Swelling and Contraction of Mitochondria from Cold-hardened and Nonhardened Wheat and Rye Seedlings

A comparison of mitochondria isolated from 2 and 24 C grown winter wheat (Triticum aestivum L.) and winter rye (Secale cereale L.) seedlings revealed no correlation between changes in swelling and contraction characteristics and extent of cold hardiness. The swelling response changed markedly due to growth at low temperature, but the change was similar for the four cultivars examined. The swelling response was also observed to change rapidly during aging of isolated mitochondria, either at 2 or 24 C. Spontaneously swollen mitochondria, isolated from 24 C grown seedlings, contracted abruptly upon addition of certain oxidizable substrates, but this response was lost when seedlings were transferred from 24 to 2 C. Studies on the effect of various substrates and respiratory inhibitors on the swelling and contraction responses indicate that inhibitors which reduce or stop electron flow through the electron transport chain also inhibit substrate induced mitochondrial contraction.     

The effect of nucleotides and inhibitors on respiration in isolated wheat mitochondria

The effect of mono-, di-, and trinucleoside phosphates and respiratory inhibitors on respiration in winter wheat (Triticum aestivum L. cv. Rideau) mitochondria has been examined. When added during state 4 respiration, subsequent to addition of ADP, all of the dinucleotides stimulated oxidation and induced respiratory control with all substrates examined. Similar results were obtained with AMP, but other mononucleotides and all trinucleotides did not affect the rate of oxidation. Nucleoside diphosphates did not stimulate respiration when added prior to the addition of ADP, but subsequent addition of AMP, ADP, or ATP re-established coupled respiration in the presence of the dinucleotides.     

Patterns of bee diversity in mosaic agricultural landscapes of central Uganda: implication of pollination services conservation for food security

Little is known about bee communities and pollination services conservation strategies in sub-Sahara Africa. A study was conducted at 26 different sites with varying local landscape characteristics in farmlands of central Uganda in 2006. Bees were sampled using coloured pantraps, handnet and line transect counts. Overall 80,883 bee individuals from 6 families and 652 species were encountered. The bee fauna was characterized by a lower diversity of Melittidae and Andrenidae and a high diversity of Apidae, Megachilidae and Halictidae. Megachile and Lasioglossum were the two most species-rich genera. The most abundant species was Apis mellifera adansonii Linnaeus (23 % of total individuals) followed by Hypotrigona gribodoi Magretti (19 %), Meliponula ferruginea Lepeletier (13 %), Lasioglossum ugandicum Cockerell (7 %), Apis mellifera scutellata Latreille (6 %), Allodapula acutigera Cockerell (6 %), Ceratina rufigastra Cockerell (5 %), Ceratina tanganyicensis Strand (5 %), Braunsapis angolensis Cockerell (5 %), Megachile rufipes Fabricius (5 %), Meliponula bocandei Spinola (5 %) and Seladonia jucundus Smith (5 %). The mean number of species recorded per study site per day ranged between 14 and 49, whereas the abundance ranged between 188 and 1,859 individuals. Study sites in areas with intense land-use had species-poor bee communities compared to sites with medium to low land-use intensities. Study sites with riparian forest fragments and wetlands, or with forest fallows in their vicinity had significantly (P < 0.05) higher species richness and diversity than sites dominated by small-scale monoculture/polyculture fields or sites dominated by either simple or complex traditional agroforestry systems. An ordination analysis also revealed that bee communities were significantly (P < 0.01) influenced by the presence of semi-natural habitats (woodlands, fallows) and forest fragments in the surrounding of fields. Thus, natural and semi-natural habitats are of great value for afrotropical farmland bee communities. There is a need to put in place strategies and policies for semi-natural and forest fragments preservation for spatio-temporal stability of pollination services in rural landscapes. Farmers are recommended to increase on-farm trees cover to safeguard and enhance pollination function and services in fields. Mimicking natural vegetation through promoting establishment of forest plantations and village community forestry in rural landscapes is also critical for conserving pollination services.     

Multi-species SIR models from a dynamical Bayesian perspective

Multi-species compartment epidemic models, such as the multi-species susceptible–infectious–recovered (SIR) model, are extensions of the classic SIR models, which are used to explore the transient dynamics of pathogens that infect multiple hosts in a large population. In this article, we propose a dynamical Bayesian hierarchical SIR (HSIR) model, to capture the stochastic or random nature of an epidemic process in a multi-species SIR (with recovered becoming susceptible again) dynamical setting, under hidden mass balance constraints. We call this a Bayesian hierarchical multi-species SIR (MSIR_B) model. Different from a classic multi-species SIR model (which we call MSIR_C), our approach imposes mass balance on the underlying true counts rather than, improperly, on the noisy observations. Moreover, the MSIR_B model can capture the discrete nature of, as well as uncertainties in, the epidemic process.     

Birds to watch: a Red Data List for East Africa

Bennun, L.A., Njoroge, P. & Pomeroy, D. 2000. Birds to watch: a Red Data List for East Africa. Ostrich 71 (1 & 2): 310–314.

The value of Red Data books and lists is well established; there has been much recent work on improving the criteria for listing species of conservation concern. So far these have been applied mainly at the global level. Regional lists can be useful, however, in improving the resolution of conservation priorities and setting an agenda for research, monitoring and conservation, especially where data are collected by amateur naturalists. A Red Data list for East African birds has been drawn up following an eight-month process that involved wide consultation within the region, defined as Uganda, Rwanda, Tanzania, Kenya and Burundi. The criteria for listing were based on those defined by IUCN, and summarised in a single, simple table that could be used for screening large numbers of species. A criterion based on geographic range eliminated from consideration vagrant species or those on the extreme edge of their range. A separate Near Threatened category (Lower Risk but very close to Vulnerable) proved useful. An additional category of Regional Responsibility captured species that are entirely or mainly confiied to East Africa, or to three habitats where the region has special responsibility: coastal forests, Albertine Rift forests, and papyrus swamps. A total of 107 species (about 8% of the regional avifauna) were listed as regionally threatened. This includes four Critical, 18 Endangered and 85 Vulnerable species, proportions very close to those expected from the theoretical probabilities of extinction in each case. One hundred and four species were listed as Near-threatened and 153 as Regional Responsibility, 87 of which are not under threat. Placing a species in a particular category of threat, for explicit reasons, poses an hypothesis about its status that can be tested with additional data. This process is now under way with the compilation of a more detailed, annotated list.     

Saikosaponin-d,a novel SERCA inhibitor,induces autophagic cell death in apoptosis-defective cells

Autophagy is an important cellular process that controls cells in a normal homeostatic state by recycling nutrients to maintain cellular energy levels for cell survival via the turnover of proteins and damaged organelles. However, persistent activation of autophagy can lead to excessive depletion of cellular organelles and essential proteins, leading to caspase-independent autophagic cell death. As such, inducing cell death through this autophagic mechanism could be an alternative approach to the treatment of cancers. Recently, we have identified a novel autophagic inducer, saikosaponin-d (Ssd), from a medicinal plant that induces autophagy in various types of cancer cells through the formation of autophagosomes as measured by GFP-LC3 puncta formation. By computational virtual docking analysis, biochemical assays and advanced live-cell imaging techniques, Ssd was shown to increase cytosolic calcium level via direct inhibition of sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase pump, leading to autophagy induction through the activation of the Ca²⁺/calmodulin-dependent kinase kinase–AMP-activated protein kinase–mammalian target of rapamycin pathway. In addition, Ssd treatment causes the disruption of calcium homeostasis, which induces endoplasmic reticulum stress as well as the unfolded protein responses pathway. Ssd also proved to be a potent cytotoxic agent in apoptosis-defective or apoptosis-resistant mouse embryonic fibroblast cells, which either lack caspases 3, 7 or 8 or had the Bax-Bak double knockout. These results provide a detailed understanding of the mechanism of action of Ssd, as a novel autophagic inducer, which has the potential of being developed into an anti-cancer agent for targeting apoptosis-resistant cancer cells.     

Medulloblastoma tumorigenesis diverges from cerebellar granule cell differentiation in patched heterozygous mice

Medulloblastoma is a cerebellar tumor that can arise through aberrant activation of Sonic hedgehog (Shh) signaling, which normally regulates cerebellar granule cell proliferation. Mutations of the Shh receptor PATCHED (PTCH) are associated with medulloblastomas, which have not been found to have loss of PTCH heterozygosity. We address whether patched (Ptc) heterozygosity fundamentally alters granule cell differentiation and contributes to tumorigenesis by increasing proliferation and/or decreasing apoptosis in Ptc+/- mice. Our data show that postnatal Ptc+/- mouse granule cell precursor growth is not globally altered. However, many older Ptc+/- mice display abnormal cerebellar regions containing persistently proliferating granule cell precursors. Since fewer Ptc+/- mice form medulloblastomas, these granule cell rests represent a developmentally disrupted, but uncommitted stage of tumorigenesis. Although Ptc+/- mouse medulloblastomas express neurodevelopmental genes, they diverge from granule cell differentiation in their discordant coexpression of postmitotic markers despite their ongoing growth. Like human medulloblastomas, mouse tumors with reduced levels of the neurotrophin-3 receptor, trkC/Ntrk3, display decreased apoptosis in vivo, illustrating the role of TrkC in regulating tumor cell survival. These results indicate that Ptc heterozygosity contributes to tumorigenesis by predisposing a subset of granule cell precursors to the formation of proliferative rests and subsequent dysregulation of developmental gene expression.     

Reproductive performance links to fine-scale spatial patterns of female grey seal relatedness

Fine-scale spatial patterns of female relatedness throughout the established grey seal breeding colony of North Rona, Scotland, were investigated by accurate mapping and spatially explicit analyses of a large sample (n = 262) of mothers using variation at nine microsatellite DNA loci. Local spatial autocorrelation analyses identified locations where seals were more highly related to the colony than average. These locations were also areas where the more successful females bred, were occupied first during each breeding season, were centrally placed locations of preferred habitat types and were likely to be the locations which were the first to be colonized historically. Mothers occupying such sites achieved higher than average pup growth rates, suggesting a founder fitness benefit.     

High-resolution imaging demonstrates dynein-based vesicular transport of activated Trk receptors

Target-derived neurotrophins signal from nerve endings to the cell body to influence cellular and nuclear responses. The retrograde signal is conveyed by neurotrophin receptors (Trks) themselves. To accomplish this, activated Trks may physically relocalize from nerve endings to the cell bodies. However, alternative signaling mechanisms may also be used. To identify the vehicle wherein the activated Trks are located and transported, and to identify associated motor proteins that would facilitate transport, we use activation-state specific antibodies in concert with immunoelectron microscopy and deconvolution microscopy. We show that the'activated Trks within rat sciatic nerve axons are preferentially localized to coated and uncoated vesicles. These vesicles are moving in a retrograde direction and so accumulate distal to a ligation site. The P-Trk containing vesicles, in turn, colocalize with dynein components, and not with kinesins. Collectively, these results indicate activated Trk within axons travel in vesicles and dynein is the motor that drives these vesicles towards the cell bodies.