Dysregulation of transforming growth factor beta signaling in scleroderma: overexpression of endoglin in cutaneous scleroderma fibroblasts

OBJECTIVE

As an initial approach to understanding the basis of the systemic sclerosis (SSc; scleroderma) phenotype, we sought to identify genes in the transforming growth factor beta (TGF beta) signaling pathway that are up-regulated in lesional SSc fibroblasts relative to their normal counterparts.

METHODS

We used gene chip, differential display, fluorescence-activated cell sorter, and overexpression analyses to assess the potential role of TGF beta signaling components in fibrosis. Fibroblasts were obtained by punch biopsy from patients with diffuse cutaneous SSc of 2-14 months' duration (mean 8 months) and from age- and sex-matched healthy control subjects.

RESULTS

Unexpectedly, we found that fibroblasts from SSc patients showed elevated expression of the endothelial cell-enriched TGF beta receptor endoglin. Endoglin is a member of the nonsignaling high-affinity TGF beta receptor type III family. The expression of endoglin increased with progression of disease. Transfection of endoglin in fibroblasts suppressed the TGF beta-mediated induction of connective tissue growth factor promoter activity.

CONCLUSION

SSc is characterized by overproduction of matrix; that is, genes that are targets of TGF beta signaling in normal fibroblasts. Our findings suggest that lesional SSc fibroblasts may overexpress endoglin as a negative feedback mechanism in an attempt to block further induction of profibrotic genes by TGF beta.

Gingival recession due to trauma caused by a lower lip stud

Body piercing seems to be increasing in popularity, with more patients attending for their routine check-up having had a tongue or lip stud placed. Many complications have been documented, some of them, particularly involving tongue piercing, can be life threatening. There appears to be fewer problems associated with lip piercing; however this case study illustrates the damage that a lip stud can cause to previously healthy gingival tissue.

Assessment of health-related quality-of-life in males with Anderson Fabry Disease before therapeutic intervention

Anderson Fabry Disease (AFD) is an extremely painful and debilitating multi-system X-linked disorder due to alpha-galactosidase enzyme deficiency. To date, no baseline data on health-related quality-of-life (HR-QoL) have been reported in males affected with this condition. In this study, 38 males with AFD completed Medical Outcomes Study Short Form, EuroQoL questionnaires and an AFD-specific questionnaire prior to the start of a trial involving replacement therapy with alpha-galactosidase. Results from these questionnaires were compared to the results from a similar HR-QoL study in males with severe haemophilia (factor VIII/IX deficiency) that used the same questionnaires and to the results of two large normative studies. The results on both questionnaires showed that in most instances males with AFD recorded significantly lower HR-QoL compared with males in the general population and individuals with severe haemophilia after adjusting for differences in age. These findings suggest therefore, that the scope for improvement in HR-QoL as a result of treatment with an appropriate agent is extremely large.

Can attention select only a fixed number of objects at a time?

Several previous studies have suggested that we may attend only a fixed number of 'objects' at a time. However, whereas findings from two-target experiments suggest that we can attend only one object at a time, other results from object-tracking and enumeration paradigms point instead to a four-object limit. Here, we note that in these previous studies the number of objects covaried with the overall size and complexity of the stimulus, such that apparent one-object or four-object limits in those tasks may reflect changes in the complexity of attended stimuli, rather than the number of objects per se. Accordingly, in the current experiments we employ stimuli in which the number of objects varies, while overall size and complexity are held constant. Using these refined measures of object-based effects, we find no evidence for a one-object or four-object limit on attention. Indeed, we conclude that the number of attended objects does not affect how efficiently we can attend a given stimulus. We propose and test an alternative approach to object-based attention limitations based on within-object and between-object feature-binding mechanisms in human vision.

Behavioral profiles of inbred strains on novel olfactory, spatial and emotional tests for reference memory in mice

Studying the behavior of genetic background strains provides important information for the design and interpretation of cognitive phenotypes in mutant mice. Our experiments examined the performance of three commonly used strains (C57BL/6J, 129S6, DBA/2J) on three behavioral tests for learning and memory that measure very different forms of memory, and for which there is a lack of data on strain differences. In the social transmission of food preference test (STFP) all three strains demonstrated intact memory for an odor-cued food that had been sampled on the breath of a cagemate 24 hours previously. While C57BL/6J and 129S6 mice showed good trace fear conditioning, DBA/2J mice showed a profound deficit on trace fear conditioning. In the Barnes maze test for spatial memory, the 129S6 strain showed poor probe trial performance, relative to C57BL/6J mice. Comparison of strains for open field exploratory activity and anxiety-like behavior suggests that poor Barnes maze performance reflects low exploratory behavior, rather than a true spatial memory deficit, in 129S6 mice. This interpretation is supported by good Morris water maze performance in 129S6 mice. These data support the use of a C57BL/6J background for studying memory deficits in mutant mice using any of these tasks, and the use of a 129S6 background in all but the Barnes maze. A DBA/2J background may be particularly useful for investigating the genetic basis of emotional memory using fear conditioning.

Prevention of spinal cord injury with time-frequency analysis of evoked potentials: an experimental study

OBJECTIVES

To verify the applicability and validity of time-frequency analysis (TFA) of evoked potential (EP) signals in detecting the integrity of spinal cord function and preventing spinal cord injury.

METHODS

The spinal cord was simulated during surgery in 20 mature rats by mechanically damaging the spinal cord. Cortical somatosensory evoked potential (CSEP), spinal somatosensory evoked potential (SSEP), cortical motor evoked potential (CMEP), and spinal cord evoked potential (SCEP) were used to monitor spinal cord function. Short time Fourier transform (STFT) was applied to the CSEP signal, and cone shaped distribution (CSD) was used as the TFA algorithm for SSEP, CMEP, and SCEP signals. The changes in the latency and amplitude of EP signals were measured in the time domain, and peak time, peak frequency, and peak power were measured in the time-frequency distribution (TFD).

RESULTS

The TFDs of EPs were found to concentrate in a certain location under normal conditions. When injury occurred, the energy decreased in peak power, and there was a greater dispersion of energy across the time-frequency range. Strong relations were found between latency and peak time, and amplitude and peak power. However, the change in peak power after injury was significantly larger than the corresponding change in amplitude (p<0.001 by ANOVA).

CONCLUSIONS

It was found that TFA of EPs provided an earlier and more sensitive indication of injury than time domain monitoring alone. It is suggested that TFA of EP signals should therefore be useful in preventing spinal cord injury during surgery.

A week of simulated night work delays salivary melatonin onset

In most studies, the magnitude and rate of adaptation to various night work schedules is assessed using core body temperature as the marker of circadian phase. The aim of the current study was to assess adaptation to a simulated night work schedule using salivary dim light melatonin onset (DLMO) as an alternative circadian phase marker. It was hypothesised that the night work schedule would result in a phase delay, manifest in relatively later DLMO, but that this delay would be somewhat inhibited by exposure to natural light. Participants worked seven consecutive simulated 8-hour night shifts (23:00-07:00 h). By night 7, there was a mean cumulative phase delay of 5.5 hours, equivalent to an average delay of 0.8 hours per day. This indicates that partial circadian adaptation occurred in response to the simulated night work schedule. The radioimmunoassay used in the current study provides a sensitive assessment of melatonin concentration in saliva that can be used to determine DLMO, and thus provides an alternative phase marker to core body temperature, at least in laboratory studies.

Calcium puffs are generic InsP3-activated elementary calcium signals and are downregulated by prolonged hormonal stimulation to inhibit cellular calcium responses

Elementary Ca2+ signals, such as ‘Ca2+ puffs’, which arise from the activation of inositol 1,4,5-trisphosphate receptors, are building blocks for local and global Ca2+ signalling. We characterized Ca2+ puffs in six cell types that expressed differing ratios of the three inositol 1,4,5-trisphosphate receptor isoforms. The amplitudes, spatial spreads and kinetics of the events were similar in each of the cell types. The resemblance of Ca2+ puffs in these cell types suggests that they are a generic elementary Ca2+ signal and, furthermore, that the different inositol 1,4,5-trisphosphate isoforms are functionally redundant at the level of subcellular Ca2+ signalling. Hormonal stimulation of SH-SY5Y neuroblastoma cells and HeLa cells for several hours downregulated inositol 1,4,5-trisphosphate expression and concomitantly altered the properties of the Ca2+ puffs. The amplitude and duration of Ca2+ puffs were substantially reduced. In addition, the number of Ca2+ puff sites active during the onset of a Ca2+ wave declined. The consequence of the changes in Ca2+ puff properties was that cells displayed a lower propensity to trigger regenerative Ca2+ waves. Therefore, Ca2+ puffs underlie inositol 1,4,5-trisphosphate signalling in diverse cell types and are focal points for regulation of cellular responses.

Dietary intakes and leisure-time physical activity in West Virginians

Poor diet and physical inactivity contribute to many chronic diseases in the United States each year. Diets low in saturated fatty acids and cholesterol and high in plant foods, i.e., fruits and vegetables, legumes and whole cereals, are protective. Physically active lifestyles are associated with lower risk of cardiovascular diseases, diabetes, obesity and some cancers. To access diet and physical activity levels in West Virginians, we conducted a study which was supported by the West Virginia Bureau for Public Health and the West Virginia University Prevention Research Center (CDC Cooperative Agreement). The purposes of this study were to estimate the proportion of the sample meeting recommendations for chronic disease prevention, and to examine if the individuals who were meeting the Surgeon General's physical activity recommendation for health are also consuming healthier diets. Our results showed that reducing saturated fatty acids and increasing consumption of folate, Vitamin E, calcium and fiber are of prime public health importance in West Virginia. Diet and activity levels were modestly related, suggesting that those who adopt a healthy diet also become more active and vice versa. Due to the cross-sectional nature of this data, it is unknown if single-strategy or dual interventions work best. Prospective studies are needed to determine optimal strategies.

Anderson-Fabry disease: clinical manifestations and impact of disease in a cohort of 98 hemizygous males

OBJECTIVES

To determine the natural history of Anderson-Fabry disease (AFD) as a baseline for efficacy assessment of potentially therapeutic drugs.

DESIGN

The first large cross sectional study of a patient cohort from the AFD clinical and genetic register (UK), maintained for the last 15 years.

MEASURES

Prevalence, mortality, frequency of AFD manifestations, and impact of disease on patient lives, assessed from the AFD register and the disease specific questionnaire.

RESULTS

The median cumulative survival was 50 years (n=51), which represents an approximately 20 year reduction of life span. Neuropathic pain was present in 77% (n=93) with mean pain score of 5 (scale 0-10) despite treatment with anticonvulsants and opiates. Pain stopped in only 11%. Cerebrovascular complications developed in 24.2% and renal failure in 30%. The onset and progression of serious AFD manifestations was highly variable. The relationship of gastrointestinal manifestations on weight, using body mass index (BMI), was significant (p=0.01). High frequency sensorineural deafness was confirmed in 78% of audiograms. Neuropathic pain and angiokeratoma were absent in five adult males (approximately 5%). Median age at diagnosis of AFD was 21.9 years (n=64).

IMPACT OF DISEASE

Attendance at school, sports, and social activity were significantly affected by AFD. Only 56.6% (n=46) of patients were employed. Psychosexual effects of genital angiokeratoma, genital pain, and impotence were not previously recognised.

CONCLUSION

The majority of males experience multiple disease manifestations and the duration of neuropathic pain was lifelong. The AFD register proved useful for the determination of baseline disease parameters in this cohort.

Complete genome sequence of Salmonella enterica serovar Typhimurium LT2

Salmonella enterica subspecies I, serovar Typhimurium (S. typhimurium), is a leading cause of human gastroenteritis, and is used as a mouse model of human typhoid fever. The incidence of non-typhoid salmonellosis is increasing worldwide, causing millions of infections and many deaths in the human population each year. Here we sequenced the 4,857-kilobase (kb) chromosome and 94-kb virulence plasmid of S. typhimurium strain LT2. The distribution of close homologues of S. typhimurium LT2 genes in eight related enterobacteria was determined using previously completed genomes of three related bacteria, sample sequencing of both S. enterica serovar Paratyphi A (S. paratyphi A) and Klebsiella pneumoniae, and hybridization of three unsequenced genomes to a microarray of S. typhimurium LT2 genes. Lateral transfer of genes is frequent, with 11% of the S. typhimurium LT2 genes missing from S. enterica serovar Typhi (S. typhi), and 29% missing from Escherichia coli K12. The 352 gene homologues of S. typhimurium LT2 confined to subspecies I of S. enterica-containing most mammalian and bird pathogens-are useful for studies of epidemiology, host specificity and pathogenesis. Most of these homologues were previously unknown, and 50 may be exported to the periplasm or outer membrane, rendering them accessible as therapeutic or vaccine targets.

Behavioral characterization of dopamine D5 receptor null mutant mice

To study behavioral functions of the D5 subtype, mice were generated with null mutations in the D5 gene. This 1st behavioral characterization of D5 null mutant mice (D5-/-) indicated normal general health, sensory abilities, and neurological reflexes. Under basal conditions, D5-/- mice were generally normal on locomotor activity, the rotarod test, acoustic startle response, prepulse inhibition, elevated plus-maze, light <--> dark exploration, Morris water maze, and cued and contextual fear conditioning. In the Porsolt forced swim test for antidepressant activity, male D5-/- mice showed lower levels of immobility. D5-/- mice showed some evidence of reduced responses to the hyperactivity-inducing effects of the D1/D5 receptor agonist SKF 81297. The ability of SKF 81297 to disrupt acoustic startle and prepulse inhibition appeared to be attenuated in D5-/- mice. These results suggest that the D5 receptor is not essential for many dopamine-mediated behaviors but may contribute to the pharmacological activation of dopaminergic pathways relevant to exploratory locomotion, startle, and prepulse inhibition.

Nuchal translucency measurement and pregnancy outcome after assisted conception versus spontaneously conceived twins

BACKGROUND

Nuchal translucency (NT) measurement for Down's syndrome screening or detecting various fetal anomalies is a reliable sonographic marker. This study evaluates the contribution of NT screening in spontaneously conceived and assisted conception twin pregnancies.

METHODS AND RESULTS

Maternal age at measurement, chorionicity, ultrasound features, karyotype results and pregnancy outcome were recorded prospectively and compared in 83 assisted reproduction treatment and 91 spontaneously conceived twins. Pregnancy outcome was evaluated according to maternal age, method of conception, NT data and chorionicity. NT measurements (> or =95 centiles of the normal range) were considered screen-positive and mid-pregnancy fetal karyotyping was advised. Complicated pregnancy outcome, which could be signalled by increased NT, was defined as either chromosomal abnormalities, severe structural defects or fetal demise. Based on NT measurements, 16 fetuses (4.6%) were found to be screen-positive. Five of them had chromosomal aneuploidy and selective termination was performed. The parents also opted for this procedure in another five fetuses because of major structural abnormality diagnosed during NT assessment. No other chromosomal or major fetal abnormality were found post-natally. Although no difference was found in NT, crown-rump length and maternal age between spontaneous and assisted reproduction technology twin pregnancies, the former group had a significantly higher rate of screen-positive results (7 versus 2%, P = 0.047), amniocentesis uptake (33 versus 22%, P = 0.014), monochorionic twining (32 versus 4%, P = 0.001) and complicated pregnancy outcome (11 versus 5%, P = 0.02).

CONCLUSION

The present study confirms that first trimester target scanning can improve outcome by early detection and management of cases with an anomalous co-twin. It also identifies some differences between spontaneously and artificially conceived twin pregnancies in relation to this area of testing.

Monopolar thermocoagulation in acardiac twinning

The paper describes the use of monopolar thermocoagulation in the treatment of acardiac twinning. The technique and outcomes of a series of 12 pregnancies which have presented for treatment at the Fetal Medicine Unit of University College London are presented.

Prior test experience compromises the anxiolytic efficacy of chlordiazepoxide in the mouse light/dark exploration test

It is now well established that prior test experience can alter behavioural baselines and attenuate/abolish the anxiolytic efficacy of benzodiazepines in the elevated plus-maze paradigm. In view of evidence that different models of anxiety measure qualitatively distinct forms of anxiety-like behaviour, it is important to establish whether the effects of prior experience extend to other widely-used tests. The present study assessed the behavioural and pharmacological sequelae of a single undrugged prior exposure to the light/dark exploration (L/D) test in mice, using ethological scoring methods. One group of adult male Swiss-Webster mice was given a single undrugged exposure to the L/D test 24 h prior to drug testing, while another group was completely naïve to the apparatus. On test day, half the animals in each experiential condition were treated with saline and half with an anxiolytic dose (10 mg/kg) of chlordiazepoxide (CDP). When administered to test-naïve animals, CDP induced a clear reduction in anxiety-like behaviour as evidenced by significant increases in exploration of the light compartment (line crossings, % line crossings, and % time) as well as reductions in stretched attend postures (SAPs) and the proportion of SAPs displayed toward the light compartment. The behavioural specificity of these effects was confirmed by the absence of a drug effect on line crossings in the dark compartment, total rearing and grooming. In complete contrast, with the sole exception of a decrease in total SAPs, CDP was without significant behavioural effect in test-experienced mice. As prior test experience did not significantly alter behavioural baselines in the L/D test, a second experiment was designed to investigate the possibility that handling/intraperitoneal injection may have precluded detection of experientially-induced changes in baseline behaviour. Results showed that handling/injection had no effect upon L/D behavioural profiles in either test-naïve or test-experienced subjects, and confirmed that prior experience itself did not modify the primary indices of anxiety in this test. Present data indicate that prior test experience seriously compromises the anxiolytic efficacy of CDP (10 mg/kg) in the mouse L/D test and, together with recent findings in the four-plate test, appear to confirm that an experientially-induced reduction in sensitivity to the anxiolytic effects of benzodiazepines is by no means unique to the elevated plus-maze.

The control of ccn2 (ctgf) gene expression in normal and scleroderma fibroblasts

Although the role of transforming growth factor beta (TGFbeta) in initiating fibrosis is well established, the role that TGFbeta plays in maintaining fibrosis is unclear. The gene encoding connective tissue growth factor (ccn2; ctgf), which promotes fibrosis, is not normally expressed in dermal fibroblasts unless TGFbeta is present. However, in dermal fibroblasts cultured from lesional areas of scleroderma, ccn2 (ctgf) is expressed constitutively. The contribution of several elements in the ccn2 (ctgf) promoter to basal and TGFbeta induced ccn2 (ctgf) expression in normal and scleroderma fibroblasts has been investigated. A functional SMAD binding site in the ccn2 (ctgf) promoter that is necessary for the TGFbeta mediated induction of this gene has been identified. The previously termed TGFbeta responsive enhancer (TGFbetaRE) in the ccn2 (ctgf) promoter has been found to be necessary for basal promoter activity in normal fibroblasts. The SMAD element is not necessary for the high ccn2 (ctgf) promoter activity seen in scleroderma fibroblasts. However, mutation of the previously termed TGFbetaRE reduces ccn2 (ctgf) promoter activity in scleroderma fibroblasts to that seen in normal fibroblasts. Thus, the maintenance of the scleroderma phenotype, as assessed by a high degree of ccn2 (ctgf) promoter activity, appears to be relatively independent of SMAD action and seems to reflect increased basal promoter activity.

Iloprost suppresses connective tissue growth factor production in fibroblasts and in the skin of scleroderma patients

Patients with scleroderma receiving Iloprost as a treatment for severe Raynaud's phenomenon report a reduction in skin tightness, suggesting that this drug inhibits skin fibrosis. Connective tissue growth factor (CTGF), a recently described profibrotic cytokine, acts downstream and in concert with TGF-beta to stimulate the fibrotic process and is involved in the fibrosis seen in scleroderma. Here we show that Iloprost, acting by elevation of cAMP, blocks the induction of CTGF and the increase in collagen synthesis in fibroblasts exposed to TGF-beta. The potency of Iloprost with respect to suppression of CTGF far exceeds that of other prostanoid receptor agonists, suggesting that its effect is mediated by the prostacyclin receptor IP. By sampling dermal interstitial fluid using a suction blister device, we show that CTGF levels are greatly elevated in the dermis of scleroderma patients compared with healthy controls and that Iloprost infusion causes a marked decrease in dermal CTGF levels. These studies suggest that Iloprost could be reducing the level of a key profibrotic cytokine in scleroderma patients and that endogenous production of eicosanoids may limit the fibrotic response to TGF-beta.

Candida albicans: adherence, signaling and virulence

The focus of this symposium was to present new information on the morphogenesis of Candida albicans, particularly how it relates to signal transduction pathways and other genes involved in the regulation of morphogenesis. In addition, we discuss the role of adherence and colonization of the oral cavity by the organism and discuss the role of mannan as an adhesin that recognizes the human red blood cell. C. albicans utilizes at least two signal pathways to regulate its conversion from a yeast form to filamentous growth (hyphae). One of these two pathways is similar to the Saccharomyces cerevisiae pseudohyphal/mating pathway, which utilizes the regulatory protein, Cphlp. The other pathway is not totally defined but requires a second regulatory protein, referred to as Efg1p. Other signal pathways may exist, which include a two-component histidine kinase and response regulator proteins. The latter pathway(s) may include proteins such as Chk1p, Ssk1p, Shi1p and Cos1p/Nik1p. Mutations in strains, which specifically target these proteins, result in morphogenesis defects and avirulence or attenuation of strains. A growth regulatory gene has also been recently defined whose expression is associated with growth cessation and which appears to be a necessary prerequisite in conversion of the organism to a filamentous growth form. Starvation of yeast cells induces exponentially grown cells (and usually non-germinative) to germinate. This phenomenon is also observed in cells that are transiently treated with metabolic inhibitors. During each of these treatments (starvation, metabolic inhibition), expression of a growth regulatory gene (CGRI) increases. Adherence of C. albicans to host cells and tissues is complex; several proteins, which appear to have host recognition functions, have been defined. In the oral cavity, C. albicans selectively adheres to salivary proteins, which are absorbed to many oral surfaces. This mechanism enables the cells to colonize surfaces of the oral cavity. An understanding of these interactions may lead to strategies to prevent oral disease. Mannan from C. albicans may provide a host recognition function for C. albicans. Recent experiments indicate that mannan binds to human red blood cells and causes hemolysis. Binding of mannan to the band 3 protein of human red blood cells has been established. This activity may be associated with the ability of the organism to utilize hemoglobin (and iron).

Rapid and radical amniodrainage in the treatment of severe twin-twin transfusion syndrome

We have evaluated the role of a rapid and radical method of amniodrainage in the treatment of severe twin-twin transfusion. The outcome of 15 patients with severe twin-twin transfusion for which a amniodrainage was performed by means of a vacuum bottle system was compared with the outcome of 15 patients with a similar condition, matched for gestational age at the time of the initial procedure and drained using a standard procedure. In the study group the amniodrainage ended when no amniotic fluid could be aspirated, whereas the women in the standard group were drained with a syringe system and the fluid was removed until the deepest amniotic fluid pool was <8 cm. At the initial procedure, the mean volume of amniotic fluid drained was significantly (p<0.05) higher (3252 vs 2153 ml) and the length of the procedure significantly (p<0.001) shorter (21 vs 41 min) in the study group than in the standard group. The mean post-procedure amniotic fluid index was significantly (p<0.001) smaller (2.9 vs 7.7 cm) after radical amniodrainage than after the standard amniodrainage. The mean number of procedures was significantly (p<0.001) lower (1.5 vs 5.6) in the study group compared to the standard group. In the study group the mean placental thickness increased significantly (p<0.001) from 9 mm before the procedure to 49 mm after, and the overall perinatal survival rate was 80% and the proportion of pregnancies with at least one survivor was 93%. The present data indicate that early, rapid and radical amniodrainage is an effective and low-cost therapy for severe twin-twin transfusion syndrome. Compared to the standard amniodrainage technique it also appears to reduce the need for multiple procedures.

Targeted gene mutation approaches to the study of anxiety-like behavior in mice

Studying the behavioral phenotypes of transgenic and gene knockout mice is a powerful means to better understand the pathophysiology of neuropsychiatric disorders and ultimately improve their treatment. This paper provides an overview of the methods and findings of studies that have tested for anxiety-related behavioral phenotypes in gene mutant mice. In the context of improving the side effect burden of benzodiazepines, gene targeting has been valuable for dissociating the functional roles (i.e., anxiolytic, sedative, amnestic) of individual GABA(A) receptor subunits. Supporting the link between abnormalities in CRH function and anxiety, CRH overexpressing transgenic mice and CRH-R2 receptor knockout mutants have displayed significantly increased anxiety-like behavior, while CRH-R1 receptor knockout mice have shown an anxiolytic-like phenotype. Consistent with an important role for the serotonergic system in anxiety, 5-HT1(A) receptor deficient mice have consistently exhibited heightened anxiety-like behavior, while the evidence from 5-HT1(B) and 5-HT2(C) deficient mice remains somewhat equivocal. Mutant mice lacking either of the monoamine degrading enzymes, MAOA or COMT, have shown a number of behavioral and neurological effects, including alterations in anxiety-like behavior. With enhanced spatial and temporal control over gene mutations, in combination with an improved battery of behavioral tests, gene mutant mice will provide an increasingly valuable tool for understanding the neural substrates of anxiety.

Comparison of time-frequency distribution techniques for analysis of spinal somatosensory evoked potential

Spinal somatosensory evoked potential (SSEP) has been employed to monitor the integrity of the spinal cord during surgery. To detect both temporal and spectral changes in SSEP waveforms, an investigation of the application of time-frequency analysis (TFA) techniques was conducted. SSEP signals from 30 scoliosis patients were analysed using different techniques; short time Fourier transform (STFT), Wigner-Ville distribution (WVD), Choi-Williams distribution (CWD), cone-shaped distribution (CSD) and adaptive spectrogram (ADS). The time-frequency distributions (TFD) computed using these methods were assessed and compared with each other. WVD, ADS, CSD and CWD showed better resolution than STFT. Comparing normalised peak widths, CSD showed the sharpest peak width (0.13+/-0.1) in the frequency dimension, and a mean peak width of 0.70+/-0.12 in the time dimension. Both WVD and CWD produced cross-term interference, distorting the TFA distribution, but this was not seen with CSD and ADS. CSD appeared to give a lower mean peak power bias (10.3%+/-6.2%) than ADS (41.8%+/-19.6%). Application of the CSD algorithm showed both good resolution and accurate spectrograms, and is therefore recommended as the most appropriate TFA technique for the analysis of SSEP signals.