Genetic Decomposition of the Heritable Component of Reported Childhood Maltreatment

Background

Decades of research have shown that environmental exposures, including self-reports of trauma, are partly heritable. Heritable characteristics may influence exposure to and interpretations of environmental factors. Identifying heritable factors associated with self-reported trauma could improve our understanding of vulnerability to exposure and the interpretation of life events.

Methods

We used genome-wide association study summary statistics of childhood maltreatment, defined as reporting of abuse (emotional, sexual, and physical) and neglect (emotional and physical) (N = 185,414 participants). We calculated genetic correlations (rg) between reported childhood maltreatment and 576 traits to identify phenotypes that might explain the heritability of reported childhood maltreatment, retaining those with |rg| > 0.25. We specified multiple regression models using genomic structural equation modeling to detect residual genetic variance in childhood maltreatment after accounting for genetically correlated traits.

Results

In 2 separate models, the shared genetic component of 12 health and behavioral traits and 7 psychiatric disorders accounted for 59% and 56% of heritability due to common genetic variants (single nucleotide polymorphism-based heritability [h2SNP]) of childhood maltreatment, respectively. Genetic influences on h2SNP of childhood maltreatment were generally accounted for by a shared genetic component across traits. The exceptions to this were general risk tolerance, subjective well-being, posttraumatic stress disorder, and autism spectrum disorder, identified as independent contributors to h2SNP of childhood maltreatment. These 4 traits alone were sufficient to explain 58% of h2SNP of childhood maltreatment.

Conclusions

We identified putative traits that reflect h2SNP of childhood maltreatment. Elucidating the mechanisms underlying these associations may improve trauma prevention and posttraumatic intervention strategies.

Common Genetic Variation and Age of Onset of Anorexia Nervosa

Background

Genetics and biology may influence the age of onset of anorexia nervosa (AN). The aims of this study were to determine whether common genetic variation contributes to age of onset of AN and to investigate the genetic associations between age of onset of AN and age at menarche.

Methods

A secondary analysis of the Psychiatric Genomics Consortium genome-wide association study (GWAS) of AN was performed, which included 9335 cases and 31,981 screened controls, all from European ancestries. We conducted GWASs of age of onset, early-onset AN (<13 years), and typical-onset AN, and genetic correlation, genetic risk score, and Mendelian randomization analyses.

Results

Two loci were genome-wide significant in the typical-onset AN GWAS. Heritability estimates (single nucleotide polymorphism-h 2) were 0.01-0.04 for age of onset, 0.16-0.25 for early-onset AN, and 0.17-0.25 for typical-onset AN. Early- and typical-onset AN showed distinct genetic correlation patterns with putative risk factors for AN. Specifically, early-onset AN was significantly genetically correlated with younger age at menarche, and typical-onset AN was significantly negatively genetically correlated with anthropometric traits. Genetic risk scores for age of onset and early-onset AN estimated from independent GWASs significantly predicted age of onset. Mendelian randomization analysis suggested a causal link between younger age at menarche and early-onset AN.

Conclusions

Our results provide evidence consistent with a common variant genetic basis for age of onset and implicate biological pathways regulating menarche and reproduction.

Identifying the Common Genetic Basis of Antidepressant Response

Background

Antidepressants are a first-line treatment for depression. However, only a third of individuals experience remission after the first treatment. Common genetic variation, in part, likely regulates antidepressant response, yet the success of previous genome-wide association studies has been limited by sample size. This study performs the largest genetic analysis of prospectively assessed antidepressant response in major depressive disorder to gain insight into the underlying biology and enable out-of-sample prediction.

Methods

Genome-wide analysis of remission (n remit = 1852, n nonremit = 3299) and percentage improvement (n = 5218) was performed. Single nucleotide polymorphism-based heritability was estimated using genome-wide complex trait analysis. Genetic covariance with eight mental health phenotypes was estimated using polygenic scores/AVENGEME. Out-of-sample prediction of antidepressant response polygenic scores was assessed. Gene-level association analysis was performed using MAGMA and transcriptome-wide association study. Tissue, pathway, and drug binding enrichment were estimated using MAGMA.

Results

Neither genome-wide association study identified genome-wide significant associations. Single nucleotide polymorphism-based heritability was significantly different from zero for remission (h 2 = 0.132, SE = 0.056) but not for percentage improvement (h 2 = -0.018, SE = 0.032). Better antidepressant response was negatively associated with genetic risk for schizophrenia and positively associated with genetic propensity for educational attainment. Leave-one-out validation of antidepressant response polygenic scores demonstrated significant evidence of out-of-sample prediction, though results varied in external cohorts. Gene-based analyses identified ETV4 and DHX8 as significantly associated with antidepressant response.

Conclusions

This study demonstrates that antidepressant response is influenced by common genetic variation, has a genetic overlap schizophrenia and educational attainment, and provides a useful resource for future research. Larger sample sizes are required to attain the potential of genetics for understanding and predicting antidepressant response.

Enhancing Discovery of Genetic Variants for Posttraumatic Stress Disorder Through Integration of Quantitative Phenotypes and Trauma Exposure Information

BACKGROUND

Posttraumatic stress disorder (PTSD) is heritable and a potential consequence of exposure to traumatic stress. Evidence suggests that a quantitative approach to PTSD phenotype measurement and incorporation of lifetime trauma exposure (LTE) information could enhance the discovery power of PTSD genome-wide association studies (GWASs).

METHODS

A GWAS on PTSD symptoms was performed in 51 cohorts followed by a fixed-effects meta-analysis (N = 182,199 European ancestry participants). A GWAS of LTE burden was performed in the UK Biobank cohort (N = 132,988). Genetic correlations were evaluated with linkage disequilibrium score regression. Multivariate analysis was performed using Multi-Trait Analysis of GWAS. Functional mapping and annotation of leading loci was performed with FUMA. Replication was evaluated using the Million Veteran Program GWAS of PTSD total symptoms.

RESULTS

GWASs of PTSD symptoms and LTE burden identified 5 and 6 independent genome-wide significant loci, respectively. There was a 72% genetic correlation between PTSD and LTE. PTSD and LTE showed largely similar patterns of genetic correlation with other traits, albeit with some distinctions. Adjusting PTSD for LTE reduced PTSD heritability by 31%. Multivariate analysis of PTSD and LTE increased the effective sample size of the PTSD GWAS by 20% and identified 4 additional loci. Four of these 9 PTSD loci were independently replicated in the Million Veteran Program.

CONCLUSIONS

Through using a quantitative trait measure of PTSD, we identified novel risk loci not previously identified using prior case-control analyses. PTSD and LTE have a high genetic overlap that can be leveraged to increase discovery power through multivariate methods.

Depression with atypical neurovegetative symptoms shares genetic predisposition with immuno-metabolic traits and alcohol consumption

BACKGROUND

Depression is a highly prevalent and heterogeneous disorder. This study aims to determine whether depression with atypical features shows different heritability and different degree of overlap with polygenic risk for psychiatric and immuno-metabolic traits than other depression subgroups.

METHODS

Data included 30 069 European ancestry individuals from the UK Biobank who met criteria for lifetime major depression. Participants reporting both weight gain and hypersomnia were classified as ↑WS depression (N = 1854) and the others as non-↑WS depression (N = 28 215). Cases with non-↑WS depression were further classified as ↓WS depression (i.e. weight loss and insomnia; N = 10 142). Polygenic risk scores (PRS) for 22 traits were generated using genome-wide summary statistics (Bonferroni corrected p = 2.1 × 10-4). Single-nucleotide polymorphism (SNP)-based heritability of depression subgroups was estimated.

RESULTS

↑WS depression had a higher polygenic risk for BMI [OR = 1.20 (1.15-1.26), p = 2.37 × 10-14] and C-reactive protein [OR = 1.11 (1.06-1.17), p = 8.86 × 10-06] v. non-↑WS depression and ↓WS depression. Leptin PRS was close to the significance threshold (p = 2.99 × 10-04), but the effect disappeared when considering GWAS summary statistics of leptin adjusted for BMI. PRS for daily alcohol use was inversely associated with ↑WS depression [OR = 0.88 (0.83-0.93), p = 1.04 × 10-05] v. non-↑WS depression. SNP-based heritability was not significantly different between ↑WS depression and ↓WS depression (14.3% and 12.2%, respectively).

CONCLUSIONS

↑WS depression shows evidence of distinct genetic predisposition to immune-metabolic traits and alcohol consumption. These genetic signals suggest that biological targets including immune-cardio-metabolic pathways may be relevant to therapies in individuals with ↑WS depression.

Assessing the Evidence for Causal Associations Between Body Mass Index, C-Reactive Protein, Depression, and Reported Trauma Using Mendelian Randomization

Background

Traumatic experiences are described as the strongest predictors of major depressive disorder (MDD), with inflammation potentially mediating the association between trauma and symptom onset. However, several studies indicate that body mass index (BMI) exerts a large confounding effect on both inflammation and MDD.

Methods

First, we sought to replicate previously reported associations between these traits in a large subset of the UK Biobank, using regression models with C-reactive protein (CRP) and MDD and as the outcome variables in 113,481 and 30,137 individuals, respectively. Second, we ran bidirectional Mendelian randomization analyses between these traits to establish a potential causal framework between BMI, MDD, reported childhood trauma, and inflammation.

Results

Our phenotypic analyses revealed no association between CRP and MDD but did suggest a strong effect of BMI and reported trauma on both CRP (BMI: β = 0.43, 95% CI = 0.43-0.43, p ≤ .001; childhood trauma: β = 0.02, 95% CI = 0.00-0.03, p = .006) and MDD (BMI: odds ratio [OR] = 1.16, 95% CI = 1.14-1.19, p ≤ .001; childhood trauma: OR = 1.99, 95% CI = 1.88-2.11, p ≤ .001). Our Mendelian randomization analyses confirmed a lack of causal relationship between CRP and MDD but showed evidence consistent with a strong causal influence of higher BMI on increased CRP (β = 0.37, 95% CI = 0.36-0.39, p ≤ .001) and a bidirectional influence between reported trauma and MDD (OR trauma-MDD = 1.75, 95% CI = 1.49-2.07, p ≤ .001; OR MDD-trauma = 1.22, 95% CI = 1.18-1.27, p ≤ .001).

Conclusions

Our findings highlight the importance of controlling for both BMI and trauma when studying MDD in the context of inflammation. They also suggest that the experience of traumatic events can increase the risk for MDD and that MDD can increase the experience of traumatic events.

Comparison of depression and anxiety symptom networks in reporters and non-reporters of lifetime trauma in two samples of differing severity

BACKGROUND

Reported trauma is associated with differences in the course and outcomes of depression and anxiety. However, no research has explored the association between reported trauma and patterns of clinically relevant symptoms of both depression and anxiety.

METHODS

We used network analysis to investigate associations between reported trauma and depression and anxiety symptom interactions in affected individuals from the Genetic Links to Anxiety and Depression (GLAD) Study (n = 17720), and population volunteers from the UK Biobank (n = 11120). Participants with current moderate symptoms of depression or anxiety were grouped into reporters and non-reporters of lifetime trauma. Networks of 16 depression and anxiety symptoms in the two groups were compared using the network comparison test.

RESULTS

In the GLAD Study, networks of reporters and non-reporters of lifetime trauma did not differ on any metric. In the UK Biobank, the symptom network of reporters had significantly greater density (7.80) than the network of non-reporters (7.05).

LIMITATIONS

The data collected in the GLAD Study and the UK Biobank are self-reported with validated or semi-validated questionnaires.

CONCLUSIONS

Reported lifetime trauma was associated with stronger interactions between symptoms of depression and anxiety in population volunteers. Differences between reporters and non-reporters may not be observed in individuals with severe depression and/or anxiety due to limited variance in the presentation of disorder.

An Exposure-Wide and Mendelian Randomization Approach to Identifying Modifiable Factors for the Prevention of Depression

OBJECTIVE

Efforts to prevent depression, the leading cause of disability worldwide, have focused on a limited number of candidate factors. Using phenotypic and genomic data from over 100,000 UK Biobank participants, the authors sought to systematically screen and validate a wide range of potential modifiable factors for depression.

METHODS

Baseline data were extracted for 106 modifiable factors, including lifestyle (e.g., exercise, sleep, media, diet), social (e.g., support, engagement), and environmental (e.g., green space, pollution) variables. Incident depression was defined as minimal depressive symptoms at baseline and clinically significant depression at follow-up. At-risk individuals for incident depression were identified by polygenic risk scores or by reported traumatic life events. An exposure-wide association scan was conducted to identify factors associated with incident depression in the full sample and among at-risk individuals. Two-sample Mendelian randomization was then used to validate potentially causal relationships between identified factors and depression.

RESULTS

Numerous factors across social, sleep, media, dietary, and exercise-related domains were prospectively associated with depression, even among at-risk individuals. However, only a subset of factors was supported by Mendelian randomization evidence, including confiding in others (odds ratio=0.76, 95% CI=0.67, 0.86), television watching time (odds ratio=1.09, 95% CI=1.05, 1.13), and daytime napping (odds ratio=1.34, 95% CI=1.17, 1.53).

CONCLUSIONS

Using a two-stage approach, this study validates several actionable targets for preventing depression. It also demonstrates that not all factors associated with depression in observational research may translate into robust targets for prevention. A large-scale exposure-wide approach combined with genetically informed methods for causal inference may help prioritize strategies for multimodal prevention in psychiatry.

Classical Human Leukocyte Antigen Alleles and C4 Haplotypes Are Not Significantly Associated With Depression

BACKGROUND

The prevalence of depression is higher in individuals with autoimmune diseases, but the mechanisms underlying the observed comorbidities are unknown. Shared genetic etiology is a plausible explanation for the overlap, and in this study we tested whether genetic variation in the major histocompatibility complex (MHC), which is associated with risk for autoimmune diseases, is also associated with risk for depression.

METHODS

We fine-mapped the classical MHC (chr6: 29.6-33.1 Mb), imputing 216 human leukocyte antigen (HLA) alleles and 4 complement component 4 (C4) haplotypes in studies from the Psychiatric Genomics Consortium Major Depressive Disorder Working Group and the UK Biobank. The total sample size was 45,149 depression cases and 86,698 controls. We tested for association between depression status and imputed MHC variants, applying both a region-wide significance threshold (3.9 × 10-6) and a candidate threshold (1.6 × 10-4).

RESULTS

No HLA alleles or C4 haplotypes were associated with depression at the region-wide threshold. HLA-B*08:01 was associated with modest protection for depression at the candidate threshold for testing in HLA genes in the meta-analysis (odds ratio = 0.98, 95% confidence interval = 0.97-0.99).

CONCLUSIONS

We found no evidence that an increased risk for depression was conferred by HLA alleles, which play a major role in the genetic susceptibility to autoimmune diseases, or C4 haplotypes, which are strongly associated with schizophrenia. These results suggest that any HLA or C4 variants associated with depression either are rare or have very modest effect sizes.

The impact of treatment delivery format on response to cognitive behaviour therapy for preadolescent children with anxiety disorders

BACKGROUND

Several delivery formats of cognitive behaviour therapy (CBT) for child anxiety have been proposed, however, there is little consensus on the optimal delivery format. The primary goal of this study was to investigate the impact of the child's primary anxiety diagnosis on changes in clinical severity (of the primary problem) during individual CBT, group CBT and guided parent-led CBT. The secondary goal was to investigate the impact of the child's primary anxiety diagnosis on rates of remission for the three treatment formats.

METHODS

A sample of 1,253 children (5-12 years; Mage = 9.3, SD = 1.7) was pooled from CBT trials carried out at 10 sites. Children had a primary diagnosis of generalised anxiety disorder (GAD), social anxiety disorder (SoAD), specific phobia (SP) or separation anxiety disorder (SAD). Children and parents completed a semistructured clinical interview to assess the presence and severity of DSM-IV psychiatric disorders at preintervention, postintervention and follow-up. Linear mixture modelling was used to evaluate the primary research question and logistic modelling was used to investigate the secondary research question.

RESULTS

In children with primary GAD, SAD or SoAD, there were no significant differences between delivery formats. However, children with primary SP showed significantly larger reductions in clinical severity following individual CBT compared to group CBT and guided parent-led CBT. The results were mirrored in the analysis of remission responses with the exception that individual CBT was no longer superior to group CBT for children with a primary SP. The difference between individual and group was not significant when follow-up data were examined separately.

CONCLUSIONS

Data show there may be greater clinical benefit by allocating children with a primary SP to individual CBT, although future research on cost-effectiveness is needed to determine whether the additional clinical benefits justify the additional resources required.

Genome-wide association study of facial emotion recognition in children and association with polygenic risk for mental health disorders

Emotion recognition is disrupted in many mental health disorders, which may reflect shared genetic aetiology between this trait and these disorders. We explored genetic influences on emotion recognition and the relationship between these influences and mental health phenotypes. Eight-year-old participants (n = 4,097) from the Avon Longitudinal Study of Parents and Children (ALSPAC) completed the Diagnostic Analysis of Non-Verbal Accuracy (DANVA) faces test. Genome-wide genotype data was available from the Illumina HumanHap550 Quad microarray. Genome-wide association studies were performed to assess associations with recognition of individual emotions and emotion in general. Exploratory polygenic risk scoring was performed using published genomic data for schizophrenia, bipolar disorder, depression, autism spectrum disorder, anorexia, and anxiety disorders. No individual genetic variants were identified at conventional levels of significance in any analysis although several loci were associated at a level suggestive of significance. SNP-chip heritability analyses did not identify a heritable component of variance for any phenotype. Polygenic scores were not associated with any phenotype. The effect sizes of variants influencing emotion recognition are likely to be small. Previous studies of emotion identification have yielded non-zero estimates of SNP-heritability. This discrepancy is likely due to differences in the measurement and analysis of the phenotype.

A Genome-Wide Test of the Differential Susceptibility Hypothesis Reveals a Genetic Predictor of Differential Response to Psychological Treatments for Child Anxiety Disorders

BACKGROUND

The differential susceptibly hypothesis suggests that certain genetic variants moderate the effects of both negative and positive environments on mental health and may therefore be important predictors of response to psychological treatments. Nevertheless, the identification of such variants has so far been limited to preselected candidate genes. In this study we extended the differential susceptibility hypothesis from a candidate gene to a genome-wide approach to test whether a polygenic score of environmental sensitivity predicted response to cognitive behavioural therapy (CBT) in children with anxiety disorders.

METHODS

We identified variants associated with environmental sensitivity using a novel method in which within-pair variability in emotional problems in 1,026 monozygotic twin pairs was examined as a function of the pairs' genotype. We created a polygenic score of environmental sensitivity based on the whole-genome findings and tested the score as a moderator of parenting on emotional problems in 1,406 children and response to individual, group and brief parent-led CBT in 973 children with anxiety disorders.

RESULTS

The polygenic score significantly moderated the effects of parenting on emotional problems and the effects of treatment. Individuals with a high score responded significantly better to individual CBT than group CBT or brief parent-led CBT (remission rates: 70.9, 55.5 and 41.6%, respectively).

CONCLUSIONS

Pending successful replication, our results should be considered exploratory. Nevertheless, if replicated, they suggest that individuals with the greatest environmental sensitivity may be more likely to develop emotional problems in adverse environments but also benefit more from the most intensive types of treatment.

Clinical Predictors of Response to Cognitive-Behavioral Therapy in Pediatric Anxiety Disorders: The Genes for Treatment (GxT) Study

OBJECTIVE

The Genes for Treatment study is an international, multisite collaboration exploring the role of genetic, demographic, and clinical predictors in response to cognitive-behavioral therapy (CBT) in pediatric anxiety disorders. The current article, the first from the study, examined demographic and clinical predictors of response to CBT. We hypothesized that the child's gender, type of anxiety disorder, initial severity and comorbidity, and parents' psychopathology would significantly predict outcome.

METHOD

A sample of 1,519 children 5 to 18 years of age with a primary anxiety diagnosis received CBT across 11 sites. Outcome was defined as response (change in diagnostic severity) and remission (absence of the primary diagnosis) at each time point (posttreatment, 3-, 6-, and/or 12-month follow-up) and analyzed using linear and logistic mixed models. Separate analyses were conducted using data from posttreatment and follow-up assessments to explore the relative importance of predictors at these time points.

RESULTS

Individuals with social anxiety disorder (SoAD) had significantly poorer outcomes (poorer response and lower rates of remission) than those with generalized anxiety disorder (GAD). Although individuals with specific phobia (SP) also had poorer outcomes than those with GAD at posttreatment, these differences were not maintained at follow-up. Both comorbid mood and externalizing disorders significantly predicted poorer outcomes at posttreatment and follow-up, whereas self-reported parental psychopathology had little effect on posttreatment outcomes but significantly predicted response (although not remission) at follow-up.

CONCLUSION

SoAD, nonanxiety comorbidity, and parental psychopathology were associated with poorer outcomes after CBT. The results highlight the need for enhanced treatments for children at risk for poorer outcomes.

Locating, quantifying and characterising radiation hazards in contaminated nuclear facilities using a novel passive non-electrical polymer based radiation imaging device

This paper provides a summary of recent trials which took place at the US Department of Energy Oak Ridge National Laboratory (ORNL) during December 2010. The overall objective for the trials was to demonstrate that a newly developed technology could be used to locate, quantify and characterise the radiological hazards within two separate ORNL hot cells (B and C). The technology used, known as RadBall(®), is a novel, passive, non-electrical polymer based radiation detection device which provides a 3D visualisation of radiation from areas where effective measurements have not been previously possible due to lack of access. This is particularly useful in the nuclear industry prior to the decommissioning of facilities where the quantity, location and type of contamination are often unknown. For hot cell B, the primary objective of demonstrating that the technology could be used to locate, quantify and characterise three radiological sources was met with 100% success. Despite more challenging conditions in hot cell C, two sources were detected and accurately located. To summarise, the technology performed extremely well with regards to detecting and locating radiation sources and, despite the challenging conditions, moderately well when assessing the relative energy and intensity of those sources. Due to the technology's unique deployability, non-electrical nature and its directional awareness the technology shows significant promise for the future characterisation of radiation hazards prior to and during the decommissioning of contaminated nuclear facilities.

Biosynthesis of carbonic anhydrase in Chlamydomonas reinhardtii during adaptation to low CO(2)

The unicellular green alga Chlamydomonas reinhardtii synthesizes carbonic anhydrase in response to low levels of CO(2) (i.e., air levels of CO(2)). This enzyme, localized predominantly in the periplasmic space of the alga (or associated with the cell wall), is an important component of the machinery required for the active accumulation of inorganic carbon by C. reinhardtii and the saturation of ribulose-1,5-bisphosphate carboxylase at low extracellular carbon concentrations. We have begun to examine the synthesis and compartmentalization of carbonic anhydrase in C. reinhardtii. The monomeric species associated with carbonic anhydrase activity is synthesized as a precursor on 80S cytoplasmic ribosomes. This precursor can be detected immunologically in the profiles of translation products when a reticulocyte lysate, cell-free system is primed with poly(A)-RNA from either air-grown C. reinhardtii or cells shifted from growth on 5% CO(2) to air for 12 hr. It is not synthesized when the in vitro system is primed with poly(A)-RNA from CO(2)-grown algae. Since translatable RNA for the polypeptide responsible for carbonic anhydrase activity was only present in cells that experienced low levels of CO(2), the adaptation process either involves the regulation of transcription of the carbonic anhydrase gene (and perhaps other genes involved in adaptation) or the post-transcriptional processing of the messenger RNA. Furthermore, the appearance of the mature polypeptide associated with carbonic anhydrase activity in the periplasmic space of C. reinhardtii is inhibited by tunicamycin, an antibiotic that prevents core glycosylation of polypeptides on the endoplasmic reticulum. Together, these results suggest that the biosynthesis of this extracellular algal enzyme involves the translation of mRNA for the carbonic anhydrase monomer on ribosomes bound to the endoplasmic reticulum, the cleavage of a signal sequence during transport of the nascent polypeptide into the lumen of the endoplasmic reticulum, and subsequent glycosylation events prior to export across the plasmalemma.

Permeability measurement of macromolecules and assessment of mucosal antigen sampling using in vitro converted M cells

INTRODUCTION

M cells are located in the epithelial layer covering the gut-associated lymphoid tissue and are responsible for delivery of macromolecules and microorganisms to the underlying lymphoid cells. It has been shown that the human colonic cell line Caco-2 can be converted to M cells in vitro following coculture with isolated lymphocytes from murine Peyer's patches. Studies were undertaken to evaluate and characterize the transepithelial transport of select macromolecules across these in vitro derived M cells.

METHODS

Caco-2 cells were converted to M cells as reported previously. The morphology of Caco-2 cells and M cells was compared by transmission electron microscopy (TEM). The transport properties of macromolecules such as horseradish peroxidase, FITC-conjugated polystyrene beads, and radiolabeled dextrans were examined. The activation of murine antigen-specific T cells following transport of the antigen ovalbumin across the M-cell barrier was assessed by measuring cytokine production.

RESULTS

M cells were shown to be irregular in shape and have fewer and shorter microvilli compared to the Caco-2 cell progenitors. These cells were still able to form tight junctions and monolayers on polycarbonate membranes. Time-course studies demonstrated that the transport of polystyrene beads and large-molecular-weight dextrans at physiological temperature across M-cell-containing monolayers was size dependent and more rapid than across Caco-2 cell monolayers. The transport of dextrans was also shown to be temperature and concentration dependent. Befitting the role of the M cell in mucosal defense, protein antigen could be delivered by these cells in order to be processed and presented to antigen-specific CD4+ T lymphocytes.

DISCUSSION

The M-cell permeability model is a functional and practical system for evaluating the transport properties of macromolecules and assessing the potential for intestinal mucosal antigen sampling to elicit immunological responses.

Using continuous quality improvement techniques to determine the causes of hospital readmission

This 6-month retrospective study provided our medical center with a profile of the population of patients readmitted within 31 days of discharge. We found that chronic illness and age greater than 65 years were the high risk factors related to patient readmissions. These 2 attributes are common in critical care patients. In addition, the study indicated that data input and collection procedures must be correctly followed in order to have accurate information on admission and readmission. Accurate information is important to management and external agencies. Accuracy is also important so that future problems with continuous quality improvement can be recognized and resources properly assigned. Recommendations for improving the data collection and reporting procedures and for improving the readmission rates were made to management, to the quality improvement coordinator, and to the quality improvement/risk management director.

Anti-epileptiform effects of audiogenic seizure priming on in vitro kindling in rat hippocampus

The effect of priming for audiogenic seizures (AGS) on the development of epileptiform activity in the hippocampus was studied using in vitro kindling (IVK) in Long-Evans rats. AGS priming consists of intense auditory stimulation during a critical period of auditory development, resulting in sound-induced clonic convulsions upon subsequent testing. Between postnatal day (PND) 28 and 50, slices from subjects primed and sham-primed for AGS on PND 18 were used for recording responses in area CA1 of hippocampus following Schaffer collateral stimulation from stratum radiatum of area CA2/CA3. The developmental priming procedure, which enhances auditory brainstem excitability, resulted in fewer afterdischarges in slices from primed subjects across initial IVK stimulation sequences. These results suggest that changes in excitability that occur with acoustic priming can initially diminish selective epileptiform response characteristics in forebrain areas such as the hippocampus.

The embryology, classification, epidemiology, and genetics of facial clefting

Facial clefting results from a variety of genetic and environmental causes. It occurs when developing facial processes fail to fuse, merge, or interact; the clefts range from mild to severe. The embryology and classification of these clefts have been characterized. Moreover, the epidemiology has been determined from population data. Unfortunately, complete understanding of the genetics of facial clefting has not been completely uncovered. Facial clefts exist within more than 300 syndromes with only a few being commented on in this article. As the human genome project continues, the understanding of facial clefting and its syndromes may continue to improve. Such knowledge could advance diagnosis and treatment of the patient and counseling of the affected family. Other articles within this issue address the management of these clefts.

Effects of low atmospheric CO(2) on plants: more than a thing of the past

In recent geological time, atmospheric CO(2) concentrations were 25-50% below the current level. Photosynthetic productivity of C(3) plants is substantially reduced at these low CO(2) levels, particularly at higher temperatures and during stress. Acclimation of photosynthesis to reduced CO(2) levels might compensate for some of this inhibition, but plants have a limited capacity to modulate Rubisco and other photosynthetic proteins following CO(2) reduction. Because of this, low CO(2) probably acted as a significant evolutionary agent, selecting plants adapted to CO(2) deficiency. Adaptations to low CO(2) might still exist in plants and might constrain responses to a rising CO(2) concentration.

Developmental and genetic audiogenic seizure models: behavior and biological substrates

Audiogenic seizure (AGS) models of developmental or genetic origin manifest characteristic indices of generalized seizures such as clonus or tonus in rodents. Studies of seizure-resistant strains in which AGS is induced by intense sound exposure during postnatal development provide models in which other neural abnormalities are not introduced along with AGS susceptibility. A critical feature of all AGS models is the reduction of neural activity in the auditory pathways from deafness during development. The initiation and propagation of AGS activity relies upon hyperexcitability in the auditory system, particularly the inferior colliculus (IC) where bilateral lesions abolish AGS. GABAergic and glutaminergic mechanisms play crucial roles in AGS, as in temporal lobe models of epilepsy, and participate in AGS modulatory and efferent systems including the superior colliculus, substantia nigra, basal ganglia and structures of the reticular formation. Catecholamine and indolamine systems also influence AGS severity. AGS models are useful for elucidating the underlying mechanisms for formation and expression of generalized epileptic behaviors, and evaluating the efficacy of modern treatment strategies such as anticonvulsant medication and neural grafting.

Tectal graft modulation of audiogenic seizures in Long-Evans rat

Audiogenic seizure (AGS) activity can be induced in the seizure-resistant Long-Evans rat by postnatal priming. This study examined the effects of unilateral lesions of the inferior colliculus (IC) and implantation of tectal grafts on AGS components. Animals were primed with a 10-kHz tone burst at 120 dB on postnatal day 14 and tested for AGS susceptibility on day 28, and then two groups were unilaterally lesioned including animals receiving embryonic day 16-17 grafts of caudal tectum. Subsequently, animals were repeatedly tested for wild running and clonic-tonic convulsion components of AGS. The results demonstrate that unilaterally grafted animals with partial IC lesions showed significant reduction in the incidence of clonus expression with greater terminal uniphasic wild running behavior. These effects were stronger than in animals with comparable unilateral lesions alone. Many neurons in graft cases were in direct contact with host tissues to provide a substrate for tissue interactions previously demonstrated to promote neuron survival and remediate IC functions.

beta-carbonic anhydrase from Pisum sativum: crystallization and preliminary X-ray analysis

Recombinant beta-carbonic anhydrase from the garden pea, Pisum sativum, was purified to homogeneity and crystallized. Crystals belong to the orthorhombic space group C222, with unit-cell parameters a = 136.3, b = 142.5, c = 201.4 A, alpha = beta = gamma = 90 degrees. Crystals typically diffracted anisotropically, with a maximal resolution of 2.0 A in the strongest direction. The calculated Matthews parameter predicts approximately eight molecules in the asymmetric unit, consistent with previous reports of the molecule being an octamer. However, examination of the self-rotation function revealed no fourfold symmetry axis and multiple weak twofold axes perpendicular to the crystallographic c axis, indicating that the oligomerization arrangement is not that of a 422 octamer.

Comparative histology and vibration of the vocal folds: implications for experimental studies in microlaryngeal surgery

OBJECTIVES/HYPOTHESIS

To determine the most suitable animal model for experimental studies on vocal fold surgery and function by a histological comparison of the microflap surgical plane and laryngeal videostroboscopy (LVS) in different species of animals. A second goal was to determine how the layered vocal fold structure in humans and three different animal species affects surgical dissection within the lamina propria.

STUDY DESIGN

Prospective laboratory.

METHODS

Three larynges each from dogs, monkeys, and pigs were compared with three ex vivo human larynges. Microflap surgery was performed on one vocal fold from each larynx. Both the operated and nonoperated vocal folds were examined histologically using stains specific for elastin, mature collagen, and ground substance. Based on the histological results, LVS was performed on two dogs and two pigs after first performing a tracheotomy for ventilation and airflow through the glottis. Arytenoid adduction sutures were placed to facilitate vocal fold adduction.

RESULTS

The distributions of the collagen and elastin fibers were found to differ among the species with concentrations varying within species. Unlike the human vocal fold, which has a higher elastin concentration in the deeper layers of the lamina propria, both the pig and the dog had a thin band of elastin concentrated just deep to the basement membrane zone in the superficial layer. Just deep to this thin band, the collagen and the elastin were less concentrated. The monkey vocal fold had a very thin mucosal layer with less elastin throughout the mucosa. The microflap dissections in each of the dog, pig, and human vocal folds were similar, being located within that portion of the superficial lamina propria where the elastin and mature collagen are less concentrated. The microflap plane in the monkey vocal fold was more deeply located near the vocalis fibers. Despite the differences in elastin concentration, the microflap plane in both the dog and the pig was found to be similar to that in humans. The dog anatomy was much more suitable for microsuspension laryngoscopy and stroboscopic examination. The dog vocal folds vibrated in a similar fashion to human vocal folds with mucosal waves and vertical phase differences, features not seen in the pig vocal folds.

CONCLUSIONS

Based on both the histological and stroboscopic results, the dog was believed to be a more suitable animal model for studies on vocal fold surgery, acknowledging that no animal's laryngeal anatomy is identical to that of the human. The dog LVS model presented allows for longitudinal laryngeal studies requiring repeated examinations at multiple time periods with histological correlation applied at sacrifice.

Integrated case management: the 21st century challenge for HMO case managers: Part I

As HMOs approach the new millennium, their care and cost management strategies still will be under attack by policy-makers, legislative bodies, the media, American businesses, and the medical professions. The HMO industry will continue to be held accountable for the efficiency of its services, the quality of its care, and the performance and outcome measures that are the results of managing both the care and medical costs of its membership. This first of a two-part series put forward the concept of an integrated CM model to manage the total care of needs of HMO members at the turn of the century. This model consists of three care management approaches commonly used in mature HMOs: demand management, CM, and DM, as illustrated in Figure 1 and defined in Table 1. This article also described the new challenges facing HMOs, physicians, and nurse case managers and how they are navigating the difficult process of mapping demand management and CM approaches to the medical, social, and environmental needs of HMO members. With the costs of chronic conditions consuming 61% of the nation's annual health bill and increased numbers of the elderly joining HMOs, HMOs strongly need to implement DM approaches for economic survival reasons alone. Part two of this series will focus on the newest care management approach: disease state management.

Mutation in ankyrin repeats of the mouse Notch2 gene induces early embryonic lethality

Notch family genes encode transmembrane proteins involved in cell-fate determination. Using gene targeting procedures, we disrupted the mouse Notch2 gene by replacing all but one of the ankyrin repeat sequences in the cytoplasmic domain with the E. coli (beta)-galactosidase gene. The mutant Notch2 gene encodes a 380 kDa Notch2-(beta)-gal fusion protein with (beta)-galactosidase activity. Notch2 homozygous mutant mice die prior to embryonic day 11.5, whereas heterozygotes show no apparent abnormalities and are fully viable. Analysis of Notch2 expression patterns, revealed by X-gal staining, demonstrated that the Notch2 gene is expressed in a wide variety of tissues including neuroepithelia, somites, optic vesicles, otic vesicles, and branchial arches, but not heart. Histological studies, including in situ nick end labeling procedures, showed earlier onset and higher incidence of apoptosis in homozygous mutant mice than in heterozygotes or wild type mice. Dying cells were particularly evident in neural tissues, where they were seen as early as embryonic day 9.5 in Notch2-deficient mice. Cells from Notch2 mutant mice attach and grow normally in culture, demonstrating that Notch2 deficiency does not interfere with cell proliferation and that expression of the Notch2-(beta)-gal fusion protein is not toxic per se. In contrast to Notch1-deficient mice, Notch2 mutant mice did not show disorganized somitogenesis, nor did they fail to properly regulate the expression of neurogenic genes such as Hes-5 or Mash1. In situ hybridization studies show no indication of altered Notch1 expression patterns in Notch2 mutant mice. The results indicate that Notch2 plays an essential role in postimplantation development in mice, probably in some aspect of cell specification and/or differentiation, and that the ankyrin repeats are indispensable for its function.

Spatial sound detection and the role of the inferior colliculus in the Long-Evans rat

The ability of Long-Evans hooded rats (n = 10) to detect sounds presented from sources in the horizontal plane at 0 degrees elevation and the effects of bilateral lesions of the inferior colliculus on these abilities were examined. Rats were trained on a directional detection task which required animals to suppress licking responses in a conditioned avoidance paradigm when 100-ms noise bursts were presented at random from speakers at 45 degrees intervals beginning at azimuth (0 degrees). A task performance rate was determined by reducing the correct lick suppression rate for signal trials by the proportion of incorrect suppression responses on non-signal trials. Higher performance rates were observed for stimuli presented from 0-90 degrees than for stimuli presented in the caudal hemifield prior to surgical procedures. Bilateral lesions restricted to the inferior colliculus reduced detection performance (p < 0.05) and shifted the best performance rates from sounds presented at 0-45 degrees to stimuli emitted from a 90 degrees source (p < 0.05). These results demonstrate that pigmented rats show differential detection levels for noise bursts presented from different locations throughout the horizontal interaural plane, and suggest that the inferior colliculus is involved in this aspect of directional hearing.

Audiogenic seizures in the developmentally primed Long-Evans rat

The Long-Evans rat is a hybrid rodent strain with little innate susceptibility to audiogenic seizures (AGS). The present study examines parameters of acoustic priming (induced susceptibility) and testing for AGS during postnatal development subsequent to auditory function, and identifies the effects of stimulus intensity, repeated testing, and gender upon AGS activity. Rats were exposed to 125-dB SPL 10-kHz tone bursts at 14-36 days of age and tested with white noise at 14 or 19 days following sound exposure. All priming/testing combinations yielded AGS susceptibility; animals primed at 18 days showed the highest incidence of clonic seizures when tested 14 days later. All subjects displayed clonus at testing intensities of 120 dB, although some seizure behaviors could be elicited at 100 dB. Repeated testing at 120 dB increased latency to clonus and clonus duration, and total wild running activity. Gender differences for AGS expression were minimal. These results demonstrate the viability of the seizure-resistant Long-Evans rat for study of AGS.

Processing of endogenous pre-mRNAs in association with SC-35 domains is gene specific

Analysis of six endogenous pre-mRNAs demonstrates that localization at the periphery or within splicing factor-rich (SC-35) domains is not restricted to a few unusually abundant pre-mRNAs, but is apparently a more common paradigm of many protein-coding genes. Different genes are preferentially transcribed and their RNAs processed in different compartments relative to SC-35 domains. These differences do not simply correlate with the complexity, nuclear abundance, or position within overall nuclear space. The distribution of spliceosome assembly factor SC-35 did not simply mirror the distribution of individual pre-mRNAs, but rather suggested that individual domains contain both specific pre-mRNA(s) as well as excess splicing factors. This is consistent with a multifunctional compartment, to which some gene loci and their RNAs have access and others do not. Despite similar molar abundance in muscle fiber nuclei, nascent transcript "trees" of highly complex dystrophin RNA are cotranscriptionally spliced outside of SC-35 domains, whereas posttranscriptional "tracks" of more mature myosin heavy chain transcripts overlap domains. Further analyses supported that endogenous pre-mRNAs exhibit distinct structural organization that may reflect not only the expression and complexity of the gene, but also constraints of its chromosomal context and kinetics of its RNA metabolism.

Histomorphometric and laryngeal videostroboscopic analysis of the effects of corticosteroids on microflap healing in the dog larynx

The histologic and functional effects of unilateral, layered corticosteroids on lateral microflap healing in 15 dogs were analyzed. Histologic sections of steroid-treated vocal folds (VFs) were studied with computer morphometry to examine differences in the tissue healing response. Paired analysis revealed increases in the inflammatory infiltrate around the microflap in the steroid-treated VFs at 2, 4, and 6 weeks (6.3%, 30.6%, and 34.9%, all with p < .02). The neovascular response in the steroid-treated VFs was less at 2 weeks (-20.9%, p < .005) but greater at 4 and 6 weeks (16.3% and 4.3%, p < .005). To better characterize the effect of steroids on the healing process, a normal, time-dependent distribution was applied to the histologic data and demonstrated a delay in the steroid-treated VF tissue response of 12 days for the inflammatory infiltrate and 21 days for the neovascular response. Qualitative and quantitative analysis of in vivo laryngeal videostroboscopy (LVS) samples taken preoperatively and at sacrifice could not identify significant differences in appearance, amplitude, mucosal wave, or suppleness between the 2 VFs. Therefore, although corticosteroids cause a delay in wound healing, LVS does not discern differences in microflap characteristics between healing steroid-treated and control VFs at 2, 4, or 6 weeks. If steroids are used, the surgeon should account for a probable delay in wound healing, but should not expect an overall difference in functional outcome.

Ethanol synthesis by genetic engineering in cyanobacteria

Cyanobacteria are autotrophic prokaryotes which carry out oxygenic photosynthesis and accumulate glycogen as the major form of stored carbon. In this research, we introduced new genes into a cyanobacterium in order to create a novel pathway for fixed carbon utilization which results in the synthesis of ethanol. The coding sequences of pyruvate decarboxylase (pdc) and alcohol dehydrogenase II (adh) from the bacterium Zymomonas mobilis were cloned into the shuttle vector pCB4 and then used to transform the cyanobacterium Synechococcus sp. strain PCC 7942. Under control of the promoter from the rbcLS operon encoding the cyanobacterial ribulose-1, 5-bisphosphate carboxylase/oxygenase, the pdc and adh genes were expressed at high levels, as demonstrated by Western blotting and enzyme activity analyses. The transformed cyanobacterium synthesized ethanol, which diffused from the cells into the culture medium. As cyanobacteria have simple growth requirements and use light, CO2, and inorganic elements efficiently, production of ethanol by cyanobacteria is a potential system for bioconversion of solar energy and CO2 into a valuable resource.

Latency alterations of the auditory brainstem response in audiogenic seizure-prone Long-Evans rats

Audiogenic seizure susceptibility in the normally seizure-resistant Long-Evans rat may result from altered processing in the auditory pathway. Representative waveform latencies of the auditory brainstem responses (ABR) were recorded to examine generator alterations at different levels of the auditory neuraxis. Male Long-Evans rats primed for audiogenic seizures (AGS) on PND 14 with a 10 kHz pure tone at 120 dB SPL for 8 min were tested for AGS on PND 28 with 120 dB SPL continuous white noise. Primed subjects displayed wild running culminating in clonic convulsions. Following behavioral testing at 4-6 months, vertex recordings of ABR waves Ia-VI were made in anesthetized subjects using pure tone stimulus bursts. AGS subjects showed marginally elevated ABR thresholds. Shorter ABR wave latencies were elicited in AGS subjects for peripheral and central auditory components with stimulus intensities above 50 dB PeSPL at 8 and 40 kHz. Interpeak intervals were reduced for waves Ia-V and III-V in AGS subjects. These results reveal that intense sound stimulation during a sensitive period of development later reduces processing time at higher intensity levels.

Estrogen treatment and age effects on auditory brainstem responses in the post-breeding Long-Evans rat

The auditory brainstem response (ABR) was recorded from 20-month-old Long Evans hooded female rats to determine if latency reductions occur from estrogen replacement. The ABR in these post-breeding age rats was also examined for reductions in response latencies as a function of adult age. Tone pip stimuli (8 and 40 kHz) were presented at 21, 51, or 81 s(-1). Aging control and ovariectomized animals showed slower response latencies for waves Ib-VI than young adults for 8 and 40 kHz stimulation at 21 s(-1). Increased stimulus rate resulted in longer latencies for all waves at 20 months. In contrast to hormone treatment effects in young adults, ABR latencies in post-breeding age estrogen-treated animals were not reduced, consistent with a general decrease in CNS responsiveness to estrogen steroids associated with age. The results also suggest that sensorineural modifications in the auditory system which prolong ABR latencies can occur early in the aging process of adult female subjects.

Postnatal cytoarchitecture of the rat medial geniculate body

The medial geniculate body (MGB) is a thalamic structure that provides vital information flow to the forebrain for complex acoustic processing. The development of cytoarchitectural features of the MGB was examined in rat to identify age-related patterns of growth in major geniculate compartments that have been described previously (Clerici and Coleman [1990] J. Comp. Neurol. 297:14-31; Clerici et al. [1990] J. Comp. Neurol. 297:32-54): the ventral (MGv), dorsal (MGd), and medial (MGm) divisions. Results show that, on the day of parturition, all major nuclei of each division are characterized, including the ovoid (OV) and ventral (LV) nuclei of MGv; the dorsal, deep dorsal (DD), caudodorsal, limitans, and suprageniculate nuclei of MGd; and the MGm. The MGv and MGd, which display comparable areas at birth, show rapid growth to postnatal day 7 (PND7), which then slows until PND11, around the time of ear canal opening; subsequently, MGv accelerates growth to reach larger adult size. From PND11 to PND16, thionin facilitates parcellation by extensive staining of dendritic processes of MGd, MGm, and lateral posterior nucleus neurons but not neurons of the MGv or the dorsal lateral geniculate nucleus. Golgi stains after birth reveal restricted dendritic arborizations in MGv cells and dichotomous branching patterns of MGd neurons. Somal size in MGB increases dramatically subsequent to afferent innervation and again following onset of auditory function. Somal growth occurs between all postnatal age groups tested for OV, LV, and DD nuclei, although LV segments related to high and low frequencies do not differ. Cell packing density predicts the expanse of major MGB divisions better than somal size. These results demonstrate the integrity and growth patterns of MGB nuclei and divisions from nascence and provide a substrate for subsequent study of anatomical and physiological development of the MGB.

Lateral laryngotomy for the removal of Teflon granuloma

Teflon injection has been used for vocal fold medialization following paralysis. Recently, numerous articles have discussed the complications of Teflon injection, including overinjection, airway obstruction. Teflon granuloma, and an abnormal mass effect creating a decreased vibratory character of the true vocal fold. Multiple techniques for Teflon removal have been described. This report details our experience with complete Teflon granuloma removal via a lateral laryngotomy under local anesthesia. Microscopic dissection of the entire granuloma and the paraglottic space was accomplished in all patients. Due to extensive destruction caused by the granuloma, the vocal ligament was resected in 3 patients; it was partially resected and reanastomosed in 1 case, and spared in 6 patients. Laryngeal reconstruction was accomplished with an inferiorly based sternohyoid muscle rotation flap and arytenoid adduction. Effortful speech secondary to pressed vocal quality resolved in all patients. Near-normal to normal vocal quality was obtained in 4 patients, with the average "voice desirability" improving 60% and the effective glottic width increasing 29%. Factors that contributed to a successful outcome included noninvolvement of the vocal ligament and sparing of the mucosal cover.

Association of carbonic anhydrase with a Calvin cycle enzyme complex in Nicotiana tabacum

Chloroplast-localized carbonic anhydrase (CA; EC 4.2.1.1), an enzyme which catalyzes the reversible hydration of CO2, appears to be associated with other enzymes of the Calvin cycle in a large multienzyme complex. Gel-filtration fast protein liquid chromatography (FPLC) of soluble proteins obtained by osmotic lysis of tobacco (Nicotiana tabacum L. cv. Carlson) chloroplasts results in the co-elution of a protein complex of greater than 600 kDa which includes CA, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), phosphoribulokinase (PRK), and ribose-5-phosphate isomerase. Anion-exchange FPLC of chloroplast extracts indicates that there is an association of CA with other proteins that modifies its elution profile in a NaCl gradient, and that Rubisco co-elutes with the fractions containing CA. Following a protocol described by Süss et al. (1993, Proc Natl Acad Sci USA 90: 5514-5518), limited protease treatment of chloroplast extracts was used to show that the association of PRK with other chloroplast proteins appears to protect a number of lysine and arginine residues which may be involved in specific protein-protein interactions. A similar treatment of CA indicates some protection of these residues when CA is associated with other chloroplast polypeptides but the level of protection is not as profound as that exhibited by PRK. In concert with previously published immunolocalization studies, these data indicate that CA may be associated with Rubisco at the stromal periphery of a Calvin cycle enzyme complex in which PRK is more centrally located and associated with thylakoid membranes.

Current concepts in oromandibular reconstruction

Oromandibular reconstruction represents an exciting and growing area within head and neck reconstructive surgery. The advent and use of free tissue transfer have revolutionized the field. Combining these newer techniques with time-proven techniques presents the reconstructive surgeon with a wide array of reconstructive options in the oromandibular region. This article considers the more common and reliable methods for oromandibular reconstruction. The authors examine the anatomic basis of each option, highlight the literature concerning each technique, and make specific recommendations based on their experience.

Effects of tectal grafts on sound localization deficits induced by inferior colliculus lesions in hooded rats

The goals of this research were to examine the role of the inferior colliculus (IC) in mediating sound localization behavior and the ability of tectal grafts to restore function after IC ablation in the Long-Evans rat. Previous work has suggested that the IC is a major center for processing of information used in localizing sound sources in space. Adult rats were trained on a lick suppression paradigm to discriminate the location of the second pulse in a noise burst pair presented in the horizontal interaural plane. Following baseline testing, rats received bilateral IC lesions, bilateral lesions followed in 1 week by bilateral tectal grafts, or were sham operated. Sound localization ability was then tested 15 to 30 days and 40 to 50 days following surgical procedures. Performance across experimental groups was statistically the same during baseline testing. During the first operative test period lesion-only and grafted animals showed deficits in sound localization ability relative to controls. By the second postoperative test period control and grafted animals did not differ statistically in sound localization ability and performance of both groups was superior to that of lesion-only animals. Histology revealed a similar extent of IC damage in lesion-only and lesion-graft animals and revealed the presence of implanted tectal tissue in all grafted animals. There was significant neuron loss in the dorsal nucleus of lateral lemniscus (DNLL) in lesion-only animals relative to grafted rats and sham controls. Behavioral results suggest that the IC of pigmented rat is important for sound localization ability. The sparing of DNLL neurons in grafted animals suggests that the tectal grafts may directly integrate into or aid intrinsic recovery of the host auditory pathway.

Identification and characterization of a gene encoding a vertebrate-type carbonic anhydrase in cyanobacteria

A gene (designated ecaA) encoding a vertebrate-like (alpha-type) carbonic anhydrase (CA) has been isolated from two disparate cyanobacteria, Anabaena sp. strain PCC 7120 and Synechococcus sp. strain PCC 7942. The deduced amino acid sequences correspond to proteins of 29 and 26 kDa, respectively, and revealed significant sequence similarity to human CAI and CAII, as well as Chlamydomonas CAHI, including conservation of most active-site residues identified in the animal enzymes. Structural similarities between the animal and cyanobacterial enzymes extend to the levels of antigenicity, as the Anabaena protein cross-reacts with antisera derived against chicken CAII. Expression of the cyanobacterial ecaA is regulated by CO2 concentration and is highest in cells grown at elevated levels of CO2. Immunogold localization using an antibody derived against the ecaA protein indicated an extracellular location. Preliminary analysis of Synechococcus mutants in which ecaA has been inactivated by insertion of a drug resistance cassette suggests that extracellular carbonic anhydrase plays a role in inorganic-carbon accumulation by maintaining equilibrium levels of CO2 and HCO3- in the periplasm.

Extended middle meatal antrostomy: the treatment of circular flow

Intranasal surgery has changed significantly over the years. The inferior meatal antrostomy has lost favor to the more physiologic middle meatal antrostomy which includes the natural ostium. Difficult-to-cure patients may exhibit mucous stasis due to circular flow between ostomies. Kennedy described circular flow in both the experimental model and the clinical arena. We have enlarged his definition of circular flow to include the flow of mucus from the natural ostium or a surgically created ostium to any accessory ostium, either natural or surgically created. We present the extended middle meatal antrostomy, a technique which prevents circular flow and allows the mucociliary system to provide for physiologic drainage of the maxillary sinus. This technique is demonstrated in this report to be safe and effective in the treatment of chronic maxillary sinusitis.

Hepatic specification of the gut endoderm in vitro: cell signaling and transcriptional control

We have studied the initial development of pluripotent gut endoderm to hepatocytes using a tissue explant system from mouse embryos. We not only find cellular interactions that specify hepatic differentiation but also those that block hepatogenesis in regions of the endoderm that normally give rise to other tissues. The results implicate both positive and negative signaling in early hepatic specification. In vivo footprinting of the albumin enhancer in precursor gut endoderm shows that the transcriptionally silent but potentially active chromatin is characterized by occupancy of an HNF-3 site. Upon hepatic specification, a host of other factors bind nearby sites as the gene becomes active. Genes in pluripotent cells therefore may be marked for potential expression by entry points in chromatin, where additional factors bind during cell type specification. The findings also provide insight into the evolutionary origin of different endodermal cell types.

Effects of tectal grafts on sound detection deficits induced by inferior colliculus lesions in hooded rats

The midbrain inferior colliculus (IC), a major integrating center for auditory processing, provides a model for structural, functional, and behavioral recovery. The present study examined the role of IC in spatial sound detection, and the effects of neural transplantation in sparing of behavioral performance. Hooded rats were presented noise bursts at ambient noise levels and 15 dB above this level randomly at one of eight locations in the horizontal plane, and rats were required to suppress licking upon detecting signal presentations. Following training, rats received bilateral IC lesions, bilateral lesions followed in 1 wk by bilateral tectal grafts (embryonic Day 18), or were sham operated. During repeated testing 15 to 30 days and 40 to 45 days following surgical procedures, rats with lesions showed impaired detection task performance when compared to grafted or sham animals. Detection ratios were statistically higher for grafted rats than for rats with lesions at repeated testing times. Performance of grafted animals was not statistically separable from the sham control group; however, grafted rats never achieved preoperative detection rates nor rates as high as sham rats. Postmortem implantation of diI crystals unilaterally into grafts demonstrated fiber labeling in the ipsilateral IC and lateral lemniscus, and retrograde labeling of neurons in the remaining host IC and dorsal nucleus of lateral lemniscus. Combined with results of previous studies, the results of this study suggest that sparing of detection performance for sounds occurring at random spatial locations may be attributable to partial integration of host-graft pathways.