Perinatal and lifetime exposure to methylmercury in the mouse: blood and brain concentrations of mercury to 26 months of age

Chronic, low-level exposures to environmental toxicants, because they often begin prenatally and then persist throughout the individual's lifetime, pose challenging issues to risk assessment. Exposure to low levels of methylmercury through the diet, based largely on consumption of fish and sea mammals, follows this pattern. Early development is considered to be a period of heightened vulnerability during which even low-level exposures may produce undetected, "silent", damage that is revealed only under conditions that challenge the functional capacities of the individual. Aging, with its diminished functional capacities and compensatory reserves provides such a challenge, but, to explore this possibility, requires basic information about blood and brain levels under conditions of chronic lifetime exposure. The current research was undertaken to provide such information. One hundred female B6C3F1/HSD mice were assigned to one of three dose groups, 0, 1, or 3 ppm methylmercury chloride administered in a 5 nM sodium carbonate drinking solution. They were bred with male CBA/J HSD mice to produce the trihybrid offspring B6C3F1/ HSD x CBA/J HSD. Dosing of the females began 4 weeks prior to breeding and continued for the two methylmercury-exposed groups throughout breeding and gestation. The methylmercury-treated litters were split into two subgroups, one exposed throughout its lifetime (set at 26 months) to the original dose, the other exposed through postnatal day 13 (PND 13). Brain and blood concentrations were assayed by cold-vapor atomic absorption. Samples were obtained on PND 4 and 21, and then at the end of months 14 and 26. On PND 4, brain and blood levels closely reflected maternal dosing. In all groups, concentrations fell sharply from PND 4 to 21, but to a greater extent in the perinatal groups. Blood levels in the 1 ppm lifetime group remained unchanged between months 14 and 26, but brain levels rose modestly. In the 3 ppm lifetime group, both brain and blood levels rose significantly between months 14 and 26, suggesting an interaction between dose and age.

Specificity of relations between children's control-related beliefs and internalizing and externalizing psychopathology

The authors examined the specificity of the relation between 3 types of control-related beliefs and internalizing and externalizing psychopathology in a sample of 290 clinic-referred children aged 7 to 17 years. Self-reported beliefs about control (the capacity to cause an intended outcome), contingency (the degree to which a desired outcome can be controlled by a relevant behavior), and competence (an individual's ability to produce the relevant behavior) across 3 domains (academic, behavioral, and social) showed more specific relations with psychopathology than have been previously reported. Among children with externalizing psychopathology, internalizing psychopathology may be specifically associated with increased self-critical awareness about their conduct; externalizing psychopathology may attenuate the specific negative relation between internalizing psychopathology and control-related beliefs in the social domain.

Altered operant responding for motor reinforcement and the determination of benchmark doses following perinatal exposure to low-level 2,3,7,8-tetrachlorodibenzo-p-dioxin

Pregnant Holtzman rats were exposed to a single oral dose of 0, 20, 60, or 180 ng/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the 18th day of gestation. Their adult female offspring were trained to respond on a lever for brief opportunities to run in specially designed running wheels. Once they had begun responding on a fixed-ratio 1 (FR1) schedule of reinforcement, the fixed-ratio requirement for lever pressing was increased at five-session intervals to values of FR2, FR5, FR10, FR20, and FR30. We examined vaginal cytology after each behavior session to track estrous cyclicity. Under each of the FR values, perinatal TCDD exposure produced a significant dose-related reduction in the number of earned opportunities to run, the lever response rate, and the total number of revolutions in the wheel. Estrous cyclicity was not affected. Because of the consistent dose-response relationship at all FR values, we used the behavioral data to calculate benchmark doses based on displacements from modeled zero-dose performance of 1% (ED(01)) and 10% (ED(10)), as determined by a quadratic fit to the dose-response function. The mean ED(10) benchmark dose for earned run opportunities was 10.13 ng/kg with a 95% lower bound of 5.77 ng/kg. The corresponding ED(01) was 0.98 ng/kg with a 95% lower bound of 0.83 ng/kg. The mean ED(10) for total wheel revolutions was calculated as 7.32 ng/kg with a 95% lower bound of 5.41 ng/kg. The corresponding ED(01) was 0.71 ng/kg with a 95% lower bound of 0.60. These values should be viewed from the perspective of current human body burdens, whose average value, based on TCDD toxic equivalents, has been calculated as 13 ng/kg.

Specificity of relations between children's control-related beliefs and internalizing and externalizing psychopathology

The authors examined the specificity of the relation between 3 types of control-related beliefs and internalizing and externalizing psychopathology in a sample of 290 clinic-referred children aged 7 to 17 years. Self-reported beliefs about control (the capacity to cause an intended outcome), contingency (the degree to which a desired outcome can be controlled by a relevant behavior), and competence (an individual's ability to produce the relevant behavior) across 3 domains (academic, behavioral, and social) showed more specific relations with psychopathology than have been previously reported. Among children with externalizing psychopathology, internalizing psychopathology may be specifically associated with increased self-critical awareness about their conduct; externalizing psychopathology may attenuate the specific negative relation between internalizing psychopathology and control-related beliefs in the social domain.

Methods to identify and characterize developmental neurotoxicity for human health risk assessment. I: behavioral effects

Alterations in nervous system function after exposure to a developmental neurotoxicant may be identified and characterized using neurobehavioral methods. A number of methods can evaluate alterations in sensory, motor, and cognitive functions in laboratory animals exposed to toxicants during nervous system development. Fundamental issues underlying proper use and interpretation of these methods include a) consideration of the scientific goal in experimental design, b) selection of an appropriate animal model, c) expertise of the investigator, d) adequate statistical analysis, and e) proper data interpretation. Strengths and weaknesses of the assessment methods include sensitivity, selectivity, practicality, and variability. Research could improve current behavioral methods by providing a better understanding of the relationship between alterations in motor function and changes in the underlying structure of these systems. Research is also needed to develop simple and sensitive assays for use in screening assessments of sensory and cognitive function. Assessment methods are being developed to examine other nervous system functions, including social behavior, autonomic processes, and biologic rhythms. Social behaviors are modified by many classes of developmental neurotoxicants and hormonally active compounds that may act either through neuroendocrine mechanisms or by directly influencing brain morphology or neurochemistry. Autonomic and thermoregulatory functions have been the province of physiologists and neurobiologists rather than toxicologists, but this may change as developmental neurotoxicology progresses and toxicologists apply techniques developed by other disciplines to examine changes in function after toxicant exposure.

Serotonin receptor gene HTR3A variants in schizophrenic and bipolar affective patients

Serotonin receptor genes have always been considered excellent candidate genes in the aetiology of neurogenetic diseases. In this study, we assessed sequence variations of the HTR3A gene. For this purpose, we established exon-specific primers and analysed DNA samples from 165 unrelated individuals including 70 schizophrenic patients, 48 patients with bipolar affective disorder and 47 healthy control persons using polymerase chain reaction/single-strand conformational polymorphism analysis. We discovered six sequence variants, five of which represent polymorphisms. These polymorphisms could not be associated with schizophrenia and bipolar affective disorder (P = 0.055-1). We also detected a missense mutation in exon 9 in a schizophrenic patient at a conserved position (Pro391Arg). To determine the incidence of this substitution an extended set of 358 schizophrenic patients and 155 control individuals was investigated. The Pro391Arg mutation was not detected in these schizophrenic patients and controls screened. However, a second missense mutation (Arg344His) was detected in one schizophrenic patient, but not in any of the controls. These results suggest that the observed mutations in HTR3A are rare and therefore do not play a major role in the aetiology of the disorder. Further studies are needed to support the hypothesis that HTR3A may contribute to the schizophrenia in these patients.

Endonuclease V of Escherichia coli prevents mutations from nitrosative deamination during nitrate/nitrite respiration

Endonuclease V (Endo V) of Escherichia coli participates in the excision repair of hypoxanthine and xanthine (deaminated adenine and guanine) in DNA. It thereby reduces the mutagenic effects of nitrous acid by attacking lesions caused by nitrosative deamination. Nitrosating agents may be produced endogenously when E. coli is grown in oxygen-poor cultures, during which nitrate and nitrite replace oxygen as preferred electron acceptors. In this study, the protective effect of Endo V was observed under such conditions. During micro-aerobic growth, an nfi (Endo V) mutation enhanced the frequency of nitrate- and nitrite-induced A:T-->G:C and G:C-->A:T transition mutations, which are consistent with a defect in the removal of DNA hypoxanthine and xanthine, respectively. Similar effects were observed in saturated, aerobic cultures but not in well-aerated, logarithmically growing ones. A narG (nitrate reductase) mutation blocked the mutagenesis of the nfi mutant by nitrate but not by nitrite. These results differed from those of previous studies in which cell suspensions generated an exogenous nitrosating agent from nitrite, but not from nitrate, in a reaction that was narG-dependent. Nitrate/nitrite metabolism is also known to generate endogenous alkylating agents through N-nitrosation. However, an nfi mutation did not appreciably enhance mutagenesis by N-methyl-N-nitrosourea, suggesting that the mutator effect of nfi is not due to a defect in alkylation repair. The overall results indicate that Endo V functions during normal growth by helping to repair nitrosatively deaminated bases in DNA, which are by-products of anaerobic nitrate/nitrite respiration.

A 2-year follow-up of the effectiveness of traditional child psychotherapy

This study examined outcomes at a 2-year follow-up assessment for child psychotherapy as it typically is delivered in outpatient settings. The treatment condition (53 children, mean age = 10.5 years) and control condition (53 children, mean age = 10.0 years) were compared with regard to rates of linear and curvilinear change for psychopathology, adaptive functioning, and consumer satisfaction. Although both conditions showed curvilinear as well as linear improvement in behavioral and emotional problems, relatively little support was found for the effectiveness of traditional child psychotherapy or for the presence of a psychotherapy "sleeper effect."

Evaluation of techniques for assessing neurobehavioral development in children

A battery of tests has been designed to explore functional disabilities in children 10-12 years of age arising from adverse conditions during early development. At these ages, it becomes possible to use more complex and challenging tests than those typically used at earlier ages. Although the battery was prompted originally by questions arising from methylmercury exposure, it was also designed for applicability to neurotoxicant exposures arising from pesticides, solvents, persistent organic pollutants such as PCBs and dioxins, other metals, and nutrient excesses and deficiencies as well. The test battery includes the following categories: (1) neuropsychological tests with established psychometric properties not widely exploited in studies of developmental neurotoxicity; (2) electrophysiological and behavioral tests of sensory functioning spanning a broader range of indices than those used generally in studies of neuropsychological development; and (3) adaptations of performance tasks used previously only in animals. The battery was developed in Rochester, New York, and then field-tested on a group of 61 children in the Republic of the Seychelles, where the Ministry of Health had established the Child Development Center. Our findings suggest a number of tests and procedures with the potential for inclusion in test batteries aimed at the exploration of adverse neurodevelopmental effects.

Seeking care for nonurgent medical conditions in the emergency department: through the eyes of the patient

INTRODUCTION

The policy goal of shifting nonurgent visits from the emergency department to nonemergency health care settings is commonly devised, planned, and implemented without considering patients' perspectives. The purpose of this study was to gain an understanding of the context in which patients choose to seek health care in an emergency department. Human science provided the framework for this exploratory descriptive research study.

METHODS

This study was conducted at an urban, university emergency department in Denver, Colo. Uninsured adult patients triaged as nonurgent who were being discharged home were eligible to participate. Eligible patients from 15 randomly selected shifts were asked to participate. Following their ED visit, open-ended interviews began with the question, "Can you tell me the story, or the chain of events, that led to your coming to the emergency department today?" Each interview was audiotaped. Transcripts were analyzed to identify common themes. Patients also rated their severity of illness from 1 (not severe) to 5 (life-threatening), and they rated their satisfaction with the health care they received from 1 (not satisfied) to 5 (extremely satisfied).

RESULTS

The 30 study participants ranged in age from 17 to 60 years; 22 participants (73%) were women. Most patients (73%) rated their severity of illness as 3 or less and their satisfaction with the health care they received as 4 or more (83%). Five themes for seeking care were identified: (1) toughing it out, (2) symptoms overwhelming self-care measures, (3) calling a friend, (4) nowhere else to go, and (5) convenience. Despite the fact that the patients had nonurgent medical problems, their stories revealed that distress in their lives had influenced their need for emergency care.

CONCLUSIONS

Access was prominent in the minds of uninsured patients seeking ED care for nonurgent medical diagnoses. Typically, patients did not perceive themselves as having an urgent problem, had been unsuccessful in gaining access to alternative non-ED health care settings, and found the emergency department to be a convenient and quality source of health care. The patients' stories relayed a context for ED visits that goes beyond medical diagnoses. This perspective has important implications for quality care delivery and for including patients in planning ways to access emergency health care.

[Sodium caseinate induces differentiation of 32D pluripotential hematopoietic cells]

AIM

To determine the role of sodium caseinate (CasNa) in the modulation of hemopoiesis.

MATERIALS AND METHODS

32D cells, a murine hemopoietic multipotential cell line dependent on interleukin-3 (IL-3) for proliferation and survival, were used. These cells were cultured with 0.5 ng/mL of IL-3, together with different concentrations of CasNa. We evaluated: proliferation (direct counting under the microscope and use of thymidine 3H), morphological differentiation (giemsa staining), cytochemistry (specific staining for monocytes and granulocytes), and function (presence of Fc receptors and reduction of nitro-blue tetrazolium). In addition, we determined cell viability through trypan blue exclusion and apoptosis using the TUNEL assay in situ.

RESULTS

We showed that CasNa induced a decrease in cell proliferation, which is dose dependent, and is neither a result of a diminished cell viability, nor due to an increase in cell death through apoptosis. In addition, CasNa induces cell differentiation towards the monocytic lineage.

CONCLUSIONS

CasNa has the capacity to differentiate 32D cells towards the monocytic lineage, and, importantly, has a potent differentiating activity on 32D cells being able to promote differentiation in a shorter time than the well known factors G-CSF and GM-CSF.

FISH deletion mapping defines a single location for the Y chromosome stature gene, GCY

At least 1 in 1000 males lacks part of the long arm of the Y chromosome. This chromosomal aberration is often associated with short stature and infertility. Deletion mapping and genotype-phenotype analysis have previously defined two non-overlapping critical regions for growth controlling gene(s), GCY(s), on the euchromatic portion of the Y chromosome long arm. These initial mapping assignments were based on the analysis of patients carrying a pure 46,XYq- karyotype as defined by classical cytogenetic karyotyping. Four genes have been assigned to the distal one of the two critical regions. To determine whether one or both of these two critical regions harbours GCY and whether one of the four genes assigned to the distal region is involved in determination of stature, nine adult patients with Yq chromosomal abnormalities were studied in detail. By PCR and FISH analysis, we showed that all patients with a previously defined pure 46,XYq- karyotype are actually mosaics with cells containing an idic(Y) or ring(Y) chromosome in association with 45,X0 cells. This leads us to conclude that (1) FISH is an absolute prerequisite for the correct identification of Y chromosomal rearrangements and (2) only patients with interstitial Y deletions are reliable predictors for the physical location of stature gene(s) on Yq. Our molecular analyses of chromosomes from patients with interstitial Yq deletions finally establishes the proximal interval between markers DYZ3 and DYS11 as the only GCY critical interval. No functional gene has so far been identified in this region adjacent to the centromere.

Vulnerability of children and the developing brain to neurotoxic hazards

For much of the history of toxicology, the sensitivity of the developing organism to chemical perturbation attracted limited attention. Several tragic episodes and new insights finally taught us that the course of early brain development incurs unique risks. Although the process is exquisitely controlled, its lability renders it highly susceptible to damage from environmental chemicals. Such disturbances, as recognized by current testing protocols and legislation such as the Food Quality Protection Act, can result in outcomes ranging from death to malformations to functional impairment. The latter are the most difficult to determine. First, they require a variety of measures to assay their extent. Second, adult responses may prove an inadequate guide to the response of the developing brain, which is part of the reason for proposing additional safety factors for children. Third, neuropsychological tests are deployed in complex circumstances in which many factors, including economic status, combine to produce a particular effect such as lowered intelligence quotient score. Fourth, the magnitude of the effect, for most environmental exposure levels, may be relatively small but extremely significant for public health. Fifth, changes in brain function occur throughout life, and some consequences of early damage may not even emerge until advanced age. Such factors need to be addressed in estimating the influence of a particular agent or group of agents on brain development and its functional expression. It is especially important to consider ways of dealing with multiple risks and their combinations in addition to the prevailing practice of estimating risks in isolation.

Vulnerability of children and the developing brain to neurotoxic hazards

For much of the history of toxicology, the sensitivity of the developing organism to chemical perturbation attracted limited attention. Several tragic episodes and new insights finally taught us that the course of early brain development incurs unique risks. Although the process is exquisitely controlled, its lability renders it highly susceptible to damage from environmental chemicals. Such disturbances, as recognized by current testing protocols and legislation such as the Food Quality Protection Act, can result in outcomes ranging from death to malformations to functional impairment. The latter are the most difficult to determine. First, they require a variety of measures to assay their extent. Second, adult responses may prove an inadequate guide to the response of the developing brain, which is part of the reason for proposing additional safety factors for children. Third, neuropsychological tests are deployed in complex circumstances in which many factors, including economic status, combine to produce a particular effect such as lowered intelligence quotient score. Fourth, the magnitude of the effect, for most environmental exposure levels, may be relatively small but extremely significant for public health. Fifth, changes in brain function occur throughout life, and some consequences of early damage may not even emerge until advanced age. Such factors need to be addressed in estimating the influence of a particular agent or group of agents on brain development and its functional expression. It is especially important to consider ways of dealing with multiple risks and their combinations in addition to the prevailing practice of estimating risks in isolation.

The developing brain and the environment: an introduction

mental retardation: timing and thresholds; (italic)b(/italic)) endocrine dysfunction and developmental disabilities: dose and target implications; (italic)c(/italic)) attention-deficit disorder-ADHD and learning disabilities; and (italic)d(/italic)) new horizons: extending the boundaries. Support for the Rochester conference came from both public and private sources. The National Institute of Environmental Health Sciences (NIEHS), the National Institute of Child Health and Human Development, and the EPA represented the federal government. The conference also received grants from several foundations: the Jennifer Altman Foundation, the Heinz Family Foundation, the National Alliance for Autism Research, the Violence Research Foundation, the Wacker Foundation, and the Winslow Foundation. The second of these conferences helped launch a new Center for Children's Health and the Environment at the Mount Sinai School of Medicine. It was held in New York City on 24-25 May 1999, and was convened specifically to consider the intersection between neurodevelopmental impairment, environmental chemicals, and prevention. Over 300 health scientists, pediatricians, and public health professionals examined the growing body of evidence linking environmental toxins to neurobehavioral disorders. The conference title was Environmental Influences on Children: Brain, Development, and Behavior. The conference began by reviewing well-known examples of deleterious effects of environmental chemicals, including lead and PCBs, on children's brains. The conferees then considered the potential impact of environmental chemicals on neurological disorders with particular focus on ADHD, autism, and Parkinson's disease. The inclusion of Parkinson's disease was intended to signal the notion that exposures in early life may have an influence on the evolution of neurological disease in later life. Support for the Mount Sinai conference came from the Superfund Basic Research Program (NIEHS); The Pew Charitable Trusts; the Institute for Health and the Environment at the University of Albany School of Public Health; the Agency for Toxic Substances and Disease Research (ATSDR); the Ambulatory Pediatric Association; Myron A. Mehlman, PhD; the National Center for Environmental Assessment (EPA); the National Center for Environmental Health (CDC); the National Institute of Child Health and Human Development; the Office of Children's Health Protection (EPA); Physicians for Social Responsibility; The New York Academy of Medicine; The New York Community Trust; and the Wallace Genetic Foundation. The impact of environmental toxins on children's health has become a topic of major concern in the federal government. Eight new research centers in children's environmental health have been established in the past 2 years with joint funding from EPA and NIEHS. Clinical units that specialize in the treatment of children with environmentally induced illness have been developed across the nation with grant support from ATSDR. The American Academy of Pediatrics has just published its (italic)Handbook of Pediatric Environmental Health (/italic)((italic)17(/italic)), the "Green Book," which is available to pediatricians throughout the Americas. Children's environmental health has climbed to a critical position as we launch the new millennium. This monograph marks a significant milestone in the evolution of this emerging discipline.

Effects of age and gender but not prenatal cocaine on random ratio and delayed spatial alternation responding in rats

This investigation employed a longitudinal analysis of rat operant behavior under two different schedules of reinforcement following prenatal exposure to cocaine. Offspring were derived from four maternal exposure groups: 50 mg/kg cocaine, their pair-fed controls, 25 mg/kg cocaine, and freely fed controls. Cocaine was administered via gavage from gestation day 6-20. A maternal fostering procedure was used. Pairs of male and female littermates were assigned to a 7-, 14-, or 21-month cohort and at the appropriate age were trained to respond on one lever in a two-lever operant chamber. Reinforcement was delivered with a series of random ratio (RR) schedules where the RR value was increased across sessions. After RR training, animals were examined with a delayed spatial alternation (DSA) procedure in the same chambers. Male offspring responded at higher rates than females during high-probability RR schedules, whereas advancing age was associated with lower response rates during low-probability RR schedules in both males and females. Prenatal cocaine exposure exerted only limited effects on RR responding during transition and did not affect DSA behavior. The results of this longitudinal analysis suggest that prenatal cocaine does not exert global or far-reaching learning deficits in prenatally exposed rats.

Differential gene expression by endothelial cells in distinct angiogenic states

Angiogenesis is a complex process that can be regarded as a series of sequential events comprising a variety of tissue cells. The major problem when studying angiogenesis in vitro is the lack of a model system mimicking the various aspects of the process in vivo. In this study we have used two in vitro models, each representing different and distinct aspects of angiogenesis. Differentially expressed genes in the two culture forms were identified using the suppression subtractive hybridization technique to prepare subtracted cDNA libraries. This was followed by a differential hybridization screen to pick up overexpressed clones. Using comparative multiplex RT-PCR we confirmed the differential expression and showed differences up to 14-fold. We identified a broad range of genes already known to play an important role during angiogenesis like Flt1 or TIE2. Furthermore several known genes are put into the context of endothelial cell differentiation, which up to now have not been described as being relevant to angiogenesis, like NrCAM, Claudin14, BMP-6, PEA-15 and PINCH. With ADAMTS4 and hADAMTS1/METH-1 we further extended the set of matrix metalloproteases expressed and regulated by endothelial cells.

Middle molecules in peritoneal equilibration test as a marker of peritoneal stress in children on continuous peritoneal dialysis

At 1 month, 3 months, 6 months, and more than 6 months after healed peritonitis, we evaluated repeated peritoneal equilibration tests (PETs) for small molecules such as urea, and middle molecules such as cystatin C, beta 2-microglobulin, and alpha 1-microglobulin. We analyzed a total of 104 PETs in 21 children aged 1.7-18.6 years (median: 9.9 years). Equilibration quotients (D/P)--that is, substrate concentration in dialysis fluid (D) divided by substrate concentration in plasma (P)--were calculated after a dwell time of 4 hours. The D/P for urea did not change after healed peritonitis. In a cross-sectional study, the D/P for middle molecules showed an increase in peritoneal permeability between 3 months and 6 months after a healed peritonitis. In a consecutive follow-up of 4 patients for more than 6 months, beta 2-microglobulin and, more impressively, alpha 1-microglobulin showed a statistically significant increase in D/P (p < 0.05) 3 months after a healed peritonitis. All differences seen were completely reversible after more than 6 months, showing that peritoneal function is rather stable if peritonitis is healed. It is noteworthy that peritoneal dysfunction lasts for up to 6 months after a completely healed peritonitis. This period might be a vulnerable phase in continuation of peritoneal dialysis.

Flavodoxin mutants of Escherichia coli K-12

The flavodoxins are flavin mononucleotide-containing electron transferases. Flavodoxin I has been presumed to be the only flavodoxin of Escherichia coli, and its gene, fldA, is known to belong to the soxRS (superoxide response) oxidative stress regulon. An insertion mutation of fldA was constructed and was lethal under both aerobic and anaerobic conditions; only cells that also had an intact (fldA(+)) allele could carry it. A second flavodoxin, flavodoxin II, was postulated, based on the sequence of its gene, fldB. Unlike the fldA mutant, an fldB insertion mutant is a viable prototroph in the presence or absence of oxygen. A high-copy-number fldB(+) plasmid did not complement the fldA mutation. Therefore, there must be a vital function for which FldB cannot substitute for flavodoxin I. An fldB-lacZ fusion was not induced by H(2)O(2) and is therefore not a member of the oxyR regulon. However, it displayed a soxS-dependent induction by paraquat (methyl viologen), and the fldB gene is preceded by two overlapping regions that resemble known soxS binding sites. The fldB insertion mutant did not have an increased sensitivity to the effects of paraquat on either cellular viability or the expression of a soxS-lacZ fusion. Therefore, fldB is a new member of the soxRS (superoxide response) regulon, a group of genes that is induced primarily by univalent oxidants and redox cycling compounds. However, the reactions in which flavodoxin II participates and its role during oxidative stress are unknown.

Vulnerability to pesticide neurotoxicity is a lifetime issue

Early development is not the only life stage during which which we see intensified responses to the adverse effects of chemicals. Vulnerability to toxic processes rises again late in life, and in many ways recapitulates the imperfect defenses deployed by the immature organism. One feature common to both early and late phases is a reduced capacity to compensate for impairment. In the first case, the functional mechanisms have yet to evolve. In the second, they have passed into what might be called a post-mature decline. Traced across the life cycle, this progression might be depicted as an inverted U. The developing brain, however, is equipped with immense plastic potential; the aging brain has lost much of its plasticity. The altered function of the aging brain, however, is not simply an outcome of how long the organism has lived. "Aging" is not a mechanistic explanation. Events occurring during life must account for the changes. Older brains are already high-maintenance properties, so that exposure to substances with neurotoxic properties, such as pesticides, may accelerate the process, or exploit its dwindling capacities to resist their effects. From this vantage point, toxicants can act in three ways to depress function during advanced age: they may interfere with brain development, leaving a legacy of diminished redundancy not apparent until it is further compromised during aging; they may hasten the progressive erosion of function observed with certain abilities; they may exert greater effects in the aging brain because the aging nervous system has already undergone a reduction in its ability to withstand toxic challenges.

Endonuclease V protects Escherichia coli against specific mutations caused by nitrous acid

Endonuclease V (deoxyinosine 3'-endonuclease) of Escherichia coli K-12 is a putative DNA repair enzyme that cleaves DNA's containing hypoxanthine, uracil, or mismatched bases. An endonuclease V (nfi) mutation was tested for specific mutator effects on a battery of trp and lac mutant alleles. No marked differences were seen in frequencies of spontaneous reversion. However, when nfi mutants were treated with nitrous acid at a level that was not noticeably mutagenic for nfi(+) strains, they displayed a high frequency of A:T-->G:C, and G:C-->A:T transition mutations. Nitrous acid can deaminate guanine in DNA to xanthine, cytosine to uracil, and adenine to hypoxanthine. The nitrous acid-induced A:T-->G:C transitions were consistent with a role for endonuclease V in the repair of deaminated adenine residues. A confirmatory finding was that the mutagenesis was depressed at a locus containing N(6)-methyladenine, which is known to be relatively resistant to nitrosative deamination. An alkA mutation did not significantly enhance the frequency of A:T-->G:C mutations in an nfi mutant, even though AlkA (3-methyladenine-DNA glycosylase II) has hypoxanthine-DNA glycosylase activity. The nfi mutants also displayed high frequencies of nitrous acid-induced G:C-->A:T transitions. These mutations could not be explained by cytosine deamination because an ung (uracil-DNA N-glycosylase) mutant was not similarly affected. However, these findings are consistent with a role for endonuclease V in the removal of deaminated guanine, i.e., xanthine, from DNA. The results suggest that endonuclease V helps to protect the cell against the mutagenic effects of nitrosative deamination.

[Cardiovascular disease in pregnancy]

There is a heterogeneous population of young women with cardiovascular disease contemplating pregnancy. Many of the conditions are rare and require teams with expertise in the management of such patients. A specific congenital or acquired cardiovascular anomaly and its physiology must be understood. The nature of prior surgical procedures and the residua and sequelae following therapy are essential to manage a pregnant woman with cardiovascular disease. Physiologic changes during pregnancy and after delivery must be known. Counseling includes maternal and fetal risk stratification and genetic counseling regarding inherited disorders. The outcome of pregnancy is favourable in many women with good functional class. These patients can be reassured. A multidisciplinary approach may be crucial to manage this population during pregnancy, labour, delivery and in the postpartum period to avoid serious maternal and fetal complications. Women with intermediate and high risk pregnancy must be followed and managed in a high risk pregnancy unit and a team from obstetricians, cardiologists, anesthetists, pediatricians, neonatologists and cardiac surgeons who are skilled in high risk pregnancies. Vaginal delivery is the method of choice in many women (class 1 woman) and cesarean section is seldom a cardiac indication. Contraindications for pregnancy are: poor maternal functional class, poor ventricular function, severe cyanosis without pulmonary hypertension (oxygen saturation < or = 85%), pulmonary vascular disease, severe mitral stenosis, severe left ventricular outflow tract obstruction, Marfan syndrome with aortic dilatation (> 40 mm) and aortic valve involvement (moderate to severe aortic regurgitation), symptomatic hypertrophic obstructive cardiomyopathy. Preconception counseling must be offered if unfavourable outcome is likely. Tubal ligation is probably the safest and most appropriate method of sterilization if there is a high risk pregnancy.

[Sensitivity and resistance of Helicobacter pylori to antibiotic treatment]

Resistance to antibiotics is considered the main reason for failure to eradicate Helicobacter pylori (HP). Resistance rates are different in developed and developing countries and are not known for Israel. We studied HP resistance rates in 40 patients who underwent esophagoduodenoscopy for various indications and were found to have gastric HP colonies. Sensitivity was determined by E-test, using clarythromycin, amoxycillin, clindamycin, erythromycin and metronidazole. The resistance rate for metronidazole was up to 67% but that for clindamycin was only 10%. HP was very sensitive to both macrolide antibiotics, erythromycin and clarythromycin.

The critical region of overlap defining the AZFa male infertility interval of proximal Yq contains three transcribed sequences

The position of deletion breakpoints in a series of four AZFa male infertility patients has been refined using new markers derived from BAC clone DNA sequence covering the AZFa male infertility interval. The proximal half of the AZFa interval is occupied by pseudogene sequences with homology to Xp22. The distal half contains an anonymous expressed sequence tag (named AZFaT1) found transcribed in brain, testis, and skeletal muscle and the DFFRY and DBY genes. All the patients have AZFaT1 and DFFRY deleted in their entirety and three patients additionally have DBY deleted. The three patients with AZFaT1, DFFRY, and DBY deleted show a severe Sertoli cell only syndrome type I phenotype, whereas the patient that has retained DBY shows a milder oligozoospermic phenotype. The expression of DBY in a cell line from this latter patient is unaltered; this shows that it is the loss of genes lying within the deletion that is responsible for the observed oligozoospermia. RT-PCR analysis of mouse testis RNA from normal and XXSxr(a) mice (devoid of germ cells) has shown that Dby is expressed primarily in somatic cells and that the level of expression is unaltered during germ cell differentiation. This contrasts with Dffry where no transcripts are detectable in XXSxr(a) mouse testis and expression occurs specifically in testis mRNA in a germ cell dependent fashion.

Upper gastrointestinal bleeding due to gastric ulcers in children with gastrostomy tubes

The authors describe four children with gastrostomy tubes (G-tubes) presenting with upper gastrointestinal bleeding due to gastric ulcers years after G-tube insertion. They review the literature and discuss the possible mechanisms of gastric ulcer formation in these patients.

Manganese in the context of an integrated risk and decision process

Current approaches to risk assessment regard it as a process that should embody both health and ecological risks, societal values, and cost-benefit analysis, that should seek the views of affected parties, and that should examine available options more holistically than in the past. Even with a single agent, manganese, the process requires a great breadth of information and keen attention to how all of its different components fit together. An evaluation of exposure variables alone needs to consider contributions from multiple media, their physical forms and pathways such as inhaled fumes and particles, and ingestion of water, food, soil, and dust (especially by children). Endpoints need also to be broadened, especially to include susceptibility across the life cycle and the impact of low-level neurotoxicity on rate of aging. Finally, the pursuit of risk reduction options for manganese should be embedded in a process that clarifies all), the consequences of a particular option, including the raising or lowering of other risks and the full economic consequences.

Hyperactive Ras as a therapeutic target in neurofibromatosis type 1

The NF1 gene encodes neurofibromin, a GTPase-activating protein (GAP) for members of the p21(ras) (Ras) family, which negatively regulates Ras output by accelerating the conversion of active Ras. GTP to inactive Ras.GDP. Analysis of tumors from patients with neurofibromatosis type 1 (NF1) has shown biochemical evidence of hyperactive Ras as well as frequent loss of the normal NF1 allele, consistent with its role as a tumor suppressor gene. Taken together, these data suggest that novel therapeutics directed against components of the Ras signaling cascade might provide effective treatments for certain pathological complications of NF1. Here we summarize data that support a role for hyperactive Ras in NF1 disease, including Ras processing, activation, and down-regulation. We review targets for rational drug design, provide preliminary results, and discuss implications for future studies. Am. J. Med. Genet. (Semin. Med. Genet.) 89:14-22, 1999.

The effectiveness of traditional child psychotherapy

This study used a randomized design to evaluate the effectiveness of child psychotherapy as typically delivered in outpatient settings. Overall results were similar to the results of nonrandomized studies of traditional child psychotherapy: Little support was found for its effectiveness, with treatment producing an overall effect size of -.08. Despite the lack of significant differences between treatment and control groups in regard to changes in child functioning, parents of children who received treatment reported higher levels of satisfaction with services than control group parents whose children received academic tutoring. Overall, the findings highlight the importance of developing, validating, and transporting effective treatments to clinical settings.

Antisense RNA gene therapy for studying and modulating biological processes

Agents that produce their effects through an antisense mechanism offer the possibility of developing highly specific alternatives to traditional pharmacological antagonists, thereby providing a novel class of therapeutic agents, ones which act at the level of gene expression. Among the antisense compounds, antisense RNA produced intracellularly by an expression vector has been used extensively in the past several years. This review considers the advantages of the antisense RNA approach over the use of antisense oligodeoxynucleotides, the different means by which one may deliver and produce antisense RNA inside cells, and the experimental criteria one should use to ascertain whether the antisense RNA is acting through a true antisense mechanism. Its major emphasis is on exploring the potential therapeutic use of antisense RNA in several areas of medicine. For example, in the field of oncology antisense RNA has been used to inhibit several different target proteins, such as growth factors, growth factor receptors, proteins responsible for the invasive potential of tumor cells and proteins directly involved in cell cycle progression. In particular, a detailed discussion is presented on the possibility of selectively inhibiting the growth of tumor cells by using antisense RNA expression vectors directed to the individual calmodulin transcripts. Detailed consideration is also provided on the development and potential therapeutic applications of antisense RNA vectors targeted to the D2 dopamine receptor subtype. Studies are also summarized in which antisense RNA has been used to develop more effective therapies for infections with certain viruses such as the human immunodeficiency virus and the virus of hepatitis B, and data are reviewed suggesting new approaches to reduce elevated blood pressure using antisense RNA directed to proteins and receptors from the renin-angiotensin system. Finally, we outline some of the problems which the studies so far have yielded and some outstanding questions which remain to be answered in order to develop further antisense RNA vectors as therapeutic agents.

Congenital leukemia: successful treatment of a newborn with t(5;11)(q31;q23)

A male neonate presented with a high white cell count, an 11q23 translocation, and M5b leukemia. He was treated at 3 days of age with intensive combination chemotherapy after progressing despite exchange transfusions. The patient achieved complete remission at 28 days of age. Therapy was completed at the age of 6 months. At the time of this report, the patient is 17 months old and remains in remission. Twenty-nine patients with congenital acute myeloid leukemia were also reviewed. Twenty of these patients received varying therapies. Ten of the treated patients achieved complete remission; two died of toxicity; and eight died of progressive disease. Two patients had a translocation affecting 11q23. Congenital leukemia is a rare and usually fatal condition in patients without Down syndrome. The patient reported here shows that survival may be achieved with very intensive chemotherapy plus supportive care, despite extremely high white blood cell counts and unfavorable translocation.

The effectiveness of traditional child psychotherapy

This study used a randomized design to evaluate the effectiveness of child psychotherapy as typically delivered in outpatient settings. Overall results were similar to the results of nonrandomized studies of traditional child psychotherapy: Little support was found for its effectiveness, with treatment producing an overall effect size of -.08. Despite the lack of significant differences between treatment and control groups in regard to changes in child functioning, parents of children who received treatment reported higher levels of satisfaction with services than control group parents whose children received academic tutoring. Overall, the findings highlight the importance of developing, validating, and transporting effective treatments to clinical settings.

Prenatal and lactational exposure to methylmercury affects select parameters of mouse cerebellar development

Animal studies of the neuropathological effects of prenatal methylmercury (MeHg) seldom use regimens that represent environmental exposures. While acute administration of high doses of MeHg to developing rodents can model some of the outcomes MeHg produces in the human cerebellum, their long-term relevance to cerebellar development is unknown. The present study was undertaken to determine the effect of chronic dietary exposure to MeHg. Pregnant mice were exposed throughout gestation to 0.0 or 4.0 ppm methylmercury in their drinking water. Postpartum exposure of pups and lactating dams continued to postnatal day (PND) 30. On PND7, 14, 21, and 30, several morphometric indices of cerebellar cortex development, as well as blood and brain levels of total Hg, were measured in pairs of male and female littermates. No signs of overt toxicity were observed in the dams or offspring. Blood and brain levels of total Hg were highest in the exposed PND7 offspring and fell throughout the sampling period despite continued exposure. In a region of molecular layer in the anterodorsal lobe, MeHg exposure reduced the density of migrating cells in PND7 offspring. Molecular layer widths were reduced in PND30 offspring. In a region of the inferior lobe of PND7 offspring, MeHg exposure reduced external granular layer widths and decreased the density of migrating cells in the molecular layer. However, MeHg did not affect cerebellar cortex development in the central lobe, suggesting a regional sensitivity to chronic, low-level MeHg exposure during development.

Mechanisms mediating the influence of alcohol on the hypothalamic-pituitary-adrenal axis responses to immune and nonimmune signals

In the rat, the acute administration of alcohol induces dose-related increases in plasma ACTH and corticosterone levels. This response depends on the delivery of the hypothalamic peptides corticotropin-releasing factor and vasopressin (VP) to the pituitary. On the other hand, exposure to an alcohol diet for 7 to 10 days significantly blunts the hypothalamic-pituitary-adrenal (HPA) axis in response to other homeostatic threats, such as mild electroshocks or immune signals. This decreased response is at least in part due to an attenuated ability of VP to increase ACTH secretion. We have previously shown that nitric oxide (NO) inhibits the pituitary response to VP. We therefore hypothesized that chronic alcohol treatment might increase levels of this gas within the HPA axis, and tested this possibility by determining whether blockade of NO formation might restore a normal pituitary response to VP. We observed that such was the case, and therefore propose that NO participates in the blunted activity of the HPA axis during prolonged exposure to alcohol. Finally, we determined whether alcohol would exert neuroendocrine effects that extended beyond the initial drug treatment. To explore this possibility, we injected rats with alcohol intragastrically for 3 days, then re-exposed them to the drug 3 to 12 days later. Rats pretreated with the vehicle and injected with alcohol several days later showed the expected significant rise in plasma ACTH and corticosterone levels, as well as a marked increase in immediate early genes mRNA levels in the paraventricular nucleus (PVN) of their hypothalamus. In contrast, animals pretreated with alcohol exhibited a blunted hormonal and hypothalamic response during the second drug exposure but, interestingly, retained a normal endocrine response to other signals, such as exposure to electro-footshocks or cytokine injection. We originally thought that this phenomenon of selective endocrine tolerance might be explained by decreased serotonin levels in the PVN. Whereas alcohol indeed decreased concentrations of this neurotransmitter in the PVN, exposure to electroshocks induced similar changes. However, an initial exposure to shocks did not blunt the ability of the HPA axis to be activated by a second shock session, by alcohol or by immune signals (delivered several days later). These results do not support the hypothesis that the decreased HPA axis response to a second alcohol challenge is mediated via decreased serotonin afferents to corticotropin-releasing factor neurons in the PVN.

Effect of antisense oligodeoxynucleotides directed to individual calmodulin gene transcripts on the proliferation and differentiation of PC12 cells

Calmodulin (CaM) is encoded by three different genes that collectively give rise to five transcripts. In the present study, we used antisense oligodeoxynucleotides targeted to unique sequences in the transcripts from the individual CaM genes to selectively block the expression of the different genes and to investigate the roles these individual genes play in the proliferation and nerve growth factor (NGF)-induced differentiation of PC12 cells. Culturing PC12 cells in the presence of oligodeoxynucleotide antisense to the transcripts from CaM genes I and II caused a significant decrease in the proliferation and a significant delay in the NGF-induced differentiation of PC12 cells when compared with untreated cells and with cells treated with the corresponding randomized oligodeoxynucleotides. However, an oligodeoxynucleotide antisense to CaM gene III did not significantly alter the proliferation or the NGF-induced differentiation of PC12 cells. The inhibition of cell proliferation could be reversed by washing out the antisense oligodeoxynucleotides. The levels of CaM in cells treated with oligodeoxynucleotides antisense to CaM genes I or II were reduced 52% or 63%, respectively, of the levels found in the control cells. However, the levels of CaM were not significantly reduced in PC12 cells treated with CaM gene III antisense oligodeoxynucleotide. None of the randomized oligodeoxynucleotides had any effect on the levels of CaM in PC12 cells. The reduced levels of CaM in PC12 cells treated with an oligodeoxynucleotide antisense to CaM gene I were accompanied by a reduction in the levels of the CaM gene I mRNAs, supporting a true antisense mechanism of action for these oligodeoxynucleotides. These results suggest that altering the level of CaM by using antisense oligodeoxynucleotides targeted to the dominant CaM transcripts in a particular cell type will specifically inhibit their proliferation and, in the case of neuronal cells, alter the course of their differentiation.

D2 dopamine antisense RNA expression vector, unlike haloperidol, produces long-term inhibition of D2 dopamine-mediated behaviors without causing Up-regulation of D2 dopamine receptors

Long-term inhibition of D2 dopamine receptors using classic D2 dopamine receptor antagonists such as haloperidol often causes a compensatory up-regulation of the D2 dopamine receptors. We investigated whether the long-term inhibition of D2 dopamine receptors using an eukaryotic expression vector housing a cDNA sequence encoding an antisense RNA directed to the D2 dopamine receptor transcript (D2 antisense vector) would also produce up-regulation of the D2 receptors. Single, bilateral injections of the D2 antisense vector into the corpora striata of mice inhibited the stereotypy induced by acute challenge injections with the D2/D3 dopamine receptor agonist quinpirole but did not inhibit the grooming induced by acute challenge injections with the D1 agonist SKF 38393. Similar treatment with the D2 antisense vector produced a long-term (>1 month) cataleptic response without producing tolerance to challenge injections with haloperidol. By contrast, catalepsy induced by a single injection of haloperidol lasted only approximately 2 days, and tolerance developed to its effects after long-term treatment. Repeated treatment of mice with haloperidol resulted in an inhibition of apomorphine-induced climbing behavior throughout the time of treatment with haloperidol, but the climbing behavior markedly increased to levels significantly higher than that of the control mice immediately after withdrawal from haloperidol treatment. This increased climbing was accompanied by increased levels of D2 dopamine receptors in the striatum. By contrast, single, bilateral intrastriatal injections of the D2 antisense vector significantly inhibited apomorphine-induced climbing for approximately 30 days but failed to increase the climbing behavior or the levels of D2 dopamine receptors in striatum over those of the control values. These results suggest that a single injection of a D2 antisense RNA expression vector into mouse striatum produces specific, long-term inhibition of D2 dopamine receptor behaviors without causing a compensatory increase in the levels or function of D2 dopamine receptors.