Densities of Vibrio vulnificus in the intestines of fish from the U.S. Gulf Coast.

Densities of Vibrio vulnificus in the intestinal contents of various finfish, oysters, and crabs and in sediment and waters of the U.S. Gulf Coast were determined by the most probable number procedure. Species were identified by enzyme immunoassay. During the winter, densities of V. vulnificus were low, and the organism was isolated more frequently from sheepshead fish than from sediment and seawater. From April to October, V. vulnificus densities were considerably higher (2 to 5 logs) in estuarine fish than in surrounding water, sediment, or nearby oysters and crustacea. Highest densities were found in the intestinal contents of certain bottom-feeding fish (10(8)/100 g), particularly those that consume mollusks and crustaceans. Densities of V. vulnificus in fish that feed primarily on plankton and other finfish were similar to those in oysters, sediment, and crabs (10(5)/100 g). V. vulnificus was found infrequently in offshore fish. The presence of high densities of V. vulnificus in the intestines of common estuarine fish may have both ecological (growth and transport) and public health (food and wound infections) implications.     

Novel monoamine oxidase inhibitors based on the privileged 2-imidazoline molecular framework

Series of structurally diverse 2-imidazoline derivatives have been synthesized by condensation of substituted aldehydes with ethylenediamine, Pd-catalyzed N-arylation of 2-imidazolines and by the formation of 1,2,4-oxadiazoles and benzoxazepines from 2-imidazoline-containing precursors. The 2-imidazoline derivatives were evaluated as potential inhibitors of human monoamine oxidase (MAO) A and B. Among the 2-imidazolines, good potency inhibitors were discovered with compound 9p (IC₅₀?=?0.012?µM) being the most potent MAO-B inhibitor, while compound 9d (IC₅₀?=?0.751?µM) was the most potent MAO-A inhibitor of the series. These potencies are in the same range as those of reference MAO inhibitors used in the clinic. Among 33 compounds evaluated, 13 exhibited IC₅₀ values in the submicromolar range for the inhibition of an MAO isoform. It is postulated that the imidazoline moieties of some of these inhibitors may be recognized by the imidazoline I₂-binding site of MAO. Good potency MAO inhibitors may be useful for the treatment of neuropsychiatric and neurodegenerative disorders such as depression and Parkinson’s disease, and future application for the treatment of prostate cancer, congestive heart failure and Alzheimer’s disease. In addition, high potency 2-imidazoline-derived MAO inhibitors may be used as potential probes for the imidazoline binding sites of the MAOs, as well as to determine alternative binding regions of imidazoline within the MAO active site.     

Double-exponential kinetics of binding and redistribution of the fluorescent dyes in cell membranes witness for the existence of lipid microdomains

New technique of detecting lateral heterogeneity of the plasma membrane of living cells by means of membrane-binding fluorescent dyes is proposed. The kinetics of dye incorporation into the membrane or its lateral diffusion inside the membrane is measured and decomposed into exponential components by means of the Maximum Entropy Method. Two distinct exponential components are obtained consistently in all cases for several fluorescent dyes, two different cell lines and in different types of experiments including spectroscopy, flow cytometry and fluorescence recovery after photobleaching. These components are attributed to the liquid-ordered and disordered phases in the plasma membrane of studied cells in their dynamic equilibrium.     

Do alternative reproductive strategies in the Wellington tree weta represent different behavioural types?

In many animal species, variation in reproductive success among individuals has led to the evolution of alternative mating strategies, which in the case of insects can often be correlated with developmental trajectories. In the Wellington tree weta, Hemideina crassidens, males can mature at the 8th, 9th or 10th instar, while females mature at the 10th instar only. A number of morphological attributes including male head and mandible size correlate with final instar number, and as these attributes represent a form of weaponry, they are often used in mate/site guarding and male–male competition. Tenth instar males have larger head/mandible/body sizes and show a conventional (guarder) reproductive strategy, whereas smaller 8th instar males typically show an unconventional (sneaker) strategy. In contrast, 9th instar males are predicted to adopt a “jack‐of‐all‐trades” strategy whereby they can fight or sneak depending context. Here, we tested whether alternative reproductive morphs exhibit strategy‐specific differences in risk‐taking associated with refuge emergence, activity and antipredator behaviour and further, whether these traits correlate to form a behavioural syndrome. We found that tree weta show consistent and repeatable differences in activity and refuge use at the individual level; however, behavioural covariances suggest that only 8th instar males exhibit a behavioural syndrome. That 9th instar males show high plasticity and variance in their gallery‐related behaviours supports the hypothesis that these males are a “jack‐of‐all‐trades.” Contrary to our predictions, antipredator behaviour was not correlated with other traits, and differences in behaviour overall were consistently more pronounced between individuals rather than between male morphs or sexes.     

Allometry of the limb bones of mammals from shrews (Sorex) to elephant (Loxodonta)

Measurements have been made of the principal leg bones of 37 species representing almost the full range of sizes of terrestrial mammals. The lengths of corresponding bones tend to be proportional to (body mass)^0·35 and the diameters to (body mass)^0·36, except in the family Bovidae in which the exponents for length are much nearer the value of 0·25 predicted by McMahon's (1973) theory of elastic similarity. Comparisons are made between mammals of similar size belonging to different orders.     

Regulatory interaction between mitochondrial genes. II. Detailed characterization of novel mutants mapping within one cluster in the cob2 region.

These studies describe the properties of three mit- mutants designated EM17, EM25, and PZ1, all mapping at two closely linked sites near one of the boundaries of the region of the mitochondrial genome concerned with the specification of cytochrome b. They all exhibit complex phenotypes affecting cytochrome b, cytochrome aa3, and additional polypeptides not found in the wild type. In the case of EM 17 this complexity can be ascribed to the presence of two mutations induced in the course of the initial mutagenic treatment: one, the cob2 mutation proper, is responsible for the loss of cytochrome b which is replaced by an altered, functionally inactive polypeptide, cytochrome b. This polypeptide can be further modified, or even eliminated, by the controlled introduction of another mutation in the cob1 segment of the cob region. The reduction in cytochrome oxidase subunit I, responsible for the effects on cytochrome aa3 and enzymatic activity in EM17, is due to a second (not mit-) mutation that has been located in the par1-proximal segment of the oxi3 region. This second mutation as well as the cob mutation can be overcome, and the respective aspect of wild type function restored to EM17, by recombination with rho- strains retaining the appropriate segment(s) of the wild type genome. The phenotype of the other two mutants is due to a single mutagenic event. This conclusion is confirmed by their ability to restore wild type functions by reversion. The mutation in EM25 appears to be due to a frameshift, which has led to premature chain termination, producing a polypeptide of Mr = 15,000 related to apocytochrome b. This change is accompanied by a decrease in the amount of subunit I of cytochrome oxidase. Revertants fall into three classes: on galactose two produce a polypeptide indistinguishable from apocytochrome b, but vary in its amount, while the third fails to increase apocytochrome b above mutant levels. Production of subunit I is increased but fails to reach wild type levels. Complete restoration of wild type functions can, however, be obtained by recombination of EM25 with rho- (cob2+) strains. Mutation PZ1 results in a complete absence of any polypeptide related to apocytochrome b and of cytochrome oxidase subunit I. These cells produce a novel polypeptide with a Mr = 45,000 not found in the wild type, and unrelated to all its normal polypeptides. Reversion or recombination with rho- (cob2+) strains results in virtually complete restoration of all wild type functions and the elimination of the novel polypeptide.     

The binding of lectins to components of plasma membranes from porcine submaxillary lymph node lymphocytes

By sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis the plasma membranes from porcine lymphocytes contain at least 30--35 glycopolypeptides and one or more glycolipids to which one or more of 12 purified lectins bind. The specificities of binding generally followed the same pattern as those of the reaction of the lectin with intact pig lymphocytes. Some lectins (e.g., the isolectin pair, Agaricus bisporus lectins A and B and a group consisting of the Lens culinaris A and B isolectins and the closely related Pisum sativum lectins) bind to almost identical populations of plasma membrane components and compete with each other for all their binding sites. Others (e.g., Concanavalin A and the Lens culinaris-Pisum sativum group and a group consisting of phytohemagglutinin-L, Ricinus communis lectin-60 and Ricinus communis lectin-120 bind in a cross reactive manner to some common binding moieties but, in addition, to certain nonshared ones. Still others (e.g., soybean agglutinin, peanut agglutinin and wheat germ agglutinin) do not share any common binding moieties with the other lectins. The amount of lectin binding and the number of membrane components to which a lectin binds is directly related to the Ka of binding of the lectin to the intact lymphocyte. Those with high Ka (Cocanavalin A Lens culinaris lectins, Pisum sativum lectins, phytohemagglutinin-L), bind to 20-30 different components giving very complex binding patterns while those with lower Ka (Agaricus bisporus lectins, wheat germ agglutinin, peanut agglutinin, and soybean agglutinin) bind to 8--13 components with easily distinguishable patterns. Soybean agglutinin binds almost exclusively to a glycolipid fraction while for the others one or more glycopolypeptides served as the major lectin-binding molecule. The Ricinus lectins, two lymphocyte toxins, bind to essentially every plasma membrane component to which the mitogen phytohemagglutinin-L binds, in fact competing for most of those plasma membrane moieties which bind phytohemagglutinin-L.     

Changes in metabolite profiles in Norway spruce shoot tips during short-day induced winter bud development and long-day induced bud flush

The seasonal change in photoperiod is a primary environmental signal influencing tree growth. Long days (LD) sustain growth, whereas short days (SD) induce winter bud formation. In this respect, metabolomic responses have been studied to a limited extent only in conifers. Here we identified changes in metabolite profile in the conifer Norway spruce after transition to SD and following re-transfer to LDs inducing bud flush. After 1 week in SD initial changes in metabolite profile was visible but for the majority of compounds magnitudes of changes were small. However, the ascorbate content was strongly reduced and there were often temporary increases in several energy metabolism-related compounds, secondary metabolites, nucleosides, amino acids and lipids. After 8 weeks in SD substantial changes were observed; proper winter buds had high pools of ABA, antioxidants, flavonoids, terpenoids, phenylpropanoids, sugars, amino acids and lipids related to stress tolerance and hardening, and low levels of nucleosides and metabolites in energy metabolism. One week after re-transfer to LD the metabolome was generally relatively similar to under long-term SD, except e.g. increased urate and strongly decreased ABA and oxidized glutathione. Two weeks later, bud flush had occurred, and the metabolite profile resembled the situation before transfer to SD. This study thus revealed comprehensive modulation of the metabolome in Norway spruce in response to a day length shift, indicating substantially increased stress resistance under SD-induced bud set, and reversal upon bud flush in LD.     

Ultrafast Redistribution of E. coli SSB along Long Single-Stranded DNA via Intersegment Transfer

Single-stranded DNA binding proteins (SSBs) selectively bind single-stranded DNA (ssDNA) and facilitate recruitment of additional proteins and enzymes to their sites of action on DNA. SSB can also locally diffuse on ssDNA, which allows it to quickly reposition itself while remaining bound to ssDNA. In this work, we used a hybrid instrument that combines single-molecule fluorescence and force spectroscopy to directly visualize the movement of Escherichia coli SSB on long polymeric ssDNA. Long ssDNA was synthesized without secondary structure that can hinder quantitative analysis of SSB movement. The apparent diffusion coefficient of E. coli SSB thus determined ranged from 70,000 to 170,000 nt²/s, which is at least 600 times higher than that determined from SSB diffusion on short ssDNA oligomers, and is within the range of values reported for protein diffusion on double-stranded DNA. Our work suggests that SSB can also migrate via a long-range intersegment transfer on long ssDNA. The force dependence of SSB movement on ssDNA further supports this interpretation.