New Medium for the Isolation and Enumeration of Pseudomonads

A new medium containing 200 ppb of 2-hydroxy-2',4,4'-trichlorodiphenyloxide (CH3565) and 10 ppm of cetyl-trimethyl-ammonium bromide (Cetrimide) in tryptic soy agar was developed and tested with 19 pure cultures of Pseudomonas, 20 microorganisms of other genera, commercially prepared ground beef, and laboratory-prepared inoculated ground beef. The new medium, CETCH agar, was compared with an antibiotic-containing medium. CETCH agar provided greater pseudomonad recoveries, a shorter incubation period prior to plate counting, and greater ease of preparation.     

Vestibular Loss and Balance Training Cause Similar Changes in Human Cerebral White Matter Fractional Anisotropy

Patients with bilateral vestibular loss suffer from severe balance deficits during normal everyday movements. Ballet dancers, figure skaters, or slackliners, in contrast, are extraordinarily well trained in maintaining balance for the extreme balance situations that they are exposed to. Both training and disease can lead to changes in the diffusion properties of white matter that are related to skill level or disease progression respectively. In this study, we used diffusion tensor imaging (DTI) to compare white matter diffusivity between these two study groups and their age- and sex-matched controls. We found that vestibular patients and balance-trained subjects show a reduction of fractional anisotropy in similar white matter tracts, due to a relative increase in radial diffusivity (perpendicular to the main diffusion direction). Reduced fractional anisotropy was not only found in sensory and motor areas, but in a widespread network including long-range connections, limbic and association pathways. The reduced fractional anisotropy did not correlate with any cognitive, disease-related or skill-related factors. The similarity in FA between the two study groups, together with the absence of a relationship between skill or disease factors and white matter changes, suggests a common mechanism for these white matter differences. We propose that both study groups must exert increased effort to meet their respective usual balance requirements. Since balance training has been shown to effectively reduce the symptoms of vestibular failure, the changes in white matter shown here may represent a neuronal mechanism for rehabilitation.     

Effect of oxygen minimum zone formation on communities of marine protists

Changes in ocean temperature and circulation patterns compounded by human activities are leading to oxygen minimum zone (OMZ) expansion with concomitant alteration in nutrient and climate active trace gas cycling. Here, we report the response of microbial eukaryote populations to seasonal changes in water column oxygen-deficiency using Saanich Inlet, a seasonally anoxic fjord on the coast of Vancouver Island British Columbia, as a model ecosystem. We combine small subunit ribosomal RNA gene sequencing approaches with multivariate statistical methods to reveal shifts in operational taxonomic units during successive stages of seasonal stratification and renewal. A meta-analysis is used to identify common and unique patterns of community composition between Saanich Inlet and the anoxic/sulfidic Cariaco Basin (Venezuela) and Framvaren Fjord (Norway) to show shared and unique responses of microbial eukaryotes to oxygen and sulfide in these three environments. Our analyses also reveal temporal fluctuations in rare populations of microbial eukaryotes, particularly anaerobic ciliates, that may be of significant importance to the biogeochemical cycling of methane in OMZs.     

Interactions between Diatoms and Bacteria

Summary: Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans.     

Ty3 Retrotransposon Hijacks Mating Yeast RNA Processing Bodies to Infect New Genomes

Retrotransposition of the budding yeast long terminal repeat retrotransposon Ty3 is activated during mating. In this study, proteins that associate with Ty3 Gag3 capsid protein during virus-like particle (VLP) assembly were identified by mass spectrometry and screened for roles in mating-stimulated retrotransposition. Components of RNA processing bodies including DEAD box helicases Dhh1/DDX6 and Ded1/DDX3, Sm-like protein Lsm1, decapping protein Dcp2, and 5’ to 3’ exonuclease Xrn1 were among the proteins identified. These proteins associated with Ty3 proteins and RNA, and were required for formation of Ty3 VLP retrosome assembly factories and for retrotransposition. Specifically, Dhh1/DDX6 was required for normal levels of Ty3 genomic RNA, and Lsm1 and Xrn1 were required for association of Ty3 protein and RNA into retrosomes. This role for components of RNA processing bodies in promoting VLP assembly and retrotransposition during mating in a yeast that lacks RNA interference, contrasts with roles proposed for orthologous components in animal germ cell ribonucleoprotein granules in turnover and epigenetic suppression of retrotransposon RNAs.     

Temporal expression and localization of protein farnesyltransferase during spermiogenesis and posttesticular sperm maturation in the hamster

Spermiogenesis and posttesticular sperm maturation in the epididymis are distinct developmental processes that result in a polarized spermatozoon possessing a plasma membrane partitioned into segment-specific domains of distinct composition and function. The mechanisms that specify the distribution of intracellular organelles and target proteins to restricted membrane domains are not well understood. In this study we examined the expression pattern and distribution of protein farnesyltransferase (FTase) in hamster spermatids and epididymal spermatozoa to determine if protein lipidation may represent a potential mechanism to regulate protein association with specific organelles or the plasma membrane. Round spermatids exhibited only weak immunostaining with antibody against the β-subunit of FTase, whereas elongating spermatids exhibited a high level of FTase expression that was segregated to the cytoplasmic lobe surrounding the anterior flagellum. Although FTase was released with the residual body, mature spermatids retained FTase within the midpiece and cytoplasmic droplet. In epididymal spermatozoa, FTase remained associated with the cytoplasmic droplet during its migration to the midpiece-principal piece junction; following release of the cytoplasmic droplet, no immunodetectable FTase was noted in the midpiece segment. Immunoblotting demonstrated the presence of both the α and β subunits of FTase in sperm lysates. The temporal expression pattern and restricted distribution of FTase in spermatids and epididymal spermatozoa suggest a potential role in regulating protein association with specific organelles and/or membrane domains of the mature spermatozoon. Mol. Reprod. Dev. 48:71–76, 1997. © 1997 Wiley-Liss, Inc.     

The relationship between oxidative/nitrative stress and pathological inclusions in Alzheimer's and Parkinson's diseases

Alzheimer's (AD) and Parkinson's diseases (PD) are late-onset neurodegenerative diseases that have tremendous impact on the lives of affected individuals, their families, and society as a whole. Remarkable efforts are being made to elucidate the dominant factors that result in the pathogenesis of these disorders. Extensive postmortem studies suggest that oxidative/nitrative stresses are prominent features of these diseases, and several animal models support this notion. Furthermore, it is likely that protein modifications resulting from oxidative/nitrative damage contribute to the formation of intracytoplasmic inclusions characteristic of each disease. The frequent presentation of both AD and PD in individuals and the co-occurrence of inclusions characteristic of AD and PD in several other neurodegenerative diseases suggests the involvement of a common underlying aberrant process. It can be surmised that oxidative/nitrative stress, which is cooperatively influenced by environmental factors, genetic predisposition, and senescence, may be a link between these disorders.     

The flavonoid chrysin attenuates colorectal pathological remodeling reducing the number and severity of pre-neoplastic lesions in rats exposed to the carcinogen 1,2-dimethylhydrazine

Phenolic compounds are naturally occurring, bioactive substances with marked antioxidant and anti-inflammatory potential. The flavonoid chrysin, found in high levels in honey bee propolis, inhibits the activity of enzymes involved in carcinogenesis. We have investigated the effect of chrysin on pre-neoplastic colorectal lesions (ACF, aberrant crypt foci) in a rat model of chemical carcinogenesis induced by 1,2-dimethylhydrazine (DMH). Female Wistar rats weighing 137.2?±?24.3 g received weekly one subcutaneous injection of DMH (20 mg/kg) for 10 weeks. The animals were divided into five groups each with seven animals: Group 1, 0.9% saline; Group 2, DMH+0.9% saline; Group 3, DMH+chrysin (10 mg/kg); Group 4, DMH+chrysin (100 mg/kg); Group 5, DMH+chrysin (200 mg/kg). Groups 2 and 3 showed a significant increase in ACF number, nucleolus organizer regions per enterocyte nucleus and nitrite/nitrate serum levels compared with Group 1. Groups 4 and 5 presented a significant reduction in all these parameters compared with Group 2. The levels of antioxidant minerals (copper, magnesium, selenium, zinc) and the number of enteroendocrine and mucin-producing cells were significantly reduced in Groups 2 and 3 but were similar in Groups 4 and 5 compared with Group 1. Chrysin, at 100 mg/kg and 200 mg/kg, was effective in attenuating pathological colorectal remodeling, reducing the number of pre-neoplastic lesions in rats exposed to DMH. Some of these effects might be attributable to the recovery of antioxidant mineral levels, a reduction in systemic nitrosative stress and an inhibition of the cellular proliferation induced by this flavonoid.