Deposition of iron and beta-amyloid plaques is associated with cortical cellular damage in rabbits fed with long-term cholesterol-enriched diets

Hypercholesterolemia is a potential trigger of Alzheimer's disease, and is thought to increase brain levels of beta-amyloid (Abeta) and iron. However, animal models to address the mechanisms by which Abeta and iron accumulation may cause neuronal damage are poorly defined. To address this question, we fed adult rabbits a 1% cholesterol-enriched diet for 7 months. This diet was associated with increased regional deposition of both iron and Abeta peptide in the brain. Iron preferentially accumulated around Abeta plaques in the adjacent cortex, but was not found in the hippocampus. Co-localization of iron and Abeta was accompanied by apoptosis, DNA damage, blood-brain barrier (BBB) disruption, as well as dysregulation in the level of the iron-regulatory proteins, ferritin and heme-oxygenase-1. We further demonstrate that the cholesterol diet-induced apoptosis is mediated by the activation of the endoplasmic reticulum stress pathway, involving the down-regulation of the endoplasmic reticulum chaperones, calreticulin, grp78 and grp94, and the activation of the growth and arrest DNA damage protein, gadd153. Our results suggest that BBB damage and disturbances in iron metabolism may render the cortex more vulnerable than the hippocampus to the cholesterol-induced cellular stress.     

First Environmental Isolations of <Emphasis Type="Italic">Cryptococcus neoformans</Emphasis> and <Emphasis Type="Italic">Cryptococcus gattii</Emphasis> in Tunisia and Review of Published Studies on Environmental Isolations in Africa

Cryptococcus neoformans and Cryptococcus gattii are pathogenic yeasts that cause cryptococcosis. These fungi were commonly associated with pigeon droppings and plant materials. The habitat of these pathogens has not been yet studied in Tunisia, although the ecology of these yeasts must be elucidated in order to establish surveillance programs and to prevent infections. The aim of this survey was to recover C. neoformans and C. gattii environmental isolates from pigeon droppings and plant materials in different areas of Sfax region, Tunisia. Nine hundred and fifty samples from leaves, wood, flowers, fruits and soil around trunk bases of 40 almond (Prunus dulcis) and 60 eucalyptus trees were collected as well as 250 pigeon droppings samples from different sites: buildings (n = 150), houses (n = 50) and zoo (n = 50). The identification of Cryptococcus neoformans complex was confirmed using the ID32C auxanogram panel (BioMérieux, Marcy l’Etoile, France); species were determined by multiplex PCR using the CN70 and CN49 primers, and mating type was determined by PCR. C. neoformans was recovered from 26 specimens of pigeon droppings (10.4%). This yeast was obtained more frequently from dry droppings (9.2%) than from moist droppings (1.2%). The mating type was determined. All the 31 environmental strains of C. neoformans and C. gattii were MATα. Out of 700 samples tested from 100 trees, only 5 isolates of Cryptococcus neoformans species complex were recovered (0.6%), two isolates of C. gattii and one isolate of C. neoformans were recovered from the wood of E. camaldulensis trees, and only two isolates of C. gattii were recovered from the wood of almond trees (Prunus dulcis Mill. var. zaaf and var. achek). These two Tunisian almond tree varieties were recorded for the first time in Africa as hosts for C. gattii. These results add new information to the ecology and epidemiology of C. neoformans species complex in Tunisia.     

Impact of Trace Element Changes on Dehydroepiandrosterone Sulfate in Healthy and Diabetic States among Middle-Age and Elderly Egyptians

The aim of this study was to confirm if there is a link between the alteration in blood levels of trace elements (chromium, copper, lead, cadmium, and zinc) and dehydroepiandrosterone sulfate (DHEAS) in healthy and diabetic states. This study is the first study to test these parameters in Egyptians. The study included 150 subjects divided into the following four groups: healthy middle-aged, healthy elderly, middle-aged diabetics, and elderly diabetics. Our results revealed a statistically significant decrease in the level of DHEAS in the elderly compared to middle-aged healthy and diabetic groups (p < 0.05). There was a significant difference between the middle-aged groups with respect to zinc, copper, chromium, and cadmium levels. Zinc and copper were lower in the diabetic subjects while chromium and cadmium were higher in the same group in comparison to healthy subjects. In the elderly groups, there were significant increases in chromium and cadmium levels in diabetic subjects rather than healthy ones. There was a significant increase in the thiobarbituric acid reactive substance level in the elderly healthy and diabetic groups and a significant decrease in the glutathione level in the elderly groups. There was no correlation between the levels of trace elements and DHEAS or between the levels of DHEAS, oxidants, and antioxidants in all of the tested groups. In conclusion, only the DHEAS level was correlated with age. There was no difference between the diabetic and healthy groups with respect to the levels of trace elements, with the exception of chromium and cadmium, which suggests the effect of pollution on the pathogenesis of diabetes in Egyptians. No correlation existed between the levels of DHEAS and trace elements, oxidants, and antioxidants. Finally, we believe that there is a large regional variation in the levels of trace elements due to different environmental exposure and nutritional factors which are responsible for contradictory results regarding the pathogenesis of diseases related to alterations in the levels of trace elements.     

Physiological changes in major soldiers of Macrotermes gilvus (Isoptera: Termitidae) induced by the endoparasitoid Misotermes mindeni (Diptera: Phoridae)

The majority of true parasitoids manipulate their host’s physiology for their own benefit. In this study, we documented the physiological changes that occurred in major soldiers of the subterranean termite Macrotermes gilvus (Hagen) (Isoptera: Termitidae) parasitized by the koinobiont larval endoparasitoid Misotermes mindeni Disney and Neoh (Diptera: Phoridae). We compared the metabolic rate, body water content, body water loss rate, cuticular permeability, and desiccation tolerance between parasitized and unparasitized major soldiers. The metabolic rate of parasitized hosts was significantly higher than that of unparasitized termites. Mean total body water content of parasitized major soldiers (64.73 ± 3.26%) was significantly lower than that of unparasitized termites (71.99 ± 2.23%). Parasitized hosts also had significantly lower total body water loss rates (5.72 ± 0.06%/h) and higher cuticular permeability (49.37 ± 11.26 μg/cm/h/mmHg) than unparasitized major soldiers (6.75 ± 0.16%/h and 60.76 ± 24.98 μg/cm/h/mmHg, respectively). Parasitized major soldiers survived almost twice as long as unparasitized termites (LT₅₀ = 6.66 h and LT₅₀ = 3.40 h, respectively) and they had significantly higher tolerance to water loss compared to unparasitized termites (45.28 ± 6.79% and 32.84 ± 7.69%, respectively). Body lipid content in parasitized hosts (19.84 ± 6.27%) was significantly higher than that of unparasitized termites (6.17 ± 7.87%). Finally, parasitized hosts had a significantly lower percentage of cuticular water content than unparasitized major soldiers (10.97 ± 1.84% and 13.17 ± 2.21%, respectively). Based on these data, we conclude that the parasitism-induced physiological changes in the host are beneficial to the parasitoids as the alterations can clearly increase the parasite’s chances of survival when exposed to extreme environmental conditions and ensure that the parasitoids are able to complete their larval development successfully before the host dies.     

Botulinum neurotoxin and dendrotoxin as probes for studies on transmitter release

Acceptors for BoNT have been detected autoradiographically on the terminal membrane of motor nerves at a density of approximately 150/micron2 and shown to mediate toxin internalization, a process deemed essential for its inhibition of transmitter release. DTX, a protein with pronounced central neurotoxicity, was shown to induce convulsive states in hippocampal slices from guinea-pig. Synaptic transmission was facilitated and spontaneous epileptiform activity produced in intact cell populations. Voltage clamp analysis of hippocampal neurones revealed that DTX specifically attenuated a transient voltage-dependent K+ conductance (A-current) and this could account for the excitatory effects observed. Proteinaceous acceptors with high affinity for DTX were identified on brain synaptosomal membranes and found to contain a 65 000 Mr polypeptide. Their location in rat brain regions was established and contrasted with that of the binding sites for beta-bungarotoxin. These findings indicate the usefulness of DTX as a probe for a protein associated with one variety of K+ channel while the larger subunit of BoNT was found to interact with a membraneous component that resides at cholinergic nerve terminals and, hence, is likely to have a unique role.     

Regulation of Gβγi-Dependent PLC-β3 Activity in Smooth Muscle: Inhibitory Phosphorylation of PLC-β3 by PKA and PKG and Stimulatory Phosphorylation of Gαi-GTPase-Activating Protein RGS2 by PKG

In gastrointestinal smooth muscle, agonists that bind to G_i-coupled receptors activate preferentially PLC-β3 via Gβγ to stimulate phosphoinositide (PI) hydrolysis and generate inositol 1,4,5-trisphosphate (IP₃) leading to IP₃-dependent Ca²⁺ release and muscle contraction. In the present study, we identified the mechanism of inhibition of PLC-β3-dependent PI hydrolysis by cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG). Cyclopentyl adenosine (CPA), an adenosine A₁ receptor agonist, caused an increase in PI hydrolysis in a concentration-dependent fashion; stimulation was blocked by expression of the carboxyl-terminal sequence of GRK2(495–689), a Gβγ-scavenging peptide, or Gα_i minigene but not Gα_q minigene. Isoproterenol and S-nitrosoglutathione (GSNO) induced phosphorylation of PLC-β3 and inhibited CPA-induced PI hydrolysis, Ca²⁺ release, and muscle contraction. The effect of isoproterenol on all three responses was inhibited by PKA inhibitor, myristoylated PKI, or AKAP inhibitor, Ht-31, whereas the effect of GSNO was selectively inhibited by PKG inhibitor, Rp-cGMPS. GSNO, but not isoproterenol, also phosphorylated Gα_i-GTPase-activating protein, RGS2, and enhanced association of Gα_i3-GTP and RGS2. The effect of GSNO on PI hydrolysis was partly reversed in cells (i) expressing constitutively active GTPase-resistant Gα_i mutant (Q204L), (ii) phosphorylation-site-deficient RGS2 mutant (S46A/S64A), or (iii) siRNA for RGS2. We conclude that PKA and PKG inhibit Gβγ_i-dependent PLC-β3 activity by direct phosphorylation of PLC-β3. PKG, but not PKA, also inhibits PI hydrolysis indirectly by a mechanism involving phosphorylation of RGS2 and its association with Gα_i-GTP. This allows RGS2 to accelerate Gα_i-GTPase activity, enhance Gαβγ_i trimer formation, and inhibit Gβγ_i-dependent PLC-β3 activity.     

Nutritional and ecological evaluation of dairy farming systems based on concentrate feeding regimes in semi-arid environments of Jordan

The objective of this study was to evaluate the nutritional and ecological aspects of feeding systems practiced under semi-arid environments in Jordan. Nine dairy farms representing the different dairy farming systems were selected for this study. Feed samples (n = 58), fecal samples (n = 108), and milk samples (n = 78) were collected from the farms and analysed for chemical composition. Feed samples were also analysed for metabolisable energy (ME) contents and in vitro organic matter digestibility according to Hohenheim-Feed-Test. Furthermore, fecal nitrogen concentration was determined to estimate in vivo organic matter digestibility. ME and nutrient intakes were calculated based on the farmer’s estimate of dry matter intake and the analysed composition of the feed ingredients. ME and nutrient intakes were compared to recommended standard values for adequate supply of ME, utilizable crude protein, rumen undegradable crude protein (RUCP), phosphorus (P), and calcium (Ca). Technology Impact Policy Impact Calculation model complemented with a partial life cycle assessment model was used to estimate greenhouse gas emissions of milk production at farm gate. The model predicts CH₄, N₂O and CO₂ gases emitted either directly or indirectly. Average daily energy corrected milk yield (ECM) was 19 kg and ranged between 11 and 27 kg. The mean of ME intake of all farms was 184 MJ/d with a range between 115 and 225 MJ/d. Intake of RUCP was lower than the standard requirements in six farms ranging between 19 and 137 g/d, was higher (32 and 93 g/d) in two farms, and matched the requirements in one farm. P intake was higher than the requirements in all farms (mean oversupply = 19 g/d) and ranged between 3 and 30 g/d. Ca intake was significantly below the requirements in small scale farms. Milk nitrogen efficiency N-_eff (milk N/intake N) varied between 19% and 28% and was mainly driven by the level of milk yield. Total CO₂ equivalent (CO₂ equ) emission ranged between 0.90 and 1.88 kg CO₂/kg ECM milk, where the enteric and manure CH₄ contributed to 52% of the total CO₂ equ emissions, followed by the indirect emissions of N₂O and the direct emissions of CO₂ gases which comprises 17% and 15%, respectively, from total CO₂ equ emissions. Emissions per kg of milk were significantly driven by the level of milk production (r² = 0.93) and of eDMI (r² = 0.88), while the total emissions were not influenced by diet composition. A difference of 16 kg ECM/d in milk yield, 9% in N-_eff and of 0.9 kg CO₂ equ/kg in ECM milk observed between low and high yielding animals. To improve the nutritional status of the animals, protein requirements have to be met. Furthermore, low price by-products with a low carbon credit should be included in the diets to replace the high proportion of imported concentrate feeds and consequently improve the economic situation of dairy farms and mitigate CO₂ equ emissions.