Qualitative and quantitative models relating otolith zone deposition to growth and condition in sexually mature male and female capelin (Mallotus villosus)

Summary Correspondence analysis (CA) is used to examine the relationship between months, between selected body components/organs and between months and components/organs for male and female capelin from 12 to 37 months of age in Balsfijorden, northern Norway (69°21N:19°06E). The CA profiles have been used to quantify condition with regard to age and season. The major features determining the condition of fish depositing hyaline or opaque otolith zones are itemized using CA, and the data modelled by Multiple Regression (MR) using a cosine curve incorporating the chief mass variables with linear age-dependency. The highest proportion of fish having outer opaque zones are found from ca. June to October, whilst the highest proportion with exterior hyaline zones are found from ca. December to May. There is a clear annual cycle in the deposition of opaque and hyaline otolith zones in both sexes, but there is a significant difference in phase of ca. 12 days between the sexes. There is a significant trend for decreasing proportions of fish having outermost opaque otolith zones with increasing age; this trend is similar in both sexes. The mean level and amplitude of the cycles are similar in both sexes. On the other hand, CA shows a 12-month cycle of storage and utilization of body materials with obvious differences between sexes. In the female protein in the fillet plays a more dominant role than lipid in the fillet in accounting for anabolic and catabolic variations in mass, whereas in the male the opposite is true. Sexual maturation is negatively correlated with fillet (somatic) growth. Variations in stomach weight (with contents) and otolith zone deposition are not significantly correlated. Nevertheless, in both sexes there is a clear positive correlation between stomach weight and liver protein and lipid implying an association between stomach weight and feeding activity. In females, however, maximum liver condition is more positively correlated with exponential ovarian growth, probably through mobilization of lipoproteins for eggs. Qualitative (CA) and quantitative (MR) models have related changes in growth and condition to the type of otolith zone deposited. The fillet of capelin is the major somatic growth site. As CA indicates a negative correlation between fillet reserves and gonad maturation, and the best MR models describing the cycle of otolith zone deposition in males and females (accounting for 93% and 70% respectively of the variation) underlined and quantified the interplay between somatic and gonad growth, it is implicit that the energy balance of the fish will be an important determinant of otolith zone deposition in sexually maturing and mature capelin.     

Cellular and lysosomal uptake of methylamine in isolated rat hepatocytes.

Upon addition of methylamine to intact cells, this lysosomotropic weak base accumulates intracellularly as the result of at least two different mechanisms: (1) facilitated diffusion across the plasma membrane, i.e. a process which is carrier-mediated and subject to both trans-stimulation (accelerative exchange) and cis-inhibition (competition) by other amines (e.g. ammonia, methylamine and triethylamine); this transport process is furthermore non-concentrative, energy-independent, and (although moderately temperature-sensitive) operative even at 0 degrees C; (2) active uptake, i.e. an energy-dependent concentrative process which is inhibited by anoxia and energy inhibitors. With time, methylamine accumulates in lysosomes and gives rise to a lysosomal swelling which is easily visible by optical microscopy, and which causes the cells to appear coarsely granular. After a 1h incubation with 10mM-methylamine, the total cell volume is increased by about 12%. Under anoxic conditions or in the presence of energy inhibitors, lysosomal swelling is abolished regardless of there being a high concentration of methylamine intracellularly (taken up by facilitated diffusion). The continuous accumulation of methylamine in lysosomes therefore seems to depend on an energy-requiring process (such as continuous proton pumping), and not only on trapping by Donnan-equilibrium-generated protons.     

Rapid and simple preparation of plasmids suitable for dideoxy DNA sequencing and other purposes.

Plasmid DNA released from bacteria by boiling in the presence of lysozyme and Triton x-100 and without further purification can be sequenced by the dideoxy method using T7 DNA polymerase, when conditions during alkali denaturation and subsequent ethanol precipitation are adjusted to remove contaminants. The samples remain in the same microcentrifuge tubes from the harvesting of the bacteria until the splitting of the sample into four aliquots for the termination reactions. Less background label is observed with end-labelled primers (radioactivity or fluorescence), but even when radioactive nucleotides are incorporated during the sequencing reactions, 250 bases or more can be read from template prepared from 1.5 ml bacterial culture. The DNA can also be cut by restriction enzymes; the purification procedure described thus provides the rapid preparation of plasmids for a variety of purposes.     

Amino acid transport systems of lysosomes: Possible substitute utility of a surviving transport system for one congenitally defective or absent

Ways in which other transport systems may compensate for one that is genetically defective are considered. Comparisons of the transport systems of organelles (here the lysosome) with the transport system at the plasma membrane has significant implications for chemotherapy.     

Mechanism for Amyloid Precursor-like Protein 2 Enhancement of Major Histocompatibility Complex Class I Molecule Degradation

Earlier studies have demonstrated interaction of the murine major histocompatibility complex (MHC) class I molecule K^d with amyloid precursor-like protein 2 (APLP2), a ubiquitously expressed member of the amyloid precursor protein family. Our current findings indicate that APLP2 is internalized in a clathrin-dependent manner, as shown by utilization of inhibitors of the clathrin pathway. Furthermore, we demonstrated that APLP2 and K^d bind at the cell surface and are internalized together. The APLP2 cytoplasmic tail contains two overlapping consensus motifs for binding to the adaptor protein-2 complex, and mutation of a tyrosine shared by both motifs severely impaired APLP2 internalization and ability to promote K^d endocytosis. Upon increased expression of wild type APLP2, K^d molecules were predominantly directed to the lysosomes rather than recycled to the plasma membrane. These findings suggest a model in which APLP2 binds K^d at the plasma membrane, facilitates uptake of K^d in a clathrin-dependent manner, and routes the endocytosed K^d to the lysosomal degradation pathway. Thus, APLP2 has a multistep trafficking function that influences the expression of major histocompatibility complex class I molecules at the plasma membrane.     

Pneumococcal CbpD is a murein hydrolase that requires a dual cell envelope binding specificity to kill target cells during fratricide

Pneumococci that are competent for natural genetic transformation express a number of proteins involved in binding, uptake, translocation and recombination of DNA. In addition, they attack and lyse non‐competent sister cells present in the same environment. This phenomenon has been termed fratricide. The key effector of pneumococcal fratricide is CbpD, a secreted protein encompassing an N‐terminal CHAP domain, two SH3b domains and a C‐terminal choline‐binding domain (CBD). CbpD is believed to degrade the cell wall of target cells, but experimental evidence supporting this hypothesis has been lacking. Here, we show that CbpD indeed has muralytic activity, and that this activity requires functional CBD and SH3b domains. To better understand the critical role played by the non‐catalytic C‐terminal region of CbpD, various translational fusions were constructed between the CBD and SH3b domains and green fluorescent protein (GFP). The results showed that the SH3b domains specifically recognize and bind peptidoglycan, while the CBD domain functions as a localization signal that directs CbpD to the septal region of the pneumococcal cell. Intriguingly, transmission electron microscopy analysis revealed that target cells attacked by CbpD ruptures at the septal region, in accordance with the binding specificity displayed by the CBD domain.     

Rock weathering creates oases of life in a High Arctic desert

During primary colonization of rock substrates by plants, mineral weathering is strongly accelerated under plant roots, but little is known on how it affects soil ecosystem development before plant establishment. Here we show that rock mineral weathering mediated by chemolithoautotrophic bacteria is associated to plant community formation in sites recently released by permanent glacier ice cover in the Midtre Lovénbreen glacier moraine (78°53′N), Svalbard. Increased soil fertility fosters growth of prokaryotes and plants at the boundary between sites of intense bacterial mediated chemolithotrophic iron‐sulfur oxidation and pH decrease, and the common moraine substrate where carbon and nitrogen are fixed by cyanobacteria. Microbial iron oxidizing activity determines acidity and corresponding fertility gradients, where water retention, cation exchange capacity and nutrient availability are increased. This fertilization is enabled by abundant mineral nutrients and reduced forms of iron and sulfur in pyrite minerals within a conglomerate type of moraine rock. Such an interaction between microorganisms and moraine minerals determines a peculiar, not yet described model for soil genesis and plant ecosystem formation with potential past and present analogues in other harsh environments with similar geochemical settings.     

Molecular mechanisms of enterotoxigenic Escherichia coli infection

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrheal illness in developing countries, and perennially the most common cause of traveller's diarrhea. ETEC constitute a diverse pathotype that elaborate heat-labile and/or heat-stable enterotoxins. Recent molecular pathogenesis studies reveal sophisticated pathogen–host interactions that might be exploited in efforts to prevent these important infections. While vaccine development for these important pathogens remains a formidable challenge, extensive efforts that attempt to exploit new genomic and proteomic technology platforms in discovery of novel targets are presently ongoing.