Laboratory and field ecotoxicology studies clarify levels of pollutants that adversely affect organisms at various life stages. We examined three well-controlled laboratory studies of hexavalent chromium (Cr-VI) toxicity to fertilization, eggs and juvenile Chinook Salmon (Oncorhynchus tshawytscha), to identify effect levels for several endpoints. These studies are relevant to Cr-VI contaminatio...

The Pariser-Parr-Pople Hamiltonian is used to calculate and identify the nature of the low-lying vertical transition energies of polydiacetylene. The model is solved using the density matrix renormalisation group method for a fixed acetylenic geometry for chains of up to 102 atoms. The non-linear optical properties of polydiacetylene are considered, which are determined by the third-order susce...

One of the most clearly defined endocrine changes during the parr-smolt transformation of anadromous salmonids is an increase in plasma levels of thyroid hormones. The role of pineal hormone melatonin in timing and synchronisation of smoltification is widely discussed. The effect of administration of exogenous thyroxine (T4) on plasma melatonin was investigated in juvenile Atlantic salmon (Salm...

Ž . Atlantic salmon Salmo salar parr were subjected to acute handling stresses and growth-monitored for at least 30 days. In fish stressed twice daily, growth rate in weight was 61% lower than Ž y1. controls after 11 days 1.00 vs. 2.57% day and over a 30 day period it was 50% lower than Ž y1. controls 1.53 vs. 3.07% day . In fish stressed once daily, growth rate was 18% lower than Ž y1. control...

Among the Tethyan larger porcelaneous foraminifera widespread from middle–late Eocene to middle Miocene, Austrotrillina Parr, 1942 is only genus showing a non-homogeneous shell structure. This consists of parakeriotheca, coated by thin, dense tectum. Four species (A. brunni, A. eocaenica, howchini, striata) have been often used as biostratigraphical markers in Mediterranean and Indo-Pacific are...

Bacterial conjugation is a form of type IV secretion used to transport protein and DNA directly to recipient bacteria. The process is cell contact-dependent, yet the mechanisms enabling extracellular events to trigger plasmid transfer to begin inside the cell remain obscure. In this study of plasmid R1 we investigated the role of plasmid proteins in the initiation of gene transfer. We find that...

The high level of escapes from Atlantic salmon farms, up to two million fishes per year in the North Atlantic, has raised concern about the potential impact on wild populations. We report on a two-generation experiment examining the estimated lifetime successes, relative to wild natives, of farm, F(1) and F(2) hybrids and BC(1) backcrosses to wild and farm salmon. Offspring of farm and "hybrids...

Bacterial plasmid partitioning systems segregate plasmids into each daughter cell. In the well-understood ParMRC plasmid partitioning system, adapter protein ParR binds to centromere parC, forming a helix around which the DNA is externally wrapped. This complex stabilizes the growth of a filament of actin-like ParM protein, which pushes the plasmids to the poles. The TubZRC plasmid partitioning...

The distribution of corner (putative ultraviolet-sensitive) cones in the retina of Atlantic salmon was examined from the small juvenile (parr) stage to the adult stage (approaching sexual maturation). Small parr weighing approximately 5 g lacked corner cones everywhere except, mainly, near the dorsal periphery. Large fish ( approximately 5 kg) approaching sexual maturation showed corner cones i...