Natal origin and dispersal of problem saltwater crocodiles in the Darwin Harbor,Australia

Management programs that successfully recovered wild saltwater crocodile (Crocodylus porosus) populations in the Northern Territory of Australia did so with an expanding commitment to maintaining public safety. One aspect of the program is the ongoing removal of resident and immigrant crocodiles within Darwin Harbor (since 1979), the main urban center. We determined the likely sources of crocodiles caught as problem animals between 2015–2017 by comparing recently developed methods for population assignment. Depending on the assignment model used, we estimated that between 30% and 50% of crocodiles in Darwin Harbor originated from the Adelaide and Mary rivers, and the Kakadu region east of Darwin, and between 20% and 30% of crocodiles originated from the Finniss, Reynolds, and Daly rivers southwest of Darwin. Saltwater crocodiles occur at particularly high densities in these catchments. The remainder came from a mixture of different sources across the Northern Territory. The most common animals captured were immature (150–180 cm) males that have traveled 100–200 km. We did not identify any relationships between the distance from the inferred origin to Darwin Harbor and the size and sex of the crocodiles, or the year of capture. The targeted removal of crocodiles from specific sites such as Darwin Harbor, near where most people live, improves public safety in the highest risk areas, without compromising abundant source populations in most areas.     

Fluorescent somatostatin receptor probes for the intraoperative detection of tumor tissue with long-wavelength visible light

Targeted fluorescent dyes are of substantial value for the intraoperative delineation of primary tumors and metastatic lesions. For this purpose long-wavelength red light (lambda=550-650 nm) offers advantages because of good tissue penetration and direct visibility. Since somatostatin receptors (SSTR) are overexpressed in a number of tumors, a series of potentially tumor-selective peptide-dye conjugates were synthesized by solid-phase peptide synthesis (SPPS). The octapeptides octreotate, Tyr(3)-octreotate and Tyr(3)-octreotide were employed and exhibited high affinity for somatostatin receptors (SSTR). The fluorescent dyes rhodamine 101, sulforhodamine B acid chloride, sulforhodamine 101 or rhodamine B isothiocyanate were conjugated either directly or via spacers, for example the peptidase-labile pentapeptide sequence Ala-Leu-Ala-Leu-Ala. The conjugates were completely assembled on the solid support: Fmoc-SPPS, cyclization via a disulfide linkage, N-terminal attachment of a spacer, and linkage to the fluorescent dye. An in vitro competition assay revealed that the conjugates bind to SSTRs with IC(50) values between 0.7 and 89 nM. The conjugates were generally stable to hydrolysis at pH 7-8 in buffer or serum. However, the rhodamine 101 conjugates revealed a loss of absorption at alkaline pH due to conversion to a neutral spirolactam form, as characterized by NMR.     

Synthesis and evaluation of imidazo[1,5-a]pyrazines as corticotropin releasing hormone receptor ligands

A novel series of imidazo[1,5-a]pyrazines was synthesized and evaluated as corticotropin releasing hormone (CRH) receptor ligands. SAR studies focused primarily on dialkylamino side chain optimization. SAR of the aryl and small alkyl substituents was also explored.     

Design, synthesis, and biological activity of novel factor Xa inhibitors: 4-aryloxy substituents of 2,6-diphenoxypyridines

A novel series of triaryloxypyridines have been designed to inhibit factor Xa, a serine protease strategically located in the coagulation cascade. Inhibitor 5e has a K(I) against factor Xa of 0.12nM and is greater than 8000- and 2000-fold selective over two related serine proteases, thrombin and trypsin, respectively. The 4-position of the central pyridine has been identified as a site that tolerates various substitutions without deleterious effects on potency and selectivity. This suggests that the 4-position of the pyridine ring is an ideal site for chemical modifications to identify inhibitors with improved pharmacokinetic characteristics. This investigation has resulted in inhibitor 5d, which has an oral availability of 6% in dogs. The synthesis, in vitro activity, and in vivo profile of this class of inhibitors is outlined.     

Synthesis and biological activity of N-Acylated ornithine analogues of daptomycin

N-Acylated ornithine analogues of daptomycin were synthesized and tested for their antibacterial efficacy.     

Orderly order in protein intrinsic disorder distribution: disorder in 3500 proteomes from viruses and the three domains of life

Intrinsically disordered proteins and intrinsically disordered protein regions are highly abundant in nature. However, the quantitative and qualitative measures of protein intrinsic disorder in species with known genomes are still not available. Furthermore, although the correlation between high fraction of disordered residues and advanced species has been reported, the details of this correlation and the connection between the disorder content and proteome complexity have not been reported as of yet. To fill this gap, we analysed entire proteomes of 3484 species from three domains of life (archaea, bacteria and eukaryotes) and from viruses. Our analysis revealed that the evolution process is characterized by distinctive patterns of changes in the protein intrinsic disorder content. We are showing here that viruses are characterized by the widest spread of the proteome disorder content (the percentage of disordered residues ranges from 7.3% in human coronavirus NL63 to 77.3% in Avian carcinoma virus). For several organisms, a clear correlation is seen between their disorder contents and habitats. In multicellular eukaryotes, there is a weak correlation between the complexity of an organism (evaluated as a number of different cell types) and its overall disorder content. For both the prokaryotes and eukaryotes, the disorder content is generally independent of the proteome size. However, disorder shows a sharp increase associated with the transition from prokaryotic to eukaryotic cells. This suggests that the increased disorder content in eukaryotic proteomes might be used by nature to deal with the increased cell complexity due to the appearance of the various cellular compartments.     

Thermal preferences of hatchling saltwater crocodiles (Crocodylus porosus) in response to time of day,social aggregation and feeding

Three month old hatchling Crocodylus porosus with data loggers in their stomachs were placed in thermal gradients, in isolation (N=16) and in groups of 4 (N=8 groups; 32 individuals). Mean T_b and variation in T_b (SD) was not different whether individual crocodiles in isolation were fasted or fed, or if individuals were housed in isolation (I) or in groups (G). However, individuals in isolation (N=16) maintained slightly lower T_bs than those in groups (N=32) during the early morning (06:00–11:00 h). The overall mean T_b recorded for fasted individuals in the isolated and group treatments (N=48) was 30.9±2.3 °C SD, with 50% of T_bs (T_set) between 29.4 °C and 32.6 °C, and a voluntary maximum and minimum of 37.6 °C and 23.2 °C respectively. During the day (11:00–17:00 h), individuals in isolation and in groups selected the warmer parts of the gradient on land, where they moved little. Outside of this quiescent period (QP), activity levels were much higher and they used the water more. There was a strong diurnal cycle for fasted individuals in isolation and in groups, with T_b during the QP (31.9±2.09 °C; N=48) significantly higher than during the non-quiescent period (NQP: 30.6±2.31 °C). Thermal variation (SD) in T_b was relatively stable throughout the day, with the highest variation at around dusk and early evening (18:00–20:00 h), which coincided with a period of highest activity. The diurnal activity cycle appears innate, and may reflect the need to engage in feeding activity at the water's edge in the early evening, despite ambient temperatures being cooler, with reduced activity and basking during the day. If so, preferred T_b may be more accurately defined as the mean T_b during the QP rather than the NQP. Implications for the thermal environment best suited for captive C. porosus hatchlings are discussed.     

EphA signaling promotes actin-based dendritic spine remodeling through slingshot phosphatase

Actin cytoskeletal remodeling plays a critical role in transforming the morphology of subcellular structures across various cell types. In the brain, restructuring of dendritic spines through actin cytoskeleletal reorganization is implicated in the regulation of synaptic efficacy and the storage of information in neural circuits. However, the upstream pathways that provoke actin-based spine changes remain only partly understood. Here we show that EphA receptor signaling remodels spines by triggering a sequence of events involving actin filament rearrangement and synapse/spine reorganization. Rapid EphA signaling over minutes activates the actin filament depolymerizing/severing factor cofilin, alters F-actin distribution in spines, and causes transient spine elongation through the phosphatases slingshot 1 (SSH1) and calcineurin/protein phosphatase 2B (PP2B). This early phase of spine extension is followed by synaptic reorganization events that take place over minutes to hours and involve the relocation of pre/postsynaptic components and ultimately spine retraction. Thus, EphA receptors utilize discrete cellular and molecular pathways to promote actin-based structural plasticity of excitatory synapses.