Tyrosinase Inhibition: General and Applied Aspects

The active site of tyrosinase is described with a view to depicting its interactions with substrates and inhibitors. Occurrence and mechanism(s) of tyrosinase-mediated browning of agrofood products are reviewed, with regard to both enzymic and chemical reactions, and their control, modulation, and inhibition. Technical and applicational implications are discussed.     

MicroRNAs expression profiles as diagnostic biomarkers of gastric cancer: a systematic literature review

Objective: The early identification of gastric cancer (GC) represents a major clinical challenge. We conducted a systematic review of studies evaluating the miRNA expression profiling as a diagnostic tool in GC.

Methods: We performed a search of PubMed, ISI Web of Science and SCOPUS databases for studies on diagnostic miRNAs and GC, published in English up to October 2017. Eligibility criteria included case-control studies evaluating blood or tissue-based miRNA expression profiles, and incorporating at least two detection phases (screening and validation).

Results: We included 27 eligible studies, that reported on 97 deregulated miRNAs either in blood or tissue, out of which 30 were reported in at least two studies. Among 22 studies on tissue-diagnostic miRNAs, 13 consistently upregulated miRNAs (miR-214, miR-21, miR-103, miR-107, miR-196a, miR-196b, miR-7, miR-135b, miR-222, miR-23b, miR-25, miR-92 and miR-93), and six consistently downregulated miRNAs (miR-148a, miR-375, miR-133b, miR-30a, miR-193a and miR-204) were reported. Ten miRNAs with inconsistent direction of expression in tissues were identified. Among the five studies performed on blood samples, only one miRNA was consistently upregulated (miR-20a).

Conclusions: This review shows that some tissue or blood miRNAs may be considered as potential biomarkers for GC diagnosis, that urgently needs to be confirmed from large prospective studies.     

The ABC transporter-encoding gene AFR1 affects the resistance of Cryptococcus neoformans to microglia-mediated antifungal activity by delaying phagosomal maturation

The pathogenic yeast Cryptococcus neoformans has evolved several strategies to survive within phagocytes. Recently, it has been demonstrated that upregulation of the ATP binding cassette transporter-encoding gene antifungal resistance 1 ( AFR1 ) is important not only for determining the resistance of C. neoformans to fluconazole but also in influencing fungal virulence. In the present study, we showed that the fluconazole-resistant AFR1- overexpressing mutant strain was not sensitive to microglia-mediated anticryptococcal activity, as compared with the fluconazole-susceptible isogenic strains, the wild type and the afr1 Δ mutant. Interestingly, although the three strains were phagocytosed to a similar extent, reduced acidification and delayed maturation were observed in phagosomes containing the AFR1 -overexpressing strain with respect to the others. These findings provide the first evidence that upregulation of the AFR1 gene affects C. neoformans –microglia interplay, adding insights to the complexity of cryptococcal virulence and to its unexpected link with azole resistance.     

Carvedilol Prevents Ovariectomy-Induced Myocardial Contractile Dysfunction in Female Rat

Carvedilol has beneficial effects on cardiac function in patients with heart failure but its effect on ovariectomy-induced myocardial contractile dysfunction remains unclear. Estrogen deficiency induces myocardial contractile dysfunction and increases cardiovascular disease risk in postmenopausal women. Our aim was to investigate whether carvedilol, a beta receptor blocker, would prevent ovariectomy-induced myocardial contractile dysfunction. Female rats (8 weeks old) that underwent bilateral ovariectomy were randomly assigned to receive daily treatment with carvedilol (OVX+CAR, 20 mg/kg), placebo (OVX) and SHAM for 58 days. Left ventricle papillary muscle was mounted for isometric tension recordings. The inotropic response to Ca²⁺ (0.62 to 3.75 mM) and isoproterenol (Iso 10⁻⁸ to 10⁻² M) were assessed. Expression of calcium handling proteins was measured by western blot analysis. Carvedilol treatment in the OVX animals: prevented weight gain and slight hypertrophy, restored the reduced positive inotropic responses to Ca²⁺ and isoproterenol, prevented the reduction in SERCA2a expression, abolished the increase in superoxide anion production, normalized the increase in p22^phox expression, and decreased serum angiotensin converting enzyme (ACE) activity. This study demonstrated that myocardial contractile dysfunction and SERCA2a down regulation were prevented by carvedilol treatment. Superoxide anion production and NADPH oxidase seem to be involved in this response.     

Diversity patterns and food web structure in a Mediterranean intermittent stream

In this work we present the results of a one‐year study on the macroinvertebrate community in an intermittent stream in southern Spain. We have studied the taxonomic composition, diversity and food web monthly in order to consider temporal variability in these parameters. More than 60 macroinvertebrate taxa have been recorded in the stream, but they do not cohabit at the same time. Many of them join the community at the beginning of the wet period. Afterwards, some new taxa incorporate but some others disappear. This leads to huge fluctuations in the diversity of the community and in the food web of different sampling dates. These variations are linked to environmental disturbances, mainly to flow peaks and minimums. From a relatively well structured, but simple, food web at the beginning of the wet period, it can be seen how several trophic levels disappear with time, and how several organisms change or extend their trophic function within it. We relate these variations to the intermediate disturbance hypothesis and discuss the resilience of the community of this intermittent stream (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mass spectrometry applications in microbiology beyond microbe identification: progress and potential

Introduction: Mass spectrometry (MS), particularly MALDI-time of flight (MALDI-TOF), has become a routine tool for microorganism identification in clinical microbiology laboratories in the last five years. The use of MALDI-TOF MS has accelerated laboratory analysis, thus providing accurate species-level information with very short turnaround times.

Areas covered: Beyond microbe identification, MALDI-TOF MS offers great opportunities for fast strain typing and detection of antimicrobial susceptibility/resistance in both bacterial and fungal organisms. Drawing on evidence from PubMed literature searches, clinical microbiology laboratory experience, and the authors’ opinions, this review summarizes recent significant advances and ongoing challenges in these areas.

Expert commentary: In the near future, it is expected that the implementation of new analytical algorithms, automation of procedures, and refinement of assays will enhance the clinical and epidemiological usefulness of MALDI-TOF and other MS technologies.     

Vascular flows and transpiration affect peach (Prunus persica Batsch.) fruit daily growth

The relative contributions of xylem, phloem, and transpiration to fruit growth and the daily patterns of their flows have been determined in peach, during the two stages of rapid diameter increase, by precise and continuous monitoring of fruit diameter variations. Xylem, phloem, and transpiration contributions to growth were quantified by comparing the diurnal patterns of diameter change of fruits, which were then girdled and subsequently detached. Xylem supports peach growth by 70%, and phloem 30%, while transpiration accounts for approximately 60% of daily total inflows. These figures and their diurnal patterns were comparable among years, stages, and cultivars. Xylem was functional at both stage I and III, while fruit transpiration was high and strictly dependent on environmental conditions, causing periods of fruit shrinkage. Phloem imports were correlated to fruit shrinkage and appear to facilitate subsequent fruit enlargement. Peach displays a growth mechanism which can be explained on the basis of passive unloading of photoassimilates from the phloem. A pivotal role is played by the large amount of water flowing from the tree to the fruit and from the fruit to the atmosphere.     

Carbohydrate availability affects growth and metabolism in peach fruit

Along with sucrose, sorbitol represents the main photosynthetic product and form of translocated carbon in peach. This study aimed at determining whether peach fruit carbohydrate metabolism is affected by changes in source–sink balance , and specifically whether sorbitol or sucrose availability regulates fruit enzyme activities and growth. In various trials, different levels of assimilate availability to growing fruits were induced in vivo by varying crop load of entire trees, leaf : fruit ratio (L:F) of fruiting shoots, or by interrupting the phloem stream (girdling) to individual fruits. In vitro, fruit tissue was incubated in presence/absence of sorbitol and sucrose. Relative growth rate (RGR), enzyme activities and carbohydrates were measured at different fruit growth stages of various peach cultivars in different years. At stage III, high crop load induced higher acid invertase (AI, EC 3.2.1.26) activities and hexose : sucrose ratios. Both sorbitol and sucrose contents were proportional to L:F, while sorbitol dehydrogenase (SDH, EC 1.1.1.14) activity was the only enzyme activity directly related to L:F in both fruit growth stages. Girdling reduced fruit RGR and all major carbohydrates after 4 days and SDH activity already after 48 h, but it did not affect sucrose synthase (SS, EC 2.4.1.13), AI and neutral invertase (NI, EC 3.2.1.27). Fruit incubation in sorbitol for 24 h induced higher SDH activities than in buffer alone. In general, assimilate availability affected both sorbitol and sucrose metabolism in peach fruit, and sorbitol may function as a signal for modulating SDH activity. Under highly competitive conditions, AI activity may be enhanced by assimilate depletion, providing a mechanism to increase fruit sink strength by increasing hexose concentrations.