Mounting evidence has established that diet-induced obesity (DIO) is associated with deficits in hippocampus-dependent memory. The bulk of research studies dealing with this topic have utilized rats fed a high-fat diet as an experimental model. To date, there has been a paucity of research studies that have established whether the memory deficits exhibited in DIO rats can be recapitulated in mice. Moreover, the majority of experiments that have evaluated memory performance in rodent models of DIO have utilized memory tests that are essentially aversive in nature (i.e., Morris water maze). The current study sought to fill an empirical void by determining if mice maintained on a high-fat diet exhibit deficits in two non-aversive memory paradigms: novel object recognition (NOR) and object location memory (OLM). Here we report that mice fed a high-fat diet over 23 weeks exhibit intact NOR, albeit a marked impairment in hippocampus-dependent OLM. We also determined the existence of corresponding aberrations in gene expression within the hippocampus of DIO mice. DIO mice exhibited significant reductions in both SIRT1 and PP1 mRNA within the hippocampus. Our data suggest that mice maintained on a high-fat diet present with impaired hippocampus-dependent spatial memory and a corresponding alteration in the expression of genes that have been implicated in memory consolidation.

Translocation is a key strategy for conserving native subspecies of cutthroat trout Oncorhynchus clarkii that have declined markedly throughout their native range. Previous research showed that successful translocations of cutthroat trout in high‐elevation southern Rocky Mountain streams were more likely in streams with warm summer water temperature and led to the hypothesis that cold summer temperatures govern translocation success by limiting recruitment. We tested this by measuring the density and size of age‐0 cutthroat trout (greenback cutthroat trout O. c. stomias and Colorado River cutthroat trout O. c. pleuriticus) in six headwater streams in north‐central Colorado that varied in thermal characteristics. Surveys were conducted at peak emergence during 3 years in two widely spaced study reaches in each stream. Fry density increased with Celsius degree‐days accumulated during the growing season but did not vary significantly among years. We used laboratory data on the growth and survivorship of age‐0 cutthroat trout in three temperature regimes that were similar to those studied in the field to determine expected survivorship and size of fry at the start of winter, which occurred several weeks after peak emergence in our warmer reaches and coincided with emergence in colder reaches. Our results support the hypothesis that recruitment of native cutthroat trout in Colorado is limited by cold water temperatures that reduce growth and recruitment. High‐elevation streams, like those studied, that accumulate 900‐1,200 Celsius degree‐days during the growing season afford the best opportunity for cutthroat trout recruitment and translocation success. Streams that provide 800‐900 degree‐days probably sustain recruitment in some years, and those with less than 800 degree‐days are generally unsuitable for translocations because of a greater risk of recruitment failure and the smaller sizes attained by fry by the onset of winter.

Water temperature fundamentally influences aquatic diversity and ecosystem health. In Colorado, temperature water quality criteria were revised in January 2007 based on a rigorous evaluation of the thermal requirements of fish species resident in Colorado. This article presents an account of how this process was conducted, and details the resultant criteria. The purpose of developing these criteria was to protect coldwater and warmwater fishes, especially native species such as cutthroat trout (Oncorhynchus clarki), from thermal stress. As such, lethal temperatures and optimal temperature conditions were determined from a literature review for species of the state, and these data were compiled into the Colorado Temperature Database. Acute and chronic thermal thresholds were then calculated for individual fish species. Finally, assemblages of fish were grouped into thermal tiers and temperature criteria were developed based on biological criteria for each assemblage. A case study is presented detailing the integration of science and policy decisions that shaped the development of Colorado's coldwater temperature criteria. Some issues were not resolved during this revision of Colorado's temperature water quality criteria, including protection from thermal shock and from gross changes in diel and seasonal thermal variability.

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A new method is demonstrated for optically trapping micron-sized absorbing particles in air and obtaining their single-particle Raman spectra. A 488-nm Gaussian beam from an Argon ion laser is transformed by conical lenses (axicons) and other optics into two counter-propagating hollow beams, which are then focused tightly to form hollow conical beams near the trapping region. The combination of the two coaxial conical beams, with focal points shifted relative to each other along the axis of the beams, generates a low-light-intensity biconical region totally enclosed by the high-intensity light at the surface of the bicone, which is a type of bottle beam. Particles within this region are trapped by the photophoretic forces that push particles toward the low-intensity center of this region. Raman spectra from individual trapped particles made from carbon nanotubes are measured. This trapping technique could lead to the development of an on-line real-time single-particle Raman spectrometer for characterization of absorbing aerosol particles.