The Augmentation of Retinogeniculate Communication during Thalamic Burst Mode.

Retinal signals are transmitted to cortex via neurons in the lateral geniculate nucleus (LGN), where they are processed in burst or tonic response mode. Burst mode occurs when LGN neurons are sufficiently hyperpolarized for T-type Ca2+ channels to deinactivate, allowing them to open in response to depolarization, which can trigger a high-frequency sequence of Na+-based spikes (i.e., burst). In contrast, T-type channels are inactivated during tonic mode and do not contribute to spiking. Although burst mode is commonly associated with sleep and the disruption of retinogeniculate communication, bursts can also be triggered by visual stimulation, thereby transforming the retinal signals relayed to the cortex. To determine how burst mode affects retinogeniculate communication, we made recordings from monosynaptically connected retinal ganglion cells and LGN neurons in male/female cats during visual stimulation. Our results reveal a robust augmentation of retinal signals within the LGN during burst mode. Specifically, retinal spikes were more effective and often triggered multiple LGN spikes during periods likely to have increased T-type Ca2+ channel activity. Consistent with the biophysical properties of T-type Ca2+ channels, analysis revealed that effect magnitude was correlated with the duration of the preceding thalamic interspike interval and occurred even in the absence of classically defined bursts. Importantly, the augmentation of geniculate responses to retinal input was not associated with a degradation of visual signals. Together, these results indicate a graded nature of response mode and suggest that, under certain conditions, bursts facilitate the transmission of visual information to the cortex by amplifying retinal signals.SIGNIFICANCE STATEMENT The thalamus is the gateway for retinal information traveling to the cortex. The lateral geniculate nucleus, like all thalamic nuclei, has two classically defined categories of spikes-tonic and burst-that differ in their underlying cellular mechanisms. Here we compare retinogeniculate communication during burst and tonic response modes. Our results show that retinogeniculate communication is enhanced during burst mode and visually evoked thalamic bursts, thereby augmenting retinal signals transmitted to cortex. Further, our results demonstrate that the influence of burst mode on retinogeniculate communication is graded and can be measured even in the absence of classically defined thalamic bursts.

Contrast gain control and retinogeniculate communication.

Visual information processed in the retina is transmitted to primary visual cortex via relay cells in the lateral geniculate nucleus (LGN) of the dorsal thalamus. Although retinal ganglion cells are the primary source of driving input to LGN neurons, not all retinal spikes are transmitted to the cortex. Here, we investigate the relationship between stimulus contrast and retinogeniculate communication and test the hypothesis that both the time course and strength of retinogeniculate interactions are dynamic and dependent on stimulus contrast. By simultaneously recording the spiking activity of synaptically connected retinal ganglion cells and LGN neurons in the cat, we show that the temporal window for retinogeniculate integration and the effectiveness of individual retinal spikes are inversely proportional to stimulus contrast. This finding provides a mechanistic understanding for the phenomenon of augmented contrast gain control in the LGN-a nonlinear receptive field property of LGN neurons whereby response gain during low-contrast stimulation is enhanced relative to response gain during high-contrast stimulation. In addition, these results support the view that network interactions beyond the retina play an essential role in transforming visual signals en route from retina to cortex.

Overlapping genetic and environmental influences among men's alcohol consumption and problems, romantic quality and social support.

BACKGROUND: Alcohol consumption and problems are associated with interpersonal difficulties. We used a twin design to assess in men the degree to which genetic or environmental influences contributed to the covariance between alcohol consumption and problems, romantic quality and social support. METHOD: The sample included adult male-male twin pairs (697 monozygotic and 487 dizygotic) for whom there were interview-based data on: alcohol consumption (average monthly alcohol consumption in the past year); alcohol problems (lifetime alcohol dependence symptoms); romantic conflict and warmth; friend problems and support; and relative problems and support. RESULTS: Key findings were that genetic and unique environmental factors contributed to the covariance between alcohol consumption and romantic conflict; genetic factors contributed to the covariance between alcohol problems and romantic conflict; and common and unique environmental factors contributed to the covariance between alcohol problems and friend problems. CONCLUSIONS: Recognizing and addressing the overlapping genetic and environmental influences that alcohol consumption and problems share with romantic quality and other indicators of social support may have implications for substance use prevention and intervention efforts.

Hearing impairment and deafness among HIV infected children and adolescents in Harare, Zimbabwe.

Background: Among HIV-infected children ear infections are recurrent and chronic, which may lead to hearing loss. Objective: To determine the prevalence, cause and severity of hearing impairment among HIV-infected children aged 5-17 years attending for HIV care in Harare. Design and Setting: An analytical cross-sectional survey conducted at Newlands Clinic, an opportunistic infections clinic in Harare. Materials and Methods: Participants underwent a standardised otoscopic examination of the ear and Pure Tone Audiometry (PTA). Factors associated with hearing impairment were investigated using multivariate logistic regression. Results: Three hundred and eighty (380) participants (55% female and mean age 11 years (SD: 3.3 years)) were consecutively recruited. The vast majority of participants (n=338; 89% were taking antiretroviral therapy (ART) for a median of 3 (IQR: 2-5) years at recruitment, and the most recent median CD4 Count (i.e. CD4 count measured within 6 months of the study recruitment) was 725 (IQR: 497-1000) cells/µL, with no difference by ART status. 61% (n= 231) of participants had an abnormal ear examination. Of the 359 participants who underwent audiometry, the prevalence of hearing impairment was 32.3% (95%CI: 27.5%-37.4%) based on a PTA threshold ≥26Db. Hearing impairment was associated with a recent CD4 count <350cell/µL (OR 2.1, P<0.037). Conclusion: There is a high prevalence of hearing impairment among HIV-infected children and adolescents. Low CD4 count remains a risk factor even among those who are on ART. We recommend that HIV infected children and adolescents, particularly those with low CD4 counts, should have routine evaluation of hearing as part of HIV care.

Evidence for multiple genetic factors underlying the DSM-IV criteria for alcohol dependence.

To determine the number of genetic factors underlying the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for alcohol dependence (AD), we conducted structural equation twin modeling for seven AD criteria, plus two summary screening questions, in 7133 personally interviewed male and female twins from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders, who reported lifetime alcohol consumption. The best-fit twin model required three genetic and two unique environmental common factors, and criterion-specific unique environmental factors. The first genetic factor was defined by high loadings for the probe question about quantity and frequency of alcohol consumption, and tolerance criterion. The second genetic factor loaded strongly on the probe question about self-recognition of alcohol-related problems and AD criteria for loss of control, desire to quit, preoccupation and activities given up. The third genetic factor had high loadings for withdrawal and continued use despite the problems criteria. Genetic factor scores derived from these three factors differentially predicted patterns of comorbidity, educational status and other historical/clinical features of AD. The DSM-IV syndrome of AD does not reflect a single dimension of genetic liability, rather, these criteria reflect three underlying dimensions that index risk for: (i) tolerance and heavy use; (ii) loss of control with alcohol associated social dysfunction and (iii) withdrawal and continued use despite problems. While tentative and in need of replication, these results, consistent with the rodent literature, were validated by examining predictions of the genetic factor scores and have implications for gene-finding efforts in AD.

The Groove Enhancement Machine (GEM): A Multi-Person Adaptive Metronome to Manipulate Sensorimotor Synchronization and Subjective Enjoyment.

Synchronization of movement enhances cooperation and trust between people. However, the degree to which individuals can synchronize with each other depends on their ability to perceive the timing of others' actions and produce movements accordingly. Here, we introduce an assistive device-a multi-person adaptive metronome-to facilitate synchronization abilities. The adaptive metronome is implemented on Arduino Uno circuit boards, allowing for negligible temporal latency between tapper input and adaptive sonic output. Across five experiments-two single-tapper, and three group (four tapper) experiments, we analyzed the effects of metronome adaptivity (percent correction based on the immediately preceding tap-metronome asynchrony) and auditory feedback on tapping performance and subjective ratings. In all experiments, tapper synchronization with the metronome was significantly enhanced with 25-50% adaptivity, compared to no adaptation. In group experiments with auditory feedback, synchrony remained enhanced even at 70-100% adaptivity; without feedback, synchrony at these high adaptivity levels returned to near baseline. Subjective ratings of being in the groove, in synchrony with the metronome, in synchrony with others, liking the task, and difficulty all reduced to one latent factor, which we termed enjoyment. This same factor structure replicated across all experiments. In predicting enjoyment, we found an interaction between auditory feedback and metronome adaptivity, with increased enjoyment at optimal levels of adaptivity only with auditory feedback and a severe decrease in enjoyment at higher levels of adaptivity, especially without feedback. Exploratory analyses relating person-level variables to tapping performance showed that musical sophistication and trait sadness contributed to the degree to which an individual differed in tapping stability from the group. Nonetheless, individuals and groups benefitted from adaptivity, regardless of their musical sophistication. Further, individuals who tapped less variably than the group (which only occurred ∼25% of the time) were more likely to feel "in the groove." Overall, this work replicates previous single person adaptive metronome studies and extends them to group contexts, thereby contributing to our understanding of the temporal, auditory, psychological, and personal factors underlying interpersonal synchrony and subjective enjoyment during sensorimotor interaction. Further, it provides an open-source tool for studying such factors in a controlled way.

Dynamics of Temporal Integration in the Lateral Geniculate Nucleus.

Before visual information from the retina reaches primary visual cortex (V1), it is dynamically filtered by the lateral geniculate nucleus (LGN) of the thalamus, the first location within the visual hierarchy at which nonretinal structures can significantly influence visual processing. To explore the form and dynamics of geniculate filtering we used data from monosynpatically connected pairs of retinal ganglion cells (RGCs) and LGN relay cells in the cat that, under anesthetized conditions, were stimulated with binary white noise and/or drifting sine-wave gratings to train models of increasing complexity to predict which RGC spikes were relayed to cortex, what we call "relay status." In addition, we analyze and compare a smaller dataset recorded in the awake state to assess how anesthesia might influence our results. Consistent with previous work, we find that the preceding retinal interspike interval (ISI) is the primary determinate of relay status with only modest contributions from longer patterns of retinal spikes. Including the prior activity of the LGN cell further improved model predictions, primarily by indicating epochs of geniculate burst activity in recordings made under anesthesia, and by allowing the model to capture gain control-like behavior within the awake LGN. Using the same modeling framework, we further demonstrate that the form of geniculate filtering changes according to the level of activity within the early visual circuit under certain stimulus conditions. This finding suggests a candidate mechanism by which a stimulus specific form of gain control may operate within the LGN.

Accounting for the association between childhood maltreatment and alcohol-use disorders in males: a twin study.

BACKGROUND: An association between childhood maltreatment and subsequent alcohol abuse and/or dependence (AAD) has been found in multiple studies of females. Less is known about the association between childhood maltreatment and AAD among males, and the mechanisms that underlie this association in either gender. One explanation is that childhood maltreatment increases risk for AAD. An alternative explanation is that the same genetic or environmental factors that increase a child's risk for being maltreated also contribute to risk for AAD in adulthood. METHOD: Lifetime diagnosis of AAD was assessed using structured clinical interviews in a sample of 3527 male participants aged 19-56 years from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders. The sources of childhood maltreatment-AAD association were estimated using both a matched case-control analysis of twin pairs discordant for childhood maltreatment and bivariate twin modeling. RESULTS: Approximately 9% of participants reported childhood maltreatment, defined as serious neglect, molestation, or physical abuse occurring before the age of 15 years. Those who experienced childhood maltreatment were 1.74 times as likely to meet AAD criteria compared with males who did not experience childhood maltreatment. The childhood maltreatment-AAD association largely reflected environmental factors in common to members of twin pairs. Additional exploratory analyses provided evidence that AAD risk associated with childhood maltreatment was significantly attenuated after adjusting for measured family-level risk factors. CONCLUSIONS: Males who experienced childhood maltreatment had an increased risk for AAD. Our results suggest that the childhood maltreatment-AAD association is attributable to broader environmental adversity shared between twins.

Economic impact of early intervention in people at high risk of psychosis.

BACKGROUND: Despite the increasing development of early intervention services for psychosis, little is known about their cost-effectiveness. We assessed the cost-effectiveness of Outreach and Support in South London (OASIS), a service for people with an at-risk mental state (ARMS) for psychosis. METHOD: The costs of OASIS compared to care as usual (CAU) were entered in a decision model and examined for 12- and 24-month periods, using the duration of untreated psychosis (DUP) and rate of transition to psychosis as key parameters. The costs were calculated on the basis of services used following referral and the impact on employment. Sensitivity analysis was used to test the robustness of all the assumptions made in the model. RESULTS: Over the initial 12 months from presentation, the costs of the OASIS intervention were pound1872 higher than CAU. However, after 24 months they were pound961 less than CAU. CONCLUSIONS: This model suggests that services that permit early detection of people at high risk of psychosis may be cost saving.

The Norwegian Institute of Public Health twin study of mental health: examining recruitment and attrition bias.

All Norwegian twin pairs born 1967-1974 and still living in Norway in 1992 were invited to a health questionnaire study (Q1). 2,570 pairs (65%) participated. These cohorts and the twin cohorts born 1967-1979 were invited to a new questionnaire study (Q2) in 1998. This time 3,334 pairs (53%) participated. Almost all pairs having participated in the 1998 study were invited to an interview study of mental health (MHS), taking place 1999-2004. 1,391 complete pairs (44%) participated. The questionnaire studies included extensive data on somatic health with fewer items on mental health and demography. Health-related and demographic information available from the Medical Birth Registry on all invited twins was applied to predict participation to the first study. A few registry variables indicating poor health predicted nonparticipation in Q1. Health information and demography from Q1 were tested as predictors of participation in the follow-up study (Q2). Monozygosity, female sex, being unmarried, having no children, and high education predicted participation, whereas few indicators of poor mental and somatic health and unhealthy lifestyle moderately predicted nonparticipation in Q2. No health indicators reported in Q2 predicted further participation. Standard genetic twin analyses of indicators of various mental disorders from Q2, validated by diagnostic data from the MHS, did not indicate differences in genetic/environmental covariance structures between participants and nonparticipants in MHS. In general the results show a moderate selection towards good mental and somatic health. Attrition from Q2 to the MHS does not appear to affect twin analyses of mental health related variables.

Leaching of nitrogen and phenolics from wood waste and co-composts used for road rehabilitation.

Rehabilitation and reforestation of disused forest roads and landings can be facilitated by the incorporation of organic matter. The British Columbia forest industry creates residual woody materials, but they are nutrient poor and may leach phenolic compounds. We assessed the potential for wood wastes (chipped cedar wood waste, sort-yard waste, hogfuel) and co-composts with shellfish waste or municipal biosolids to provide inorganic N and release phenolics and condensed tannins, compared with natural forest floor and mineral soil. Initial concentrations of tannins and phenolics were low, and 13C cross-polarization and magic-angle spinning nuclear magnetic resonance spectroscopy showed that composts were still dominated by wood. During a 426-d laboratory leaching experiment, release of phenolics from woody amendments (other than cedar wood) was lower than from native forest floor. The pH levels of woody amendments and their leachates were also within the range of native forest floor and soil (except cedar wood, which was the most acidic material). Co-composts had higher total N and available P, greatly reduced tannins and phenolics, and negligible leaching of polyphenols. Uncomposted materials released very little N during the incubation. Hogfuel-biosolids compost released a large amount of nitrate, but only during the first 100 d. Shrimp-wood compost released moderate amounts of ammonium and nitrate throughout the incubation, had high available P and low tannin content, and released less polyphenols than did native forest floors. Our results indicate that appropriate use of these amendments does not pose an environmental risk with regard to the parameters measured in this study.

Recreating a functioning forest soil in reclaimed oil sands in northern alberta: an approach for measuring success in ecological restoration.

During oil-sands mining all vegetation, soil, overburden, and oil sand is removed, leaving pits several kilometers wide and up to 100 m deep. These pits are reclaimed through a variety of treatments using subsoil or a mixed peat-mineral soil cap. Using nonmetric multidimensional scaling and cluster analysis of measurements of ecosystem function, reclamation treatments of several age classes were compared with a range of natural forest ecotypes to discover which treatments had created ecosystems similar to natural forest ecotypes and at what age this occurred. Ecosystem function was estimated from bioavailable nutrients, plant community composition, litter decomposition rate, and development of a surface organic layer. On the reclamation treatments, availability of nitrate, calcium, magnesium, and sulfur were generally higher than in the natural forest ecotypes, while ammonium, P, K, and Mn were generally lower. Reclamation treatments tended to have more bare ground, grasses, and forbs but less moss, lichen, shrubs, trees, or woody debris than natural forests. Rates of litter decomposition were lower on all reclamation treatments. Development of an organic layer appeared to be facilitated by the presence of shrubs. With repeated applications of fertilizers, measured variables for the peat-mineral amendments fell within the range of natural variability at about 20 yr. An intermediate subsoil layer reduced the need for fertilizer and conditions resembling natural forests were reached about 15 yr after a single fertilizer application. Treatments over tailings sand receiving only one application of fertilizer appeared to be on a different trajectory to a novel ecosystem.

Carbon accounting in the United Kingdom water sector: a review.

The UK is committed to greenhouse gas (GHG) emission reduction targets and has introduced a number of initiatives to achieve these. Until recently, these targeted energy-intensive industries and, thus, the water sector was not significantly affected. However, from 2010, UK water companies will need to report their emissions under the Carbon Reduction Commitment (CRC). Both Ofwat (the economic regulator for water companies in England and Wales) and the Northern Ireland Authority for Utility Regulation (NIAUR) now require annual reporting of GHG emissions in accordance with both Defra Guidelines and the CRC. Also, carbon impacts must now be factored into all water industry investment planning in England and Wales. Building on existing approaches, the industry has developed standardised carbon accounting methodologies to meet both of these requirements. This process has highlighted gaps in knowledge where further research is needed.

Prospective, randomized, single-blind, controlled study to compare two methods of performing adenoidectomy.

OBJECTIVE: To compare adenoidectomy using suction-diathermy ablation to curettage adenoidectomy with respect to operative time and adenoid regrowth at 6 months after surgery. STUDY DESIGN: A prospective, randomized, single-blind, study to compare two methods of performing adenoidectomy. A group of 100 children, undergoing adenoidectomy alone or in combination with tonsillectomy, were randomized into two groups and underwent either suction diathermy or curettage adenoidectomy by a single surgeon. SETTING: A tertiary care Paediatric Hospital. METHOD: Indication for surgery, adenoidal size, duration of surgery and complications were recorded and compared. Six-month follow-up was conducted and adenoidal size and symptom status were recorded and compared. Statistical analysis was performed using Microsoft Excel. RESULTS: One hundred patients participated in this study and underwent adenoidectomy alone or adenotonsillectomy. Ninety-two patients returned for follow-up and 91 patients completed the study. The two treatment groups were well matched for age and gender. The main indications for both groups were snoring, nasal obstruction and obstructive sleep apnoea. For adenoidectomy alone there was no significant difference in duration of surgery between the curette and suction diathermy groups. When performing tonsillectomy and adenoidectomy together suction diathermy took significantly longer to complete than curettage (P<0.001). Overall 96% of patients' symptoms had either improved or resolved. The post-operative comparison at 6 months showed a significant difference in the residual adenoidal size between the two groups, the suction diathermy group being generally smaller than the curettage group. CONCLUSIONS: Suction diathermy was better at reducing the adenoidal size 6 months after surgery. Although the difference in size was statistically significant it did not seem to be of clinical significance.

Tracheostomy in human immuno-deficiency virus infected children at the Red Cross War Memorial Children's Hospital, Cape Town, South Africa.

UNLABELLED: Tracheostomy in adults with HIV/AIDS has been reported to be associated with both high and early mortality of 47-100%. There is minimal data regarding the role of tracheostomy in HIV infected children. We did a retrospective analysis of HIV positive children that underwent tracheostomy at our institution over a 5-year period, 2002-2006. A total of 70 tracheostomies were done during the period and 15 (21.4%) of these children were confirmed as HIV infected. The average age at presentation for HIV infected children with upper airway obstruction resulting eventually in tracheostomy was 9.4 months and 60% were under 1 year of age. Only three (20%) were on Anti-Retroviral Therapy (ART) prior to presentation. The cause of upper airway obstruction was croup in 14 (93%) of these 15 children. Following tracheostomy all were treated with ART. To date six children have been successfully decannulated (40%) and there have been three deaths (20%) which were unrelated to tracheostomy. CONCLUSION: Tracheostomy in HIV positive children is not associated with the high mortality that has been reported in adults provided such children are started on treatment with antiretroviral therapy.

An investigation of the significance of Actinomycosis in tonsil disease.

OBJECTIVES: The objective of the study was to establish the incidence of Actinomycosis in the tonsils of children undergoing tonsillectomy or adenotonsillectomy, and to evaluate its role in clinical tonsillar disease. METHODS: This was a prospective controlled study done at the Red Cross Children's Hospital in Cape Town, South Africa over an 8-month period and included all children undergoing tonsillectomy or adenotonsillectomy. All resected tonsils were examined for the presence of Actinomycosis and any signs of significant cryptitis or active tonsillitis. A comparison was made in the incidence of Actinomycosis in children with obstructive sleep apnoea, recurrent tonsillitis or obstructive sleep apnoea and recurrent tonsillitis. The data was further analysed to determine the statistical significance of the association between Actinomycosis of the tonsils and age, sex and histopathological and clinical diagnosis. RESULTS: A total of 344 tonsils were analysed on 172 patients. We found 20 patients (11.6%) with Actinomycosis in the tonsils. The mean age of patients with Actinomycosis was 7.25 years and without Actinomycosis was 5.4 years (p=0.002). Most specimens (16) had no evidence of tissue reaction to Actinomyces, and their presence was found to be due to colonisation of the tonsils only. Actinomycosis was present in 11% of patients with obstructive sleep apnoea, 11% of patients with recurrent tonsillitis and in 9% with obstructive sleep apnoea and recurrent tonsillitis. The difference in incidence of Actinomycosis between these three groups (p=0.94), and between the recurrent tonsillitis group alone compared to the obstructive group (p=0.83), was not statistically significant. There was therefore no statistical significance found between Actinomyces and OSA+/- recurrent tonsillitis. CONCLUSIONS: There was no correlation found between the presence of tonsillar Actinomycosis and recurrent tonsillitis and/or obstructive tonsillar hypertrophy. Histopathologic findings showed no evidence of tissue reaction to Actinomyces and its presence was found to be due to colonisation of the tonsils only. The series did however show a statistically significant correlation between Actinomycosis colonisation and age with Actinomycosis being more common in older children, especially those over 5 years of age.

Is topical local anaesthesia necessary when performing paediatric flexible nasendoscopy? A double-blind randomized controlled trial.

OBJECTIVE: To evaluate the effectiveness of lignocain 2% and oxymetazoline 0.025% compared to oxymetazoline 0.025% alone when administered prior to fibreoptic nasendoscopy in paediatric patients. STUDY DESIGN: Prospective, randomized controlled, double-blind study. A group of 56 children, undergoing nasendoscopy to determine adenoidal size, were randomized into two groups and received either lignocain 2% and oxymetazoline 0.025% or oxymetazoline 0.025% alone prior to fibreoptic nasendoscopy. SETTING: A tertiary care Paediatric Hospital. METHOD: The endoscopist recorded the ease of performance of the procedure, cooperation of patient and quality of the view achieved using a visual analogue scale (VAS). The pain and anxiety levels of the child were recorded before, during and immediately after the procedure, using a VAS. The duration of performing the procedure was recorded from insertion of the endoscope into the nostril until removal. RESULTS: All 56 children were able to undergo the endoscopy and the full anxiety and pain assessment was done. Three children were excluded because they have undergone nasendoscopies before. Of the 53 patients included, 27 children received solution A (oxymetazoline 0.025%) and 26 children received solution B (oxymetazoline 0.025% and lignocain 2%). There was no statistical difference between the two groups regarding the duration of the endoscopy, quality of view, ease of performance and cooperation of the patients. The median pain and anxiety scores were not significantly different between the two groups. CONCLUSIONS: This study concludes that the use of a decongestant (oxymetazoline) for paediatric nasendoscopy is just as effective as the use of oxymetazoline with lignocain. Pain and anxiety is not increased in the absence of lignocain.

The effect of S-adenosylhomocysteine on DNA methylation in isolated rat liver nuclei.

DNA methylation was studied in vitro using whole nuclei from regenerating rat liver. Methyl incorporation from S-adenosyl-[Me-3H]methionine in nuclei from regenerating liver was four times higher than that of normal liver. The effect of S-adenosylhomocysteine on DNA methylation was examined, and it was found at equal molar concentrations of S-adenosylhomocysteine to to S-adenosylmethionine that DNA methylation was competitively inhibited 50%.

The structure of ribonuclease P protein from Staphylococcus aureus reveals a unique binding site for single-stranded RNA.

Ribonuclease P (RNaseP) catalyses the removal of the 5'-leader sequence from pre-tRNA to produce the mature 5' terminus. The prokaryotic RNaseP holoenzyme consists of a catalytic RNA component and a protein subunit (RNaseP protein), which plays an auxiliary but essential role in vivo by binding to the 5'-leader sequence and broadening the substrate specificity of the ribozyme. We determined the three-dimensional high-resolution structure of the RNaseP protein from Staphylococcus aureus (117 amino acid residues) by nuclear magnetic resonance (NMR) spectroscopy in solution. The protein has an alphabeta-fold, similar to the ribonucleoprotein domain. We used small nucleic acid molecules as a model for the 5'-leader sequence to probe the propensity for generic single-stranded RNA binding on the protein surface. The NMR results reveal a contiguous interaction site, which is identical with the previously identified leader sequence binding site in RNaseP holoenzyme. The conserved arginine-rich motif does not bind single-stranded RNA. It is likely that this peptide segment binds selectively to double-stranded sections of P RNA, which are conformationally more rigid. Given the essentiality of RNaseP for the viability of the organism, knowledge of the S. aureus protein structure and insight into its interaction with RNA will help us to develop RNaseP and RNaseP protein as targets for novel antibiotics against this pathogen.

RNA as a drug target.

Historically, the pharmaceutical industry has focused on proteins, rather than nucleic acids, as drug targets. But recent advances in the fields of RNA synthesis, structure determination and therapeutic target identification make the systematic exploitation of RNA as a drug target a realistic goal.