Blooms of Pseudo-nitzschia and domoic acid in the San Pedro Channel and Los Angeles harbor areas of the Southern California Bight, 2003–2004

Abundances of Pseudo-nitzschia spp. and concentrations of particulate domoic acid (DA) were determined in the Southern California Bight (SCB) along the coasts of Los Angeles and Orange Counties during spring and summer of 2003 and 2004. At least 1500 km² were affected by a toxic event in May/June of 2003 when some of the highest particulate DA concentrations reported for US coastal waters were measured inside the Los Angeles harbor (12.7 μg DA L⁻¹). Particulate DA levels were an order of magnitude lower in spring of 2004 (February and March), but DA concentrations per cell at several sampling stations during 2004 exceeded previously reported maxima for natural populations of Pseudo-nitzschia (mean = 24 pg DA cell⁻¹, range = 0–117 pg DA cell⁻¹). Pseudo-nitzschia australis dominated the Pseudo-nitzschia assemblage in spring 2004. Overall, DA-poisoning was implicated in >1400 mammal stranding incidents within the SCB during 2003 and 2004. Ancillary physical and chemical data obtained during our regional surveys in 2004 revealed that Pseudo-nitzschia abundances, particulate DA and cellular DA concentrations were inversely correlated with concentrations of silicic acid, nitrogen and phosphate, and to specific nutrient ratios. Particulate DA was detected in sediment traps deployed at 550 and 800 m depth during spring of 2004 (0.29–7.6 μg DA (g sediment dry weight)⁻¹). The highest DA concentration in the traps was measured within 1 week of dramatic decreases in the abundances of Pseudo-nitzschia in surface waters. To our knowledge these are the deepest sediment trap collections from which DA has been detected. Sinking of the spring Pseudo-nitzschia bloom may constitute a potentially important link between DA production in surface waters and benthic communities in the coastal ocean near Los Angeles. Our study indicates that toxic blooms of Pseudo-nitzschia are a recurring phenomenon along one of the most densely populated coastal stretches of the SCB and that the severity and magnitude of these events can be comparable to or greater than these events in other geographical regions affected by domoic acid.     

Oxidant stress during simulated ischemia primes cardiomyocytes for cell death during reperfusion

Ischemia-reperfusion injury induces oxidant stress, and the burst of reactive oxygen species (ROS) production after reperfusion of ischemic myocardium is sufficient to induce cell death. Mitochondrial oxidant production may begin during ischemia prior to reperfusion because reducing equivalents accumulate and promote superoxide production. We utilized a ratiometric redox-sensitive protein sensor (heat shock protein 33 fluorescence resonance energy transfer (HSP-FRET)) to assess oxidant stress in cardiomyocytes during simulated ischemia. HSP-FRET consists of the cyan and yellow fluorescent protein fluorophores linked by the cysteine-containing regulatory domain from bacterial HSP-33. During ischemia, ROS-mediated oxidation of HSP-FRET was observed, along with a decrease in cellular reduced glutathione levels. These findings were corroborated by measurements using redox-sensitive green fluorescent protein, another protein thiol ratiometric sensor, which became 93% oxidized by the end of simulated ischemia. However, cell death did not occur during ischemia, indicating that this oxidant stress is not sufficient to induce death before reperfusion. However, interventions that attenuate ischemic oxidant stress, including antioxidants or scavengers of residual O(2) that attenuate/prevent ROS generation during ischemia, abrogated cell death during simulated reperfusion. These findings reveal that, in isolated cardiomyocytes, sublethal H(2)O(2) generation during simulated ischemia regulates cell death during simulated reperfusion, which is mediated by the reperfusion oxidant burst.     

Studies on the activity of brown adipose tissue in suckling,pre-obese, obob mice

The properties and activity of brown adipose tissue have been investigated in suckling, pre-obese, $\text{ob}\text{ob}$ mice in order to determine whether decreased thermogenesis in the tissue precedes the development of obesity in this mutant. At 14 days of age there was no difference between the $\text{ob}\text{ob}$ and normal animals in the total amount of interscapular brown adipose tissue, and the DNA content, protein content, and cytochrome oxidase activity of the tissue were similar in the two groups of mice. Respiration rates of brown adipose tissue mitochondria in the presence of albumin were, however, greater in the normal than the $\text{ob}\text{ob}$ animals, although after the addition of GDP to recouple the mitochondria there was no difference between the two groups. The mitochondrial membrane potential, measured with [³H]methyltriphenylphosphonium, was less affected by exogenous GDP in $\text{ob}\text{ob}$ mice than in normal animals. GDP binding to brown adipose tissue mitochondria, an index of the proton conductance pathway, was much greater in normal than in $\text{ob}\text{ob}$ mice at both 10 and 14 days of age; the decreased GDP binding in the mutant animals was found to result from a reduction in the number of binding sites. It is concluded that brown adipose tissue mitochondria of pre-obese $\text{ob}\text{ob}$ mice are more tightly coupled than those of normal siblings, and that the activity of the ‘thermogenic’ proton conductance pathway is lower in the mutant animals. A decrease in thermogenesis in brown adipose tissue is therefore an early event in the development of the $\text{ob}\text{ob}$ mouse and precedes the appearance of obesity.     

Bacteriological Survey of Raw Beef Patties Produced at Establishments Under Federal Inspection

At the time of manufacture, 76% of 74 sets of raw beef patties collected in 42 federally inspected establishments had aerobic plate counts of 1,000,000 or fewer/g; 84% contained 100 or fewer coliforms/g; 92% contained 100 or fewer Escherichia coli/g; and 85% contained 100 or fewer Staphylococcus aureus/g (geometric means of 10 patties/set). Salmonellae were isolated from only three (0.4%) of 735 beef patties.     

ULTRASTRUCTURE OF THE CARPOSPOROPHYTE AND CARPOSPOROGENESIS IN THE PARASITIC RED ALGA PLOCAMIOCOLAX PULVINATA SETCH, (GIGARTINALES,PLOCAMIACEAE) 1

The ultrastructure of the carposporophyte and carposporogenesis is described for the parasitic red alga Plocamiocolax pulvinata Setch. After presumed fertilization the zygote nucleus is apparently transferred to the auxiliary cell which initiates gonimoblast cell production. These gonimoblast cells differentiate into storage or generative cells. Storage gonimoblast cells (SGC) are large and multinucleate, contain large quantities of starch and are located nearest the auxiliary cell, when compared to the smaller uninucleate, devoid of starch, generative gonimoblast cells (GGC) that form terminal lobes of carpospores. In addition, compressed membrane bodies and annulate lamellae are common in these cells. During carposporophyte maturation the amount of starch in the SGC's decreases and eventually the auxiliary cell, as well as SGC's, degenerate. Generative gonimoblast cells (GGC's) cleave repeatedly to form carpospores which are interconnected by small pit connections. Stage one-carpospores are recognized by their elongated shape, the formation of small     

DNA Polymerase α Subunit Residues and Interactions Required for Efficient Initiation Complex Formation Identified by a Genetic Selection

Biophysical and structural studies have defined many of the interactions that occur between individual components or subassemblies of the bacterial replicase, DNA polymerase III holoenzyme (Pol III HE). Here, we extended our knowledge of residues and interactions that are important for the first step of the replicase reaction: the ATP-dependent formation of an initiation complex between the Pol III HE and primed DNA. We exploited a genetic selection using a dominant negative variant of the polymerase catalytic subunit that can effectively compete with wild-type Pol III α and form initiation complexes, but cannot elongate. Suppression of the dominant negative phenotype was achieved by secondary mutations that were ineffective in initiation complex formation. The corresponding proteins were purified and characterized. One class of mutant mapped to the PHP domain of Pol III α, ablating interaction with the ϵ proofreading subunit and distorting the polymerase active site in the adjacent polymerase domain. Another class of mutation, found near the C terminus, interfered with τ binding. A third class mapped within the known β-binding domain, decreasing interaction with the β₂ processivity factor. Surprisingly, mutations within the β binding domain also ablated interaction with τ, suggesting a larger τ binding site than previously recognized.     

Isolation of a Novel Phage with Activity against Streptococcus mutans Biofilms

Streptococcus mutans is one of the principal agents of caries formation mainly, because of its ability to form biofilms at the tooth surface. Bacteriophages (phages) are promising antimicrobial agents that could be used to prevent or treat caries formation by S. mutans. The aim of this study was to isolate new S. mutans phages and to characterize their antimicrobial properties. A new phage, ɸAPCM01, was isolated from a human saliva sample. Its genome was closely related to the only two other available S. mutans phage genomes, M102 and M102AD. ɸAPCM01 inhibited the growth of S. mutans strain DPC6143 within hours in broth and in artificial saliva at multiplicity of infections as low as 2.5x10^-5. In the presence of phage ɸAPCM01 the metabolic activity of a S. mutans biofilm was reduced after 24 h of contact and did not increased again after 48 h, and the live cells in the biofilm decreased by at least 5 log cfu/ml. Despite its narrow host range, this newly isolated S. mutans phage exhibits promising antimicrobial properties.