Warm ischemic preconditioning improves mitochondrial redox balance during and after mild hypothermic ischemia in guinea pig isolated hearts

Ischemic preconditioning (IPC) induces distinctive changes in mitochondrial bioenergetics during warm (37 degrees C) ischemia and improves function and tissue viability on reperfusion. We examined whether IPC before 2 h of hypothermic (27 degrees C) ischemia affords additive cardioprotection and improves mitochondrial redox balance assessed by mitochondrial NADH and flavin adenine dinucleotide (FAD) autofluorescence in intact hearts. A mediating role of ATP-sensitive K(+) (K(ATP)) channel opening was investigated. NADH and FAD fluorescence was measured in the left ventricular wall of guinea pig isolated hearts assigned to five groups of eight animals each: hypothermia alone, hypothermia with ischemia, IPC with cold ischemia, 5-hydroxydecanoic acid (5-HD) alone, and 5-HD with IPC and cold ischemia. IPC consisted of two 5-min periods of warm global ischemia spaced 5 min apart and 15 min of reperfusion before 2 h of ischemia at 27 degrees C and 2 h of warm reperfusion. The K(ATP) channel inhibitor 5-HD was perfused from 5 min before until 5 min after IPC. IPC before 2 h of ischemia at 27 degrees C led to better recovery of function and less tissue damage on reperfusion than did 27 degrees C ischemia alone. These improvements were preceded by attenuated increases in NADH and decreases in FAD during cold ischemia and the reverse changes during warm reperfusion. 5-HD blocked each of these changes induced by IPC. This study indicates that IPC induces additive cardioprotection with mild hypothermic ischemia by improving mitochondrial bioenergetics during and after ischemia. Because effects of IPC on subsequent changes in NADH and FAD were inhibited by 5-HD, this suggests that mitochondrial K(ATP) channel opening plays a substantial role in improving mitochondrial bioenergetics throughout mild hypothermic ischemia and reperfusion.     

Prevalence of trypanosomes,salivary gland hypertrophy virus and Wolbachia in wild populations of tsetse flies from West Africa

Background

Tsetse flies are vectors of African trypanosomes, protozoan parasites that cause sleeping sickness (or human African trypanosomosis) in humans and nagana (or animal African trypanosomosis) in livestock. In addition to trypanosomes, four symbiotic bacteria Wigglesworthia glossinidia, Sodalis glossinidius, Wolbachia, Spiroplasma and one pathogen, the salivary gland hypertrophy virus (SGHV), have been reported in different tsetse species. We evaluated the prevalence and coinfection dynamics between Wolbachia, trypanosomes, and SGHV in four tsetse species (Glossina palpalis gambiensis, G. tachinoides, G. morsitans submorsitans, and G. medicorum) that were collected between 2008 and 2015 from 46 geographical locations in West Africa, i.e. Burkina Faso, Mali, Ghana, Guinea, and Senegal.

Results

The results indicated an overall low prevalence of SGHV and Wolbachia and a high prevalence of trypanosomes in the sampled wild tsetse populations. The prevalence of all three infections varied among tsetse species and sample origin. The highest trypanosome prevalence was found in Glossina tachinoides (61.1%) from Ghana and in Glossina palpalis gambiensis (43.7%) from Senegal. The trypanosome prevalence in the four species from Burkina Faso was lower, i.e. 39.6% in Glossina medicorum, 18.08%; in Glossina morsitans submorsitans, 16.8%; in Glossina tachinoides and 10.5% in Glossina palpalis gambiensis. The trypanosome prevalence in Glossina palpalis gambiensis was lowest in Mali (6.9%) and Guinea (2.2%). The prevalence of SGHV and Wolbachia was very low irrespective of location or tsetse species with an average of 1.7% for SGHV and 1.0% for Wolbachia. In some cases, mixed infections with different trypanosome species were detected. The highest prevalence of coinfection was Trypanosoma vivax and other Trypanosoma species (9.5%) followed by coinfection of T. congolense with other trypanosomes (7.5%). The prevalence of coinfection of T. vivax and T. congolense was (1.0%) and no mixed infection of trypanosomes, SGHV and Wolbachia was detected.

Conclusion

The results indicated a high rate of trypanosome infection in tsetse wild populations in West African countries but lower infection rate of both Wolbachia and SGHV. Double or triple mixed trypanosome infections were found. In addition, mixed trypanosome and SGHV infections existed however no mixed infections of trypanosome and/or SGHV with Wolbachia were found.

     

Synthesis of RGD amphiphilic cyclic peptide as fibrinogen or fibronectin antagonist

This paper investigates the effect of the incorporation of adiazaethylene glycol derivative (Deg, 2) into a cyclic peptide containingthe tripeptide sequence Arg-Gly-Asp (RGD). This motif is a common structuralelement of many integrin ligands. The synthesis of cyclo-(Arg-Gly-Asp-Deg)(7) has been accomplished in solution using standard peptide chemistry. Theintent was to improve the bioavailability of this new RGD cyclic peptide,which is shown to interact with _IIb33or _{5 1} receptors. A preliminary stepfor the conformational study of peptide 7 was done in DMSO-d₆using nuclear magnetic resonance spectroscopy techniques.     

Grass Physiognomic Trait Variation in African Herbaceous Biomes

African herbaceous biomes will likely face drastic changes in the near future, due to climate change and pressures from increasing human activities. However, these biomes have been simulated only by dynamic global vegetation models and failing to include the diversity of C₄ grasses has limited the accuracy of these models. Characterizing the floristic and physiognomic diversity of these herbaceous biomes would enhance the parameterization of C₄ grass plant functional types, thereby improving simulations. To this end, we used lowermost and uppermost values of three grass physiognomic traits (culm height, leaf length, and leaf width) available in most floras to identify several grass physiognomic groups that form the grass cover in Senegal. We then checked the capacity of these groups to discriminate herbaceous biomes and mean annual precipitation domains. Specifically, we assessed whether these groups were sufficiently generic and robust to be applied to neighboring (Chad) and distant (South Africa) phytogeographic areas. The proportions of two physiognomic groups, defined by their lowermost limits, delineate steppe from savanna and forest biomes in Senegal, and nama‐karoo, savanna, and grassland biomes in South Africa. Proportions of these two physiognomic groups additionally delineate the mean annual precipitation domains <600 mm and >600 mm in Senegal, Chad, and South Africa, as well as the <250 mm and >1000 mm domains in South Africa. These findings should help to identify and parameterize new C₄ grass plant functional types in vegetation models applied to West and South Africa.     

Multi-host ectomycorrhizal fungi are predominant in a Guinean tropical rainforest and shared between canopy trees and seedlings

The diversity of ectomycorrhizal (ECM) fungi on adult trees and seedlings of five species, Anthonotha fragrans, Anthonotha macrophylla, Cryptosepalum tetraphyllum, Paramacrolobium coeruleum and Uapaca esculenta, was determined in a tropical rain forest of Guinea. Ectomycorrhizae were sampled within a surface area of 1600 m(2), and fungal taxa were identified by sequencing the rDNA Internal Transcribed Spacer region. Thirty-nine ECM fungal taxa were determined, of which 19 multi-hosts, 9 single-hosts and 11 singletons. The multi-host fungi represented 92% (89% when including the singletons in the analysis) of the total abundance. Except for A. fragrans, the adults of the host species displayed significant differentiation for their fungal communities, but their seedlings harboured a similar fungal community. These findings suggest that there was a potential for the formation of common mycorrhizal networks in close vicinity. However, no significant difference was detected for the δ(13)C and δ(15)N values between seedlings and adults of each ECM plant, and no ECM species exhibited signatures of mixotrophy. Our results revealed (i) variation in ECM fungal diversity according to the seedling versus adult development stage of trees and (ii) low host specificity of ECM fungi, and indicated that multi-host fungi are more abundant than single-host fungi in this forest stand.     

Effect of plant growth regulators,temperature and sucrose on shoot proliferation from the stem disc of Chinese jiaotou (<Emphasis Type="Italic">Allium chinense</Emphasis>) and in vitro bulblet formation

In vitro shoot proliferation from stem disc of Allium chinense, a vegetatively propagated plant, was investigated in this experiment. In the present study, shoots were formed directly on stem discs on a medium containing 1 mg/l N⁶-benzyladenine (BA) and 0.5 mg/lα-naphthaleneacetic acid (NAA). These shoots were further cultured on MS media supplemented with various levels of BA in combination with NAA, and new shoot clusters developed easily from the explants cultured despite considerable differences in the induction of shoot clusters with different levels of BA and NAA. The most productive combination of growth regulators proved to be 1.0 mg/l BA and 1.0 mg/l NAA, in which about 17 shoots were produced per cluster in 8 weeks culture. Most of the formed shoots were rooted 15 days after being cultured on MS media supplemented with 0.1–1.0 mg/l NAA. The survival rate of the plantlets under ex vitro conditions was 95% in pots filled with a peat: sand (2:1 v/v) mixture after two weeks. In vitro bulblet formation were strongly promoted by the high temperature of 30°C compared to that at 25, 20 and 15°C, and 12% (w/v) sucrose appeared to be optimal for bulblet development. Results from this study demonstrated that A. chinense could be in vitro propagated by using stem discs and in vitro bulblet formation could be achieved.     

Pre-synaptic and post-synaptic localization of EphA4 and EphB2 in adult mouse forebrain

The ephrin receptors EphA4 and EphB2 have been implicated in synaptogenesis and long-term potentiation in the cerebral cortex and hippocampus, where they are generally viewed as post-synaptic receptors. To determine the precise distribution of EphA4 and EphB2 in mature brain synapses, we used subcellular fractionation and electron microscopy to examine the adult mouse forebrain/midbrain. EphA4 and EphB2 were both enriched in microsomes and synaptosomes. In synaptosomes, they were present in the membrane and the synaptic vesicle fractions. While EphA4 was tightly associated with PSD-95-enriched post-synaptic density fractions, EphB2 was easily extracted with detergents. In contrast, both receptors were found in the pre-synaptic active zone fraction. By electron microscopy, EphA4 was mainly detected in axon terminals, whereas EphB2 was more frequently detected in large dendritic shafts, in the hippocampus and cerebral cortex. However, in the ventrobasal thalamus, EphB2 was detected most frequently in axon terminals and thin dendritic shafts. The localization of EphA4 and EphB2 in multiple compartments of neurons and synaptic junctions suggests that they interact with several distinct scaffolding proteins and play diverse roles at synapses.     

Dynamic buffering of mitochondrial Ca2+ during Ca2+ uptake and Na+-induced Ca2+ release

In cardiac mitochondria, matrix free Ca²⁺ ([Ca²⁺]_m) is primarily regulated by Ca²⁺ uptake and release via the Ca²⁺ uniporter (CU) and Na⁺/Ca²⁺ exchanger (NCE) as well as by Ca²⁺ buffering. Although experimental and computational studies on the CU and NCE dynamics exist, it is not well understood how matrix Ca²⁺ buffering affects these dynamics under various Ca²⁺ uptake and release conditions, and whether this influences the stoichiometry of the NCE. To elucidate the role of matrix Ca²⁺ buffering on the uptake and release of Ca²⁺, we monitored Ca²⁺ dynamics in isolated mitochondria by measuring both the extra-matrix free [Ca²⁺] ([Ca²⁺]_e) and [Ca²⁺]_m. A detailed protocol was developed and freshly isolated mitochondria from guinea pig hearts were exposed to five different [CaCl₂] followed by ruthenium red and six different [NaCl]. By using the fluorescent probe indo-1, [Ca²⁺]_e and [Ca²⁺]_m were spectrofluorometrically quantified, and the stoichiometry of the NCE was determined. In addition, we measured NADH, membrane potential, matrix volume and matrix pH to monitor Ca²⁺-induced changes in mitochondrial bioenergetics. Our [Ca²⁺]_e and [Ca²⁺]_m measurements demonstrate that Ca²⁺ uptake and release do not show reciprocal Ca²⁺ dynamics in the extra-matrix and matrix compartments. This salient finding is likely caused by a dynamic Ca²⁺ buffering system in the matrix compartment. The Na⁺- induced Ca²⁺ release demonstrates an electrogenic exchange via the NCE by excluding an electroneutral exchange. Mitochondrial bioenergetics were only transiently affected by Ca²⁺ uptake in the presence of large amounts of CaCl₂, but not by Na⁺- induced Ca²⁺ release.