Association between prenatal exposure to methylmercury and developmental outcomes in Seychellois children: effect modification by social and environmental factors

The Seychelles Child Development Study (SCDS) is testing the hypothesis that prenatal exposure to low doses of MeHg from maternal consumption of fish is associated with the child's developmental outcomes. No deleterious relationships between exposure to MeHg and cognitive functions have been identified in the primary analysis of the main cohort through 66 months of age. We performed secondary analyses to determine if effect modification (EM) from social and environmental factors was affecting associations between MeHg and outcomes.

METHODS

MeHg exposure was determined by analysis of maternal hair growing during pregnancy. Children in our Main Study cohort were evaluated at 6.5 months (N = 740) for visual recognition memory and visual attention using the Fagan Infantest, at 19 months (N = 738) and 29 months (N = 736) with the Bayley Scales of Infant Development (BSID). Interactions between MeHg and Caregiver Intelligence, Family Income and Home Environment were examined by multiple regression analysis.

RESULTS

The median prenatal MeHg exposure was 5.9 ppm (Range 0.5-26.7 ppm). No EM occurred for preferential looking or visual attention at 6.5 months, for the BSID Psychomotor Scale at either 19 or 29 months, or for activity level at 29 months as measured by the BSID Infant Behavior Record. Interactions between MeHg level and both caregiver intelligence and family income were statistically significant for the BSID Mental Scale at 19 months but not at 29 months. These showed enhancement of MDI scores with increasing maternal MeHg in higher caregiver IQ groups at several levels of family income.

CONCLUSIONS

In Seychellois children, consistent major EM by social or environmental factors were not identified. The small EM by caregiver intelligence and social factors at 19 months is consistent with the enhanced performance we reported when this cohort was examined at 66 months.

Effects of prenatal and postnatal methylmercury exposure from fish consumption on neurodevelopment: outcomes at 66 months of age in the Seychelles Child Development Study

CONTEXT

Human neurodevelopmental consequences of exposure to methyl-mercury (MeHg) from eating fish remain a question of public health concern.

OBJECTIVE

To study the association between MeHg exposure and the developmental outcomes of children in the Republic of Seychelles at 66 months of age.

DESIGN

A prospective longitudinal cohort study.

PARTICIPANTS

A total of 711 of 779 cohort mother-child pairs initially enrolled in the Seychelles Child Development Study in 1989.

SETTING

The Republic of Seychelles, an archipelago in the Indian Ocean where 85% of the population consumes ocean fish daily.

MAIN OUTCOME MEASURES

Prenatal and postnatal MeHg exposure and 6 age-appropriate neurodevelopmental tests: the McCarthy Scales of Children's Abilities, the Preschool Language Scale, the Woodcock-Johnson Applied Problems and Letter and Word Recognition Tests of Achievement, the Bender Gestalt test, and the Child Behavior Checklist.

RESULTS

The mean maternal hair total mercury level was 6.8 ppm and the mean child hair total mercury level at age 66 months was 6.5 ppm. No adverse outcomes at 66 months were associated with either prenatal or postnatal MeHg exposure.

CONCLUSION

In the population studied, consumption of a diet high in ocean fish appears to pose no threat to developmental outcomes through 66 months of age.

Tear break-up time: clinical procedures and their effects

Three successive (representative) values of fluorescein-instillation TBUT (tear break-up time) were obtained from a group of young Hong Kong (HK)-Chinese. The median TBUT1, TBUT2 and TBUT3 were 3.2, 3.8 and 4.5 sec, respectively. Wilcoxon signed-rank tests showed that TBUT1 was significantly different from TBUT2 and TBUT3, but there was no difference between TBUT2 and TBUT3. It is therefore important, when measuring the TBUT, to specify which TBUT value was taken as the representative TBUT. Fluorescein was reapplied about six min after the first application, and the TBUT value re-determined (TBUTR). The median TBUTR was not significantly different from TBUT1. The subjects were requested to return another day and TBUT values (TBUTW) were determined, with the subjects opening their eyes as wide as possible, such that the palpebral aperture size was increased. The mean +/- SD normal palpebral aperture size was 10.0 +/- 1.3 mm, and the mean +/- SD palpebral aperture size with the eyes wide open was 11.4 +/- 1.5 mm. The median TBUTW (3.6 sec) was significantly longer than the median TBUT1 (3.0 sec), but this difference appeared to be due to the extremely long TBUTW of one subject; no significant difference was found between the median TBUTW (3.4 sec) and TBUT1 (2.8 sec) when data from this subject were excluded. There was no significant correlation between changes in palpebral size and TBUT value.

Effects of prenatal methylmercury exposure from a high fish diet on developmental milestones in the Seychelles Child Development Study

Mercury is widespread in the environment and exists in several physical and chemical forms. Prenatal exposure to methylmercury disrupts brain development. The most common mode of prenatal methylmercury exposure is maternal fish consumption. Studies of human prenatal exposure in Iraq following maternal ingestion of methylmercury treated grain suggested that maternal hair mercury concentrations above 10 ppm may be related to delayed developmental milestones and neurological abnormalities. This level of exposure can be achieved by frequent consumption of fish. The Seychelles Child Development Study analyzed developmental milestones similar to those determined in Iraq in a large controlled, prospective study of children exposed prenatally to methylmercury when their mothers ate fish. As part of this ongoing study, cohort children were evaluated at 6.5, 19, 29, and 66 months of age. At 19 months care-givers were asked at what age the child walked (n=720 out of 738) and talked (n=680). Prenatal mercury exposure was determined by atomic absorption analysis of maternal hair segments corresponding to hair growth during the pregnancy. The median mercury level in maternal hair was 5.8 ppm with a range of 0.5-26.7 ppm. The mean age (in months) at walking was 10.7 (SD = 1.9) for females and 10.6 (SD = 2.0) for males. The mean age at talking (in months) was 10.5 (SD = 2.6) for females, and 11.0 (SD = 2.9) for males. After adjusting for covariates and statistical outliers, no association was found between the age at which Seychellois children walked or talked and prenatal exposure to mercury. Normal ages at achievement of the developmental milestones walking and talking were found in Seychellois toddlers following prenatal exposure to methylmercury from a maternal fish diet. These results do not support the lowest effect levels in young children following prenatal methylmercury exposure predicted by the dose response analysis of the Iraq data. More detailed studies in older children are needed to determine if there are adverse effects in fish eating populations.

Substratum topography influences susceptibility of Salmonella enteritidis biofilms to trisodium phosphate

Established (48- and 72-h) Salmonella enteritidis biofilms grown in glass flow cells with or without artificial crevices (0.5-, 0.3-, and 0.15-mm widths) were subjected to a 10% trisodium phosphate (TSP) solution under different flow regimens (0.3, 0.6, 1.2, and 1.8 cm s-1). The abundance of biofilm remaining after TSP treatment, the biocidal efficacy of TSP, and the factors which contributed to bacterial survival were then evaluated by using confocal laser microscopy and a fluorescent viability probe. Biofilm age affected the amount of biofilm which remained following a 15-s exposure to TSP. After TSP treatment of 48-h biofilms, 29% of the original biofilm remained at the biofilm-liquid interface, whereas 75% of the biofilm remained at the base (the attachment surface). Following TSP treatment of 72-h biofilms, 27% of the biofilm material remained at the biofilm-liquid interface, 73% remained at the 5-micron depth, and 91% remained at the biofilm base. Results obtained using the BacLight viability probe indicated that TSP exposure killed all the cells in 48-h biofilms, whereas in the thicker 72-h biofilms, surviving bacteria (approximately 2% of the total) were found near the 5- and 0-micron depths. In the presence of artificially constructed crevices, an inverse relationship was shown to exist between bacterial survival (ranging from approximately 13 to 83% of total biofilm material) and crevice width. This relationship was further influenced by the velocity of TSP flow; high TSP flow velocities (1.8 cm s-1) resulted in the lowest number of surviving bacteria at the base of crevices (approximately 42% survival). Extended time courses demonstrated that after TSP stress was relieved, biofilms continued to grow within crevices but not in systems without crevices. It is suggested that advective TSP flux into crevices and through the biofilm matrix was enhanced under conditions of high flow. These results suggest that the inherent roughness of the substratum on which the biofilm was grown and the timing of TSP application are important factors controlling the efficacy of TSP treatment.

A randomized, double-blind trial of parenteral low dose versus high dose interferon-beta in combination with cryotherapy for treatment of condyloma acuminatum

Forty-nine subjects were enrolled in a study comparing two dosages of parenterally administered interferon (IFN)-beta in combination with cryotherapy for the treatment of anogenital warts. Subjects were randomized to receive subcutaneous injections of either 2 x 10(6) or 4 x 10(6) IU/m2 of IFN-beta (Biogen) three times a week for a total of 6 weeks. Cryotherapy was administered concomitantly by aerosolization of liquid nitrogen at 10-day intervals. Systemic side- effects were modest in intensity and included fever, chills, myalgia, and headaches (flu-like symptoms). During the first 2 weeks of therapy, they were more common in the high dose group than in the low dose group (P = 0.02). Using survival analysis, there was no significant difference between the two groups in rates of resolution of warts present at baseline (P = 0.62). However, the rate of new lesion formation during the study was significantly lower in the high dose group (P = 0.04).

Bacterial plasmolysis as a physical indicator of viability

Bacterial plasmolytic response to osmotic stress was evaluated as a physical indicator of membrane integrity and hence cellular viability. Digital image analysis and either low-magnification dark-field, high-magnification phase-contrast, or confocal laser microscopy, in conjunction with pulse application of a 1.5 M NaCl solution, were used as a rapid, growth-independent method for quantifying the viability of attached biofilm bacteria. Bacteria were considered viable if they were capable of plasmolysis, as quantified by changes in cell area or light scattering. When viable Salmonella enteritidis biofilm cells were exposed to 1.5 M NaCl, an approximately 50% reduction in cell protoplast area (as determined by high-magnification phase-contrast microscopy) was observed. In contrast, heat- and formalin-killed S. enteritidis cells were unresponsive to NaCl treatment. Furthermore, the mean dark-field cell area of a viable, sessile population of Pseudomonas fluorescens cells (approximately 1,100 cells) increased by 50% as a result of salt stress, from 1,035 +/- 162 to 1,588 +/- 284 microns2, because of increased light scattering of the condensed, plasmolyzed cell protoplast. Light scattering of ethanol-killed control biofilm cells underwent little change following salt stress. When the results obtained with scanning confocal laser microscopy and a fluorescent viability probe were compared with the accuracy of plasmolysis as a viability indicator, it was found that the two methods were in close agreement. Used alone or in conjunction with fluorochemical probes, physical indicators of membrane integrity provided a rapid, direct, growth-independent method for determining the viability of biofilm bacteria known to undergo plasmolysis, and this method may have value during efficacy testing of biocides and other antimicrobial agents when nondestructive time course analyses are required.

Therapeutic efficacy and complications of excisional biopsy of condyloma acuminatum

BACKGROUND AND OBJECTIVES

Among the various treatment modalities for condyloma acuminatum, excisional cold-blade surgery appears excellent but it has been little studied and little used, particularly for lesions not located in the perianal area.

GOALS

To examine the efficacy and complications of scissors excision of single anogenital warts.

STUDY DESIGN

Retrospective analysis of single warts completely excised with scissors for the purpose of biopsy before patient entry in a randomized, placebo-controlled study of the efficacy and safety of various parenteral interferons in combination with cryotherapy.

RESULTS

Of 152 patients entered in the main study, 85 patients were available for analysis. At 4 and 16 weeks after excision, 16 of 85 (19%) and 14 of 68 (21%) of the excised lesions recurred. After at 6 least months of follow-up, 2 of 11 (18%) of the excision sites demonstrated some evidence of pigmentation changes.

CONCLUSIONS

Scissors excision of single anogenital warts has a high rate of success and acceptable long-term side-effects.

Pharmacologic management of postdural puncture headache

OBJECTIVE

To discuss the pathogenesis, incidence, and clinical presentation of postdural puncture headaches (PDPHs) and to provide a comprehensive evaluation on the pharmacologic management of PDPH.

DATA SOURCE

A MEDLINE search was used to identify pertinent literature published in English including review articles, case reports, letters, and abstracts. Information was also extracted from textbooks for background purposes.

STUDY SELECTION

All clinical studies, case reports, abstracts, and letters were included because of the limited amount of literature available on the pharmacologic therapy for PDPH. Related research articles and review articles were also used to provide background information on PDPH.

DATA EXTRACTION

Methodology and results from clinical trials and abstracts were described and evaluated. Case reports and letters were summarized and critically reviewed for the feasibility of the different treatment modalities. Information on the pathophysiology, incidence and severity, and clinical presentation of PDPH was extracted from related research articles, review articles, and textbooks.

DATA SYNTHESIS

The epidural blood patch (EBP) is one of the most effective treatments for PDPH. Pharmacologic management of PDPH offers a less invasive treatment modality than the EBP. Numerous drug therapies have been presented in the literature, though few merit clinical application. Caffeine therapy, both oral and parenteral, is the most commonly used pharmacologic treatment modality. Theophylline and sumatriptan are potentially promising agents for the treatment of PDPH. Epidural administration of fluids and drugs is also effective in the treatment of PDPH. Epidural adrenocorticotropic hormone and epidural morphine also demonstrate some potential in the treatment of PDPH. Individual patient characteristics (i.e., HIV, sepsis) need to be considered when deciding on a treatment. More reports, especially clinical studies, are necessary before a definitive statement can be made regarding any one treatment. In the meantime, therapy will be guided by clinical judgement based on the literature reviewed in this article.

CONCLUSIONS

Intravenous and oral caffeine are effective and noninvasive treatments for PDPH. Epidural NaCl 0.9% or dextran are alternatives when the EBP is unsuccessful or contraindicated. Several methods of pharmacologic management have been cited in the literature, but all require further evaluation.

A randomized, double-blind, placebo-controlled trial of systemically administered interferon-alpha, -beta, or -gamma in combination with cryotherapy for the treatment of condyloma acuminatum

One hundred fifty-two patients were enrolled in a study to evaluate 3 interferon (IFN) preparations used in combination with cryotherapy for treatment of anogenital warts. Subjects received subcutaneous injections (2 x 10(6) units/m2) of IFN-alpha n1, -beta, -gamma or placebo 3 times a week for 6 weeks and cryotherapy with liquid nitrogen. Subjects were followed < or = 1 year. Among patients followed > or = 12 weeks, two-thirds had a complete response. No significant differences in rates of complete response (P = .37) or reappearance of a wart at the initial site (P = .20) were noted among the treatment groups. However, patients who received IFN-beta or -gamma developed new warts at a significantly lower frequency (P = .02). IFN administration was associated with side effects but was well tolerated. IFN-beta was the least toxic of the 3 preparations and had the best therapeutic ratio.

Variation in the affinity of amitriptyline for muscarine receptor subtypes

The affinity of amitriptyline for muscarine M1 receptors was studied in the rat cerebral cortex and rabbit vas deferens utilizing binding studies as well as inhibition of carbachol-induced phosphoinositide hydrolysis in the cerebral cortex and blockade of the muscarinic prejunctional inhibition of sympathetic nerve stimulation in the rabbit vas deferens. The inhibition constants (KI) or dissociation constants (KB) obtained were approximately 6- to 20-fold lower than those obtained at muscarine M2 receptors in rat atria (binding and negative inotropic response) indicating that amitriptyline exhibits a degree of muscarine M1 receptor selectivity.

Isolation of the fourth ventricle causing transtentorial herniation: neurosonographic findings in premature infants

OBJECTIVE

Significant posthemorrhagic enlargement of the fourth ventricle occurs only in a small minority of patients. Although entrapment or isolation of any ventricle can occur, the fourth ventricle is the most common site. This study was undertaken to better understand enlargement of the fourth ventricle after intraventricular hemorrhage and the neurosonographic features of isolation and transtentorial herniation.

MATERIALS AND METHODS

The sonographic records of 1535 premature neonates were reviewed for evidence of intracranial hemorrhage and ventriculomegaly. Cranial sonography was performed within the first 3 days of life in all neonates born in our hospital and within the first week of admission for transferred neonates. Follow-up sonograms were obtained at weekly intervals until discharge from the nursery. Intracranial hemorrhages were classified as severe when the hemorrhage was associated with hydrocephalus, intraparenchymal hemorrhage, or both.

RESULTS

Intracranial hemorrhage occurred in 761 (50%) of 1535 patients, with severe hemorrhages in 229. Ten had massive enlargement of the fourth ventricle with isolation in six of the 10 after shunt placement. Isolation of the fourth ventricle causing transtentorial herniation occurred in three. Of the patients with isolation of the fourth ventricle, two had associated infection and ventriculitis caused by Klebsiella oxytoca and one had Candida ventriculoencephalitis.

CONCLUSION

The early recognition of the neurosonographic features of an enlarged fourth ventricle causing transtentorial herniation has important therapeutic implications. Although isolation can occur after intraventricular hemorrhage alone, infection and ventriculitis are significant factors in the development of an isolated fourth ventricle.

Gonadotropin-releasing hormone neuronal cell lines

Gonadotropin-releasing hormone (GnRH) cell lines were developed by genetically targeted tumorigenesis in transgenic mice. The cell lines designated GT1 cells have a neuronal phenotype, express neuronal but not glial markers and express the GnRH gene at high levels. The GnRH prohormone is processed in the cells to multiple molecular forms including biologically active GnRH and GnRH-associated peptide. Basal secretion of GnRH from the cells is regulated in part by fast Na+ channels necessary for propagated action potentials. In many instances, basal GnRH release is pulsatile with an interpulse frequency similar to that seen in castrated rodents, suggesting that GnRH neurons are the pulse generator and are capable of synchronizing their secretion in vitro. The secretion of GnRH is stimulated by depolarization and by the neurotransmitter norepinephrine. In related studies we have demonstrated that expression of Simian virus 40 T antigen in GnRH neurons of transgenic mice leads to hypothalamic hypogonadism due to the inability of GnRH nerve terminals to organize in the median eminence. These findings support the use of genetically-directed tumorigenesis to establish highly differentiated GnRH neuronal cell lines that are a valuable model to study the cell biology and regulation of the neurons.

Infection of mural thrombus: a case report and literature review

Infection of mural thrombus over an area of old myocardial infarct was found in an elderly woman with cholangitis. This case is unique since cholangitis was thought to be the cause of septicaemia and ventricular aneurysm was not present.

Molecular mechanisms of cell-cell interaction in Dictyostelium discoideum

During development of the cellular slime mold Dictyostelium discoideum, cells migrate in response to cAMP to form aggregates, which give rise to fruiting bodies consisting of two major cell types: spores and stalk cells. Multicellularity is achieved by the expression of two types of cell-cell adhesion sites. The EDTA-sensitive binding sites are expressed at the initial stage of development. At the aggregation stage, cells acquire EDTA-resistant binding sites, which are mediated by a cell-surface glycoprotein of Mr80,000 (gp80). gp80 is preferentially associated with cell surface filopodia, which are probably involved in the initiation of contact formation between cells. Covaspheres conjugated with gp80 bind specifically to aggregation-stage cells. The binding can be inhibited by precoating cells with an anti-gp80 monoclonal antibody, thus suggesting that gp80 mediates cell-cell binding via homophilic interaction. The structure of gp80 predicted from its cDNA sequence can be divided into three major domains: a membrane anchor, a hinge, and a globular region. An analysis of fusion proteins containing different gp80 segments shows that the cell-binding activity resides in the globular region. In the postaggregation stages, gp80 is replaced by other surface glycoproteins in maintaining cell-cell adhesion. One of them has a Mr of 150,000 (gp150). Anti-gp150 antibodies have no effect on aggregation-stage cells, but they disrupt cell-cell adhesion at subsequent stages. It becomes evident that the complex phenomena of cell adhesion and tissue organization involve the participation of a number of surface glycoproteins.