproductive success, but increased lifetime breeding success for both sexes, arising through increased male longevity and increased female fecundity. This work suggests that improved understanding of the causes and consequences of fitness differences will likely require us to better account for habitat‐derived individual variation, and to do so for the sexes appropriately.     

Arterial stiffness in hypertensive and type 2 diabetes patients in Ghana: comparison of the cardio-ankle vascular index and central aortic techniques

Background

Diabetes and hypertension increase arterial stiffness and cardiovascular events in all societies studied so far; sub-Saharan African studies are sparse. We investigated factors affecting arterial function in Ghanaians with diabetes, hypertension, both or neither.

Method

Testing the hypothesis that arterial stiffness would progressively increase from controls to multiply affected patients, 270 participants were stratified into those with diabetes or hypertension only, with both, or without either. Cardio-ankle vascular index (CAVI), heart–ankle pulse wave velocity (haPWV), aortic PWV (PWVao) by Arteriograph, aortic and brachial blood pressures (BP), were measured.

Results

In patients with both diabetes and hypertension compared with either alone, values were higher of CAVI (mean?±?SD, 8.3?±?1.2 vs 7.5?±?1.1 and 7.4?±?1.1 units; p?<?0.05), PWVao (9.1?±?1.4 vs 8.7?±?1.9 and 8.1?±?0.9 m/s; p?<?0.05) and haPWV (8.5?±?1 vs 7.9?±?1 and 7.2?±?0.7 m/s; p?<?0.05) respectively. In multivariate analysis, age, having diabetes or hypertension and BMI were independently associated with CAVI in all participants (β?=?0.49, 0.2, 0.17 and -0.2 units; p?<?0.01, respectively). Independent determinants of PWVao were heart rate, systolic BP and age (β?=?0.42, 0.27 and 0.22; p?<?0.01), and for haPWV were systolic BP, age, BMI, diabetes and hypertension status (β?=?0.46, 0.32, -0.2, 0.2 and 0.11; p?<?0.01).

Conclusion

In this sub-Saharan setting with lesser atherosclerosis than the western world, arterial stiffness is significantly greater in patients with coexistent diabetes and hypertension but did not differ between those with either diabetes or hypertension only. Simple, reproducibly measured PWV/CAVI may offer effective and efficient targets for intervention.

     

Adult neurogenesis and pattern separation in rodents: A critical evaluation of data,tasks and interpretation

The ability to discriminate and store similar inputs as distinct representations in memory is thought to rely on a process called pattern separation in the dentate gyrus of the hippocampus. Recent computational and empirical findings support a role for adult-born granule neurons in spatial pattern separation. We reviewed rodent studies that have manipulated both hippocampal adult neurogenesis and assessed pattern separation. The majority of studies report a supporting role of adult born neurons in pattern separation as measured at the behavioral level. However, closer evaluation of the published findings reveals variation in both pattern separation tasks and in the interpretation of behavioral performance that, taken together, suggests that the role of hippocampal adult neurogenesis in pattern separation may be less established than is currently assumed. Assessment of pattern separation at the network level through the use of immediate early gene expression, optogenetic, pharmacogenetic and/or in vivo electrophysiology studies could be instrumental in further confirming a role of adult born neurons in pattern separation further. Finally, hippocampal adult neurogenesis and pattern separation are not an exclusive pair, as evidence for hippocampal adult neurogenesis contributing to the temporal separation of events in memory, forgetting and cognitive flexibility has also been found. We conclude that whereas current empirical evidence for the involvement of hippocampal adult neurogenesis in pattern separation seems supportive, there is a need for careful interpretation of behavioral findings and an integration of the various proposed functions of adult born neurons.     

Strong Interplay between Sodium and Oxygen in Kesterite Absorbers: Complex Formation,Incorporation, and Tailoring Depth Distributions

Sodium and oxygen are prevalent impurities in kesterite solar cells. Both elements are known to strongly impact performance of the kesterite devices and can be connected to efficiency improvements seen after heat treatments. The sodium distribution in the kesterite absorber is commonly reported, whereas the oxygen distribution has received less attention. Here, a direct relationship between sodium and oxygen in kesterite absorbers is established using secondary ion mass spectrometry and explained by defect analyses within the density functional theory. The calculations reveal a binding energy of 0.76 eV between the substitutional defects Na_Cu and O_S in the nearest neighbor configuration, indicating an abundance of Na? O complexes in kesterite absorbers at relevant temperatures. Oxygen incorporation is studied by introducing isotopic ¹⁸O at different stages of the Cu₂ZnSnS₄/Mo/soda‐lime glass baseline processing. It is observed that oxygen from the Mo back contact and contaminations during the sulfurization are primary contributors to the oxygen distribution. Indeed, unintentional oxygen incorporation leads to immobilization of sodium. This results in a strong correlation between sodium and oxygen, in excellent agreement with the theoretical calculations. Consequently, oxygen availability should be monitored to optimize postdeposition heat treatments to control impurities in kesterite absorbers and ultimately, the solar cell efficiency.     

Structural analysis of ligand‐bound states of the Salmonella type III secretion system ATPase InvC

Translocation of virulence effector proteins through the type III secretion system (T3SS) is essential for the virulence of many medically relevant Gram‐negative bacteria. The T3SS ATPases are conserved components that specifically recognize chaperone–effector complexes and energize effector secretion through the system. It is thought that functional T3SS ATPases assemble into a cylindrical structure maintained by their N‐terminal domains. Using size‐exclusion chromatography coupled to multi‐angle light scattering and native mass spectrometry, we show that in the absence of the N‐terminal oligomerization domain the Salmonella T3SS ATPase InvC can form monomers and dimers in solution. We also present for the first time a 2.05 å resolution crystal structure of InvC lacking the oligomerization domain (InvCΔ79) and map the amino acids suggested for ATPase intersubunit interaction, binding to other T3SS proteins and chaperone–effector recognition. Furthermore, we validate the InvC ATP‐binding site by co‐crystallization of InvCΔ79 with ATPγS (2.65 å) and ADP (2.80 å). Upon ATP‐analogue recognition, these structures reveal remodeling of the ATP‐binding site and conformational changes of two loops located outside of the catalytic site. Both loops face the central pore of the predicted InvC cylinder and are essential for the function of the T3SS ATPase. Our results present a fine functional and structural correlation of InvC and provide further details of the homo‐oligomerization process and ATP‐dependent conformational changes underlying the T3SS ATPase activity.     

Sperm number assessed by flow cytometry in species of Daphnia (Crustacea,Cladocera)

Daphnia magna and Daphnia pulex are two important model species in ecotoxicology. In daphniids, studies of the effects of contaminants have mostly focused on female life history traits, yet it would also be important to examine male reproductive traits, particularly in relation to endocrine disruptors. In this study, we developed a protocol that uses flow cytometry to measure sperm number in individual males of different species of Daphnia. We tested our protocol on 114 males from several clones of three common species of Daphnia. Sperm count varied widely among individuals and reached high numbers (up to 1.45 × 10⁵). Positive relationships between male length and sperm number were observed in D. pulex and Daphnia pulicaria, but not in D. magna. Important inter‐clonal differences in sperm production were observed in all species, with some clones producing very little sperm. Duplicated sperm samples showed on average only 6% difference in sperm counts. Sperm counts were stable at least over a 2‐hr period and up to 5 hr for most samples. This sperm isolation protocol and flow cytometric enumeration approach will be of major interest to ecotoxicologists.