The effect of long-term spaceflight on drug potency and the risk of medication failure.

Pharmaceuticals selected for exploration space missions must remain stable and effective throughout mission timeframes. Although there have been six spaceflight drug stability studies, there has not been a comprehensive analytical analysis of these data. We sought to use these studies to quantify the rate of spaceflight drug degradation and the time-dependent probability of drug failure resulting from the loss of active pharmaceutical ingredient (API). Additionally, existing spaceflight drug stability studies were reviewed to identify research gaps to be addressed prior to exploration missions. Data were extracted from the six spaceflight studies to quantify API loss for 36 drug products with long-duration exposure to spaceflight. Medications stored for up to 2.4 years in low Earth orbit (LEO) exhibit a small increase in the rate of API loss with a corresponding increase in risk of product failure. Overall, the potency for all spaceflight-exposed medications remains within 10% of terrestrial lot-matched control with a ~1.5 increase in degradation rate. All existing studies of spaceflight drug stability have focused primarily on repackaged solid oral medications, which is important because non-protective repackaging is a well-established factor contributing to loss of drug potency. The factor most detrimental to drug stability appears to be nonprotective drug repackaging, based on premature failure of drug products in the terrestrial control group. The result of this study supports a critical need to evaluate the effects of current repackaging processes on drug shelf life, and to develop and validate suitable protective repackaging strategies that help assure the stability of medications throughout the full duration of exploration space missions.

Tooth Color Change and Erosion: Hydrogen Peroxide Versus Non-peroxide Whitening Strips.

AIM: The study evaluated the efficacy and potential erosion of non-peroxide strips compared to hydrogen peroxide (HP) whitening strips (WSs). METHODS: Color evaluation samples (N=64) were distributed into four groups and treated according to manufacturer's directions. NC: Negative control treated with water; BT: Non-peroxide Brilliant Dissolving Strips; FM: Non-peroxide Fancymay Teeth WSs; WS: Crest 3D Brilliance HP White Strips. A contact-type spectrophotometer was used to measure color at baseline (T1), 1-day posttreatment (T2), and 1-week posttreatment (T3). Teeth were cut to a rectangular block for micro-CT erosion assessment. The samples (N=30) were divided into five groups. In addition to the four groups for color assessment, a positive control (PC) treated with 0.25% citric acid was added. The samples were scanned, reconstructed, and measured for erosion depth using a micro-CT analysis program software. Kruskal-Wallis test was used to determine differences in color change and erosion depth among the groups. Tests of hypotheses were two-sided with an alpha level of 0.05. RESULTS: The mean ΔE*ab at 1-day/1-week posttreatment were 2.4/2.5, 2.8/2.9, 2.8/3.2, and 8.6/11.0 for NC, BT, FM, and WS, respectively. There was a statistically significant difference for ΔE*ab at 1-day and 1-week posttreatment (p<0.001). Group WS had the highest color change, while the other three groups did not differ from each other (p>0.05). Mean erosion depths in microns were 0.52, 0.58, 0.42, 0.49, and 29.55 for NC, BT, FM, WS, and PC, respectively. There was a statistically significant difference among the groups (p=0.004). Group PC had the greatest erosion, while the other groups had negligible erosion that did not differ from each other (p>0.05). CONCLUSION: Peroxide WSs had superior whitening efficacy compared to non-peroxide strips. None of the tested products compromised tooth structure integrity through enamel erosion.

Genetic variation in the developmental regulation of cortical avpr1a among prairie voles.

Early experiences can have enduring impacts on brain and behavior, but the strength of these effects can be influenced by genetic variation. In principle, polymorphic CpGs (polyCpGs) may contribute to gene-by-environment interactions (G × E) by altering DNA methylation. In this study, we investigate the influence of polyCpGs on the development of vasopressin receptor 1a abundance in the retrosplenial cortex (RSC-V1aR) of prairie voles (Microtus ochrogaster). Two alternative alleles ('HI'/'LO') predict RSC avpr1a expression, V1aR abundance and sexual fidelity in adulthood; these alleles differ in the frequency of CpG sites and in methylation at a putative intron enhancer. We hypothesized that the elevated CpG abundance in the LO allele would make homozygous LO/LO voles more sensitive to developmental perturbations. We found that genotype differences in RSC-V1aR abundance emerged early in ontogeny and were accompanied by differences in methylation of the putative enhancer. As predicted, postnatal treatment with an oxytocin receptor antagonist (OTA) reduced RSC-V1aR abundance in LO/LO adults but not their HI/HI siblings. Similarly, methylation inhibition by zebularine increased RSC-V1aR in LO/LO adults, but not in HI/HI siblings. These data show a gene-by-environment interaction in RSC-V1aR. Surprisingly, however, neither OTA nor zebularine altered adult methylation of the intronic enhancer, suggesting that differences in sensitivity could not be explained by CpG density at the enhancer alone. Methylated DNA immunoprecipiation-sequencing showed additional differentially methylated regions between HI/HI and LO/LO voles. Future research should examine the role of these regions and other regulatory elements in the ontogeny of RSC-V1aR and its developmentally induced changes.

Methylation of avpr1a in the cortex of wild prairie voles: effects of CpG position and polymorphism.

DNA methylation can cause stable changes in neuronal gene expression, but we know little about its role in individual differences in the wild. In this study, we focus on the vasopressin 1a receptor (avpr1a), a gene extensively implicated in vertebrate social behaviour, and explore natural variation in DNA methylation, genetic polymorphism and neuronal gene expression among 30 wild prairie voles (Microtus ochrogaster). Examination of CpG density across 8 kb of the locus revealed two distinct CpG islands overlapping promoter and first exon, characterized by few CpG polymorphisms. We used a targeted bisulfite sequencing approach to measure DNA methylation across approximately 3 kb of avpr1a in the retrosplenial cortex, a brain region implicated in male space use and sexual fidelity. We find dramatic variation in methylation across the avrp1a locus, with pronounced diversity near the exon-intron boundary and in a genetically variable putative enhancer within the intron. Among our wild voles, differences in cortical avpr1a expression correlate with DNA methylation in this putative enhancer, but not with the methylation status of the promoter. We also find an unusually high number of polymorphic CpG sites (polyCpGs) in this focal enhancer. One polyCpG within this enhancer (polyCpG 2170) may drive variation in expression either by disrupting transcription factor binding motifs or by changing local DNA methylation and chromatin silencing. Our results contradict some assumptions made within behavioural epigenetics, but are remarkably concordant with genome-wide studies of gene regulation.

Antegrade continence enema (ACE): predictors of outcome in 111 patients.

PURPOSE: The antegrade continence enema (ACE) is used as a means of managing faecal incontinence and constipation with varying outcomes. We aim to evaluate our outcomes of ACEs and identify predictors of outcome. METHODS: A retrospective case-note review of patients ≤16 years of age undergoing an ACE (March 2000-September 2013) was carried out. Data collected included: patient demographics, functional outcomes and complications. Data are quoted as median (range) and compared using Mann-Whitney and Fisher's exact test. Univariate analysis was performed to identify predictors of successful outcomes. P < 0.05 is significant. Successful outcome = total continence/occasional leakage and failed outcome = regular soiling and/or constipation. RESULTS: 111 patients with complete data sets underwent an ACE [59% male, median age = 9.5 years (3.4-16 years)] and median follow-up = 48 months (4 months-11 years 4 months). Underlying diagnoses were idiopathic constipation (n = 68), anorectal malformation (n = 27), neuropathic bowel (n = 7), Hirschsprung disease (n = 5) and gastrointestinal dysmotility (n = 4). Social continence was achieved in 87/111 (78%). Fifteen percent of patients underwent reversal of ACE due to resolution of symptoms. There was no difference in outcomes related to diagnosis, gender, age or follow-up duration. Complication rate was 20.7% (23/111). CONCLUSIONS: The ACE is safe and effective in the management of intractable constipation and soiling. No predictors of outcome were identified.

Impact of atmospheric boundary layer depth variability and wind reversal on the diurnal variability of aerosol concentration at a valley site.

The development of the atmospheric boundary layer (ABL) plays a key role in affecting the variability of atmospheric constituents such as aerosols, greenhouse gases, water vapor, and ozone. In general, the concentration of any tracers within the ABL varies due to the changes in the mixing volume (i.e. ABL depth). In this study, we investigate the impact on the near-surface aerosol concentration in a valley site of 1) the boundary layer dilution due to vertical mixing and 2) changes in the wind patterns. We use a data set obtained during a 10-day field campaign in which a number of remote sensing and in-situ instruments were deployed, including a ground-based aerosol lidar system for monitoring of the ABL top height (zi), a particle counter to determine the number concentration of aerosol particles at eight different size ranges, and tower-based standard meteorological instruments. Results show a clearly visible decreasing trend of the mean daytime zi from 2900 m AGL (above ground level) to 2200 m AGL during a three-day period which resulted in increased near-surface pollutant concentrations. An inverse relationship exists between the zi and the fine fraction (0.3-0.7 µm) accumulation mode particles (AMP) on some days due to the dilution effect in a well-mixed ABL. These days are characterized by the absence of daytime upvalley winds and the presence of northwesterly synoptic-driven winds. In contrast, on the days with an onset of an upvalley wind circulation after the morning transition, the wind-driven local transport mechanism outweighs the ABL-dilution effect in determining the variability of AMP concentration. The interplay between the ABL depth evolution and the onset of the upvalley wind during the morning transition period significantly governs the air quality in a valley and could be an important component in the studies of mountain meteorology and air quality.

Botulinum toxin use in paediatric colorectal surgery.

PURPOSE: To evaluate outcomes of intrasphincteric botulinum toxin injection (ISBTI) in children with intractable constipation. METHODS: Retrospective case-note review of patients ≤ 16 years of age undergoing ISBTI between January 2010 and February 2014. Data collected included patient demographics, diagnosis, complications, follow-up duration and functional outcomes. Successful outcome was defined as resolution/improvement in symptoms and failed when there was no change in symptoms. Statistical analyses were performed using PRISM (GraphPad, CA, USA). p values <0.05 were considered as significant. RESULTS: 43 patients [male 29, median age 5 years 9 months (range 13 months-13 years 5 months)] underwent 86 ISBTIs. Underlying diagnoses were idiopathic constipation (67 %), Hirschsprung disease (26 %), anorectal malformation (5 %), gastrointestinal dysmotility (2 %). 72 % (31/43) reported improvement in symptoms after the first ISBTI. 39 % of patients had recurrence of symptoms at 12-month median follow-up. 10 patients non-responsive to ISBTI required an antegrade continence enema or stoma. There was no correlation between age (p = 0.3), gender (p = 0.7), diagnosis (p = 0.84), or number of ISBTIs (p = 0.17) with successful outcome. CONCLUSION: Successful outcomes occurred in 72 % patients after the first ISBTI. 25 % required further surgical management of their symptoms. Further work is required to help predict which patients will benefit from ISBTI.

A polymorphism in the promoter region of the human interleukin-16 gene is not associated with asthma or atopy in an Australian population.

BACKGROUND: IL-16 is an immunomodulatory cytokine whose expression is increased in the bronchial mucosa, bronchoalveolar lavage fluid and induced sputum of asthmatic patients. It has been suggested that IL-16 has a regulatory role in the pathophysiology of asthma. A single-nucleotide polymorphism (T(-295)C) has been described in the promoter region of the gene and it has been hypothesized that this polymorphism may be associated with altered levels of IL-16 expression, and account for the increased levels of IL-16 seen in the asthmatic airway. OBJECTIVE: To determine the association between the T(-295)C promoter polymorphism and asthma, disease severity and atopy in a large Australian Caucasian population. METHODS: We used PCR and restriction fragment length polymorphism analysis to establish the allele frequency of the T(-295)C promoter polymorphism in a random Australian Caucasian population (n=176) and to characterize the polymorphism in a large Australian Caucasian population of mild (n=273), moderate (n=230) and severe (n=77) asthmatic patients, and non-asthmatic controls (n=455). Genotype association analyses were performed using chi(2) tests. RESULTS: The polymorphic C allele was present in 19% of the asthmatic population and 21% of the non-asthmatic population. There was no association between the polymorphism and asthma (P=0.153) nor with asthma severity (P=0.417) or atopy (P=0.157) in this population. CONCLUSION: Although it has been hypothesized that the T(-295)C promoter polymorphism may be associated with increased IL-16 gene expression, it is not associated with asthma, disease severity or atopy in this Australian population.

Polymorphisms in the 5-lipoxygenase activating protein (ALOX5AP) gene are not associated with asthma in an Australian population.

BACKGROUND: The cysteinyl-leukotrienes (cys-LTs) are important pro-inflammatory mediators in asthma, and have been shown to have a role in specific disease subtypes, including asthma severity. Few studies have investigated the role of polymorphisms in the ALOX5AP gene, encoding 5-lipoxygenase activating protein (FLAP), and asthma. We hypothesized that polymorphisms in this gene are associated with asthma and in particular, with asthma severity, in an Australian population. OBJECTIVE: To screen the coding region of the ALOX5AP gene for polymorphisms and to determine the association between previously described polymorphisms and asthma and asthma severity in an Australian population. METHODS: We used PCR-SSCP and PCR-RFLP analysis to examine a previously described promoter polyA variable repeat polymorphism and two intronic polymorphisms (IVS2+12C>A, IVS2+105T>C), and to screen all five exons of the gene for new polymorphisms, in a large Australian population of randomly selected, non-asthmatic controls (n=457), mild asthmatics (n=274), moderate asthmatics (n=231) and severe asthmatics (n=79). RESULTS: We confirmed the presence of two polymorphisms in intron 2 and found no association between these polymorphisms and asthma or asthma severity, nor between a promoter polymorphism in the ALOX5AP gene and asthma or asthma severity. Gene fragment analysis of the promoter polymorphism revealed novel, conserved repeat numbers in our population, and no new polymorphisms were found in the coding region of the gene. CONCLUSION: These findings in a large, well characterized asthma population, reveal that, while FLAP is an important enzyme in cys-LTs biosynthesis, polymorphisms in the ALOX5AP gene are not likely to be functionally associated with the asthma phenotype.

Urinary leukotriene E4 and 9 alpha, 11 beta-prostaglandin F concentrations in mild, moderate and severe asthma, and in healthy subjects.

BACKGROUND: Airway inflammation in asthma is associated with cysteinyl leukotriene and prostaglandin D(2) production. Measurement of urinary metabolites of these eicosanoids may be useful for monitoring asthma patients. However, the influence of asthma phenotype and severity on basal urinary excretion of these metabolites is unknown. OBJECTIVE: To compare urinary leukotriene (LT)E(4) and 9 alpha, 11 beta-prostaglandin (PG)F(2) concentrations in large groups of mild, moderate and severe asthmatic patients and healthy control subjects. METHODS: Asthma severity, treatment and aspirin sensitivity were assessed by questionnaire in 168 asthmatic patients. Basal LTE(4) and 9 alpha, 11 beta-PGF(2) concentrations were measured in urine samples from these patients and from 175 control subjects using enzyme immunoassays. RESULTS: Urinary LTE(4) was correlated with 9 alpha, 11 beta-PGF(2) in both control subjects and asthmatic patients (P<0.002). Median LTE(4) and 9 alpha, 11 beta-PGF(2) concentrations in patients with severe asthma were significantly reduced compared with mild asthmatic patients (P<0.05 and <0.001, respectively). Urinary 9 alpha, 11 beta-PGF(2), but not LTE(4) was lower in asthmatic patients using inhaled corticosteroids (P<0.02). Multiple regression analysis indicated that urinary 9 alpha, 11 beta-PGF(2) concentration was negatively correlated with asthma severity (P=0.003) and also with % predicted FEV(1) (forced expiratory volume in 1 s) (P=0.005). CONCLUSIONS: Baseline urinary LTE(4) and 9 alpha, 11 beta-PGF(2) concentrations are of limited value in discriminating between patients with different severities of asthma. Reduced urinary LTE(4) and 9 alpha, 11 beta-PGF(2) in patients with severe asthma suggest that direct or indirect effects of high-dose corticosteroid therapy combined with other factors associated with severe asthma may influence eicosanoid production. However, the negative association of urinary 9 alpha, 11 beta-PGF(2) with lung function suggests an adverse effect of chronic PGD(2) production on lung function in asthma, irrespective of severity.

Severe perineal pain after enterocystoplasty in bladder exstrophy.

OBJECTIVE: To describe a previously unreported complication (severe perineal pain) after bladder reconstruction and enterocystoplasty in patients with bladder exstrophy. PATIENTS AND METHODS: The notes were reviewed retrospectively for four patients (two boys and two girls) with classical bladder exstrophy who had severe penile or perineal pain after bladder reconstruction. They were all continent and using intermittent catheterization. A range of conservative management failed and all patients subsequently required excision of their native bladders between 1997 and 2000. RESULTS: All four patients had perineal or penile pain which began 4 months to 8 years after bladder augmentation. Investigations included plain abdominal X-ray, renal and bladder ultrasonography, computerized tomography of the pelvis, video-urodynamics and cysto-urethroscopy. When therapeutic interventions such as more frequent bladder washouts, analgesic and anticholinergic drugs, and cystolithotomy (two patients) were unsuccessful in alleviating the symptoms, all had their native bladder excised. Histological examination of the excised tissue showed neither normal urothelium nor enteric mucosa at the margins of the excision; two patients already had squamous metaplasia within what represented the bladder, and in the others squamous epithelium was present amongst the enteric mucosa. All four children were pain-free with a follow-up of 2-6 years. CONCLUSION: All four patients developed severe referred bladder pain that was probably secondary to the abnormal retained bladder remnants. Cystectomy cured the pain and may also have removed a potential site of future malignant tumour.

Vestigial preference functions in neural networks and túngara frogs.

Although there is a growing interest in understanding how perceptual mechanisms influence behavioral evolution, few studies have addressed how perception itself is shaped by evolutionary forces. We used a combination of artificial neural network models and behavioral experiments to investigate how evolutionary history influenced the perceptual processes used in mate choice by female túngara frogs. We manipulated the evolutionary history of artificial neural network models and observed an emergent bias toward calls resembling known ancestral states. We then probed female túngara frogs for similar preferences, finding strong biases toward stimuli that resemble a call hypothesized for a recent ancestor. The data strongly suggest that female túngara frogs exhibit vestigial preferences for ancestral calls, and provide a general strategy for exploring the role of historical contingency in perceptual biases.

Non-toxic ubiquitous over-expression of utrophin in the mdx mouse.

Duchenne muscular dystrophy (DMD) is an inherited, severe muscle wasting disease caused by the loss of the cytoskeletal protein, dystrophin. Patients usually die in their late teens or early twenties of cardiac or respiratory failure. We have previously demonstrated that the dystrophin related protein, utrophin is able to compensate for the loss of dystrophin in the mdx mouse, the mouse model of the disease. Expression of a utrophin transgene under the control of an HSA promoter results in localization of utrophin to the sarcolemma and prevents the muscle pathology. Here we show that the over-expression of full-length utrophin in a broad range of tissues is not detrimental in the mdx mouse. These findings have important implications for the feasibility of the up-regulation of utrophin in therapy for DMD since they suggest that tissue specific up-regulation may not be necessary.

How evolutionary history shapes recognition mechanisms.

Evolutionary psychologists have emphasized the importance of natural selection in shaping cognitive functions, but historical contingency has not received direct study. This is crucial because in response to selection, complex traits tend to be fine-tuned or jury-rigged rather than totally reconstructed. We hypothesize that the neural and cognitive strategies an animal employs in signal recognition are influenced by the strategies used by its ancestors. The responses of female túngara frogs to ancestral calls and to calls of other closely related species are influenced by history. By training artificial neural networks with a series of calls that mimic the species' past history of call evolution or various control histories, we have shown that only networks that evolved through the mimetic history predict the response biases of túngara frogs.

Pharmacokinetics of naratriptan in adolescent subjects with a history of migraine.

Naratriptan is a novel 5-HT1 agonist developed to treat acute migraine. The study objective was to characterize the pharmacokinetics of oral naratriptan in adolescent migraine patients outside a migraine attack. Subjects received a single 2.5 mg naratriptan tablet. Serial serum samples for naratriptan concentrations were collected over 24 hours. Blood pressure, pulse rate, and 12-lead ECG were recorded at baseline and at regular intervals after dosing. Seven patients--3 males and 4 females, 12 to 16 years of age--received drug and completed the study. The geometric mean and 95% confidence interval maximum concentration (Cmax) was 8.0 ng/mL (5.9-10.7), elimination half-life (t1/2) was 4.9 hours (4.5-5.4), area under the concentration-time curve (AUC) was 74.6 ng.h/mL (56.6-98.2), and apparent total clearance (Cl/F) was 558.8 mL/min (424.3-735.9). The median time to maximal concentration (tmax) was 4 hours, with a range of 1.5 to 4. Blood pressure, pulse rate, and ECG parameters did not change significantly from baseline. No serious adverse events or subject withdrawal after drug administration occurred. Oral naratriptan pharmacokinetic parameters in adolescents were similar to values reported in adults. Naratriptan doses for adolescents older than 12 years of age would be expected to be similar to adult doses.

Small cell lung carcinoma exhibits greater phospholipase C-beta1 expression and edelfosine resistance compared with non-small cell lung carcinoma.

Aberrant signal transduction pathways involved in the development of metastatic disease are poorly defined in both small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC). Neuropeptide-driven positive feedback loops stimulating cell proliferation are characteristic of SCLC. The activation of phospholipase C (PLC)-beta1 is an early and common response to stimulation of G protein-coupled receptors by these neuroendocrine growth factors. The importance of PLC-beta in neuropeptide signaling prompted us to compare PLC-beta isoform expression and activity in four independent SCLC cell lines and four independent NSCLC cell lines. We found that PLC-beta1 is more highly expressed in SCLC than in NSCLC, as indicated by Western blotting of cell lysates. All SCLC lines studied express PLC-beta1; only one of the NSCLC lines investigated showed detectable levels of the enzyme. NSCLC lines are significantly more sensitive to the antiproliferative effects of ET-18-OCH3 (edelfosine) compared with the SCLC lines, as indicated by [3H]thymidine uptake. The only SCLC cell line (NCI-H345) that is as sensitive as the NSCLC cell lines to ET-18-OCH3 also expresses uniquely low levels of PLC-beta1. The participation of PLC-beta1 in signaling by SCLC growth factor receptors is indicated by our finding that PLC-beta1 (but not PLC-beta3) coimnunoprecipitates with G(alpha)q/11 upon activation of neurotensin receptors; this association is inhibited by ET-18-OCH3. Ca2+ mobilization mediated by neurotensin receptors is also inhibited by ET-18-OCH3. The binding of GTPgammaS to G(alpha)q/11 upon treatment of SCLC cells with neurotensin is not inhibited by ET-18-OCH3. These findings indicate that ET-18-OCH3 does not interfere with G(alpha)q/11 activation but rather inhibits the association of G(alpha)q/11 with PLC-beta1. Our data suggest that PLC-beta is an important mediator of both SCLC and NSCLC proliferation. Differences in PLC-beta1 expression may be exploitable in the development of effective diagnostic and therapeutic tools.

Left coronary artery anomaly: an often unsuspected cause of sudden death in the military athlete.

More than 300,000 cases of sudden cardiac death (SCD) occur in the United States each year. Left coronary artery anomaly (LCAA), although rare, is second only to hypertrophic cardiomyopathy as the most common cause of SCD associated with structural cardiovascular abnormalities. This case illustrates SCD secondary to LCAA in a military athlete. A 19-year-old soldier collapsed after an 8-km run. On arrival at the emergency room, he was unresponsive and in asystole. Despite successful resuscitation and aggressive management, the patient died the next morning. Autopsy revealed an anomalous left coronary artery. LCAA-associated SCD is rare and usually seen in young individuals who collapse (and/or die) while exercising. A substantial proportion of these individuals experience prodromal symptoms of exertional chest pain, syncope, and/or sudden collapse. Early recognition and intervention are key to survival. Rapid, early imaging and invasive therapeutic measures leading to surgical correction may be the difference between life and death.

Unique in vivo associations with SmgGDS and RhoGDI and different guanine nucleotide exchange activities exhibited by RhoA, dominant negative RhoA(Asn-19), and activated RhoA(Val-14).

We compared the in vivo characteristics of hemagglutinin (HA)-tagged RhoA, dominant negative RhoA(Asn-19), and activated RhoA(Val-14) stably expressed in Chinese hamster ovary (CHO) cells. Proteins co-precipitating with these HA-tagged GTPases were identified by peptide sequencing or by Western blotting. Dominant negative RhoA(Asn-19) co-precipitates with the guanine nucleotide exchange factor (GEF) SmgGDS but does not detectably interact with other expressed GEFs, such as Ost or Dbl. SmgGDS co-precipitates minimally with wild-type RhoA and does not detectably associate with RhoA(Val-14). The guanine nucleotide dissociation inhibitor RhoGDI co-precipitates with RhoA, and to a lesser extent with RhoA(Val-14), but does not detectably co-precipitate with RhoA(Asn-19). Wild-type RhoA is predominantly in the [(32)P]GDP-bound form, RhoA(Val-14) is predominantly in the [(32)P]GTP-bound form, and negligible levels of [(32)P]GDP or [(32)P]GTP are bound to RhoA(Asn-19) in (32)P-labeled cells. Immunofluorescence analyses indicate that HA-RhoA(Asn-19) is excluded from the nucleus and cell junctions. Microinjection of SmgGDS cDNA into CHO cells stably expressing HA-RhoA causes HA-RhoA to be excluded from the nucleus and cell junctions, similar to the distribution of RhoA(Asn-19). Our findings indicate that the expression of RhoA(Asn-19) may specifically inhibit signaling pathways that rely upon the SmgGDS-dependent activation of RhoA.

Altered phenytoin pharmacokinetics in children with severe, acute traumatic brain injury.

The purpose of this study was to determine if phenytoin protein binding and metabolism were altered in prepubescent pediatric patients within the first 10 days following severe, acute traumatic brain injury. Patients (n = 10) received phenytoin loading doses (15-20 mg/kg) followed by a maintenance regimen (7 mg/kg/day) initiated within 12 hours of the loading dose. Phenytoin serum concentrations were measured serially on days 1, 2, 3, 5, 7, 9, and 10 at 1, 6, and 12 hours. Time-invariant and time-variant Michaelis-Menten pharmacokinetic models were fit to the unbound phenytoin concentration-time data (ADAPT II). Albumin concentrations significantly decreased over time (p < 0.001) and were predictive of the phenytoin binding ratio (r2 = 0.373, p < 0.0001). The time-variant model provided a superior fit of the data in 7 patients with no difference between models in 3 patients. Rapid inhibition of metabolism (Vmaxbaseline = 2.82 +/- 2.35 mg/kg/day) was observed initially following injury. This was followed by induction of metabolism as reflected by a Vmaxinduced of 20.79 +/- 13.71 mg/kg/day, which was approximately twofold higher than reported values for nonstressed children. Children with severe, acute neurotrauma were found to have markedly altered protein binding and phenytoin metabolism.

History influences signal recognition: neural network models of túngara frogs.

Animals often attend to only a few of the cues provided by the complex displays of conspecifics. We suggest that these perceptual biases are influenced by mechanisms of signal recognition inherited from antecedent species. We tested this hypothesis by manipulating the evolutionary history of artificial neural networks, observing how the resulting networks respond to many novel stimuli and comparing these responses to the behaviour of females in phonotaxis experiments. Networks with different evolutionary histories proved equally capable of evolving to recognize the call of the túngara frog, Physalaemus pustulosus, but exhibited distinct responses to novel stimuli. History influenced the ability of networks to predict known responses of túngara frogs; network accuracy was determined by how closely the network history approximated the hypothesized history of the túngara frog. Our findings emphasize the influence of past selection pressures on current perceptual mechanisms, and demonstrate how neural network models can be used to address behavioural questions that are intractable through traditional methods.