Theoretical insights into the metal chelating and antimicrobial properties of the chalcone based Schiff bases

The emergence of multi-drug resistant pathogens in infectious disease conditions accentuates the need for the design of new classes of antimicrobial agents that could defeat the multidrug resistance problems. As a new class of molecules, the Heterocyclic Schiff base is of considerable interest, owing to their preparative accessibility, structural flexibilities, versatile metal chelating properties, and inherent biological activities. In the present study, CAM-B3LYP/LANL2DZ and M062X/DEF2-TZVP level of density functional method is used to explore the complexation of chalcone based Schiff base derivatives by Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ metal ions. The HL(1-3)-Co²⁺, HL(1-3)-Ni²⁺ and HL(1-3)-Zn²⁺ complexes formed the distorted tetrahedral geometry. Whereas, the HL(1-3)-Cu²⁺ complexes prefers distorted square-planar geometry. The BSSE corrected interaction energies of the studied complexes reveals that Cu²⁺ ion forms the most stable complexes with all three chalcone based Schiff bases. Of the three Schiff bases studied, the HL2 Schiff base acts as a potent chelating agent and forms the active metal complexes than the HL1 and HL3 Schiff bases. Further, the strength of the interaction follows the order as Cu^2+?>?Ni^2+?>?Co^2+?>?Zn²⁺. The QTAIM analysis reveals that the interaction between the metal ions and coordinating ligand atoms are electrostatic dominant. The metal interaction increases the π-delocalisation of electrons over the entire chelate. Hence, the antimicrobial activity of the metal complexes is more effective than the free Schiff bases. Moreover, the HL(1-3)-Cu²⁺ complexes shows higher antimicrobial activities than the other complexes studied.     

Daily rhythms of leukocytes populations,biochemical and enzymatic blood parameters in a carnivorous freshwater catfish (Lophiosilurus alexandri)

The aim of this study was to investigate the daily rhythms of hematological, biochemical and enzymatic parameters of the blood of a nocturnal model of fish (Lophiosilurus alexandri) bred in the laboratory (F1). Thirty-six juveniles were stocked in six tanks of a recirculation aquaculture system for 20 days. The fish were exposed to a light:dark cycle of 12:12 h and were fed 1% of biomass twice a day with commercial diet. The daily rhythms of hematological, biochemical and enzymatic parameters were then measured at six sampling times “zeitgeber time = ZT” at four-hour intervals under light:dark 12:12 h (lights on = ZT0, at 8.00 a.m). No differences were observed to alkaline phosphatase, glucose, cortisol, aspartate aminotransferase, superoxide dismutase, total protein and hematocrit (p > 0.05). However, white blood cell count, Lymphocytes (LYN), Neutrophils (NEU), Eosinophil and Neutrophils to Lymphocytes ratio were significant different between sample times (p < 0.05). Also, a significant difference in alanine transaminase was observed, with a peak of production at nighttime. In contrast, glutathione peroxidase peaked at 8:00. Uric acid, magnesium and Calcium (Ca⁺⁺) showed statistically significant differences (p < 0.05). A significant difference was observed (p < 0.05), with a peak of albumin at 08:00 and triglycerides at 12:00, while cholesterol was low (p < 0.05) at 08:00 and higher from 12:00 to 04:00. Cosinor analysis revealed also rhythmicity to SOD, UA, Mg and Ca⁺⁺, ALB and CHO (p < 0.05). In conclusion, the time of day must be considered a key factor when using blood parameters as biomarkers for disease, health and welfare in the L. alexandri aquaculture.     

Evaluation of organic insecticides for management of spotted‐wing drosophila (Drosophila suzukii) in berry crops

Spotted‐wing drosophila, Drosophila suzukii (Matsumura), is an invasive pest affecting fruit production in many regions of the world. Insecticides are the primary tactic for controlling D. suzukii in organic as well as conventional production systems. Organic growers have a greater challenge because fewer insecticides are approved for use in organic agriculture. The most effective organically approved product is spinosad, but alternatives are needed because of label restrictions limiting the number of applications per year, toxicity to beneficial arthropods and the risk of developing resistance. We evaluated several organically approved insecticides against D. suzukii in laboratory assays and field trials conducted on organic blueberry and raspberry farms. Spinosad was consistently the most effective insecticide, but a few other insecticides such as azadirachtin + pyrethrins, Chromobacterium subtsugae and sabadilla alkaloids showed moderate activity. None of the treatments had long residual activity. Mortality started to decline by 3 days after treatment, and by 5 days after application, the treatments were not different from the controls. These products may be useful in rotation programmes, necessary for reducing reliance on spinosad and mitigating resistance. Cultural and biological control approaches are needed in fruit production for D. suzukii management, but insecticides will likely continue to be the dominant management tactic while these other approaches are being optimized and adopted.     

Maturity and fertility of rhesus monkey oocytes collected at different intervals after an ovulatory stimulus (human chorionic gonadotropin) in in vitro fertilization cycles

In rhesus monkeys undergoing ovarian stimulation for in vitro fertilization (IVF), a midcycle injection of human chorionic gonadotropin (hCG) substitutes for the LH surge and induces preovulatory oocyte maturation. The time interval between injection and oocyte collection, ideally, allows for the completion of oocyte maturation without ovulation, which would reduce the number of oocytes available for harvest. To evaluate the influence of this time interval on oocyte parameters following hCG administration, we conducted a series of gonadotropin treatment protocols in 51 animals in which the interval from hCG administration to follicular aspiration was systematically varied from 27 to 36 hr. Follicle number and size, evaluated prior to hCG administration by sonography, did not vary significantly or consistently with preovulatory maturation time. Oocytes were harvested by laparotomy or laparoscopy, and scored for maturity before insemination. The percentage of mature, metaphase II (MII) oocytes at recovery increased significantly with increasing preovulatory time and was inversely proportional to that of metaphase I (MI) oocytes. However, oocyte yield tended toward a progressive decrease with increasing preovulatory maturation times from a high of 27 oocytes at 27 hr to a low of 17 oocytes/animal at the 36 hr time interval. Fertilization levels declined significantly from a high of 50% at 27 hr to a low of 30% at 36 hr. Thus, although higher percentages of mature oocytes were recovered at the longer time intervals, optimal oocyte/embryo harvests were realized after the shorter time intervals (27 and 32 hr) and are most compatible with the goal of achieving high yields of fertile oocytes and embryos following gonadotropin stimulation in rhesus monkeys. © 1996 Wiley-Liss, Inc.     

A genetic strategy for differential screening of meiotic germ-cell cDNA libraries

The goals of this work were to create germ-cell-stage-specific cDNA libraries from mouse spermatogenic cells and to employ a novel two-step genetic screen to identify gene sequences present during the critical meiotic stage of spermatogenesis. Highly enriched germ-cell fractions were prepared from adult and juvenile mouse testes, and purity of these fractions was extensively analyzed by light and electron microscopy. Standard techniques were used to prepare cDNA libraries from populations of mixed leptotene and zygotene (L/Z) spermatocytes, pachytene (P) spermatocytes, and round spermatids. These libraries were analyzed with respect to representation of sequences from ubiquitously expressed genes, and from genes expressed at specific germ-cell stages as well as from genes expressed in testicular somatic cells. For the first step of the screening procedure, testicular cDNA was prepared from mutant mice carrying the T(X;11)38H chromosomal translocation that causes spermatogenic arrest at early meiotic prophase. This mixed cDNA probe was used to screen the libraries from L/Z and P spermatocytes to detect sequences that failed to hybridize. The clones identified were characterized for ability to hybridize to various germ-cell-specific cDNAs to verify that they represented sequences present in normal spermatogenic meiotic cells. These clones were then subjected to a second screening with another mutant probe; this time the cDNA probe was from testes of sterile mice bearing the T(X;16)16H chromosomal translocation that causes spermatogenic arrest at late meiotic prophase. This screen identified 27 clones that were not represented in testicular cDNA from T38-bearing mice or from T16-bearing mice. These clones may represent sequences essential for normal completion of the genetic events of meiosis during spermatogenesis. Likewise, the secondary screen identified 19 clones that were not represented in testicular cDNA from T38-bearing mice but were represented in testicular cDNA of T16-bearing mice. These clones are thus gene sequences present in spermatogenic cells during the time from early meiotic prophase to mid-to-late prophase. This strategy represents the first use of genetic aberrations in differential screening to identify genes expressed at specific times during mammalian spermatogenesis. © 1996 Wiley-Liss, Inc.