Spectral resolution of monkey primary auditory cortex (A1) revealed with two-noise masking

An important function of the auditory nervous system is to analyze the frequency content of environmental sounds. The neural structures involved in determining psychophysical frequency resolution remain unclear. Using a two-noise masking paradigm, the present study investigates the spectral resolution of neural populations in primary auditory cortex (A1) of awake macaques and the degree to which it matches psychophysical frequency resolution. Neural ensemble responses (auditory evoked potentials, multiunit activity, and current source density) evoked by a pulsed 60-dB SPL pure-tone signal fixed at the best frequency (BF) of the recorded neural populations were examined as a function of the frequency separation (DeltaF) between the tone and two symmetrically flanking continuous 80-dB SPL, 50-Hz-wide bands of noise. DeltaFs ranged from 0 to 50% of the BF, encompassing the range typically examined in psychoacoustic experiments. Responses to the signal were minimal for DeltaF = 0% and progressively increased with DeltaF, reaching a maximum at DeltaF = 50%. Rounded exponential functions, used to model auditory filter shapes in psychoacoustic studies of frequency resolution, provided excellent fits to neural masking functions. Goodness-of-fit was greatest for response components in lamina 4 and lower lamina 3 and least for components recorded in more superficial cortical laminae. Physiological equivalent rectangular bandwidths (ERBs) increased with BF, measuring nearly 15% of the BF. These findings parallel results of psychoacoustic studies in both monkeys and humans, and thus indicate that a representation of perceptual frequency resolution is available at the level of A1.     

Effect of defocusing and of distracted attention upon recordings of the visual evoked potential

Pattern reversal visual stimuli are used to evoke potentials (VEPs) for assessment of visual acuity and for localizing defects along the visual pathways. Our goal was to assess the importance of attention and defocusing to the recordings of pattern VEP. Forty-one volunteers with normal (6/6) corrected visual acuity participated in this study. Twenty-one were asked to defocus intentionally the visual stimulus (located 200cm away) by fixating at a target 25 or 50cm from the eye. Twenty other subjects performed auditory tasks to distract their attention from the visual stimulus. Pattern VEPs were elicited by different check sizes. The amplitude and time-to-peak of the P₁₀₀ wave were measured. Intentional defocusing caused amplitude reduction and prolongation of the time-to-peak in young subjects (20–34years old). With the smallest checks used (7.5) we could not record a reliable response from 43 of the young subjects (6 out of 14). In older patients (35–61years old), intentional defocusing induced negligible effects on pattern VEPs regardless of check size. There were no effects of auditory distraction upon the pattern VEPs. Our data suggest that intentional defocusing can produce false positive results (reduced VEP with prolonged time-to-peak) only when small checks are used in young subjects. Divided attention has negligible effect on the recordings of pattern VEPs. With proper controls, the pattern VEP test can be used for objective assessment of visual function.     

Identification of many microRNAs that copurify with polyribosomes in mammalian neurons

Localized translation in mammalian dendrites may play a role in synaptic plasticity and contribute to the molecular basis for learning and memory. The regulatory mechanisms that control localized translation in neurons are not well understood. We propose a role for microRNAs (miRNAs), a class of noncoding RNAs, as mediators of neuronal translational regulation. We have identified 86 miRNAs expressed in mammalian neurons, of which 40 have not previously been reported. A subset of these miRNAs exhibits temporally regulated expression in cortical cultures. Moreover, all of the miRNAs that were tested cofractionate with polyribosomes, the sites of active translation. These findings indicate that a large, diverse population of miRNAs may function to regulate translation in mammalian neurons.     

Acute mastoiditis in children: Pseudomonas aeruginosa as a leading pathogen

OBJECTIVE: Acute mastoiditis is a serious bacterial infection of the temporal bone and is the most common complication of otitis media. The goal of this study is to assess the clinical features, pathogens, management, and outcome of acute mastoiditis in children in northern Israel. METHODS: A systematic review of medical records of all children who were admitted with acute mastoiditis from January 1990 through December 2000. RESULTS: Fifty-seven children were included. Median was age: 36 months. In 26 patients (45.6%) mastoiditis complicated the first episode of acute otitis media (AOM). Twenty-five children (44%) received antibiotic treatment prior to admission. Frequent symptoms included mastoid area erythema in 54 children (94.7%), proptosis of the auricle in 52 children (91.2%) and fever in 43 children (75.4%). Middle ear, and subperiostal culture yielded growth of pathogen in 30 children (75%), two cultures yielded more then one pathogen. The most frequent pathogens were: Pseudomonas aeruginosa in 10 children (25%), Streptococcus pneumoniae in eight children (20%), Group A streptococcus in six children (15%). The highest incidence of Streptococcus pneumoniae was found in children who did not suffer from AOM before admission (35 vs. 5%). Fifty-two (91.2%) children were cured with antibiotic treatment alone. Seventeen children underwent computed tomography (CT) of the mastoid. Mastoid bone destruction was demonstrated in six children and subperiostal abscess in eight. Mastoidectomy was performed in five children. CONCLUSIONS: The diagnosis of acute mastoiditis can be made on clinical basis alone requiring CT only when complications are suspected. Half of the children admitted with acute mastoiditis had no previous history of recurrent AOM. In those children S. pneumoniae was the leading pathogen while P. aeruginosa was more prevalent in children with recurrent AOM. Most of the children recovered with medical therapy alone, without surgical intervention.     

Pregnancies in Gaucher disease: a 5-year study

OBJECTIVE: The study was undertaken to investigate the outcome of pregnancies in Gaucher disease, particularly in enzyme-treated women. STUDY DESIGN: A retrospective study was performed of pregnant women evaluated at a referral clinic. RESULTS: There were 43 (17 treated, 26 untreated) women with 66 pregnancies (23 treated, 43 untreated). The live birth rate was 78.3% among treated, 86.0% among untreated. One treated woman had three spontaneous abortions; 3 untreated women had one each. Four pregnancies in each group had postpartum bleeding, 7 requiring transfusions. Postpartum infections were prevalent among treated. Cesarean sections were generally for historic reasons. There was no exacerbation of Gaucher disease, except one bone crisis. CONCLUSION: Most untreated women with milder disease enjoyed an uncomplicated course. Enzyme-treated patients (ie, with more severe disease) had more bleeding and infections post partum, but few had spontaneous abortions. Hematologic consultation is recommended. A review of world experience with pregnant patients with Gaucher disease is included.     

DNA bending and unbending by MutS govern mismatch recognition and specificity

DNA mismatch repair is central to the maintenance of genomic stability. It is initiated by the recognition of base-base mismatches and insertion/deletion loops by the family of MutS proteins. Subsequently, ATP induces a unique conformational change in the MutS-mismatch complex but not in the MutS-homoduplex complex that sets off the cascade of events that leads to repair. To gain insight into the mechanism by which MutS discriminates between mismatch and homoduplex DNA, we have examined the conformations of specific and nonspecific MutS-DNA complexes by using atomic force microscopy. Interestingly, MutS-DNA complexes exhibit a single population of conformations, in which the DNA is bent at homoduplex sites, but two populations of conformations, bent and unbent, at mismatch sites. These results suggest that the specific recognition complex is one in which the DNA is unbent. Combining our results with existing biochemical and crystallographic data leads us to propose that MutS: (i) binds to DNA nonspecifically and bends it in search of a mismatch; (ii) on specific recognition of a mismatch, undergoes a conformational change to an initial recognition complex in which the DNA is kinked, with interactions similar to those in the published crystal structures; and (iii) finally undergoes a further conformational change to the ultimate recognition complex in which the DNA is unbent. Our results provide a structural explanation for the long-standing question of how MutS achieves mismatch repair specificity.     

Early Identification of Potential SSDI Entrants in California: The Predictive Value of State Disability Insurance and Workers’ Compensation Claims

Purpose Examine the potential for using information in short-term disability claims to identify workers at high risk of leaving the workforce and entering Social Security Disability Insurance (SSDI). Methods We analyze state-wide California data on claimants of State Disability Insurance (SDI) and Workers’ Compensation (WC) and present statistics on: (1) characteristics (primary diagnosis, sex, age, geography, wage level) by claim duration (0–3, 4–6, 7–12, 12?+ months); and (2) the ability of initial claim characteristics to predict duration of at least 12 months. All data are for claims with disability lasting more than 1 week. Results 22.2% of SDI claims last longer than 6 months and 12.5% last 12 months. More WC claims reach these durations: 33.7 and 18.6%, respectively. Long-term SDI and WC claimants are similar to SSDI awardees, nationwide, but differ in age distribution; they are typically younger. Conclusions Characteristics of SDI and WC claims can help predict claims likely to last 12 months, but more information is needed to effectively target early intervention services. Waiting longer to intervene improves targeting but risks missing opportunities where early intervention could be more effective. Collecting additional information at SDI or WC entry or soon thereafter could improve both the efficiency and timing of interventions.