2-n-Pentyl-4-quinolinol produced by a marine Alteromonas sp. and its potential ecological and biogeochemical roles

Bacterium-bacterium interactions occur at intimate spatial scales on the order of micrometers, but our knowledge of interactions at this level is rudimentary. Antagonism is a potential interaction in such microenvironments. To study the ecological role of antibiosis, we developed a model system involving an antibiotic-producing isolate (SWAT5) derived from a marine particle and its dominant antibiotic product, 2-n-pentyl-4-quinolinol (PQ). This system was used to address questions about the significance of this antibiotic for microbial ecology and carbon cycling on particles. We characterized the chemical and inhibitory properties of PQ in relation to the mechanisms used by particle-associated bacteria in interacting with particles and with other attached bacteria. PQ was produced by SWAT5 only on surfaces. When SWAT5 was grown in polysaccharide matrices, PQ diffused within the matrices but not into the surrounding seawater. SWAT5 might thus be able to generate a localized zone of high antibiotic concentration on particles suspended or sinking through seawater. Target bacterial respiration was most sensitive to PQ (75 nM), while inhibition of DNA synthesis, protein synthesis, and bacterial motility required higher (micromolar) PQ levels. The presence of PQ altered the composition of the bacterial community that colonized and developed in a model particle system. PQ also inhibited Synechococcus and phytoplankton growth. Our results suggest that antibiosis may significantly influence community composition and activities of attached bacterial and thus regulate the biogeochemical fate of particulate organic matter in the ocean.     

Development of isothiocyanate-enriched broccoli,and its enhanced ability to induce phase 2 detoxification enzymes in mammalian cells

Broccoli florets contain low levels of 3-methylsuphinylpropyl and 4-methylsulphinylbutyl glucosinolates. Following tissue disruption, these glucosinolates are hydrolysed to the corresponding isothiocyanates (ITCs), which have been associated with anticarcinogenic activity through a number of physiological mechanisms including the induction of phase II detoxification enzymes and apoptosis. In this paper, we describe the development of ITC-enriched broccoli through the introgression of three small segments of the genome of Brassica villosa, a wild relative of broccoli, each containing a quantitative trait locus (QTL), into a broccoli genetic background, via marker-assisted selection and analysis of glucosinolates in the florets of backcross populations. Epistatic and heterotic effects of these QTLs are described. The ITC-enriched broccoli had 80-times the ability to induce quinone reductase (a standard assay of phase II induction potential) when compared to standard commercial broccoli, due both to an increase in the precursor glucosinolates and a greater conversion of these into ITCs.     

Role of dynein, dynactin, and CLIP-170 interactions in LIS1 kinetochore function

Mutations in the human LIS1 gene cause type I lissencephaly, a severe brain developmental disease involving gross disorganization of cortical neurons. In lower eukaryotes, LIS1 participates in cytoplasmic dynein-mediated nuclear migration. We previously reported that mammalian LIS1 functions in cell division and coimmunoprecipitates with cytoplasmic dynein and dynactin. We also localized LIS1 to the cell cortex and kinetochores of mitotic cells, known sites of dynein action. We now find that the COOH-terminal WD repeat region of LIS1 is sufficient for kinetochore targeting. Overexpression of this domain or full-length LIS1 displaces CLIP-170 from this site without affecting dynein and other kinetochore markers. The NH2-terminal self-association domain of LIS1 displaces endogenous LIS1 from the kinetochore, with no effect on CLIP-170, dynein, and dynactin. Displacement of the latter proteins by dynamitin overexpression, however, removes LIS1, suggesting that LIS1 binds to the kinetochore through the motor protein complexes and may interact with them directly. We find that of 12 distinct dynein and dynactin subunits, the dynein heavy and intermediate chains, as well as dynamitin, interact with the WD repeat region of LIS1 in coexpression/coimmunoprecipitation and two-hybrid assays. Within the heavy chain, interactions are with the first AAA repeat, a site strongly implicated in motor function, and the NH2-terminal cargo-binding region. Together, our data suggest a novel role for LIS1 in mediating CLIP-170-dynein interactions and in coordinating dynein cargo-binding and motor activities.     

Increased prevalence of Brucella suis and pseudorabies virus antibodies in adults of an isolated feral swine population in coastal South Carolina

Two hundred twenty seven adult (> 8 mo) feral swine (Sus scrofa) trapped from April through July 1999 at three locations on a coastal South Carolina (USA) peninsula with restricted ingress and egress were tested for Brucella suis and pseudorabies virus (PRV) antibodies. Approximately 44% of the animals tested positive for B. suis antibodies and 61% tested positive for antibodies to PRV. Previous surveys (1976 and 1992) of feral swine at the same location with similar methods indicated lower seroprevalences (28% and 18% for B. suis and 0% and 19% for PRV). We also found 39% of feral swine seropositive (n = 179) for Trichinella spiralis and 49% seropositive (n = 181) for Toxoplasma gondii. Results of repeated sampling demonstrated that seroprevalence to pathogens can increase with time in an isolated, unhunted population of feral swine suggesting an increased risk to local domestic livestock and potentially to human health.     

Contraction-induced injury to single muscle fibers: velocity of stretch does not influence the force deficit

We tested the null hypothesis that theseverity of injury to single muscle fibers following a singlepliometric (lengthening) contraction is not dependent on the velocityof stretch. Each single permeabilized fiber obtained from extensordigitorum longus muscles of rats was maximally activated and thenexposed to a single stretch of either 5, 10, or 20% strain [%of fiber length (L_f)] ata velocity of 0.5, 1.0, or 2.0 L_f /s. Theforce deficit, the difference between maximum tetanic isometric force(P_o) before and after the stretch expressed as apercentage of the control value forP_o before the stretch, provided anestimate of the magnitude of muscle injury. Despite a fourfold rangefrom the lowest to the highest velocities, force deficits were notdifferent among stretches of the same strain. At stretches of 20%strain, even an eightfold range of velocities produced no difference inthe force deficit, although 40% of the fibers were torn apart at a velocity of 4 L_f /s. We conclude that, withinthe range of velocities tolerated by single permeabilized fibers, theseverity of contraction-induced injury is not related to the velocityof stretch.

     

2-n-Pentyl-4-Quinolinol Produced by a Marine Alteromonas sp. and Its Potential Ecological and Biogeochemical Roles

Bacterium-bacterium interactions occur at intimate spatial scales on the order of micrometers, but our knowledge of interactions at this level is rudimentary. Antagonism is a potential interaction in such microenvironments. To study the ecological role of antibiosis, we developed a model system involving an antibiotic-producing isolate (SWAT5) derived from a marine particle and its dominant antibiotic product, 2-n-pentyl-4-quinolinol (PQ). This system was used to address questions about the significance of this antibiotic for microbial ecology and carbon cycling on particles. We characterized the chemical and inhibitory properties of PQ in relation to the mechanisms used by particle-associated bacteria in interacting with particles and with other attached bacteria. PQ was produced by SWAT5 only on surfaces. When SWAT5 was grown in polysaccharide matrices, PQ diffused within the matrices but not into the surrounding seawater. SWAT5 might thus be able to generate a localized zone of high antibiotic concentration on particles suspended or sinking through seawater. Target bacterial respiration was most sensitive to PQ (75 nM), while inhibition of DNA synthesis, protein synthesis, and bacterial motility required higher (micromolar) PQ levels. The presence of PQ altered the composition of the bacterial community that colonized and developed in a model particle system. PQ also inhibited Synechococcus and phytoplankton growth. Our results suggest that antibiosis may significantly influence community composition and activities of attached bacterial and thus regulate the biogeochemical fate of particulate organic matter in the ocean.     

Contractile properties of EDL and soleus muscles of myostatin-deficient mice.

Myostatin is a negative regulator of muscle mass. The impact of myostatin deficiency on the contractile properties of healthy muscles has not been determined. We hypothesized that myostatin deficiency would increase the maximum tetanic force (P(o)), but decrease the specific P(o) (sP(o)) of muscles and increase the susceptibility to contraction-induced injury. The in vitro contractile properties of extensor digitorum longus (EDL) and soleus muscles from wild-type (MSTN(+/+)), heterozygous-null (MSTN(+/-)), and homozygous-null (MSTN(-/-)) adult male mice were determined. For EDL muscles, the P(o) of both MSTN(+/-) and MSTN(-/-) mice were greater than the P(o) of MSTN(+/+) mice. For soleus muscles, the P(o) of MSTN(-/-) mice was greater than that of MSTN(+/+) mice. The sP(o) of EDL muscles of MSTN(-/-) mice was less than that of MSTN(+/+) mice. For soleus muscles, however, no difference in sP(o) was observed. Following two lengthening contractions, EDL muscles from MSTN(-/-) mice had a greater force deficit than that of MSTN(+/+) or MSTN(+/-) mice, whereas no differences were observed for the force deficits of soleus muscles. Myostatin-deficient EDL muscles had less hydroxyproline, and myostatin directly increased type I collagen mRNA expression and protein content. The difference in the response of EDL and soleus muscles to myostatin may arise from differences in the levels of a myostatin receptor, activin type IIB. Compared with the soleus, the amount of activin type IIB receptor was approximately twofold greater in EDL muscles. The results support a significant role for myostatin not only in the mass of muscles but also in the contractility and the composition of the extracellular matrix of muscles.