Winter flounder Y

cDNAs encoding for neuropeptide Y (NPY), cocaine and amphetamine regulated transcript (CART) and cholecystokinin (CCK) were cloned in winter flounder, a species that undergoes a period of natural fasting during the winter. Tissue distribution studies show that these peptides are present in several peripheral tissues, including gut and gonads, as well as within the brain. We assessed the effects of season and fasting on the expression of these peptides. Our results show that NPY and CCK, but not CART, show seasonal differences in expression with higher hypothalamic NPY and lower gut CCK expression levels in the winter. In the summer, fasting induced an increase in hypothalamic NPY expression levels and a decrease in gut CCK levels, but did not affect hypothalamic CART expression levels. None of the peptides examined was affected by fasting in the winter. Our results suggest that NPY and CCK, but maybe not CART, might have a major role in the regulation of feeding in winter flounder and might contribute to the seasonal fluctuations in appetite in this species.

The abuse of antibiotics has resulted in the emergence of multi-drug-resistant bacteria. Staphylococcus aureus is a frequent cause of infections, and antibiotic-resistant S. aureus has become a serious problem. Antimicrobial peptides play an important role in innate immunity and are attracting increasing attention as alternative antibiotics. In a previous study, pleurocidin, derived from winter flounder, was identified as a 25-amino acid antimicrobial peptide with no cytotoxicity toward mammalian cells and low hemolytic activity. In the present study, pleurocidin was observed to exhibit antimicrobial activity against gram-positive and gram-negative bacteria, especially against drug resistant S. aureus. Pleurocidin retained its antibacterial activity against drug resistant S. aureus in the presence of a physiological salt concentration. Membrane depolarization assays and propidium iodide uptake indicated that pleurocidin kills bacteria by damaging the integrity of the bacterial membrane. DNA binding assays revealed that pleurocidin binds to DNA. Thus, pleurocidin targets not only the bacterial membrane, but also their DNA. S. aureus biofilms have become a serious problem because of increased resistance to antibiotics. Therefore, we investigated the effect of pleurocidin on biofilm inhibition and eradication using crystal violet staining and microscopic observation. Pleurocidin inhibited and eradicated biofilms at low concentrations. Taken together, the results suggested that pleurocidin is a promising candidate therapeutic agent to treat drug-resistant bacteria and biofilm-related infections.

A cDNA made to antifreeze protein mRNA of the winter flounder was cloned in the plasmid pBR322 and its sequence was determined by the method of Maxam and Gilbert. Its sequence codes for a precursor protein that is 82 amino acids in length. This precursor has both a signal polypeptide and a prosequence before the mature protein of 38 amino acid residues. The mature protein matches in composition one of the alanine-rich serum antifreeze proteins that was purified by ion-exchange and reverse-phase chromatography. The composition of the pro- sequence is similar to that of the native protein except that it contains five prolines. The mature protein, but not the pro- sequence, contains three of the 11-residue repeats previously observed [Lin, Y. & Gross, J. K. (1981) Proc. Natl. Acad. Sci. USA 78, 2825-2829] in two other antifreeze protein components.