Novel Chitosan-Based Schiff Base Compounds: Chemical Characterization and Antimicrobial Activity.

Chitosan (CS) and its derivatives are receiving considerable attention for their great biocompatibility and broad-spectrum activities in many fields. In this work, we aimed to characterize the antimicrobial activity of novel chitosan Schiff bases (CSSB). CS was synthesized by double deacetylation of chitin (Cn) after its extraction from the armors of crustaceans Astacus leptodactylus, and CSSB-1 and CSSB-2 were synthesized by interaction of CS with 4-(2-chloroethyl) benzaldehyde (aldehyde-1) and 4-(bromoethyl) benzaldehyde (aldehyde-2), respectively, at room temperature. The synthesized compounds were characterized by elemental analysis, gel permeation chromatography (GPC), infrared spectroscopy (FTIR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The antimicrobial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria and against yeasts (Candida albicans) was significantly increased due to their higher solubility as compared to unmodified CS opening perspectives for the use of these compounds for antimicrobial prevention in different fields as, for example, food industry, cosmetics, or restoration.

Effect of signal acquisition method on the fetal heart rate analysis with phase rectified signal averaging.

Phase rectified signal averaging (PRSA) is increasingly used for fetal heart rate (FHR) monitoring, both with traces acquired with external Doppler cardiotocography (D-FHR), and with transabdominal fetal electrocardiography (ta-FHR). However, it is unclear to what extend the acquisition method influences the PRSA analysis, whether results from using one acquisition method are comparable to those based on FHR acquired by the other method, and if not, which should be the preferred method. To address these questions, we applied PRSA analysis to 28 antepartum synchronous recordings of the FHR using simultaneously D-FHR and ta-FHR. The data included late-onset intrauterine growth restricted (IUGR) fetuses (n = 20) and non-IUGR fetuses (n = 8), all of them at gestation ⩾34 weeks. PRSA analysis depends on two parameters intrinsic to the algorithm, T and S. We analyzed the data using parameters that included all values adopted by other researchers previously (derived from a literature search in PubMed and Google Scholar). T and S were adjusted for the difference in acquisition techniques. We found that the correlation between PRSA analysis based on D-FHR and ta-FHR decreased with decreasing values of the PRSA parameters T and S. Therefore, the acquisition technique affects PRSA values for high resolution PRSA (low values of T and S). In conclusion, for low resolution PRSA, the results from both acquisition methods are comparable. Because ta-FHR signals provide beat to beat data and thus capture more subtle differences in the heart rate variation than D-FHR signals (pre-processed by commercial monitors), we assumed that ta-FHR may provide potentially valuable extra information compared to D-FHR. However, no parameter settings or acquisition method seemed to have a diagnostic value for identifying the late-onset IUGR babies in our dataset.

Synthesis and characterization of new chitosan-based Schiff base compounds.

Chitin (Cn) was extracted from the armors of crustaceans Astacus leptodactylus (Lake Sevan, Armenia) and then converted to chitosan (Cs), its deacetylated derivative. Novel Schiff bases (CsSB) were synthesized by interaction of Cs with 4-(2-chloroethyl)benzaldehyde (aldehyde-1) and 4-(2-bromoethyl)benzaldehyde (aldehyde-2), and underwent dehydrohalogenation, under basic conditions (10°C), to yield respective vinyl derivatives. All newly synthesized compounds were structurally characterized by solubility tests, elemental analysis, infrared spectroscopy (FTIR), thermogravimetry (TGA), proton nuclear magnetic resonance ((1)H NMR), and X-ray diffraction (XRD).

Human fetal growth is constrained below optimal for perinatal survival.

OBJECTIVE: The use of fetal growth charts assumes that the optimal size at birth is at the 50(th) birth-weight centile, but interaction between maternal constraints on fetal growth and the risks associated with small and large fetal size at birth may indicate that this assumption is not valid for perinatal mortality rates. The objective of this study was to investigate the distribution and timing (antenatal, intrapartum or neonatal) of perinatal mortality and morbidity in relation to birth weight and gestational age at delivery. METHODS: Data from over 1 million births occurring at 28-43 weeks' gestation from singleton pregnancies without congenital abnormalities in the period from 2002 to 2008 were collected from The Netherlands Perinatal Registry. The distribution of perinatal mortality according to birth-weight centile and gestational age at delivery was studied. RESULTS: In the 1 170 534 pregnancies studied, there were 5075 (0.43%) perinatal deaths. The highest perinatal mortality occurred in those with a birth weight below the 2.3(rd) centile (25.4/1000 births) and the lowest mortality was in those with birth weights between the 80(th) and 84(th) centiles (2.4/1000 births), according to routinely used growth charts. Antepartum deaths were lowest in those with birth weight between the 90(th) and 95(th) centiles. Data were almost identical when the analysis was restricted to infants born at ≥ 37 weeks' gestation. CONCLUSION: From an immediate survival perspective, optimal fetal growth requires a birth weight between the 80(th) and 84(th) centiles for the population. Median birth weight in the population is, by definition, substantially lower than these centiles, implying that the majority of fetuses exhibit some form of maternal constraint on growth. This finding is consistent with adaptations that have evolved in humans in conjunction with a large head and bipedalism, to reduce the risk of obstructed delivery. These data also fit remarkably well with those on long-term adult cardiovascular and metabolic health risks, which are lowest in cases with a birth weight around the 90(th) centile.

Average acceleration and deceleration capacity of fetal heart rate in normal pregnancy and in pregnancies complicated by fetal growth restriction.

OBJECTIVE: To study fetal heart rate (FHR), its short term variability (STV), average acceleration capacity (AAC), and average deceleration capacity (ADC) throughout uncomplicated gestation, and to perform a preliminary comparison of these FHR parameters between small-for dates (SFD) and control fetuses. METHODS: Prospective observational study of 7 h FHR-recordings obtained with a fetal-ECG monitor in the second half of uncomplicated pregnancies (n = 90) and pregnancies complicated by fetal SFD (n = 30). FHR and STV were calculated according to established analysis. True beat-to-beat FHR, recorded at 1 ms accuracy, was used to calculate AAC and ADC using Phase Rectified Signal Averaging (PRSA). Mean values of FHR, STV, AAC, and ADC derived from recordings in SFD fetuses were compared with the reference curves. RESULTS: Compared with the control group the mean z-scores for STV, AAC, and ADC in SFD fetuses were lower by 1.0 SD, 1.5 SD, and 1.7 SD, respectively (p < 0.0001 for all comparisons). In SFD fetuses, both the AAC and ADC z-scores were lower than the STV z-scores (p < 0.02 and p < 0.002, respectively). CONCLUSIONS: Analysis of the AAC and ADC as recorded with a high resolution fECG recorder may differentiate better between normal and SFD fetuses than STV.