Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.     

Recurrent Pseudo-nitzschia calliantha (Bacillariophyceae) and Alexandrium insuetum (Dinophyceae) winter blooms induced by agricultural runoff

A winter bloom dominated by Pseudo-nitzschia calliantha Lundholm, Moestrup et Hasle (Bacillariophyceae), a potential domoic acid producer, is reported for the first time in the Aegean Sea, Greece, in a semi-enclosed embayment (Kalloni Gulf) surrounded by agricultural land and drained by intermittent rivers. Abundances of this species in the inner part of the Gulf during February were extremely high (max 1.1 × 10⁷ cells l⁻¹). The species Alexandrium insuetum Balech (Dinophyceae) was also found in considerable cell numbers (max 1.4 × 10⁵ cells l⁻¹) during the bloom and reached up to 40% of the total biovolume. This study demonstrates an evident cause and effect relationship between nutrient inflows originating from agricultural activities in the watershed and the development of a potential HAB. The massive bloom formation was observed soon after an episodic rainfall event during the fertilizer application period (December to February). A bloom was also observed the following year, but it was less pronounced due to the fact that rainfalls were more evenly spaced in time and were of moderate intensity.     

Quorum Sensing Peptides Selectively Penetrate the Blood-Brain Barrier

Bacteria communicate with each other by the use of signaling molecules, a process called ‘quorum sensing’. One group of quorum sensing molecules includes the oligopeptides, which are mainly produced by Gram-positive bacteria. Recently, these quorum sensing peptides were found to biologically influence mammalian cells, promoting i.a. metastasis of cancer cells. Moreover, it was found that bacteria can influence different central nervous system related disorders as well, e.g. anxiety, depression and autism. Research currently focuses on the role of bacterial metabolites in this bacteria-brain interaction, with the role of the quorum sensing peptides not yet known. Here, three chemically diverse quorum sensing peptides were investigated for their brain influx (multiple time regression technique) and efflux properties in an in vivo mouse model (ICR-CD-1) to determine blood-brain transfer properties: PhrCACET1 demonstrated comparatively a very high initial influx into the mouse brain (K_in = 20.87 μl/(g×min)), while brain penetrabilities of BIP-2 and PhrANTH2 were found to be low (K_in = 2.68 μl/(g×min)) and very low (K_in = 0.18 μl/(g×min)), respectively. All three quorum sensing peptides were metabolically stable in plasma (in vitro) during the experimental time frame and no significant brain efflux was observed. Initial tissue distribution data showed remarkably high liver accumulation of BIP-2 as well. Our results thus support the potential role of some quorum sensing peptides in different neurological disorders, thereby enlarging our knowledge about the microbiome-brain axis.     

Differential maintenance of penile responses and copulatory behavior by gonadal hormones in castrated male rats

Sexually experienced male rats were castrated and immediately received implants of Silastic tubing containing either testosterone (T), dihydrotestosterone (DHT), estradiol (E), or nothing (blank). The ability of these hormone treatments to maintain precastration levels of copulatory behavior and ex copula penile responses was assessed for 40 days after castration. Throughout the study T- and E-treated males, but not males with DHT or blank implants, maintained normal copulatory behavior. In contrast males treated with T and DHT, but not E or blanks, maintained penile responses ex copula. In blank-treated males, penile-response latencies increased more rapidly than did intromission latencies. These results, together with those of previous studies, appear to rule out a role for estradiol and reinforce the role of androgens in the activation of rats' penile-response potential ex copula. Similarly, the results support the conclusion that in castrated male rats estradiol treatment is sufficient for the activation of masculine copulatory behavior, and that the penile actions necessary for intromission are not dependent on androgen. Thus, the evocability of penile actions and their relative androgen dependence are context sensitive.     

Unusual occurrence of EcoP1 and EcoP15 recognition sites and counterselection of type II methylation and restriction sequences in bacteriophage T7 DNA

Selected and counterselected oligodeoxynucleotide sequences were identified in the total sequence of bacteriophage T7 DNA using a statistical criterion derived for a probability model of the Markov chain type. All extremely rare tetra- and pentadeoxynucleotides are (or contain) recognition sequences for the Escherichia coli DNA methylases dam or dcm. Most of the 37 hexadeoxynucleotides absent from T7 DNA are recognition sequences for type II modification/restriction enzymes of E. coli or related species. In contrast to most restriction sites counterselected during evolution, the EcoP1 site GGTCT occurs 126 times in the T7 genome, and phage T7 replication is severely repressed in P1-lysogenic host cells. We demonstrate that the frequency of the EcoP1 site is determined by that of the overlapping recognition sites for T7 primase, an essential phage enzyme. The recognition site of a type III enzyme, EcoP15, is also not counterselected. In T7 DNA all 36 EcoP15 sites are arranged in such a manner that the sequence CAGCAG is confined to the H strand, the complementary sequence CTGCTG to the L strand. This "strand bias" is highly significant and, therefore, very probably selected. A functional relation between this strand bias and the refractive behaviour of phage T7 to EcoP15 restriction is suspected.     

Albumin binding of photobilirubin II.

Photobilirubin II, a stereoisomer of bilirubin, binds to human serum albumin at a single binding site (K = 2.2 x 10(6)M-1), presumably the high-affinity bilirubin-binding site. Binding in the secondary (class II) binding sites is of minor importance. The results are discussed with respect to photometabolism of bilirubin and as a possible source of error in the determination of bilirubin unbound to albumin.     

Epitope mapping of antibodies directed against hypervariable region 1 in acute self-limiting and chronic infections due to hepatitis C virus.

Epitopes of hypervariable region 1 (HVR1) were mapped by enzyme-linked immunosorbent assay using follow-up sera of patients, all of whom were infected with the same isolate of hepatitis C virus (HCV). Our results suggest that (i) an early appearance (up to month 13 postinfection) of antibodies directed to the N terminus of HVR1 is associated with acute self-limiting infections of HCV and (ii) isolate-independent antibodies which are mainly directed to the C terminus of HVR1 seem to persist in chronically infected patients. The relevance of HVR1-specific antibodies for neutralization was evaluated by characterization of a rabbit serum.