Differences in cell wall polysaccharide composition between embryogenic and non-embryogenic calli of <Emphasis Type="Italic">Medicago arborea</Emphasis> L.

Analysis of cell wall polysaccharide composition of embryogenic and non-embryogenic calli obtained from hypocotyl and petiole explants from Medicago arborea L. revealed significant differences. For calli induced from both hypocotyls and petioles, levels of total sugars, pectins, and hemicelluloses were higher in embryogenic than in non-embryogenic calli. Whereas in the residual cellulose fraction, the highest levels of sugar were detected in non-embryogenic calli. When comparing the two donor sources of callus explants, the highest total sugar levels were detected in embryogenic calli induced from petioles, mainly in the pectin fraction and to a lesser extent in the hemicellulose fraction. Moreover, analysis of uronic acids revealed higher levels in embryogenic calli, primarily in the pectin fraction. Analysis of those sugars associated with cell walls of calli suggested that these polysaccharides consisted of pectic polysaccharides and glucans, and that their levels were higher in embryogenic than non-embryogenic calli.     

High Heterogeneity within Methicillin-Resistant Staphylococcus aureus ST398 Isolates,Defined by Cfr9I Macrorestriction-Pulsed-Field Gel Electrophoresis Profiles and spa and SCCmec Types

During recent years, the animal-associated methicillin-resistant Staphylococcus aureus clone ST398 has extensively been studied. The DNA of these isolates turned out to be refractory to SmaI restriction, and consequently, SmaI is unsuitable for subtyping this clone by standard pulsed-field gel electrophoresis (PFGE). Very recently, ST398 DNA was shown to be digested by Cfr9I, a neoschizomer of SmaI. In the present study, we employed Cfr9I PFGE on 100 German and 5 Dutch ST398 isolates and compared their PFGE profiles, protein A gene variable repeat regions (spa types), and types of the staphylococcal cassette chromosome mec (SCCmec). The isolates (from healthy carrier pigs, clinical samples from pigs, dust from farms, milk, and meat) were assigned to 35 profiles, which were correlated to the SCCmec type. A dendrogram with the Cfr9I patterns assigned all profiles to two clusters. Cluster A grouped nearly all isolates with SCCmec type V, and cluster B comprised all SCCmec type IVa and V* (a type V variant first identified as III) carriers plus one isolate with SCCmec type V. Both clusters also grouped methicillin-susceptible S. aureus isolates. The association of the majority of isolates with SCCmec type V in one large cluster indicated the presence of a successful subclone within the clonal complex CC398 from pigs, which has diversified. In general, the combination of Cfr9I PFGE with spa and SCCmec typing demonstrated the heterogeneity of the series analyzed and can be further used for outbreak investigations and traceability studies of the MRSA ST398 emerging clone.Methicillin-resistant Staphylococcus aureus (MRSA) strains are an important cause of hospital-acquired infections worldwide (8). However, MRSA strains are not confined to health care settings, and during the last 10 years community-acquired MRSA has increasingly been reported (8). In 2003, a clone of MRSA associated with pig farming and not related to the traditional hospital- and community-acquired MRSA emerged in the Netherlands (37), where it now amounts to >30% of human MRSA cases (16). This clone has also been detected in healthy and sick animals, in food of animal origin, and in humans from other European countries, Canada, the United States, the Dominican Republic, and China (5, 7, 31, 38, 39). This emerging MRSA clone belongs to the multilocus sequence type ST398, which includes different spa types (mainly t011, t034, and t108). The majority of the ST398 isolates reported are MRSA, although methicillin-susceptible (MSSA) strains have been described as well (15, 34). Resistance to methicillin and other β-lactam antibiotics is caused by the mecA gene, which is located on a mobile genetic element, the staphylococcal cassette chromosome mec (SCCmec). The SCCmec cassette consists of the mec gene complex, the ccr gene complex, and the junkyard regions. Based on the variability and combinations of these genetic elements, several types of SCCmec and several variants of the types have been described (9). Three SCCmec types (III, IVa, and V) were identified in ST398 isolates (25). However, recent investigations have shown that some ST398 isolates typed as SCCmec type III using the method of Zhang et al. (40) proved to be type V after further sequencing (21, 35).For typing S. aureus, pulsed-field gel electrophoresis (PFGE) of the whole genome by macrorestriction with the SmaI endonuclease is still considered as the “gold standard” (26). However, the isolates of the ST398 clone are nontypeable (NT) by PFGE using SmaI (3, 4). Consequently, comparison between these isolates and the typeable ones from humans and animals is not possible. The nontypeability is due to the action of a novel C5-cytosine methyltransferase which modifies the consensus sequence C^mCNGG at the second cytosine (3, 4). Other enzymes with a different recognition sequence from SmaI have been used for PFGE typing of the ST398 clone, including EagI and ApaI (22, 28, 31, 38), but the patterns obtained cannot be compared to S. aureus patterns generated with SmaI. XmaI, a neoschizomer of SmaI that recognizes the same sequence cutting at a different position, only generates partial digestions (3, 4). Recently, the use of Cfr9I, another neoschizomer of SmaI whose activity is not reduced on ST398 methylated DNA, has been recommended. This enzyme had been successfully used for typing SmaI NT macrolide-resistant Streptococcus pyogenes isolates (6, 30), and now it is being applied for typing ST398 isolates, i.e., from human origin (5, 11, 36) and, to a lesser extent, from animals (3, 36). The aim of this study was to characterize a large collection of recent ST398 isolates by Cfr9I PFGE as well as other methods (spa typing, multilocus sequence typing [MLST], and SCCmec typing). Most of them were recovered in Germany from different sources, including animals and foods.     

Diphenyl diselenide and diphenyl ditelluride: neurotoxic effect in brain of young rats, in vitro

This study examined whether maturity of rat brain may be relevant for the sensitivity to diphenyl diselenide (PhSe)₂ and diphenyl ditelluride (PhTe)₂ on [³H]glutamate uptake and release, in vitro. Brain synaptosomes were isolated from young (14- and 30-day-old) and adult rats and incubated at different concentrations of (PhSe)₂ or (PhTe)₂. The results demonstrated that the highest concentration (100 μM) of (PhSe)₂ and (PhTe)₂ inhibited the [³H]glutamate uptake by synaptosomes of brain at all ages. In the adult brain, (PhSe)₂ did not inhibit the [³H]glutamate uptake at the lowest concentration (10 μM). The highest concentration of (PhTe)₂ inhibited the [³H]glutamate uptake more in the 14-day-old than in the 30-day-old rats or adult rats. In the 30-day-old animals, the highest concentration of (PhSe)₂, and the lowest concentration of (PhTe)₂, increased the basal [³H]glutamate release. At the highest concentration, (PhTe)₂ increased the basal and K⁺-stimulated glutamate release on all ages evaluated. The results suggest that (PhSe)₂ and (PhTe)₂ caused alterations on the homeostasis of the glutamatergic system at the pre-synaptic level. These alterations were age-, concentration-, and compound-dependent. The maturity of rat brain is relevant for the glutamatergic system sensitivity to (PhSe)₂ and (PhTe)₂ .     

Effect of culture medium and illumination on the acid invertase activity in callus of Medicago strasseri

The different acid invertase activity (total, soluble, wall-bound and extracellular) in calli induced on explants (cotyledon, petiole, hypocotyl and leaf) originated from Medicago strasseri seedlings were evaluated. In cultures subjected to 16 h photoperiod, the highest total, soluble and extracellular activities were found in calli from leaves cultured in medium 12 (MS with 0.01 mg·dm⁻³ (0.045 μM) of TDZ), elevated amounts of total and wall-bound invertase being found in calli induced on petioles in 12G medium (MS with 0.01 mg·dm⁻³ (0.045 μM) TDZ and 3.104 mg·dm⁻³ glycerol). In cultures maintained in darkness, the activity detected was lower than that observed in cultures under light conditions. The highest amounts of enzyme was bound in calli cultured on medium 12 (total and extracellular invertase) -leaves- and medium 12D (MS with 0.001 mg·dm⁻³ (0.0045 μM) TDZ) (soluble invertase) -using hypocotyls. In general, the different forms of invertase activity studied seem to appear in greatest amounts in calli induced under light conditions using leaves as explant and TDZ as growth regulator.     

Testing for linkage under robust genetic models.

Robust genetic models are used to assess linkage between a quantitative trait and genetic variation at a specific locus using allele-sharing data. Little is known about the relative performance of different possible significance tests under these models. Under the robust variance components model approach there are several alternatives: standard Wald and likelihood ratio tests, a quasilikelihood Wald test, and a Monte Carlo test. This paper reports on the relative performance (significance level and power) of the robust sibling pair test and the different alternatives under the robust variance components model. Simulations show that (1) for a fixed sample size of nuclear families, the variance components model approach is more powerful than the robust sibling pair approach; (2) when the number of nuclear families is at least approximately 100 and heritability at the trait locus is moderate to high (>0.20) all tests based on the variance components model are equally effective; (3) when the number of nuclear families is less than approximately 100 or heritability at the trait locus is low (<0. 20), on balance, the Monte Carlo test provides the best power and is the most valid. The different testing procedures are applied to determine which are able to detect the known association between low density lipoprotein cholesterol and the common genotypes at the locus encoding apolipoprotein E. Results from this application show that the robust sibling pair method may be more effective in practice than that indicated by simulations.     

Genetic diversity of two African and sixteen South American populations determined on the basis of six hypervariable loci

A total of 582 individuals (1,164 chromosomes) from two African, eight African-derived South American, five South American Amerindian, and three Brazilian urban populations were studied at four variable number of tandem repeat (VNTR) and two short tandem repeat (STR) hypervariable loci. These two sets of loci did not show distinct allele profiles, which might be expected if different processes promoted their molecular differentiation. The two African groups showed little difference between them, and their intrapopulational variation was similar to those obtained in the African-derived South American communities. The latter showed different degrees of interpopulation variability, despite the fact that they presented almost identical average degrees of non-African admixture. The F_ST single locus estimates differed in the five sets of populations, probably due to genetic drift, indicating the need to consider population structure in the evaluation of their total variability. A high interpopulational diversity was found among Amerindian populations in relation to Brazilian African-derived isolated communities. This is probably a consequence of the differences in the patterns of gene flow and genetic drift that each of these semi-isolated groups experienced. Am J Phys Anthropol 109:425–437, 1999. © 1999 Wiley-Liss, Inc.     

A data mining based clinical decision support system for survival in lung cancer

BackgroundA clinical decision support system (CDSS ) has been designed to predict the outcome (overall survival) by extracting and analyzing information from routine clinical activity as a complement to clinical guidelines in lung cancer patients.Materials and methodsProspective multicenter data from 543 consecutive (2013–2017) lung cancer patients with 1167 variables were used for development of the CDSS. Data Mining analyses were based on the XGBoost and Generalized Linear Models algorithms. The predictions from guidelines and the CDSS proposed were compared.ResultsOverall, the highest (> 0.90) areas under the receiver-operating characteristics curve AUCs for predicting survival were obtained for small cell lung cancer patients. The AUCs for predicting survival using basic items included in the guidelines were mostly below 0.70 while those obtained using the CDSS were mostly above 0.70. The vast majority of comparisons between the guideline and CDSS AUCs were statistically significant (p < 0.05). For instance, using the guidelines, the AUC for predicting survival was 0.60 while the predictive power of the CDSS enhanced the AUC up to 0.84 (p = 0.0009). In terms of histology, there was only a statistically significant difference when comparing the AUCs of small cell lung cancer patients (0.96) and all lung cancer patients with longer (≥ 18 months) follow up (0.80; p < 0.001).ConclusionsThe CDSS successfully showed potential for enhancing prediction of survival. The CDSS could assist physicians in formulating evidence-based management advice in patients with lung cancer, guiding an individualized discussion according to prognosis.     

Healing of skin wounds in the African catfish Clarias gariepinus

The African catfish Clarias gariepinus was used as a model for wound healing and tissue regeneration in a scale-less fish. A temporal framework of histological and cell proliferation markers was established after wound induction in the dorsolateral cranial region, by removing the epidermal and dermal layers, including stratum adiposum (SA). Wound closure and epidermis formation was initiated within 3 h post-procedure (hpp) with migration and concomitant proliferation of epidermal cells from the wound borders. The wound was covered by this primary epidermal front 12 hpp and fusion of the opposing epidermal fronts occurred within 24 hpp. Attachment of the newly formed epidermal layer to the underlying dermis was observed 48 hpp concomitant with a second wave of cell proliferation at the wound edge. Normal epidermal thickness within the wound was achieved 72 hpp. Formation of a basement membrane occurred by 120 hpp with concomitant emergence of the SA from the wound borders. Wound healing in C. gariepinus skin involved closure of the wound and re-epithelization through cell migration with a single wave of early cell proliferation not documented in other species. Furthermore, covering of the wound by epithelium as well as the reappearance of the basement membrane and SA occurred sooner than in other fish species.