Assessment of lexical semantic judgment abilities in alcohol-dependent subjects: An fMRI study

Neuropsychological studies have shown that alcohol dependence is associated with neurocognitive deficits in tasks requiring memory, perceptual motor skills, abstraction and problem solving, whereas language skills are relatively spared in alcoholics despite structural abnormalities in the language-related brain regions. To investigate the preserved mechanisms of language processing in alcohol-dependents, functional brain imaging was undertaken in healthy controls (n=18) and alcohol-dependents (n=16) while completing a lexical semantic judgment task in a 3 T MR scanner. Behavioural data indicated that alcohol-dependents took more time than controls for performing the task but there was no significant difference in their response accuracy. fMRI data analysis revealed that while performing the task, the alcoholics showed enhanced activations in left supramarginal gyrus, precuneus bilaterally, left angular gyrus, and left middle temporal gyrus as compared to control subjects. The extensive activations observed in alcoholics as compared to controls suggest that alcoholics recruit additional brain areas to meet the behavioural demands for equivalent task performance. The results are consistent with previous fMRI studies suggesting compensatory mechanisms for the execution of task for showing an equivalent performance or decreased neural efficiency of relevant brain networks. However, on direct comparison of the two groups, the results did not survive correction for multiple comparisons; therefore, the present findings need further exploration.     

Weighting of Spatial and Spectro-Temporal Cues for Auditory Scene Analysis by Human Listeners

The auditory system creates a neuronal representation of the acoustic world based on spectral and temporal cues present at the listener''s ears, including cues that potentially signal the locations of sounds. Discrimination of concurrent sounds from multiple sources is especially challenging. The current study is part of an effort to better understand the neuronal mechanisms governing this process, which has been termed “auditory scene analysis”. In particular, we are interested in spatial release from masking by which spatial cues can segregate signals from other competing sounds, thereby overcoming the tendency of overlapping spectra and/or common temporal envelopes to fuse signals with maskers. We studied detection of pulsed tones in free-field conditions in the presence of concurrent multi-tone non-speech maskers. In “energetic” masking conditions, in which the frequencies of maskers fell within the ±1/3-octave band containing the signal, spatial release from masking at low frequencies (∼600 Hz) was found to be about 10 dB. In contrast, negligible spatial release from energetic masking was seen at high frequencies (∼4000 Hz). We observed robust spatial release from masking in broadband “informational” masking conditions, in which listeners could confuse signal with masker even though there was no spectral overlap. Substantial spatial release was observed in conditions in which the onsets of the signal and all masker components were synchronized, and spatial release was even greater under asynchronous conditions. Spatial cues limited to high frequencies (>1500 Hz), which could have included interaural level differences and the better-ear effect, produced only limited improvement in signal detection. Substantially greater improvement was seen for low-frequency sounds, for which interaural time differences are the dominant spatial cue.     

Distribution of MT1 Melatonin Receptor Promoter-Driven RFP Expression in the Brains of BAC C3H/HeN Transgenic Mice

The pineal hormone melatonin activates two G-protein coupled receptors (MT₁ and MT₂) to regulate in part biological functions. The MT₁ and MT₂ melatonin receptors are heterogeneously distributed in the mammalian brain including humans. In the mouse, only a few reports have assessed the expression of the MT₁ melatonin receptor expression using 2-iodomelatonin binding, in situ hybridization and/or polymerase chain reaction (PCR). Here, we described a transgenic mouse in which red fluorescence protein (RFP) is expressed under the control of the endogenous MT₁ promoter, by inserting RFP cDNA at the start codon of MTNR1a gene within a bacterial artificial chromosome (BAC) and expressing this construct as a transgene. The expression of RFP in the brain of this mouse was examined either directly under a fluorescent microscope or immunohistochemically using an antibody against RFP (RFP-MT₁). RFP-MT₁ expression was observed in many brain regions including the subcommissural organ, parts of the ependyma lining the lateral and third ventricles, the aqueduct, the hippocampus, the cerebellum, the pars tuberalis, the habenula and the habenula commissure. This RFP-MT₁ transgenic model provides a unique tool for studying the distribution of the MT₁ receptor in the brain of mice, its cell-specific expression and its function in vivo.     

Melanin in <Emphasis Type="Italic">Fonsecaea pedrosoi</Emphasis>: a trap for oxidative radicals

Background  

The pathogenic fungus Fonsecaea pedrosoi constitutively produces the pigment melanin, an important virulence factor in fungi. Melanin is incorporated in the cell wall structure and provides chemical and physical protection for the fungus.     

土壤低剂量芘污染对蚯蚓若干生化指标的影响

通过人工污染土壤的方法,设计芘的暴露浓度为0、60、120、240、480、960μg.kg-1.暴露实验进行1、3、7和14d后,分别检测蚯蚓内脏中细胞色素P450含量、谷胱甘肽转移酶(GST)、超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性和丙二醛(MDA)含量.结果表明,在供试浓度范围内,蚯蚓内脏中各生化指标对污染物暴露指示的敏感性存在差异:其中P450含量、GST和SOD活性最为敏感;POD和CAT活性次之;而MDA含量未对低剂量的芘暴露起到明显的指示作用.研究同时发现,低剂量污染物暴露的时间效应要强于剂量效应的影响.因而,在进行生态毒性诊断时,采用多指标和多时段的检测对增强指示的灵敏性和有效性尤为重要.     

Fish cell culture: A new cell line fromCynoscion nebulosus

Summary A new fibroblast-like cell line, CyN, has been developed from muscle tissue of the marine fishCynoscion nebulosus (the spotted weakfish). A subline, CyN-1, was characterized fully and carried through 100 subcultures. CyN-1 is heteroploid and has a modal chromosome number of 49. The line is susceptible to LT-1, lymphocystis, eastern equine encephalitis and vesicular stomatitis viruses. Optimal growth occurred at 25° to 34° C in growth medium adjusted to 0.150m NaCl. This study was supported in part by the National Oceanographic and Atmospheric Administration, Office of Sea Grant No. 04-3-158-58.     

The kleptoplastic sea slug Elysia clarki prolongs photosynthesis by synthesizing chlorophyll a and b

Several species of kleptoplastic, sacoglossan sea slug photosynthesize using chloroplasts sequestered inside their digestive cells from algal food sources. However, sequestered chloroplasts alone are not sufficient for months-long, continuous photosynthesis and maintenance of the chloroplasts in absence of the algal nucleus. Some type of plastid maintenance mechanism must be present to help sustain photosynthetic activity in the long term kleptoplastic species, such as Elysia clarki. We demonstrate that E. clarki starved for 2 weeks are able to synthesize chlorophylls, but that slugs starved for 14 weeks no longer synthesize chlorophyll. The subsidence of chlorophyll synthesis is coincident with the cessation of photosynthesis by the starved slugs, but it is not yet known if the cessation of pigment synthesis is the cause or some other aspect of plastid degradation produces a loss of synthetic ability.     

Fish cell culture: Characteristics of a cell line from the silver perch,Bairdiella chrysura

Summary A cell line designated SP-1 was established from tissue of the silver perch,Bairdiella chrysura. Cells were fibroblast-like and grew best at 26°C in Leibovitz medium (L-15) containing 15% fetal bovine serum and 0.150m sodium chloride. Passage 1 to passage 9 SP-1 cells contained a chromosome number of 48; at passages 27 and 50 the modal numbers were 51 and 54, respectively. Confirmation of the origin of SP-1 cells was made by the cytotoxic antibody dye-exclusion test. This cell line supported the growth of lymphocystis virus from the silver perch but was not found to replicate various other fish and mammalian viruses. This study was supported in part by fund supplied by the Faculty Research Council of the University of Southern Mississippi and by the National Oceanographic and Atmospheric Administration, Office of Sea Grant No. 04-3-158-58. A portion of these results were presented at the 26th Annual Meeting of the Tissue Culture Association, Motreal, Canada, 1975.