Perception's shadow: long-distance synchronization of human brain activity

Transient periods of synchronization of oscillating neuronal discharges in the frequency range 30-80 Hz (gamma oscillations) have been proposed to act as an integrative mechanism that may bring a widely distributed set of neurons together into a coherent ensemble that underlies a cognitive act. Results of several experiments in animals provide support for this idea. In humans, gamma oscillations have been described both on the scalp (measured by electroencephalography and magnetoencephalography) and in intracortical recordings, but no direct participation of synchrony in a cognitive task has been demonstrated so far. Here we record electrical brain activity from subjects who are viewing ambiguous visual stimuli (perceived either as faces or as meaningless shapes). We show for the first time, to our knowledge, that only face perception induces a long-distance pattern of synchronization, corresponding to the moment of perception itself and to the ensuing motor response. A period of strong desynchronization marks the transition between the moment of perception and the motor response. We suggest that this desynchronization reflects a process of active uncoupling of the underlying neural ensembles that is necessary to proceed from one cognitive state to another.

Brain events related to normal and moderately scrambled faces

The neural basis of normal and scrambled face processing was investigated by recording evoked potentials from 21 electrodes at standard EEG sites, with respect to a nose reference. Temporal negativities were found that result from two overlapping phenomena: they arise from the polarity reversal on temporal electrodes of the vertex P2, a positive wave peaking about 170-200 ms after the onset of a face stimulus, and also from an overlapping 'processing negativity' of long duration associated with the processing difficulty of the scrambled face stimulus. The comparisons of scalp potential and current density mappings support the proposal that some neuronal networks are active both for faces and scrambled faces and are compatible with the involvement of the superior temporal sulcus, the inferotemporal cortex and the parahippocampal and fusiform gyri, whereas the processing negativity would only involve the deepest generators of this network. Furthermore, the encoding of both faces and scrambled faces seems to take place predominantly in the right hemisphere.

Seen Gaze-Direction Modulates Fusiform Activity and Its Coupling with Other Brain Areas during Face Processing

Gaze-contact is often a preliminary to social interaction and so constitutes a signal for the allocation of processing resources to the gazing face. We investigated how gaze direction influences face processing in an fMRI study, where seen gaze and head direction could independently be direct or deviated. Direct relative to averted gaze elicited stronger activation for faces in ventral occipitotemporal cortices around the fusiform gyrus, regardless of head orientation. Moreover, direct gaze led to greater correlation between activity in the fusiform and the amygdala, a region associated with emotional responses and stimulus saliency. By contrast, faces with averted gaze (again, regardless of head orientation) yielded increased correlation between activity in the fusiform and the intraparietal sulcus, a region associated with shifting attention to the periphery.

Contrast polarity and face recognition in the human fusiform gyrus

Functional imaging has revealed face-responsive visual areas in the human fusiform gyrus, but their role in recognizing familiar individuals remains controversial. Face recognition is particularly impaired by reversing contrast polarity of the image, even though this preserves all edges and spatial frequencies. Here, combined influences of familiarity and priming on face processing were examined as contrast polarity was manipulated. Our fMRI results show that bilateral posterior areas in fusiform gyrus responded more strongly for faces with positive than with negative contrast polarity. An anterior, right-lateralized fusiform region is activated when a given face stimulus becomes recognizable as a well-known individual.

Spatial and temporal factors during processing of audiovisual speech: a PET study

Speech perception can use not only auditory signals, but also visual information from seeing the speaker's mouth. The relative timing and relative location of auditory and visual inputs are both known to influence crossmodal integration psychologically, but previous imaging studies of audiovisual speech focused primarily on just temporal aspects. Here we used Positron Emission Tomography (PET) during audiovisual speech processing to study how temporal and spatial factors might jointly affect brain activations. In agreement with previous work, synchronous versus asynchronous audiovisual speech yielded increased activity in multisensory association areas (e.g., superior temporal sulcus [STS]), plus in some unimodal visual areas. Our orthogonal manipulation of relative stimulus position (auditory and visual stimuli presented at same location vs. opposite sides) and stimulus synchrony showed that (i) ventral occipital areas and superior temporal sulcus were unaffected by relative location; (ii) lateral and dorsal occipital areas were selectively activated for synchronous bimodal stimulation at the same external location; (iii) right inferior parietal lobule was activated for synchronous auditory and visual stimuli at different locations, that is, in the condition classically associated with the 'ventriloquism effect' (shift of perceived auditory position toward the visual location). Thus, different brain regions are involved in different aspects of audiovisual integration. While ventral areas appear more affected by audiovisual synchrony (which can influence speech identification), more dorsal areas appear to be associated with spatial multisensory interactions.

Urodynamic findings in chronic retention of urine and their relevance to results of surgery

Fifty-five consecutive male patients aged 18-77 with chronic retention of urine were investigated urodynamically. All were shown to have obstructed micturition. Inflow cystometry defined two groups, one with high-pressure and one with low-pressure filling. Recent-onset enuresis and upper-tract dilatation as seen on radiography were significantly associated with high-pressure bladder filling. Postoperative studies showed that patients with high-pressure filling on preoperative cystometryhad a better response to outflow-tract surgery. The poor response of the patients with low-pressure filling was due to a high incidence of inadequate detrusor contraction leading to persistent residual urine. Thus urodynamic studies may be used to indicate which patients are likely to benefit from prostatectomy and, after the operation, whether the obstruction has been relieved.

Face and shape repetition effects in humans: a spatio-temporal ERP study

The neural bases of repetition effects for faces and non-significant shapes was studied using Mooneys' faces presented upright (face) or upside down (shape) with a repetition interval of 8 min 30 s-1. Scalp potentials and current density maps on 30 electrodes were compatible with an involvement of the infero-temporal and fusiform gyri (from 50 to at least 250 ms), mainly on the right, for both faces and shapes; the hippocampus and adjacent areas (around 300 ms), specifically for faces; the medial temporal lobes (450-650 ms) again independent of stimulus meaning. These results suggest that the facilitation of perception due to repetition involves both neocortical specialized areas and the medial temporal lobe, with different timings of activation. They further suggest that memory updating takes place more rapidly for faces than for meaningless shapes and that face recognition may be, at least partly, functionally encapsulated.

Water or antiseptic for periurethral cleaning before urinary catheterization: a randomized controlled trial

BACKGROUND

Despite a lack of empiric data to support the practice, traditionally, antiseptic solutions have been used to clean the periurethral area before inserting an indwelling catheter. The purpose of this study was to compare urinary colonization rates of subjects whose periurethral area was cleaned with water versus chlorhexidine 0.1% before the insertion of an indwelling urinary catheter.

METHODS

Obstetric patients who required urinary catheterization as part of their routine care were randomly assigned to either the "water" or "chlorhexidine" group with a sealed envelope. A sterile specimen of urine was collected 24 hours after insertion of the catheter.

RESULTS

Of the 436 patients (86.2%) with complete data (water group, 219; antiseptic group, 217), 38 (8.7%) had urinary tract bacteriuria >10(6) cfu/L. Rates of urinary tract infection were similar in each group (water group, 8.2%; antiseptic group, 9.2%; odds ratio 1.13; 95% confidence interval 0.58-2.21).

CONCLUSION

The practice of periurethral cleaning with an antiseptic did not decrease the rates of bacteriuria in this population and is probably not useful.

Clinical utility of hygroscopic heat and moisture exchangers in intensive care patients

OBJECTIVE

To compare the degree of bacterial circuit colonization, frequency of ventilator-associated pneumonia (VAP), character of respiratory secretions, rewarming of hypothermic patients, disposable costs, and air flow resistance in intensive care patients ventilated using either a heat and moisture exchanger (HME) or hot water (HW) humidifier circuit.

DESIGN

A prospective, randomized blinded trial of patients in the intensive care unit undergoing mechanical ventilation.

SETTING

A metropolitan teaching hospital.

PATIENTS

One hundred sixteen patients undergoing mechanical ventilation for a minimum period of 48 hrs were enrolled.

INTERVENTIONS

Patients were randomized to three ventilation groups using a) an HW circuit with a 2-day circuit change (n = 41); or b) a bacterial-viral filtering HME in the circuit, with either a 2-day (n = 42); or c) a 4-day circuit change (n = 33).

MEASUREMENTS AND MAIN RESULTS

Circuit colonization was assessed using quantitative culture of washings taken from the circuit tubing and semiquantitative culture of swabs from the Y connectors. Sixty-seven percent of HW circuits became contaminated compared with 12% in the two HME groups (p < .0001). Median colony counts were lower in the HME groups (p < .0001). If circuits at first circuit change were contaminated in the HW group, 89% of subsequent circuit changes became contaminated compared with 0% and 25% for the 2- and 4-day HME groups, respectively. The frequency of VAP, the time to resolution of admission hypothermia, and the volume and fluidity of secretions were similar for all groups. The resistance of the HME after 24 hrs of use was < 0.025 cm H2O/L at gas flows of 40 L/min. HME use resulted in a cost reduction of $1.48 (Australian)/day.

CONCLUSIONS

Circuits with a bacterial-viral filtering HME are less readily colonized by bacteria. Contamination is a random event. Humidification technique has no influence on the frequency rate of VAP, the effectiveness of rewarming, nor the character of the respiratory secretions. Breathing resistance is generally low and disposable costs are reduced when an HME is used.

Mutations of the XLRS1 gene cause abnormalities of photoreceptor as well as inner retinal responses of the ERG

Intensity-series rod and cone ERGs were recorded in 19 patients with XLRS and 26 control eyes. All patients were examined by one ophthalmologist and diagnosed on the basis of fundus appearance and evidence of the disease in other males in the same family. Mutations in the XLRS1 gene have been identified in 15 of the patients. Dark-adapted ERGs were significantly different from controls for all test conditions and for both a-wave and b-wave responses. Abnormalities were detectable in all patients but there was considerable variation in the severity of abnormality. One third of the patients had the dark-adapted 'negative-wave' response typically associated with inner retinal disorder, but about one third showed only mild depression of the b-wave while the remainder had abnormally low a-waves in addition to depressed b-waves. Light-adapted responses were also affected and both a-wave and b-wave responses differed significantly from controls, but the 'negative-wave' response was not seen in any patient. The severity of the ERG abnormality did not correlate with the classification of fundus appearance or patient age suggesting that retinal function is relatively stable throughout life. The severity of ERG abnormalities did not correlate with the type of mutation and responses could differ between affected males within the same family. These results indicate considerable heterogeneity of ERG response without clinical, age or genetic correlate. The abnormal a-wave responses indicate that photoreceptor as well as inner retinal layer function may be affected in XLRS, at least in some patients.

Silvazine (silver sulfadiazine and chlorhexidine) activity against 200 clinical isolates

The study was undertaken to examine the in vitro efficacy of Silvazine against micro-organisms commonly found in burn wounds. Two hundred non-replicative sequential clinical isolates were collected over a 2-month period. These comprised 50 Staphylococcus aureus (methicillin sensitive), 50 Staphylococcus aureus (methicillin resistant), 50 coagulase negative staphylococci and 50 Pseudomonas aeruginosa. As there is no standard test method, the method chosen was a pour plate overlay of micro-organisms placed on a Mueller Hinton base containing duplicate wells of 0.1 ml Silvazine. Plates were incubated at 35 degrees C for up to 48 h prior to examination. All organisms tested showed zones of growth inhibition. The mean diameters of the zones of growth inhibition were similar within genera. S. aureus 19.7 +/- 1.6 mm, MRSA 16.9 +/- 1.6 mm, P.aeruginosa 15.3 +/- 1.1 mm and coagulase negative staphylococci 20.8 +/- 2.1 mm. There was no bacterial regrowth within the zones of growth inhibition following long-term plate storage. In vitro testing of Silvazine has confirmed its efficiency against common burn wound isolates.

Magnetoencephalographic evidence of early processing of direction of gaze in humans

Despite the crucial importance of direction of gaze in social interactions, it is only recently that there has been interest in human brain responses to gaze direction. Using full-head magnetoencephalography, we investigated the correlates of direction of gaze in full faces and in eyes-only stimuli, measuring the early face-responsive component between 145 and 225 ms. Faces with eyes forward or averted had larger responses than faces with eyes up or closed. For eyes-only stimuli the shortest latencies were seen for eyes averted and the smallest amplitudes were seen for eyes closed. The data were explained by two dipoles in inferior-temporal regions, which showed greater activation for upright faces than face parts or inverted faces, as well as some sensitivity to direction of gaze in this very early stage of processing.

Comparison of the immediate, residual, and cumulative antibacterial effects of Novaderm R,* Novascrub R,* Betadine Surgical Scrub, Hibiclens, and liquid soap

BACKGROUND

Triclosan (Irgasan), an antibacterial active against staphylococci and coliform bacteria, has been formulated for use as a handwash. There has been only one previous report of the use of the glove juice test to determine the immediate, residual, and cumulative effects of a 1% triclosan-based handwash product. There have been no previous studies on the use of 1% triclosan combined with povidone-iodine (PI) in a handwash product.

METHODS

The glove juice technique was used to document and compare the immediate, 3-hour residual, and 5-day cumulative effects on the mean log10 bacterial counts of 1% triclosan-based handwash product and 1% triclosan with 5% PI. A standardized surgical handwashing technique was used before sample collection. These results and the identity and type of the aerobic bacteria cultured from the samples were compared with the results of standardized washing and glove juice sampling with 4% weight/volume chlorhexidine gluconate (CHG), 7.5% PI, and a nonantimicrobial liquid soap.

RESULTS

All five tested products showed significant log10 reduction from baseline on day 1, hour 0 (p < 0.05). There was no significant difference between the mean log10 bacterial count when 7.5% PI, 4% CHG, and 1% triclosan with 5% PI were compared with each other immediately after washing (p > 0.05). There was a significant difference between 1% triclosan and the liquid soap when they were each compared with 4% CHG, 7.5% PI, and 1% triclosan with 5% PI. There was no statistically significant difference between the 1% triclosan product and the liquid soap (p > 0.20). All products were effective at reducing the immediate bacterial count from the baseline level. All formulations except the liquid soap showed significant cumulative effect (p < 0.05) after multiple washes, with no significant difference between the cumulative effects of the liquid soap and 1% triclosan (p > 0.05). Both products differed significantly (p < 0.05) from the CHG, PI, and triclosan with PI. CHG, PI, and triclosan with PI showed effects significantly different from each other (p < 0.05).

CONCLUSIONS

Triclosan combined with PI resulted in the prevention of bacterial regrowth at 3 hours such as occurred when PI alone was used. Triclosan-containing products have a small cumulative effect, although not as great as that produced by CHG. The triclosan-based products did not appear to select for gram-negative bacterial overgrowth, although the study period may have been too short to detect such an effect.

Challenging endoscopy reprocessing guidelines: a prospective study investigating the safe shelf life of flexible endoscopes in a tertiary gastroenterology unit

BACKGROUND AND STUDY AIMS

Professional practice guidelines for endoscope reprocessing recommend reprocessing endoscopes between each case and proper storage following reprocessing after the last case of the list. There is limited empirical evidence to support the efficacy of endoscope reprocessing prior to use in the first case of the day; however, internationally, many guidelines continue to recommend this practice. The aim of this study is to estimate a safe shelf life for flexible endoscopes in a high-turnover gastroenterology unit.

MATERIALS AND METHODS

In a prospective observational study, all flexible endoscopes in active service during the 3-week study period were microbiologically sampled prior to reprocessing before the first case of the day (n = 200). The main outcome variables were culture status, organism cultured, and shelf life.

RESULTS

Among the total number of useable samples (n = 194), the overall contamination rate was 15.5%, with a pathogenic contamination rate of 0.5%. Mean time between last case one day and reprocessing before the first case on the next day (that is, shelf life) was 37.62 h (SD 36.47). Median shelf life was 18.8 h (range 5.27-165.35 h). The most frequently identified organism was coagulase-negative Staphylococcus, an environmental nonpathogenic organism.

CONCLUSIONS

When processed according to established guidelines, flexible endoscopes remain free from pathogenic organisms between last case and next day first case use. Significant reductions in the expenditure of time and resources on reprocessing endoscopes have the potential to reduce the restraints experienced by high-turnover endoscopy units and improve service delivery.

Differential processing of part-to-whole and part-to-part face priming: an ERP study

We provide electrophysiological evidence supporting the hypothesis that part and whole face processing involve distinct functional mechanisms. We used a congruency judgment task and studied part-to-whole and part-to-part priming effects. Neither part-to-whole nor part-to-part conditions elicited early congruency effects on face-specific ERP components, suggesting that activation of the internal representations should occur later on. However, these components showed differential responsiveness to whole faces and isolated eyes. In addition, although late ERP components were affected when the eye targets were not associated with the prime in both conditions, their temporal and topographical features depended on the latter. These differential effects suggest the existence of distributed neural networks in the inferior temporal cortex where part and whole facial representations may be stored.

An ERP study of famous face incongruity detection in middle age

Age-related changes in famous face incongruity detection were examined in middle-aged (mean = 50.6) and young (mean = 24.8) subjects. Behavioral and ERP responses were recorded while subjects, after a presentation of a "prime face" (a famous person with the eyes masked), had to decide whether the following "test face" was completed with its authentic eyes (congruent) or with other eyes (incongruent). The principal effects of advancing age were (1) behavioral difficulties in discriminating between incongruent and congruent faces; (2) a reduced N400 effect due to N400 enhancement for both congruent and incongruent faces; (3) a latency increase of both N400 and P600 components. ERPs to primes (face encoding) were not affected by aging. These results are interpreted in terms of early signs of aging.

Hybrid diffractive-refractive lenses and achromats

Hybrid elements containing optical power with both diffractive (holographic) and refractive components are shown to be useful for obtaining arbitrary or, in special cases, achromatic dispersive characteristics. In one configuration a volume holographic element is coated on the surface of a crown glass lens, and by varying the power distributions among the refractive and holographic components while maintaining constant overall optical power the effective Abbe V numbers of the resultant hybrid element are shown to span all real numbers excepting a narrow interval around zero. In the achromat case (V number = infinity), both refractive and diffractive components are of the same sign resulting in much smaller glass curvatures than in all-refractive achromat doublets or apochromat triplets. The large separation between holographic partial dispersions and available glass partial dispersions is shown to lead to hybrid three-color achromats with greatly reduced glass curvatures. Applications are expected to include broadband achromatic objectives and chromatic aberration corrector plates in high performance optical systems. Such corrector plates may have any net power (including zero) while exhibiting effective V numbers that are positive or negative and that span a wide range, e.g., +/-1 or +/-1000. Further advantages include reducing the need for choosing high dispersion glasses, which may be costly and difficult to grind or polish. High diffraction efficiency and broad spectral bandwidths (in excess of 3000 A) are obtained in the holographic optical elements using single-element central-stop and cascaded element designs.

System size, energy, pseudorapidity, and centrality dependence of elliptic flow

This Letter presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system.

Review article: the current treatment of non-cardiac chest pain

BACKGROUND

Non-cardiac chest pain is one of the most common functional gastrointestinal disorders. By recognising that gastro-oesophageal reflux disease (GERD), oesophageal dysmotility and oesophageal hypersensitivity are the main underlying mechanisms of NCCP, a more directed therapeutic approach has been developed.

AIM

To determine the value of the current therapeutic modalities for NCCP.

METHODS

Electronic (Pubmed/Medline/Cochrane central) and manual search.

RESULTS

Double-dose PPI treatment for two months is a reasonable first choice approach in patients with NCCP because GERD is the most common aetiology. Studies evaluating the role of medical therapy in NCCP patients with hypercontractile oesophageal motility suggest a limited value to muscle relaxants like calcium channel blockers (nifedipine, diltiazem), nitrates and sildenafil. While most trials evaluating pain modulators are small and many are not placebo-controlled, these type of medications appear efficacious in both patients with NCCP due to oesophageal dysmotility and those with functional chest pain. Cognitive behavioural therapy has been extensively studied in patients with functional chest pain with good results. Other psychological techniques such as hypnotherapy, group therapy or coping skills have been scarcely studied but appear to be effective in NCCP patients.

CONCLUSION

Medical, endoscopic and surgical therapeutic options are available for the treating physician, although some patients with non-cardiac chest pain may require a multimodal therapeutic approach.

Acute neuroinflammation induces AIS structural plasticity in a NOX2-dependent manner

Background

Chronic microglia-mediated inflammation and oxidative stress are well-characterized underlying factors in neurodegenerative disease, whereby reactive inflammatory microglia enhance ROS production and impact neuronal integrity. Recently, it has been shown that during chronic inflammation, neuronal integrity is compromised through targeted disruption of the axon initial segment (AIS), the axonal domain critical for action potential initiation. AIS disruption was associated with contact by reactive inflammatory microglia which wrap around the AIS, increasing association with disease progression. While it is clear that chronic microglial inflammation and enhanced ROS production impact neuronal integrity, little is known about how acute microglial inflammation influences AIS stability. Here, we demonstrate that acute neuroinflammation induces AIS structural plasticity in a ROS-mediated and calpain-dependent manner.

Methods

C57BL/6J and NOX2^−/− mice were given a single injection of lipopolysaccharide (LPS; 5 mg/kg) or vehicle (0.9% saline, 10 mL/kg) and analyzed at 6 h–2 weeks post-injection. Anti-inflammatory Didox (250 mg/kg) or vehicle (0.9% saline, 10 mL/kg) was administered beginning 24 h post-LPS injection and continued for 5 days; animals were analyzed 1 week post-injection. Microglial inflammation was assessed using immunohistochemistry (IHC) and RT-qPCR, and AIS integrity was quantitatively analyzed using ankyrinG immunolabeling. Data were statistically compared by one-way or two-way ANOVA where mean differences were significant as assessed using Tukey’s post hoc analysis.

Results

LPS-induced neuroinflammation, characterized by enhanced microglial inflammation and increased expression of ROS-producing enzymes, altered AIS protein clustering. Importantly, inflammation-induced AIS changes were reversed following resolution of microglial inflammation. Modulation of the inflammatory response using anti-inflammatory Didox, even after significant AIS disruption occurred, increased the rate of AIS recovery. qPCR and IHC analysis revealed that expression of microglial NOX2, a ROS-producing enzyme, was significantly increased correlating with AIS disruption. Furthermore, ablation of NOX2 prevented inflammation-induced AIS plasticity, suggesting that ROS drive AIS structural plasticity.

Conclusions

In the presence of acute microglial inflammation, the AIS undergoes an adaptive change that is capable of spontaneous recovery. Moreover, recovery can be therapeutically accelerated. Together, these findings underscore the dynamic capabilities of this domain in the presence of a pathological insult and provide evidence that the AIS is a viable therapeutic target.

Speckle reduction using multiple tones of illumination

The occurrence and smoothing of speckle are studied as a function of the line width for a highly collimated illuminating source. A general theory is presented for speckling in the image of a partially diffuse, phase type of object, which has a variable number of random scattering centers per resolution element. Then, an expression is derived for the wavelength spacing required to decouple the speckle patterns arising from two monochromatic tones in an imaging system, thereby establishing that it is feasible to smooth speckle using multicolor illumination. This theory is verified in a series of experiments using both laser illumination and band-limited light from a carbon arc. With highly collimated sources, we show that speckle appears laserlike for an imaged diffuser even up to line widths of 5 A. Then, smoothing of speckle is demonstrated in the imaging of a diffuser and for a section of an optic nerve when the illumination is provided by six narrow lines spread over 1500 A. Since with color-blind, panchromatic viewing the speckle smooths, a direct extension of this method to holographic microscopy, using a multitone laser, should permit one to record and reconstruct holograms of diffraction-limited resolution that are essentially speckle-free.

Comparison of the antibacterial efficacy of 4% chlorhexidine gluconate and 1% triclosan handwash products in an acute clinical ward

The antibacterial efficacy of 4% chlorhexidine gluconate (CHG) and 1% triclosan as handwash antiseptics is well established. Few published studies have identified hand bacteria found in glove juice samples, and most studies have used nonclinical study subjects. We report a longitudinal comparative study to determine the effect of 4% CHG and 1% triclosan on the composition of the hand bacterial flora of clinical staff in a specialist surgical unit. Prehandwash and posthandwash samples were collected on 3 separate occasions throughout each day by using the glove juice method and a supervised handwashing technique. Total bacterial counts were determined as well as counts for specific pathogens including methicillin-resistant Staphylococcus aureus and coliforms. Both 4% CHG and 1% triclosan were found to effectively reduce the total hand bacterial count preduty (P =.0001). Four percent CHG also was consistently more effective at reducing the total count than was 1% triclosan. However, 1% triclosan eliminated methicillin-resistant S aureus, whereas 4% CHG failed to do so (P =.0001). Gram-negative bacteria were more likely to be eliminated after the use of 4% CHG compared with 1% triclosan. This study is the first to report the effects of 1% triclosan on the bacterial flora present on the hands of clinical staff and demonstrates the ability of 1% triclosan to eliminate methicillin-resistant S aureus.

Does tea tree oil have a place in the topical treatment of burns?

Burnaid is a sorbalene-based cream containing 40 mg/g of tea tree oil and 1 mg/g of triclosan. This investigation was carried out to determine the effect of Burnaid, a commercial tea tree oil preparation, against Enterococcus faecalis (ATCC29212), Staphylococcus aureus (ATCC29213), Escherichia coli (ATCC25922), and Pseudomonas aeruginosa (ATCC27853), with the activity of the base product in the commercial preparation. The organisms were suspended in sterile saline (0.5 McFarland Standard) and inoculated onto horse blood agar (E. faecalis and S. aureus) or Mueller-Hinton agar (E. coli and P. aeruginosa). One hundred microliters of Burnaid unsterilized, Burnaid sterilized and the base product (Tinasolve) were placed in duplicate in wells cut into the agar plates. Sterility and inactivation cultures were also performed on the samples. None of the samples were found to be contaminated with bacteria prior to testing. Only S. aureus and E. coli showed zones of growth inhibition around the Burnaid and Tinasolve. Zones of growth inhibition (22 mm) were similar for the active product (Burnaid) and the base (Tinasolve). There was no activity against E. faecalis or P. aeruginosa. In view of our findings and literature indicating the cytotoxicity of tea tree oil against human fibroblasts and epithelial cells, it is recommended that this product should not be used on burn wounds.

Purification and Characterization of Ornithine Decarboxylase from Aspergillus terreus; Kinetics of Inhibition by Various Inhibitors

l-Ornithine decarboxylase (ODC) is the rate-limiting enzyme of de novo polyamine synthesis in humans and fungi. Elevated levels of polyamine by over-induction of ODC activity in response to tumor-promoting factors has been frequently reported. Since ODC from fungi and human have the same molecular properties and regulatory mechanisms, thus, fungal ODC has been used as model enzyme in the preliminary studies. Thus, the aim of this work was to purify ODC from fungi, and assess its kinetics of inhibition towards various compounds. Forty fungal isolates were screened for ODC production, twenty fungal isolates have the higher potency to grow on L-ornithine as sole nitrogen source. Aspergillus terreus was the most potent ODC producer (2.1 µmol/mg/min), followed by Penicillium crustosum and Fusarium fujikuori. These isolates were molecularly identified based on their ITS sequences, which have been deposited in the NCBI database under accession numbers MH156195, MH155304 and MH152411, respectively. ODC was purified and characterized from A. terreus using SDS-PAGE, showing a whole molecule mass of ~110 kDa and a 50 kDa subunit structure revealing its homodimeric identity. The enzyme had a maximum activity at 37 °C, pH 7.4-7.8 and thermal stability for 20 h at 37 °C, and 90 days storage stability at 4 °C. A. terreus ODC had a maximum affinity (K_m) for l-ornithine, l-lysine and l-arginine (0.95, 1.34 and 1.4 mM) and catalytic efficiency (k_cat/K_m) (4.6, 2.83, 2.46 × 10^-5 mM^-1·s^-1). The enzyme activity was strongly inhibited by DFMO (0.02 µg/mL), curcumin (IC₅₀ 0.04 µg/mL), propargylglycine (20.9 µg/mL) and hydroxylamine (32.9 µg/mL). These results emphasize the strong inhibitory effect of curcumin on ODC activity and subsequent polyamine synthesis. Further molecular dynamic studies to elucidate the mechanistics of ODC inhibition by curcumin are ongoing.