This investigation involved the synthesis of metal complexes to test the hypothesis that structural changes and metal coordination in pyridine thiosemicarbazones affect cell growth and cell proliferation in vitro. Thiosemicarbazones are well known to possess antitumor, antiviral, antibacterial, antimalarial, and other activities. Extensive research has been carried out on aliphatic, aromatic, heterocyclic and other types of thiosemicarbazones and their metal complexes. Due to the pronounced reactivity exhibited by metal complexes of heterocyclic thiosemicarbazones, synthesis and structural characterization of di-2-pyridylketone 4N-phenyl thiosemicarbazone and diphenyl tin (Sn) and platinum (Pt) complexes were undertaken. Shewanella oneidensis MR-1, a metal ion-reducing bacterium, was used as a model organism to explore the biological activity under aerobic conditions. A comparision of the cytotoxic potential of selected ligand and metal-complex thiosemicarbazones on cell growth in wild type MR-1 and mutant DSP-010 Shewanella oneidensis strains at various concentrations (0, 5, 10, 15, 20 or 25 ppm) was performed. The wild type (MR-1) grown in the presence of increasing concentrations of Sn- thiosemicarbazone complexes was comparatively more sensitive (mean cell number = 4.8 X 108 + 4.3 X 107 SD) than the DSP-010, a spontaneous rifampicillin derivative of the parent strain (mean cell number = 5.6 x 108 + 6.4 X 107 SD) under comparable aerobic conditions (p=0.0004). No differences were observed in the sensitivity of the wild and mutant types when exposed to various concentrations of diphenyl Pt- thiosemicarbazone complex (p= 0.425) or the thiosemicarbazone ligand (p=0.313). Growth of MR-1 in the presence of diphenyl Sn- thiosemicarbazone was significantly different among treatment groups (p=0.012). MR-1 cell numbers were significantly higher at 5ppm than at 10 to 20ppm (p = 0.05). The mean number of DSP-010 variant strain cells also differed among diphenyl Sn- thiosemicarbazone complex treated groups (p=0.051). In general, there was an increasing trend in the number of cells from about 5.0 X 108 cells (methanol control group) to about 6.0 X 108 cells (25ppm). The number of cells in methanol control group was significantly lower than cell numbers at 20ppm and 25ppm (p = 0.05), and numbers at 5ppm treatment were lower than at 20 and 25ppm (p = 0.05). Furthermore, a marginally significant difference in the number of MR-1 cells was observed among diphenyl Pt- thiosemicarbazone complex treatment groups (p = 0.077), and an increasing trend in the number of cells was noted from ~5.0 X 108 cells (methanol control group) to ~5.8 X 108 cells (20ppm). In contrast, the DSP-010 variant strain showed no significant differences in cell numbers when treated with various concentrations of diphenyl Pt- thiosemicarbazone complex (p = 0.251). Differences in response to Sn- metal complex between MR-1 and DSP-010 growing cultures indicate that biological activity to thiosemicarbazone metal complexes may be strain specific.
Habitat loss and degradation, and their interaction with other threats, are driving declines in animal populations worldwide. One potential approach for mitigating these threats is to create artificial habitat structures as substitutes for lost or degraded natural structures. Here, we provide – to the best of our knowledge – the first general definition of artificial habitat structures and synthesize important considerations for their effective use. We show that such structures represent a versatile conservation tool that has been trialed in a variety of contexts globally, albeit with varying degrees of success. The design of these structures must be well informed by the drivers of natural habitat selection, and their use should be part of an experimental framework to enable evaluation and refinement. We highlight possible ecological risks associated with the use of artificial habitat structures and urge that they not be exploited as inappropriate biodiversity offsets or for greenwashing. Looking forward, cross‐disciplinary collaborations will facilitate the development of sophisticated and effective structures to assist animal conservation in this era of rapid global change.
The rapid and large-scale urbanization of peri-urban areas poses major and complex challenges for wildlife conservation. We used population viability analysis (PVA) to evaluate the influence of urban encroachment, fire, and fauna crossing structures, with and without accounting for inbreeding effects, on the metapopulation viability of a medium-sized ground-dwelling mammal, the southern brown bandicoot (Isoodon obesulus), in the rapidly expanding city of Perth, Australia. We surveyed two metapopulations over one and a half years, and parameterized the PVA models using largely field-collected data. The models revealed that spatial isolation imposed by housing and road encroachment has major impacts on I. obesulus. Although the species is known to persist in small metapopulations at moderate levels of habitat fragmentation, the models indicate that these populations become highly vulnerable to demographic decline, genetic deterioration, and local extinction under increasing habitat connectivity loss. Isolated metapopulations were also predicted to be highly sensitive to fire, with large-scale fires having greater negative impacts on population abundance than small-scale ones. To reduce the risk of decline and local extirpation of I. obesulus and other small- to medium-sized ground-dwelling mammals in urbanizing, fire prone landscapes, we recommend that remnant vegetation and vegetated, structurally-complex corridors between habitat patches be retained. Well-designed road underpasses can be effective to connect habitat patches and reduce the probability of inbreeding and genetic differentiation; however, adjustment of fire management practices to limit the size of unplanned fires and ensure the retention of long unburnt vegetation will also be required to ensure persistence. Our study supports the evidence that in rapidly urbanizing landscapes, a pro-active conservation approach is required that manages species at the metapopulation level and that prioritizes metapopulations and habitat with greater long-term probability of persistence and conservation capacity, respectively. This strategy may help us prevent future declines and local extirpations, and currently relatively common species from becoming rare.
The object of this study was to determine whether the inducer(s) of DNA synthesis in mammalian cells accumulates gradually throughout the G1 period or becomes available suddenly at the G1-S transition. HeLa cells, synchronized at various points in the G1 period, were fused by using UV-inactivated Sendai virus. Early G1 cells were fused with mid-G1 or late G1 cells and late G1 cells were fused with mid-G1 cells. The G1 traverse of mono-, bi-, and trinucleated cells was studied. The bi- and trinucleated cells of mid-G1 and late G1 parents traversed the G1 period significantly faster than did their mononucleated counterparts. The reduction in the duration of the G1 period was proportional to the number and age of nuclei at the time of fusion. There was no significant difference between the mono- and binucleated cells of the early G1 parent in their rates of entry into S period. In light of these findings, a model is proposed in which the inducer(s) of DNA synthesis accumulates gradually throughout the G1 period, reaching a critical level at the G1-S boundary when DNA replication is initiated; after reaching a peak during early or mid-S period, it declines to below the critical level when DNA synthesis ceases.
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