Experimental and Numerical Analyses of the Pull-out Response of a Steel Post/Bovine Bone Cementless Fixation

Effect of initial interference fit on pull-out strength in cementless fixation between bovine tibia and smooth stainless steel post was investigated in this study.Compressive behavior of bovine spongious bone was studied using mechanical testing in order to evaluate the elastic-plastic properties in different regions of the proximal tibia.Friction tests were carried out in the aim to evaluate the friction behavior of the contact between bovine spongious bone and stainless steel.A cylindrical stainless steel post inserted in a pre-drilled bovine tibia with an initial interference fit was taken as an in vitro model to assess the contribution of post fixation to the initial stability of the Total Knee Arthroplasty (TKA) tibial component.Pull-out experiments were carried out for different initial interference fits.Finite Element Models (FEM) using local elastic-plastic properties of the bovine bone were developed for the analysis of the experimental ultimate pull-out force results.At the post/bone interface,Coulomb friction was considered in the FEM calculations with pressure-dependent friction coefficient.It was found that the FEM results of the ultimate force are in good agreement with the experimental results.The analysis of the FEM interfacial stresses indicates that the micro-slip initiation depends on the local bone properties.     

Charge clusters signatures in prokaryotic proteomes: Temperature-dependence and distribution

The identification and the screening of Charged Clusters (CCs) residues in proteins is a key analysis to assess any quantitative structure-function correlation in proteins. Here, we present a proteome wide scan for the occurrence of (CCs) in 99292 proteins using a new tool. Finding Clusters Charge in Protein Sequences Program (FCCP). The FCCP has been employed to search CCs in 35 prokaryotic proteomes (7 Psychrophiles, 10 Mesophiles, 9 thermophiles and for 9 hyperthermophiles). A new repository of 855 CC has been created. Results showed that the mapped proteins containing positive and negative charge clusters are mostly transmembrane proteins while the conserved CCs within the same proteome are transposases or involved in DNA binding and integration. Interestingly, the negative charged cluster was associated to bacteria growth's temperature (p=0.002) acting as proteins' core signature. Taken together the various results provide a consistent picture of these screened CCs in terms of its potentials functional roles.     

Nitrogen and carbon relationships between the parasitic weed Orobanche foetida and susceptible and tolerant faba bean lines

The parasitic weed Orobanche foetida (Poiret) is an emergent agronomical problem on faba bean in Tunisia. The Tunisian breeding programs for faba bean resistance to O. foetida have produced several tolerant lines including the line XBJ90.03-16-1-1-1, which limits both parasite attachments to the host roots and growth of the attached parasites. The present study aims to provide a better understanding of the nutritional relationships between the parasite and this tolerant line in comparison with the susceptible Bachaar genotype. Phloem saps of faba bean were harvested using phloem exudation experiments. The major organic compounds potentially transferred from both faba bean genotypes to the parasite were identified as sucrose, raffinose, stachyose, citrate, malate, asparagine (ASN), aspartate (ASP), glutamine, glutamate, serine, alanine and GABA. However, the phloem exudates of the tolerant line were highly deficient in nitrogen when compared to that of the susceptible line. When attached to roots of the tolerant line, the parasite displayed limited activities of soluble invertases in tubercles, and especially in shoots, suggesting that the low performance of the broomrapes attached to the tolerant line resulted from a reduced capacity to utilize the host-derived carbohydrates. On the other hand, the mechanisms involved in the osmotic adjustment and primary metabolism of the parasite did not differ significantly according to the host genotype: mineral cations, especially potassium and calcium, predominated as the major osmotically-active compounds in both tubercles and shoots; shoots accumulated preferentially hexoses as organic solutes although tubercles accumulated preferentially starch and soluble amino acids, especially ASP and ASN. This suggests an important role for a glutamine-dependent asparagine synthetase (EC 6.3.5.4) in the N metabolism of the parasite.     

Antibacterial Potent of Acetylated and Non-Acetylated Clove Bud Essential Oils and Their Main Compounds

Clove bud is a medicinal plant used traditionally in Asia for the treatment of various disease. Previously, Clove oil is a potential source of an antimicrobial compounds especially vis-a-vis bacterial pathogens. However, the compound responsible for this activity remains to be investigated. Essential oil (EO) clove, acetylated essential oil clove, eugenol, and acetyleugenol were evaluate as an antibacterial potential agent against Staphyloccocus aureus (SE), Escherichia coli (EC) and Pseudomonas aeruginosa (PA). Essential oil containing eugenol was extracted from buds of Eugenia caryophyllata commonly named clove (Syzygium aromaticum (L.) (Family Myrtaceae) by a simple hydrodistillation. The analysis of the essential oils (EOs) using gas chromatography-mass spectrometry (GC-MS) shows eugenol as the major constituent with 70.14 % of the total. The Eugenol was isolated from the EO using chemical treatment. Afterwards, the EO and eugenol were converted to acetylated EO and acetyleugenol, respectively using acetic anhydride. The antibacterial result revealed that all compounds showed a strong activity against the three strains. The Staphyloccocus aureus and Pseudomonas aeruginosa were extremely sensitive against eugenol with an inhibition diameters of 25 mm. The MIC values of eugenol versus S. aureus and P. aeruginosa were 0.58 and 2.32 mg/mL, respectively, while the MIB values were 2.32 mg/mL and 9.28 mg/mL.     

Effect of the Aegean Sea barrier between Europe and Asia on differentiation in Juniperus drupacea (Cupressaceae)

Juniperus drupacea is an eastern Mediterranean mountain tree with a disjunct geographical range. We hypothesized that this disjunct occurrence (the Peloponnese in Europe and the Taurus and Lebanon Mountains in Asia) should be reflected in the patterns of genetic and morphological diversity and differentiation. Nuclear microsatellite markers (nSSR) and biometric variables of the cones and seeds were examined on material sampled from four populations in Europe and eight in Asia. The Asian populations were characterized by a higher level of genetic diversity than the European populations. The genetic differentiation among populations was moderate but significant (F_ST = 0.101, P < 0.001). According to the clustering performed with BAPS, six genetically and geographically groups of populations were found: I and II from the Peloponnese; III from the Taurus Mountains; IV and V from the Anti‐Taurus Mountains; and VI from the Lebanon Mountains. The level of genetic differentiation among these six groups (4.30%, P = 0.012) probably reflects long‐lasting genetic isolation during the Pleistocene, as limited genetic admixture was found. In accordance with genetic analysis, the biometric investigations indicated a high level of morphological divergence between the European and Asian populations of the species, with further differentiation between the populations from the Taurus and Lebanon Mountains.     

Quantitative Determination of Gymnodimine-A by High Performance Liquid Chromatography in Contaminated Clams from Tunisia Coastline

Quantitative determination by high performance liquid chromatography (HPLC) was performed for gymnodimine-A (GYM-A), a phycotoxin responsible for the contamination of Tunisian clams. This study demonstrates a rapid and reproducible HPLC-ultraviolet (UV) method for extraction, detection and quantification of GYM-A in toxic clams. The extraction of GYM-A from the digestive gland of clams in acetone, subsequent clean-up with diethyl ether and extraction with dichloromethane is the more valid protocol. Chromatography analyses were performed using a gradient of acetonitrile–water (10:90 to 90:10), containing trifluoroacetic acid (0.1%) for 20 min at 1 mL/min rate with a C18 column. Recovery rates exceeded 96%, and limits of detection and quantification were 5 ng/mL and 8 ng/g digestive gland, respectively. Repeatability and reproducibility were tested for various samples containing different levels of GYM-A. A significant correlation was observed between toxicity level of samples and the determined amount of GYM-A. Also, the persistence of GYM-A in contaminated clams from Boughrara lagoon was demonstrated. The kinetics discharge study of GYM-A in controlled medium, during 1 month, showed that the process of depuration was biphasic with an exponential discharge of 75% of the total amount of sequestered GYM-A during the first 12 days followed by a slow discharge (>10%) for the subsequent days up to the seventeenth day. This is the first time that a quantitative study of GYM-A in clams from Tunisian coasts is performed through the development of a new method for detection and quantify of this phycotoxin. We found HPLC-UV a reliable and suitable alternative to the mouse bioassay.     

The marine phycotoxin gymnodimine targets muscular and neuronal nicotinic acetylcholine receptor subtypes with high affinity

Gymnodimines (GYMs) are phycotoxins exhibiting unusual structural features including a spirocyclic imine ring system and a trisubstituted tetrahydrofuran embedded within a 16-membered macrocycle. The toxic potential and the mechanism of action of GYM-A, highly purified from contaminated clams, have been assessed. GYM-A in isolated mouse phrenic hemidiaphragm preparations produced a concentration- and time-dependent block of twitch responses evoked by nerve stimulation, without affecting directly elicited muscle twitches, suggesting that it may block the muscle nicotinic acetylcholine (ACh) receptor (nAChR). This was confirmed by the blockade of miniature endplate potentials and the recording of subthreshold endplate potentials in GYM-A paralyzed frog and mouse isolated neuromuscular preparations. Patch-clamp recordings in Xenopus skeletal myocytes revealed that nicotinic currents evoked by constant iontophoretical ACh pulses were blocked by GYM-A in a reversible manner. GYM-A also blocked, in a voltage-independent manner, homomeric human alpha7 nAChR expressed in Xenopus oocytes. Competition-binding assays confirmed that GYM-A is a powerful ligand interacting with muscle-type nAChR, heteropentameric alpha3beta2, alpha4beta2, and chimeric alpha7-5HT(3) neuronal nAChRs. Our data show for the first time that GYM-A broadly targets nAChRs with high affinity explaining the basis of its neurotoxicity, and also pave the way for designing specific tests for accurate GYM-A detection in shellfish samples.     

Structural Correlates of Rotavirus Cell Entry

Cell entry by non-enveloped viruses requires translocation into the cytosol of a macromolecular complex—for double-strand RNA viruses, a complete subviral particle. We have used live-cell fluorescence imaging to follow rotavirus entry and penetration into the cytosol of its ∼700 Å inner capsid particle (“double-layered particle”, DLP). We label with distinct fluorescent tags the DLP and each of the two outer-layer proteins and track the fates of each species as the particles bind and enter BSC-1 cells. Virions attach to their glycolipid receptors in the host cell membrane and rapidly become inaccessible to externally added agents; most particles that release their DLP into the cytosol have done so by ∼10 minutes, as detected by rapid diffusional motion of the DLP away from residual outer-layer proteins. Electron microscopy shows images of particles at various stages of engulfment into tightly fitting membrane invaginations, consistent with the interpretation that rotavirus particles drive their own uptake. Electron cryotomography of membrane-bound virions also shows closely wrapped membrane. Combined with high resolution structural information about the viral components, these observations suggest a molecular model for membrane disruption and DLP penetration.     

Tunisian isolates of Trichoderma spp. and Bacillus subtilis can control Botrytis fabae on faba bean

Faba bean crops worldwide are often attacked by different diseases, particularly chocolate spot caused by Botrytis fabae Sard. Fungal and bacterial isolates collected from faba bean and barley leaves in Tunisia were evaluated for their antagonistic potential against B. fabae. In a test on detached leaves, the highest rate of decrease in disease severity was scored by Trichoderma viride, followed by T. harzianum, the fungicide Carbendazim then Bacillus subtilis. Under glasshouse conditions, all tested fungi resulted in significant disease severity reduction. T. viride reduced the rate of chocolate spot infestation on leaves and stems by 35% and 31.5%, respectively, when the rate on the control was 100%. For T. harzianum, Carbendazim and B. Subtilis, the rates of infestation on the leaves were 41.7%, 43.1% and 59.7%, respectively. On the stems, T. harzianum scored the lowest rate of 54.2% followed by B. subtilis with 79.2% then Carbendazim with 87.5%. Two consecutive seasons of field trials using the Trichoderma species, B. subtilis and Carbendazim showed significant and consistent reduction in the severity of chocolate spot infestation rates. The highest protection against the disease was obtained from T. viride. Based on these results, Tunisian isolates of Trichoderma spp. can be recommended for developing commercial bio-fungicides for integrated management of chocolate spot.