Distinct disease mutations in DNMT3A result in a spectrum of behavioral, epigenetic, and transcriptional deficits

Phenotypic heterogeneity in monogenic neurodevelopmental disorders can arise from differential severity of variants underlying disease, but how distinct alleles drive variable disease presentation is not well understood. Here, we investigate missense mutations in DNA methyltransferase 3A (DNMT3A), a DNA methyltransferase associated with overgrowth, intellectual disability, and autism, to uncover molecular correlates of phenotypic heterogeneity. We generate a Dnmt3aP900L/+ mouse mimicking a mutation with mild to moderate severity and compare phenotypic and epigenomic effects with a severe R878H mutation. P900L mutants exhibit core growth and behavioral phenotypes shared across models but show subtle epigenomic changes, while R878H mutants display extensive disruptions. We identify mutation-specific dysregulated genes that may contribute to variable disease severity. Shared transcriptomic disruption identified across mutations overlaps dysregulation observed in other developmental disorder models and likely drives common phenotypes. Together, our findings define central drivers of DNMT3A disorders and illustrate how variable epigenomic disruption contributes to phenotypic heterogeneity in neurodevelopmental disease.

NSD1 deposits histone H3 lysine 36 dimethylation to pattern non-CG DNA methylation in neurons

During postnatal development, the DNA methyltransferase DNMT3A deposits high levels of non-CG cytosine methylation in neurons. This methylation is critical for transcriptional regulation, and loss of this mark is implicated in DNMT3A-associated neurodevelopmental disorders (NDDs). Here, we show in mice that genome topology and gene expression converge to shape histone H3 lysine 36 dimethylation (H3K36me2) profiles, which in turn recruit DNMT3A and pattern neuronal non-CG methylation. We show that NSD1, an H3K36 methyltransferase mutated in NDD, is required for the patterning of megabase-scale H3K36me2 and non-CG methylation in neurons. We find that brain-specific deletion of NSD1 causes altered DNA methylation that overlaps with DNMT3A disorder models to drive convergent dysregulation of key neuronal genes that may underlie shared phenotypes in NSD1- and DNMT3A-associated NDDs. Our findings indicate that H3K36me2 deposited by NSD1 is important for neuronal non-CG DNA methylation and suggest that the H3K36me2-DNMT3A-non-CG-methylation pathway is likely disrupted in NSD1-associated NDDs.

Distinct disease mutations in DNMT3A result in a spectrum of behavioral, epigenetic, and transcriptional deficits

Phenotypic heterogeneity is a common feature of monogenic neurodevelopmental disorders that can arise from differential severity of missense variants underlying disease, but how distinct alleles impact molecular mechanisms to drive variable disease presentation is not well understood. Here, we investigate missense mutations in the DNA methyltransferase DNMT3A associated with variable overgrowth, intellectual disability, and autism, to uncover molecular correlates of phenotypic heterogeneity in neurodevelopmental disease. We generate a DNMT3A P900L/+ mouse model mimicking a disease mutation with mild-to-moderate severity and compare phenotypic and epigenomic effects with a severe R878H mutation. We show that the P900L mutation leads to disease-relevant overgrowth, obesity, and social deficits shared across DNMT3A disorder models, while the R878H mutation causes more extensive epigenomic disruption leading to differential dysregulation of enhancers elements. We identify distinct gene sets disrupted in each mutant which may contribute to mild or severe disease, and detect shared transcriptomic disruption that likely drives common phenotypes across affected individuals. Finally, we demonstrate that core gene dysregulation detected in DNMT3A mutant mice overlaps effects in other developmental disorder models, highlighting the importance of DNMT3A-deposited methylation in neurodevelopment. Together, these findings define central drivers of DNMT3A disorders and illustrate how variable disruption of transcriptional mechanisms can drive the spectrum of phenotypes in neurodevelopmental disease.

NSD1 deposits histone H3 lysine 36 dimethylation to pattern non-CG DNA methylation in neurons

During postnatal development the DNA methyltransferase DNMT3A deposits high levels of non-CG cytosine methylation in neurons. This unique methylation is critical for transcriptional regulation in the mature mammalian brain, and loss of this mark is implicated in DNMT3A-associated neurodevelopmental disorders (NDDs). The mechanisms determining genomic non-CG methylation profiles are not well defined however, and it is unknown if this pathway is disrupted in additional NDDs. Here we show that genome topology and gene expression converge to shape histone H3 lysine 36 dimethylation (H3K36me2) profiles, which in turn recruit DNMT3A and pattern neuronal non-CG methylation. We show that NSD1, the H3K36 methyltransferase mutated in the NDD, Sotos syndrome, is required for megabase-scale patterning of H3K36me2 and non-CG methylation in neurons. We find that brain-specific deletion of NSD1 causes alterations in DNA methylation that overlap with models of DNMT3A disorders and define convergent disruption in the expression of key neuronal genes in these models that may contribute to shared phenotypes in NSD1- and DNMT3A-associated NDD. Our findings indicate that H3K36me2 deposited by NSD1 is an important determinant of neuronal non-CG DNA methylation and implicates disruption of this methylation in Sotos syndrome.

Highlights

Topology-associated DNA methylation and gene expression independently contribute to neuronal gene body and enhancer non-CG DNA methylation patterns.Topology-associated H3K36me2 patterns and local enrichment of H3K4 methylation impact deposition of non-CG methylation by DNMT3A. Disruption of NSD1 in vivo leads to alterations in H3K36me2, DNA methylation, and gene expression that overlap with models of DNMT3A disorders.

Effects of dietary supplementation of gestating sows with adenosine 5 '-monophosphate or adenosine on placental angiogenesis and vitality of their offspring

Our previous study found that dietary nucleotide supplementation, including adenosine 5 '-monophosphate (AMP), could increase AMP content in sow milk and promote piglet growth, but its effects on placental efficiency and piglet vitality remains unknown. This experiment aimed to investigate the effects of dietary AMP or its metabolite adenosine (ADO) supplementation on sow reproductive performance and placental angiogenesis. A total of 135 sows with a similar farrowing time were blocked by backfat and body weight (BW) at day 65 of gestation, and assigned to 1 of 3 dietary treatment groups (n = 45 per treatment): basal diet, basal diet supplemented with 0.1% AMP, or 0.1% ADO, respectively. Placental analysis and the characteristics of sows and piglets unveiled that compared with control (CON) group, AMP or ADO supplementation could improve sow placental efficiency (P<0.05) and newborn piglet vitality (P<0.05), increase piglet birth weight (P<0.05), and reduce stillbirth rate (P<0.05). More importantly, AMP or ADO supplementation could increase the contents of AMP, ADO, and their metabolites in placentae (P<0.05). Meanwhile, AMP or ADO supplementation could also increase placental vascular density (P<0.05) and the expression of vascular endothelial growth factor A (P<0.05), as well as promote the migration and tube formation of porcine iliac artery endothelial cells (P<0.05). Overall, maternal dietary AMP or ADO supplementation could increase their contents in the placenta, thereby improving placental angiogenesis and neonatal piglet vitality.

APC7 mediates ubiquitin signaling in constitutive heterochromatin in the developing mammalian brain

Neurodevelopmental cognitive disorders provide insights into mechanisms of human brain development. Here, we report an intellectual disability syndrome caused by the loss of APC7, a core component of the E3 ubiquitin ligase anaphase promoting complex (APC). In mechanistic studies, we uncover a critical role for APC7 during the recruitment and ubiquitination of APC substrates. In proteomics analyses of the brain from mice harboring the patient-specific APC7 mutation, we identify the chromatin-associated protein Ki-67 as an APC7-dependent substrate of the APC in neurons. Conditional knockout of the APC coactivator protein Cdh1, but not Cdc20, leads to the accumulation of Ki-67 protein in neurons in vivo, suggesting that APC7 is required for the function of Cdh1-APC in the brain. Deregulated neuronal Ki-67 upon APC7 loss localizes predominantly to constitutive heterochromatin. Our findings define an essential function for APC7 and Cdh1-APC in neuronal heterochromatin regulation, with implications for understanding human brain development and disease.

Exercise intensities modulate cognitive function in spontaneously hypertensive rats through oxidative mediated synaptic plasticity in hippocampus

Background

Oxidative damage in the brain may lead to cognitive impairments. There was considerable debate regarding the beneficial effects of physical exercise on cognitive functions because exercise protocols have varied widely across studies.

Purpose

We investigated whether different exercise intensities alter performance on cognitive tasks.

Methods

The experiment was performed on spontaneously hypertensive rats (6 months at the established phase of hypertension) distributed into 3 groups: sedentary, low-intensity exercise, and high-intensity exercise.

Results

Systolic blood pressure measurements confirmed hypertension in spontaneously hypertensive rats. In comparison to normotensive Wistar-Kyoto rats, sedentary spontaneously hypertensive rats had similar escape latencies and a similar preference for the correct quadrant in the probe trial. Compared to the sedentary group, the low-intensity exercise group had significantly better improvements in spatial memory assessed by Morris water maze. Low-intensity exercise was associated with attenuated reactive oxygen species, as measured by dihydroethidine fluorescence and nitrotyrosine staining in the dentate gyrus of the hippocampus. This was coupled with increased numbers of neurons and dendritic spines as well as a significant upregulation of synaptic density. In contrast, the beneficial effects of low-intensity exercise are abolished in high-intensity exercise as shown by increased free radical levels and an impairment in spatial memory.

Conclusions

We concluded that exercise is an effective strategy to improve spatial memory in spontaneously hypertensive rats even at an established phase of hypertension. Low-intensity exercise exhibited better improvement on cognitive deficits than high-intensity exercise by attenuating free radical levels and improving downstream synaptic plasticity.

Funding Acknowledgement

Type of funding sources: None.

[Subcutaneous sparganosis: a case report]

This case report presents the diagnosis and treatment of a case with subcutaneous sparganosis.

DNMT3A Haploinsufficiency Results in Behavioral Deficits and Global Epigenomic Dysregulation Shared across Neurodevelopmental Disorders

Mutations in DNA methyltransferase 3A (DNMT3A) have been detected in autism and related disorders, but how these mutations disrupt nervous system function is unknown. Here, we define the effects of DNMT3A mutations associated with neurodevelopmental disease. We show that diverse mutations affect different aspects of protein activity but lead to shared deficiencies in neuronal DNA methylation. Heterozygous DNMT3A knockout mice mimicking DNMT3A disruption in disease display growth and behavioral alterations consistent with human phenotypes. Strikingly, in these mice, we detect global disruption of neuron-enriched non-CG DNA methylation, a binding site for the Rett syndrome protein MeCP2. Loss of this methylation leads to enhancer and gene dysregulation that overlaps with models of Rett syndrome and autism. These findings define the effects of DNMT3A haploinsufficiency in the brain and uncover disruption of the non-CG methylation pathway as a convergence point across neurodevelopmental disorders.

The chromatin remodeling enzyme Chd4 regulates genome architecture in the mouse brain

The development and function of the brain require tight control of gene expression. Genome architecture is thought to play a critical regulatory role in gene expression, but the mechanisms governing genome architecture in the brain in vivo remain poorly understood. Here, we report that conditional knockout of the chromatin remodeling enzyme Chd4 in granule neurons of the mouse cerebellum increases accessibility of gene regulatory sites genome-wide in vivo. Conditional knockout of Chd4 promotes recruitment of the architectural protein complex cohesin preferentially to gene enhancers in granule neurons in vivo. Importantly, in vivo profiling of genome architecture reveals that conditional knockout of Chd4 strengthens interactions among developmentally repressed contact domains as well as genomic loops in a manner that tightly correlates with increased accessibility, enhancer activity, and cohesin occupancy at these sites. Collectively, our findings define a role for chromatin remodeling in the control of genome architecture organization in the mammalian brain.

MeCP2 Represses Enhancers through Chromosome Topology-Associated DNA Methylation

The genomes of mammalian neurons contain uniquely high levels of non-CG DNA methylation that can be bound by the Rett syndrome protein, MeCP2, to regulate gene expression. How patterns of non-CG methylation are established in neurons and the mechanism by which this methylation works with MeCP2 to control gene expression is unclear. Here, we find that genes repressed by MeCP2 are often located within megabase-scale regions of high non-CG methylation that correspond with topologically associating domains of chromatin folding. MeCP2 represses enhancers found in these domains that are enriched for non-CG and CG methylation, with the strongest repression occurring for enhancers located within MeCP2-repressed genes. These alterations in enhancer activity provide a mechanism for how MeCP2 disruption in disease can lead to widespread changes in gene expression. Hence, we find that DNA topology can shape non-CG DNA methylation across the genome to dictate MeCP2-mediated enhancer regulation in the brain.

ME-Class2 reveals context dependent regulatory roles for 5-hydroxymethylcytosine

Since the discovery of 5-hydroxymethylcytosine (5hmC) as a prominent DNA modification found in mammalian genomes, an emergent question has been what role this mark plays in gene regulation. 5hmC is hypothesized to function as an intermediate in the demethylation of 5-methylcytosine (5mC) and in the reactivation of silenced promoters and enhancers. Further, weak positive correlations are observed between gene body 5hmC and gene expression. We previously demonstrated that ME-Class is an effective tool to understand relationships between whole-genome bisulfite sequencing data and expression. In this work, we present ME-Class2, a machine-learning based tool to perform integrative 5mCG, 5hmCG and expression analysis. Using ME-Class2 we analyze whole-genome single-base resolution 5mCG and 5hmCG datasets from 20 primary tissue and cell samples to reveal relationships between 5hmCG and expression. Our analysis indicates that conversion of 5mCG to 5hmCG within 2 kb of the transcription start site associates with distinct functions depending on the summed level of 5mCG + 5hmCG. Unchanged levels of 5mCG + 5hmCG (conversion from 5mCG to stable 5hmCG) associate with repression. Meanwhile, decreases in 5mCG + 5hmCG (5hmCG-mediated demethylation) associate with gene activation. Our results demonstrate that ME-Class2 will prove invaluable to interpret genome-wide 5mC and 5hmC datasets and guide mechanistic studies into the function of 5hmCG.

Lipid profiles as potential mediators linking body mass index to osteoporosis among Chinese adults: the Henan Rural Cohort Study

This study is to examine the relationship between body mass index (BMI) and osteoporosis in rural areas of China, and then explore whether this association was mediated by lipid profiles. Results showed that with the increasing of BMI, the risk of osteoporosis was reduced, and lipid profiles mediate this association.

INTRODUCTION

To examine the relationship between BMI and osteoporosis, and explore whether this association was mediated by lipid profiles.

METHODS

A total of 8272 participants (18-79 years) were enrolled from the Henan Rural Cohort Study. The bone mineral density of the calcaneus was measured using an ultrasonic bone density apparatus. Logistic regression and restricted cubic splines were used to evaluate the odds ratio (OR) and 95% confidence intervals (95% CI). Mediation analysis using bootstrap was performed to examine the contribution of lipid profiles to BMI-related osteoporosis.

RESULTS

The crude and age-standardized prevalence of osteoporosis were 15.93% and 11.77%, respectively. The mean BMIs were 24.12 kg/m² for participants with osteoporosis and 25.06 kg/m² for non-osteoporosis participants (P < 0.001). After adjusting for potential confounders, subjects with obesity had a lower OR of osteoporosis (0.493 [95% CI: 0.405-0.600], P_trend < 0.001) compared with normal-weight individuals. Mediation analysis showed that lipid profile partly mediated the relationship between BMI and osteoporosis with indirect effect OR (95% CI) of 0.985 (0.978-0.992), and the proportion explained of BMI was 15.48% for lipid profile.

CONCLUSION

With the increasing of BMI, the risk of osteoporosis was reduced in the Chinese adult population, and lipid profiles may be a potential mediator linking reduced risk of osteoporosis. Elucidating the underlying mechanisms will facilitate developing feasible preventive and therapeutic measures for osteoporosis. Chinese clinical trial register: ChiCTR-OOC-15006699.

Pioglitazone improves the ability of learning and memory via activating ERK1/2 signaling pathway in the hippocampus of T2DM rats

OBJECTIVE

To explore the correlation between effect of PIO (pioglitazone, PIO) on learning as well as memory and ERK1/2 (extracellular signal regulated kinase 1/2, ERK1/2) pathway in T2DM (type 2 diabetes mellitus, T2DM) rats, further to elucidate the potential mechanism of PIO in improvement of learning and memory.

METHODS

12-week-old male SD rats (number of 10 per group) were randomly divided into control group (CON), T2DM group (DM) and T2DM +PIO group (DM+PG). Rats in DM and DM+PG groups were given high fat diet for 20 weeks, then treated with Streptozotocin (27mg/kg) by intraperitoneal injection at 21week. After 72h, the FBG (fasting blood glucose, FBG) was greater than 7.0mmol/L can considered T2DM rats. DM+PG group was treated with PIO (10 mg·kg^-1·d^-1) by gavage daily. After Hyperinsulinemic-Euglycemic Clamp Study and Morris water maze test at 30-week, all of animals were sacrificed. The expressions of RKIP (Raf-1 kinase inhibitor protein, RKIP) and ERK1/2 in hippocampus were detected using Western Blot and real-time PCR.

RESULTS

The FBG level: DM group (7.68±0.54mmol/L) was higher than CON group (5.35±0.63mmol/L) and DM+PG group (6.07±0.84mmol/L), the differences were considered statistically significant (P <0.05). Hyperinsulinemic-Euglycemic Clamp Studies: GIR (glucose infusion rate, GIR) of DM group (21.02±5.10 mg·kg^-1·d^-1) was less than CON group (27.64±3.87 mg·kg^-1·d^-1) and DM+PG group (26.04 ±5.41 mg·kg^-1·d^-1), the differences were considered statistically significant (P <0.05). Morris water maze training: The escape latencies and searching platform performance of DM group (24.54±5.02s) decreased significantly compared with CON group (16.73±4.02s) and DM+PG group (18.05±4.12s) (P <0.05). Changes of RKIP, ERK, p-ERK protein relative content in rat hippocampus: Compared with CON groupand DM+PG group, the relative content of RKIP in DM group remarkably increased (P<0.01); ERK protein levels were not considered statistically significant among the three groups (P>0.05); The relative content of p-ERK1/2 protein in CON group and DM+PG group rats dorsal were higher than those in group DM, the difference was considered statistically significant (P<0.01). Changes in hippocampus of rat RKIP and ERK gene relative content: Compared with CON group and DM+PG group, levels of RKIP mRNA in DM group were significantly increased (P<0.01); ERK mRNA levels were not considered statistically significant among the three groups (P>0.05).

CONCLUSION

Activation of ERK1/2 signal transduction pathway via reducing RKIP in the hippocampus may be one of the mechanisms of PIO to improve the learning and memory of the T2DM rats.

First Report of Burkholderia andropogonis Causing Bacterial Leaf Spot of Betel Palm in Hainan Province, China

In May 2009, a severe bacterial disease of arecanut (Areca catechu L.) with an incidence of 100% was observed in a plantation of about 8,400 plants in Wenchang City, Hainan Province, China (19°47.171' N, 110°54.335' E). Symptoms consisted of small circular to elongated brown lesions, ranging from 1 to 105 mm in length and 1 to 21 mm in width, surrounded by yellow halos. White colonies, without fluorescent or diffusible pigments, were consistently recovered on King's B Medium plates from lesions surface-sterilized in 70% ethyl alcohol for 1 min. All isolates were gram-negative and each had a single, polar, sheathed flagellum. Isolates were identified as a Burkholderia sp. based on physiological and biochemical tests: oxidase and catalase positive, negative for arginine dihydrolase, gelatin hydrolysis and starch hydrolysis, and negative for acid production from levan (1,3). Sequences (approx. 1,400 bp each) of the 16S rRNA gene amplified from four isolates using primer pair 27F/1492R (2) (GenBank Accession Nos. JX415481, JX415479, JX415482, and JX415483) shared 99% sequence identity with that of Burkholderia andropogonis strain 6369 (DQ786951). Representative isolates Y11 (China General Microbiological Culture Collection Center No. CGMCC 1.12337), Y30 (CGMCC 1.12338), W15, and W20 were compared with B. andropogonis strain NCPPB No. 1012 and all caused a hypersensitive reaction on leaves of Nicotiana benthamiana. Isolate pathogenicity was tested twice with a total of three replications per isolate. Two young leaves each of 2-year-old arecanut plants were infiltrated with a bacterial suspension of 10⁸ CFU/ml, then covered individually with plastic bags for 48 h, and incubated at 100% relative humidity with 16 h of daylight at 25°C by day and 8 h of darkness at 20°C by night. After 7 days, small water-soaked spots with yellow halos were observed and 60 days after inoculation, lesions developed similar to those caused by B. andropogonis in the field. Koch's postulates were fulfilled by reisolating bacteria from typical lesions on inoculated plants. These bacteria were identical to inoculated strains in colony morphology and sequences of the 16S ribosomal RNA gene. To our knowledge, this is the first report of B. andropogonis infection on betel in Hainan Province, mainland China. This disease was first reported in Taiwan, a province of China. Conditions of high humidity and high temperature support disease outbreaks and infection can result in severe economic losses. In 2012, this disease also appeared on a number of plantations located in other counties. As betel is, economically, the second most important crop in Hainan Province, measures should be required to control this disease, especially in typhoon seasons. References: (1) S. H. Hseu et al. Plant Pathol. Bull. 16:131, 2007. (2) D. J. Lane. In: E. Stackebrandt, et al. Nucleic acid techniques in bacterial systematics. John Wiley & Sons, Chichester, United Kingdom, pp. 115-175, 1991. (3) X. Li and S. H. De Boer. Plant Dis. 89:1132. 2005.

Accelerated cellular senescence in solid tumor therapy

Accelerated cellular senescence (ACS) is an emerging concept that implicates sustained, telomere-independent cell cycle arrest of neoplastic cells in response to chemotherapeutic agents, ionizing radiation, oxidative stress, or the presence of selective oncogenic stimuli. Recent evidence suggests that a subset of tumor cells induced in a state of reversible ACS can escape cell cycle arrest and resume proliferation accounting for cancer progression. The purpose of this review is to describe our current understanding of ACS including signaling pathways of senescence escape, role of senescence biomarkers, and rationale for senescence-based therapy. This article is part of a Special Issue entitled "Apoptosis: Four Decades Later".

Antibody response to GD3 ganglioside is independent of NKT cells

BACKGROUND

NKT cells recognize glycolipids presented by CD1d on antigen-presenting cells (APC) and have been largely characterized by their ability to be activated by alpha-galactosylceramide, a glycolipid not expressed on mammalian cells. We have shown previously that GD3 can be cross-presented by CD1d to NKT cells and is the first tumor-derived glycolipid recognized by NKT cells. But the ability of NKT cells to modulate B-cell responses to tumor glycolipids that are themselves recognized by NKT cells has not been explored.

METHODS

We tested whether NKT cells are required for antibody (Ab) responses to GD3. We immunized wild-type mice, mice deficient in invariant chain NKT cells (iNKT cells) and mice deficient in total NKT cells against GD3. Ab titer against GD3 was measured by ELISA.

RESULTS

We found the IgM and IgG responses against GD3 were similar among the three strains of mice, including the IgG isotypes induced. Pre-expanded NKT cells to GD3 did not affect the anti-GD3 Ab response.

DISCUSSION

We conclude that Ab responses to GD3 are independent of NKT cells and that strategies to manipulate NKT cells in vivo are not likely to enhance the anti-GD3 Ab response induced by vaccines.

Nurses as providers of emotional support to patients with MDR-TB

AIM

To identify the forms and means of emotional support that nurses provide to patients living with multidrug-resistant tuberculosis (MTR-TB) in Lima, Peru.

BACKGROUND

A fundamental role of nurses is to provide emotional support, defined as all the strategies that a health team employs to assure the psychosocial well-being of the patient. However, neither the forms of emotional support nor the means used by nurses in resource-poor settings have been much written about. This paper describes a qualitative study of a team of seven nurses working in a programme that provides individualized MDR-TB treatment to patients in Lima, Peru. It describes the various forms of support that facilitated the ability of patients to adhere to treatment despite socio-economic difficulties, social stigma, drug side effects, problems related to different stages of treatment and concurrent illnesses/special situations.

METHODS

Qualitative study methods were employed over the course of 8 years to observe nurses and patients in an MDR-TB treatment programme. These included participant observation, structured observation sessions of nurses with their patients and focus groups with seven nurses.

CONCLUSION

Through theme and content analyses of qualitative data, ten situations related to MDR-TB treatment were found. These ten issues served as an analytical framework used to identify and discuss the various types of emotional support provided by both formal and informal means. This type of support focused on problems related to different stages of treatment, social stigma of the illness, treatment adherence, side effects, socio-economic difficulties, death and concurrent illnesses/special situations.

PRACTICE IMPLICATIONS

The essential role of the nurse as a provider of emotional support in the development or implementation of similar programmes with MDR-TB should, in future, be taken into account.

Associations of body fat and its changes over time with quality of life and prospective mortality in hemodialysis patients

BACKGROUND

In maintenance hemodialysis (MHD) patients, a larger body size is associated with better survival but a worse self-reported quality of life (QoL). It is not clear whether muscle mass or body fat confers the survival advantage.

OBJECTIVE

We hypothesized that both a low baseline body fat percentage and a loss of fat over time were independently associated with higher mortality but with a better QoL score.

DESIGN

In 535 adult MHD patients, body fat was measured directly with the use of near infrared interactance and QoL was measured with a Short Form 36 questionnaire. The patients were followed for < or =30 mo.

RESULTS

Across four 12% increments of body fat at baseline, the reported QoL scores were progressively lower (P < 0.01). After a multivariate adjustment for demographics and surrogates of muscle mass and inflammation (ie, midarm muscle circumference, serum creatinine, and proinflammatory cytokines), 46 patients with body fat of <12% had a death hazard ratio (HR) 4 times that of 199 patients with body fat content between 24% and 36% (HR: 4.01; 95% CI: 1.61, 9.99; P = 0.003). In 411 MHD patients whose body fat was remeasured after 6 mo, a fat loss (< or =-1%) was associated with a death risk 2 times that of patients who gained fat (> or =1%) after a multivariate adjustment (HR: 2.06; 95% CI: 1.05, 4.05; P = 0.04).

CONCLUSIONS

A low baseline body fat percentage and fat loss over time are independently associated with higher mortality in MHD patients even after adjustment for demographics and surrogates of muscle mass and inflammation, whereas a tendency toward a worse QoL is reported by MHD patients with a higher body fat percentage. Obesity management in dialysis patients may need reconsideration.

Association between serum bicarbonate and death in hemodialysis patients: is it better to be acidotic or alkalotic?

The optimal acid-base status for survival in maintenance hemodialysis (MHD) patients remains controversial. According to recent reports, acidosis is associated with improved survival in MHD patients. It was hypothesized that this inverse association is due to a confounding effect of the malnutrition-inflammation complex syndrome (MICS). Associations between baseline (first 3 mo averaged) predialysis serum bicarbonate (HCO3(-)) and 2-yr mortality were examined in 56,385 MHD patients who were treated in virtually all DaVita dialysis clinics across the United States. The range of HCO3(-) was divided into 12 categories (< 17, > or = 27, and 10 groups in between). Three sets of Cox regression models were evaluated to estimate hazard ratios of all-cause and cardiovascular death in both incident and prevalent patients: (1) Unadjusted, (2) multivariate case mix adjusted (which also included dialysate HCO3(-) and Kt/V), and (3) adjusted for case mix and nine markers of MICS (body mass index; erythropoietin dose; protein intake; serum albumin; creatinine; phosphorus; calcium; ferritin and total iron binding capacity; and blood hemoglobin, WBC, and lymphocytes). There were significant inverse associations between serum HCO3(-) and serum phosphorus and estimated protein intake. The lowest unadjusted mortality was associated with predialysis HCO3(-) in the 17- to 23-mEq/L range, whereas values > or = 23 mEq/L were associated with progressively higher all-cause and cardiovascular death rates. This association, however, reversed after case-mix and MICS multivariate adjustment, so that HCO3(-) values >22 mEq/L had lower death risk. Although previous epidemiologic studies indicated an association between high serum HCO3(-) and increased mortality in MHD patients, this effect seems to be due substantially to the effect of MICS on survival.

Association between serum bicarbonate and death in hemodialysis patients: is it better to be acidotic or alkalotic?

The optimal acid-base status for survival in maintenance hemodialysis (MHD) patients remains controversial. According to recent reports, acidosis is associated with improved survival in MHD patients. It was hypothesized that this inverse association is due to a confounding effect of the malnutrition-inflammation complex syndrome (MICS). Associations between baseline (first 3 mo averaged) predialysis serum bicarbonate (HCO3(-)) and 2-yr mortality were examined in 56,385 MHD patients who were treated in virtually all DaVita dialysis clinics across the United States. The range of HCO3(-) was divided into 12 categories (< 17, > or = 27, and 10 groups in between). Three sets of Cox regression models were evaluated to estimate hazard ratios of all-cause and cardiovascular death in both incident and prevalent patients: (1) Unadjusted, (2) multivariate case mix adjusted (which also included dialysate HCO3(-) and Kt/V), and (3) adjusted for case mix and nine markers of MICS (body mass index; erythropoietin dose; protein intake; serum albumin; creatinine; phosphorus; calcium; ferritin and total iron binding capacity; and blood hemoglobin, WBC, and lymphocytes). There were significant inverse associations between serum HCO3(-) and serum phosphorus and estimated protein intake. The lowest unadjusted mortality was associated with predialysis HCO3(-) in the 17- to 23-mEq/L range, whereas values > or = 23 mEq/L were associated with progressively higher all-cause and cardiovascular death rates. This association, however, reversed after case-mix and MICS multivariate adjustment, so that HCO3(-) values >22 mEq/L had lower death risk. Although previous epidemiologic studies indicated an association between high serum HCO3(-) and increased mortality in MHD patients, this effect seems to be due substantially to the effect of MICS on survival.

Reverse epidemiology: a spurious hypothesis or a hardcore reality?

In maintenance hemodialysis (MHD) patients, associations between demographic, clinical and laboratory values and mortality, including cardiovascular death, are significantly different and, in some cases, in the opposite direction of those derived from the general population. This phenomenon, termed 'reverse epidemiology', is not limited to MHD patients but is also observed in populations that encompass an estimated 20 million Americans including those with an advanced age, heart failure, malignancies, and AIDS. A significant portion of this reversal may be due to the overwhelming effect of the malnutrition-inflammation complex syndrome (MICS). Since two thirds of MHD patients die within 5 years of initiation of dialysis treatment, traditional cardiovascular risk factors such as obesity, hypercholesterolemia and hypertension cannot exert a long-term deleterious impact, and instead, their short-term beneficial effects on MICS provides a survival advantage. In order to improve survival and quality of life in MHD patients, extrapolated ideal norms derived from the general population should be substituted with novel norms obtained from outcome-oriented epidemiologic analyses while accounting for the differential effect of MICS in different case-mix subgroups.

Effect of displacement and distortion of potential energy surfaces and overlapping resonances of electronic transitions on surface-enhanced Raman scattering: Models and ab initio theoretical calculation

A previously developed theory for the temperature-dependent resonance Raman scattering is used to study the surface-enhanced Raman scattering. Two models, the displaced oscillator model and the displaced-distorted oscillator model, based on the harmonic potential energy surfaces are carried out to calculate the surface-enhanced Raman scattering excitation profiles of the pyridine molecule adsorbed on a silver electrode, for which the density functional theory method is applied to evaluate the potential energy surfaces of the adsorption structure. In this framework, the distortion effect on the surface-enhanced Raman scattering will be discussed by comparing both models. The overlapping resonance of multiexcited electronic transitions is also studied, in which the interference between electronic transitions has been taken into account. It will be used to study the abnormal band at 1005.6 cm(-1) with the exciting radiation 457.9 nm.

Theoretical differential Raman scattering cross-sections of totally-symmetric vibrational modes of free pyridine and pyridine-metal cluster complexes

The differential Raman scattering cross-sections of totally-symmetric vibrational modes for pyridine and pyridine-metal clusters have been calculated by using ab initio and density functional methods. The results are compared with experimental data and a good agreement is obtained. In particular, we can theoretically reproduce the significant changes in the relative Raman intensities of the nu(12) mode in pyridine-metal cluster complexes. We focus on two mechanisms for these Raman intensities changes: (1) the chemical interaction between the pyridine and the metal clusters; and (2) the charge transfer mechanism. For the pyridine-silver cluster complexes, we find that due to the weak bonding, the chemical interaction does not influence the relative intensities of the Raman peaks of the nu(1) and nu(12) modes. However, in the case where the copper or the gold clusters are attached to pyridine, the intensity of the band of the nu(12) mode is weakened significantly. We also find that the charge transfer mechanism increases the asymmetry of the bands of the nu(1) and nu(12) modes on all three metals.

Systemically expressed soluble Tie2 inhibits intraocular neovascularization

Retinal and choroidal neovascularization are the most frequent causes of severe and progressive vision loss. Studies have demonstrated that Tie2, an endothelial-specific receptor tyrosine kinase, plays a key role in angiogenesis. In this study, we determined whether adenovirus-mediated gene delivery of extracellular domain of the Tie2 receptor (ExTek) could inhibit experimental retinal and choroidal neovascularization. Immunofluorescence histochemistry with a monoclonal antibody to human Tie2 showed that Tie2 expression is prominent around and within the base of newly formed blood vessels of retinal and choroidal neovascular lesions. A single intramuscular injection of adenovirus expressing ExTek genes achieved plasma levels of ExTek exceeding 500 microg/ml in mice for 10 days (in neonates) and 7 days (in adults). This treatment inhibited retinal neovascularization by 47% (p < 0.05) in a murine model of ischemia-induced retinopathy. The same treatment reduced the incidence and extent of sodium fluorescein leakage from choroidal neovascular lesions by 52% (p < 0.05) and 36% (p < 0.01), respectively, in a laser-induced murine choroidal neovascularization model. The same mice showed a 45% (p < 0.001) reduction of integrated area of the choroidal neovascularization. These findings indicate that Tie2 signaling is a common component of the angiogenic pathway in both retinal and choroidal neovascularization, providing a potentially useful target in the treatment of intraocular neovascular diseases.

Tolerance to cyclosporin A-induced autologous graft-versus-host disease is mediated by a CD4+CD25+ subset of recent thymic emigrants

Our previous studies revealed that both the autoeffector and immunoregulatory T cells in cyclosporin A (CSA)-induced autologous graft-vs-host disease are recent thymic emigrants (RTEs). The autoeffector cells appear in and are released from the thymus during the first week of CSA treatment, whereas the immunoregulatory thymocytes appear during the second week but are not released until several days after cessation of CSA treatment. In the present study, the antigenic phenotypes of these functional T cell subsets were determined by immunomagnetic separation and flow immunocytometric analysis. During CSA wk 1, the autoeffector T cells in both the thymus and lymph node (LN) expressed a CD4+8+ double-positive (DP) phenotype, after which those in the LN became CD8 single positive (SP). Timed thymectomy experiments confirmed that the CD8-SP autoeffector T cells in LN originated from these DP RTEs. During CSA wk 2, the immunoregulatory thymocytes also displayed a DP phenotype. However, they were not exported to the periphery until several days after CSA treatment had been interrupted and they had acquired a CD4-SP phenotype. In LN, these immunoregulatory RTEs expressed the CD25+ marker characteristic of anergic/suppressor T cells. Cell separation and mixing experiments demonstrated that the autoeffector T cells persist in LN after cessation of CSA treatment, but their activity is not detectable in the presence of recently exported CD4+ T cells. Hence, the results indicate that tolerance to CSA-induced autologous graft-vs-host disease is actively mediated by CD25+CD4+ RTEs that suppress the function of CD8 autoeffector T cells.

Relationship between phenotypes of cell-function differentiation and pathobiological behavior of gastric carcinomas

AIM

To reveal the correlation between the functional differentiation phenotypes of gastric carcinoma cells and the invasion and metastasis by a new way of cell-function classification.

METHODS

Surgically resected specimens of 361 gastric carcinomas(GC) were investigated with enzyme-, mucin-, and tumor-related marker immunohistochemistry. According to the direction of cell-function differentiation, stomach carcinomas were divided into five functionally differentiated types.

RESULTS

(1) Absorptive function differentiation type (AFDT): there were 82 (22.7%) patients including 76 (92.7%) aged 45 years. Sixty-nine (84.1%) cases belonged to the intestinal type. Thirty-eight (46.3%) expressed CD44v6 and 9 (13.6%) of 66 male patients developed liver metastasis. The 5-year survival rate of patients in this group (58.5%) was higher than those with the other types (P<0.01). (2) Mucin secreting function differentiation type (MSFDT): 54 (15%) cases. Fifty-three (98.1%) tumors had penetrated the serosa, 12 (22.2%) expressed ER and 22 (40.7%) expressed CD44v6. The postoperative 5-year survival rate was 28.6%. (3) Absorptive and mucin-producing function differentiation type (AMPFDT): there were 180 (49.9%) cases, including 31 (17.2%) aged younger than 45 years. The tumor was more common in women (62, 34.4%,) and expressed more frequently estrogen receptors (ER) (129, 81.7%) than other types (P<0.01). Ovary metastasis was found in 12 (19.4%) out of 62 female subjects. The patients with this type GC had the lowest 5-year survival rate (24.7%) among all types. (4) Specific function differentiation type (SFDT): 13 (3.6%) cases. Nine (69.2%) tumors of this type derived from APUD system, the other 4 (30.7%) were of different histological differentiation. Sixty per cent of the patients survived at least five years. (5) Non-function differentiation type (NFDT): 32 (8.9%) cases. Nineteen (59.4%) cases had lymph node metastases but no one with liver or ovary metastasis. The 5-year survival rate was 28.1%.

CONCLUSION

This new cell-function classification of GC is helpful in indicating the characteristics of invasion and metastasis of GC with different cell-function differentiation phenotypes. Further study is needed to disclose the correlation between the cell-functional differentiation phenotypes and the relevant genotypes and the biological behavior of gastric carcinoma.

Analysis of ingredient and heating value of municipal solid waste

Great differences between municipal solid wastes (MSW) produced at different places and different times in terms of such parameters as physical ingredient and heating value lead to difficulty in effective handling of MSW. In this paper, ingredient, heating value and their temporal varying trends of typical MSW in Beijing were continuously measured and analyzed. With consideration of the process in pyrolysis and incineration, correlation between physical ingredients and heating values was induced, favorable for evaluation of heating value needed in handling of MSW from simple analysis of physical ingredients of it.

Promoter-specific targeting of human SWI-SNF complex by Epstein-Barr virus nuclear protein 2

The multiprotein human SWI-SNF (hSWI-SNF) complex is a chromatin-remodeling machine that facilitates transcription by overcoming chromatin-mediated gene repression. We had previously shown that hSNF5/INI1, an intrinsic, consistent component of the hSWI/SNF complex, is associated with Epstein-Barr nuclear antigen 2 (EBNA2) and have proposed that EBNA2 directs this complex to key EBNA2-responsive viral and cellular genes. Using chromatin immunoprecipitation and quantitative PCR, we show that antibodies directed against components of the hSWI-SNF complex preferentially precipitate chromatin-associated DNA that contains a targeted EBNA2-responsive element in the context of both episomal and cellular chromatin. This enrichment does not occur in EBNA2-negative cells or when the EBNA2-responsive element is mutated. The stable association of the hSWI-SNF complex with the EBNA2-responsive promoter can also be disrupted by deletion of the TATA element, suggesting that EBNA2 in itself is insufficient to mediate stable targeting of the hSWI-SNF complex. These results demonstrate that recruitment of the hSWI-SNF complex to selected promoters can occur in vivo through its interaction with site-specific activator proteins and that stable targeting may require the presence of basal transcription factors.

Leukemic HRX fusion proteins inhibit GADD34-induced apoptosis and associate with the GADD34 and hSNF5/INI1 proteins

One of the most common chromosomal abnormalities in acute leukemia is a reciprocal translocation involving the HRX gene (also called MLL, ALL-1, or HTRX) at chromosomal locus 11q23, resulting in the formation of HRX fusion proteins. Using the yeast two-hybrid system and human cell culture coimmunoprecipitation experiments, we show here that HRX proteins interact directly with the GADD34 protein. We have found that transfected cells overexpressing GADD34 display a significant increase in apoptosis after treatment with ionizing radiation, indicating that GADD34 expression not only correlates with apoptosis but also can enhance apoptosis. The amino-terminal third of the GADD34 protein was necessary for this observed increase in apoptosis. Furthermore, coexpression of three different HRX fusion proteins (HRX-ENL, HRX-AF9, and HRX-ELL) had an anti-apoptotic effect, abrogating GADD34-induced apoptosis. In contrast, expression of wild-type HRX gave rise to an increase in apoptosis. The difference observed here between wild-type HRX and the leukemic HRX fusion proteins suggests that inhibition of GADD34-mediated apoptosis may be important to leukemogenesis. We also show here that GADD34 binds the human SNF5/INI1 protein, a member of the SNF/SWI complex that can remodel chromatin and activate transcription. These studies demonstrate, for the first time, a gain of function for leukemic HRX fusion proteins compared to wild-type protein. We propose that the role of HRX fusion proteins as negative regulators of post-DNA-damage-induced apoptosis is important to leukemia progression.

Cyclosporin A-induced autologous graft-versus-host disease: a prototypical model of autoimmunity and active (dominant) tolerance coordinately induced by recent thymic emigrants

Cyclosporin A (CSA)-induced autologous graft-vs-host disease (autoGVHD) is an autoimmune syndrome initiated by autoeffector T cells presumed to be exported from the thymus during CSA treatment. The appearance of noncytotoxic immunoregulatory T cell activity after cessation of CSA treatment is also thymus dependent. In the present study, we have tested the hypothesis that both autoeffector and immunoregulatory T cells in CSA-treated rats are recent thymic emigrants (RTEs). Local syngeneic graft-vs-host reaction (synGVHR) and timed thymectomy (Tx) assays revealed that autoeffector T cells appear initially in the thymus and are promptly exported to lymph nodes (LN) during the first week of CSA treatment. In contrast, immunoregulatory thymocytes are first detectable by local synGVHR inhibition assays during the second week of CSA treatment but are not exported to LN until approximately 4 days post-CSA. Both the autoeffector and immunoregulatory T cells in LN express Thy-1, a selective marker for RTEs in the rat. However, the autoeffector RTEs have a CD4+8+ phenotype, whereas the immunoregulatory RTEs have a CD4+8- phenotype. Thus, the coordinate formation in and release from the thymus cortex and medulla of autoeffector and immunoregulatory T cells in CSA-treated rats directly demonstrates that centrally induced, nondeletional tolerance can serve as a fail-safe mechanism by which clones of autoeffector T cells that have escaped intrathymic negative selection for self-MHC class II Ag can be suppressed postthymically.

A role for tectal midline glia in the unilateral containment of retinocollicular axons

Retinal fibers approach close to the tectal midline but do not encroach on the other side. Just before the entry of retinal axons into the superior colliculus (SC), a group of radial glia differentiates at the tectal midline; the spatiotemporal deployment of these cells points to their involvement in the unilateral containment of retinotectal axons. To test for such a barrier function of the tectal midline cells, we used two lesion paradigms for disrupting their radial processes in the neonatal hamster: (1) a heat lesion was used to destroy the superficial layers of the right SC, including the midline region, and (2) a horizontally oriented hooked wire was inserted from the lateral edge of the left SC toward the midline and was used to undercut the midline cells, leaving intact the retinorecipient layers in the right SC. In both cases, the left SC was denervated by removing its contralateral retinal input. Animals were killed 12 hr to 2 weeks later, after intraocular injections of anterograde tracers to label the axons from the remaining eye. Both lesions resulted in degeneration of the distal processes of the tectal raphe glia and in an abnormal crossing of the tectal midline by retinal axons, leading to an innervation of the opposite ("wrong") tectum. The crossover occurred only where glial cell attachments were disrupted. These results document that during normal development, the integrity of the midline septum is critical in compartmentalizing retinal axons and in retaining the laterality of the retinotectal projection.

Giant ossified cavernous hemangioma of an extremity associated with an equinovarus deformity

A 39-year-old woman suffered from swelling and tenderness of the right leg for 31 years. Imaging studies showed a large soft tissue lesion on the right side extending from the proximal portion of the thigh to the ankle. She underwent several operations due to the leg mass and associated equinovarus deformity of the right ankle. The pathologic findings were those of an ossified cavernous hemangioma. This appears to be one of the largest hemangiomas to be reported. It revealed the three types of calcification characteristic of hemangiomas. Equinovarus deformity of the ankle caused by contracture of the calf in this case was probably related to repeated bleeding.

Direct thymic involvement in anterior chamber-associated immune deviation: evidence for a nondeletional mechanism of centrally induced tolerance to extrathymic antigens in adult mice

Recent reports have suggested that the dichotomy between central (thymic) and peripheral T cell tolerance is not absolute and that self-tolerance in perinatal animals may also involve the intrathymic generation and release to the periphery of Ag-specific immunoregulatory T cells. We have expanded this concept to include tolerance to non self Ags administered extrathymically to adult animals. In this study, we use the anterior chamber-associated immune deviation (ACAID) to demonstrate that central regulation of acquired peripheral tolerance can be induced in adult mice by the intraocular administration of low doses of nonself Ag. The results show that adult thymectomy prevents the inhibition of trinitrophenol (TNP)-specific delayed-type hypersensitivity, which normally occurs after injection of TNP-BSA into the anterior chamber (AC) of the eye. Thymocytes obtained from mice 1 to 3 days, but not 5 to 7 days, after AC injection of TNP-BSA or BSA alone specifically transfer inhibition of delayed-type hypersensitivity to mice primed with the homologous Ag. The latter observation, when correlated with the time of onset of ACAID, suggests that immunoregulatory T cells are formed in the thymus within 24 h and are exported to the peripheral lymphoid tissues between 2 and 5 days after AC injection of Ag. Immunomagnetic separation of thymocytes revealed that the immunoregulatory activity resides within the minor subset of CD4-, CD8-, TCR-alphabeta+ cells, previously postulated to induce fas ligand-mediated apoptosis and Th1 to Th2 immune deviation. Hence, the present study identifies ACAID as a prototypical model of centrally induced, nondeletional tolerance to extrathymic nonself Ags.

Direct thymic involvement in anterior chamber-associated immune deviation: evidence for a nondeletional mechanism of centrally induced tolerance to extrathymic antigens in adult mice

Recent reports have suggested that the dichotomy between central (thymic) and peripheral T cell tolerance is not absolute and that self-tolerance in perinatal animals may also involve the intrathymic generation and release to the periphery of Ag-specific immunoregulatory T cells. We have expanded this concept to include tolerance to non self Ags administered extrathymically to adult animals. In this study, we use the anterior chamber-associated immune deviation (ACAID) to demonstrate that central regulation of acquired peripheral tolerance can be induced in adult mice by the intraocular administration of low doses of nonself Ag. The results show that adult thymectomy prevents the inhibition of trinitrophenol (TNP)-specific delayed-type hypersensitivity, which normally occurs after injection of TNP-BSA into the anterior chamber (AC) of the eye. Thymocytes obtained from mice 1 to 3 days, but not 5 to 7 days, after AC injection of TNP-BSA or BSA alone specifically transfer inhibition of delayed-type hypersensitivity to mice primed with the homologous Ag. The latter observation, when correlated with the time of onset of ACAID, suggests that immunoregulatory T cells are formed in the thymus within 24 h and are exported to the peripheral lymphoid tissues between 2 and 5 days after AC injection of Ag. Immunomagnetic separation of thymocytes revealed that the immunoregulatory activity resides within the minor subset of CD4-, CD8-, TCR-alphabeta+ cells, previously postulated to induce fas ligand-mediated apoptosis and Th1 to Th2 immune deviation. Hence, the present study identifies ACAID as a prototypical model of centrally induced, nondeletional tolerance to extrathymic nonself Ags.

Epstein-Barr virus nuclear protein 2 (EBNA2) binds to a component of the human SNF-SWI complex, hSNF5/Ini1

Epstein-Barr nuclear antigen 2 (EBNA2), one of the six viral nuclear proteins expressed in latently infected B lymphocytes, is essential to the immortalization of B cells by Epstein-Barr virus (EBV). EBNA2 promotes transcriptional transactivation of viral and cellular genes by acting as an adapter molecule that binds to cellular sequence-specific DNA-binding proteins, JK recombination signal-binding protein (RBP-JK), and PU.1 and engages multiple members of the RNA polymerase II transcription complex. In the present study, we show that EBNA2 also interacts with hSNF5/Ini1, the human homolog of the yeast transcription factor SNF5. Gel filtration fractionation of partially purified EBV-positive lymphocyte nuclear extracts shows that a fraction of EBNA2 coelutes with both hSNF5/Ini1 and BRG1, a human homolog of SWI/SNF2, in the high-molecular-mass region (1.5 to 2.0 MDa) of a Superose 6 chromatogram. An affinity-purified rabbit antibody directed against hSNF5/Ini1 coimmunoprecipitates EBNA2 from this high-molecular-mass nuclear protein fraction, demonstrating that EBNA2 and hSNF5/Ini1 interact in vivo. This interaction is restricted to a subpopulation of phosphorylated viral EBNA2. Deletion mutation analysis of EBNA2 shows that the proline-rich aminoterminal end and a domain within the divergent region of EBNA2 mediate EBNA2-hSNF5/Ini1 interaction. Since the SNF-SWI complex participates in gene regulation through the alteration of nucleosome configuration and may be a component of the RNA polymerase II holoenzyme, the EBNA2-hSNF5/Ini1 interaction supports the hypothesis that EBNA2 facilitates transcriptional transactivation by acting as a transcription adapter molecule. We postulate that EBNA2 engages the hSNF-SWI complex to generate an open chromatin conformation at the EBNA2-responsive target genes, thereby potentiating the function of the RBP-JK-EBNA2-polymerase II transcription complex.

Association of beta 1 integrin with phosphotyrosine in growth cone filopodia

Filopodia of growth cones are key elements in the transduction of extracellular cues that guide axon growth during development. How they are specialized to carry out this role is poorly understood. We previously had found tyrosine phosphorylated protein to be heavily concentrated at the tips of many filopodia of Aplysia growth cones in certain culturing conditions, suggesting that tyrosine phosphorylation might be involved in filopodial specialization. Immunocytochemistry was used to analyze the protein composition of the tip aggregates to determine whether there was an association of the tip phosphorylation with any important extracellular cue. beta 1 integrin, a subunit of the receptor for laminin-type neurite growth promoters, coconcentrated with phosphotyrosine at filopodial tips of both Aplysia and mouse growth cones. Several observations indicated that the association of beta 1 integrin with phosphotyrosine is close. beta 1 integrin and phosphotyrosine are known to colocalize at focal contacts, sites of adhesion of cells to the extracellular matrix, but the composition and behavior of the tip aggregates mark them as distinct structures. Also found in the tip aggregates was a member of the ezrin-radixin-moesin family of proteins, which are thought to link membrane proteins to submembranous bundles of actin filaments. Use of an inhibitor of protein-tyrosine kinases to deplete tip phosphotyrosine also caused disappearance of beta 1 integrin from the tip, suggesting a role for tyrosine phosphorylation in facilitating interaction of growth cones with certain environmental cues by fostering the aggregation of receptors in filopodia.

Abnormalities in the export and fate of recent thymic emigrants in diabetes-prone BB/W rats

Abnormalities in postthymic T cell development in the BB/W rat model of autoimmune insulin-dependent diabetes mellitus (IDDM) result in part from a lymphopenia (lyp) gene defect. To better characterize these abnormalities, the phenotypes of T cells from diabetes-prone (DP) and diabetes-resistant (DR) coisogenic rats were analyzed by multiparameter flow immunocytometry (FCM). Marked decreases in the numbers of Thy1- RT6+ T cells, most of which are CD8+, were documented in DP rats by live-gating. Conversely, an approximately 3-fold increase was observed in the percentage of Thy1+ RT6- T cells, which normally serve as the precursors of both Thy1- RT6+ and Thy1- RT6- T cell subsets in rats. These results suggested that, at a minimum, an arrest in maturation of the Thy1+ precursors of RT6+ T cells occurs postthymically in DP rats. To determine more precisely the stage(s) in T cell development at which lymphopenia occurs, the export and fate of recent thymic emigrants (RTE's) and their immediate descendants in DP rats was traced after intrathymic (i.t.) labelling with fluorescein isothiocyanate (FITC). The results showed that in DP, as compared with DR, rats: 1) 5-fold fewer RTE's are exported from the thymus per 24 hr; 2) more than 80% of the RTE's are CD4+; 3) most of the immediate descendants of RTE's disappear from the peripheral lymphoid tissues within one week after export from the thymus; and 4) few of the descendants of the RTE's that do survive differentiate into RT6+ T cells. Staining with propidium iodide revealed that a significantly higher proportion of Thy1+ T cells in DP than in DR rats are in cycle (S/G2/M), thereby accounting for their disproportionately high numbers relative to RTE's. These results indicate that, in addition to defective thymic export, most of the immediate descendants of RTE's in DP rats undergo non-productive proliferation and death at the time (3-7 days postthymic) at which their counterparts in DR rats differentiate into Thy1- RT6+ T cells. The resulting deficiency of immunoregulatory T cells, acting in concert with defective intrathymic selection of effector T cell precursors, appears to conspire to markedly enhance the predisposition of DP rats to autoimmunity.

Tyrosine phosphorylation and protrusive structures of the growth cone

Protein-tyrosine kinase, such as those of the trk and Eph families, serve as membrane receptors for extracellular cues which regulate the rate and direction of growth of numerous groups of axons. Certain cytoplasmic protein-tyrosine kinases, such as src, are also abundant in growth cones. But, how protein-tyrosine phosphorylation regulates the growth cone is poorly understood. We discuss here potential roles for tyrosine phosphorylation in the protrusive structures of the growth cone, especially filopodia, which are important in detecting cues. A particular focus is the integrin receptor for substrate-bound growth promoters like laminin. Changes in tyrosine phosphorylation may be important in both facilitating and mediating the interaction of filopodia with these growth promoters.

Computed tomography and magnetic resonance imaging of diffuse pigmented villonodular synovitis: report of a case

We describe the computed tomographic (CT) and magnetic resonance imaging (MRI) features of a surgically proven case of diffuse pigmented villonodular synovitis (PVNS) of the knee in a 34-year-old woman. A complex mass consisting of solid and multicystic components was clearly demonstrated by CT and MRI. The solid part showed homogeneous hypodense attenuation relative to adjacent muscles on CT scans, but it showed inhomogeneous signal intensity on spin echo T1- and T2-weighted images (WI). The solid component enhanced homogeneously on CT scans but heterogeneously on MR images. Multiseptated enhancement of the cystic component on both CT and MR images were displayed. All of the above features were better demonstrated on MRI. Multiple marked hypointense round and patchy areas, and also a few areas isointense to subcutaneous fat within the lesion were also found on T1WI, proton density WI and T2WI. These characteristic MRI features of PVNS correlated well with its histologic structures: depositions of hemosiderin and fat in the proliferative synovial villi and bloody cystic content. These features may help to distinguish PVNS from other disease entities arising from the synovium.

Inhibition of formation of filopodia after axotomy by inhibitors of protein tyrosine kinases

The activity of motile protrusions of the growth cone--filopodia, veils, and lamellipodia--is essential for directed growth of a neuronal process. The regulation of the formation of these protrusions is not well understood. Numerous filopodia and veils or lamellipodia form within minutes of transection of an Aplysia axon in culture, as the initial components of growth cones of regenerating neurites. Axotomy, therefore, provides a robust and reliable protocol for analyzing the formation of these protrusions. We evaluated the involvement of protein phosphorylation in the regulation of protrusive activity. Of the inhibitors of protein kinases assayed, only the inhibitors of protein tyrosine kinases--genistein, lavendustin A, herbimycin A, and erbstatin analogue--suppressed the formation of protrusions, as assessed by high magnification video microscopy. These drugs did not work by preventing resealing of the axon, as evident from visual inspection and by the unimpaired effectiveness of genistein or lavendustin in preventing formation of filopodia when applied after resealing. Inhibition of protein tyrosine kinases not only prevented the formation of actin-based protrusions, but also caused deterioration of the actin network underlying the protrusive area of preexisting growth cones. Consistent with an involvement of protein tyrosine phosphorylation in the generation of protrusive structures, immunocytochemistry revealed that aggregates of phosphotyrosine appeared at the margins of the axon, from which protrusions emerge shortly after axotomy. These results suggest a role for protein tyrosine phosphorylation in the formation and maintenance of actin-based protrusive structures.

Glial environment in the developing superior colliculus of hamsters in relation to the timing of retinal axon ingrowth

We have examined the developmental changes of glial cell organization in the superior colliculus of embryonic and neonatal hamsters in reference to the known sequence of retinal axon ingrowth and arborization in the midbrain. Immunolocalization of vimentin, a marker for neuronal and glial cell precursors, reveals a uniform distribution of radially oriented cells, with perikarya located at the ventricular surface and thin, elongated processes fanning out toward the pia. These vimentin-positive cells, referred to as the lateral radial cells, are present in the tectum from embryonic day (E) 10 (earliest day examined) until approximately postnatal day (P) 5. Vimentin expression in the lateral radial cells decreases markedly during the second week of postnatal life: application of DiI to the ventricular surface reveals that the pial attachment of the lateral radial cells is withdrawn and that the radial processes are gradually pulled back toward the ventricular zone. By P14, virtually no vimentin-positive radial cells are detectable in the superior colliculus. At no time during development are the lateral radial cells immunopositive for the glial fibrillary acidic protein (GFAP); however, shorter, vimentin-positive astrocytic profiles can be seen in the tectum around the time the radial fibers have been withdrawn, suggesting that at least some radial cells are transformed into astrocytes that will colonize the mature colliculus. At approximately E12, a second group of cells, referred to as the midline radial glia, is detected at the tectal midline. These cells are tightly bundled, forming a raphe in the tectum. They are intensely vimentin positive from E13 until at least P14. From the time of birth, the midline radial cells also exhibit intense immunoreactivity for GFAP. The lateral radial cells are present in the superior colliculus prior to and during the period of neurogenesis but remain well past the time when collicular neuronal migration is completed. Pial processes of the lateral radial cells are present within the superficial tectal layers during the time retinal axons are entering this target; they may be involved in directing the growth and initial collateralization of retinotectal axons. Their withdrawal from retinorecipient collicular zones begins at about the time arbors are being elaborated on retinal axons. In contrast, the midline glia become distinct just prior to the time retinal axons enter the superior colliculus and persist during the time retinotectal projections are being fully established. These raphe glia may be involved in maintaining the laterality of the retinotectal projection.

Brachial plexus neuropathy secondary to septic arthritis and osteomyelitis: report of two cases

Two infants, delivered uneventfully, later developed right brachial plexus palsy secondary to pyogenic osteomyelitis and arthritis of the right shoulder joint. Weakness of right arms occurred at the sixth and tenth days of age respectively. Both had right arm tenderness on palpation and passive movement. Roentgenograms of their right shoulder joints showed irregular radiolucency of the proximal margin of right humerus head. In both cases, electromyography revealed various degrees of significant denervation pattern for the C5-C7 innervated muscles. Pus culture from right shoulder joints grew Streptococcus viridans and Staphylococcus aureus, respectively. After antibiotic therapy and arthrotomy with drainage, weakness improved gradually following continuous rehabilitation. Follow-up at six months of age showed almost complete recovery of right upper extremity function in one patient, but mild residual weakness in the other. Follow-up electromyography studies showed continued improvement. The possible mechanism of this rare occurrence is discussed.

Regulated tyrosine phosphorylation at the tips of growth cone filopodia

Several types of evidence suggest that protein-tyrosine phosphorylation is important during the growth of neuronal processes, but few specific roles, or subcellular localizations suggestive of such roles, have been defined. We report here a localization of tyrosine-phosphorylated protein at the tips of growth cone filopodia. Immunocytochemistry using a mAb to phosphorylated tyrosine residues revealed intense staining of the tips of most filopodia of Aplysia axons growing slowly on a polylysine substrate, but of few filopodia of axons growing rapidly on a substrate coated with Aplysia hemolymph, which has growth-promoting material. Cytochalasin D, which causes F-actin to withdraw rapidly from the growth cone, caused the tyrosine-phosphorylated protein to withdraw rapidly from filopodia, suggesting that the protein associates or interacts with actin filaments. Phosphotyrosine has previously been found concentrated at adherens junctions, where bundles of actin filaments terminate, but video-enhanced contrast-differential interference contrast and confocal interference reflection microscopy demonstrated that the filopodial tips were not adherent to the substrate. Acute application of either hemolymph or inhibitors of protein-tyrosine kinases to neurons on polylysine resulted in a rapid loss of intense staining at filopodial tips concomitant with a lengthening of the filopodia (and their core bundles of actin filaments). These results demonstrate that tyrosine-phosphorylated protein can be concentrated at the barbed ends of actin filaments in a context other than an adherens junction, indicate an association between changes in phosphorylation and filament dynamics, and provide evidence for tyrosine phosphorylation as a signaling mechanism in the filopodium that can respond to environmental cues controlling growth cone dynamics.

The effect of temperature and oligonucleotide primer length on the specificity and efficiency of amplification by the polymerase chain reaction

The polymerase chain reaction (PCR) is most effectively performed using a thermostable DNA polymerase such as that isolated from Thermus aquaticus. Since temperature and oligonucleotide length are known to control the specificity of oligonucleotide hybridization, we have investigated the effect of oligonucleotide length, base composition, and the annealing temperature on the specificity and efficiency of amplification by the PCR. Generally, the specificity of PCR is controlled by the length of the oligonucleotide and/or the temperature of annealing of the primer to the template. An empirical relationship between oligonucleotide length and ability to support amplification was determined. This relationship allows for the design of specific oligonucleotide primers. A model is proposed which helps explain the observed dependence of PCR on annealing temperature and length of the primer.