Plasma exosome profiles from dairy cows with divergent fertility phenotypes

Cell-to-cell communication in physiological and pathological conditions may be influenced by neighboring cells, distant tissues, or local environmental factors. Exosomes are specific subsets of extracellular vesicles that internalize and deliver their content to near and distant sites. Exosomes may play a role in the maternal-embryo crosstalk vital for the recognition and maintenance of a pregnancy; however, their role in dairy cow reproduction has not been established. This study aimed to characterize the exosome profile in the plasma of 2 strains of dairy cow with divergent fertility phenotypes. Plasma was obtained and characterized on the basis of genetic ancestry as fertile (FERT; <23% North American genetics, New Zealand Holstein-Friesian strain, n=8) or subfertile (SUBFERT; >92% North American genetics, North American Holstein-Friesian strain, n=8). Exosomes were isolated by differential and buoyant density centrifugation and characterized by size distribution (nanoparticle tracking analysis, NanoSight NS500, NanoSight Ltd., Amesbury, UK), the presence of CD63 (Western blot), and their morphology (electron microscopy). The total number of exosomes was determined by quantifying the immunoreactive CD63 (ExoELISA kit, System Biosciences), and the protein content established by mass spectrometry. Enriched exosome fractions were identified as cup-shape vesicles with diameters around 100 nm and positive for the CD63 marker. The concentration of exosomes was 50% greater in FERT cows. Mass spectrometry identified 104 and 117 proteins in FERT and SUBFERT cows, of which 23 and 36 were unique, respectively. Gene ontology analysis revealed enrichment for proteins involved in immunomodulatory processes and cell-to-cell communication. Although the role of exosomes in dairy cow reproduction remains to be elucidated, their quantification and content in models with divergent fertility phenotypes could provide novel information to support both physiological and genetic approaches to improving dairy cow fertility.

COL4A1 mutations associated with a characteristic pattern of intracranial calcification

Intracranial calcification (ICC) is a relatively common radiological finding in children undergoing investigation for neurological disorders. Many causes are recognised, and ICC is often regarded as a non-specific sign.From an ongoing study of ICC, we identified 5 patients with characteristic radiological features, in whom a mutation in the COL4A1 gene was found.All patients had CT and MR imaging. MR images demonstrated features of periventricular leukomalacia with irregular dilatation of the lateral ventricles with or without porencephaly, loss of hemispheric white matter volume, and high signal on T2 and FLAIR sequences within periventricular and deep white matter. Calcification was apparent on MR in 4 patients. CT scans demonstrated spot and linear calcification in the subependymal region and around areas of porencephaly. Calcification was also visible in the deep cerebral white matter and basal ganglia. 1 patient showed calcification in the central pons.ICC occurs in COL4A1-related disease. The radiological features are distinct from other conditions demonstrating recognisable patterns of ICC, such as congenital cytomegalovirus infection and Aicardi-Goutiéres syndrome. In the absence of a known risk factor for periventricular leukomalacia, the presence of these radio-logical findings should suggest the possibility of COL4A1-related disease.

IFPA Meeting 2010 Workshop Report I: Immunology; ion transport; epigenetics; vascular reactivity; epitheliochorial placentation; proteomics

Workshops are an important part of the IFPA annual meeting. At IFPA Meeting 2010 there were twelve themed workshops, six of which are summarized in this report. 1. The immunology workshop focused on normal and pathological functions of the maternal immune system in pregnancy. 2. The transport workshop dealt with regulation of ion and water transport across the syncytiotrophoblast of human placenta. 3. The epigenetics workshop covered DNA methylation and its potential role in regulating gene expression in placental development and disease. 4. The vascular reactivity workshop concentrated on methodological approaches used to study placental vascular function. 5. The workshop on epitheliochorial placentation covered current advances from in vivo and in vitro studies of different domestic species. 6. The proteomics workshop focused on a variety of techniques and procedures necessary for proteomic analysis and how they may be implemented for placental research.

Recombinant interferon beta or glatiramer acetate for delaying conversion of the first demyelinating event to multiple sclerosis

BACKGROUND

Immunomodulatory drugs have been shown to be only modestly effective in clinically definite relapsing remitting multiple sclerosis (RRMS). It has been hypothesized that their efficacy could be higher if used at the first appearance of symptoms, that is in the clinically isolated syndromes (CIS) suggestive of demyelinating events, a pathology which carries a high risk to convert to clinically definite MS (CDMS).

OBJECTIVES

The objective of this review was to assess the effects of immunomodulatory drugs compared to placebo in adults in preventing conversion from CIS to CDMS which means the prevention of a second attack.

SEARCH STRATEGY

We searched the Cochrane MS Group Trials Register (June 2007), Cochrane Central Register of Controlled Trials (CENTRAL)The Cochrane Library Issue 3, 2007, MEDLINE (January 1966 to June 2007), EMBASE (January 1974 to June 2007) and reference lists of articles. We also contacted manufacturers and researchers in the field.

SELECTION CRITERIA

The trials selected were double-blind, placebo-controlled, randomised trials of CIS patients treated with immunomodulatory drugs.

DATA COLLECTION AND ANALYSIS

Study selection have been independently done by two reviewers. Two further reviewers independently assessed trial quality and extracted and analysed data. Study authors were contacted for additional informations. Adverse effects information was collected from the trials.

MAIN RESULTS

Only three trials tested the efficacy of interferon (IFN) beta including a total of 1160 participants (639 treatment, 521 placebo); no trial tested the efficacy of glatiramer acetate (GA). The metanalyses showed that the proportion of patients converting to CDMS was significantly lower in IFN beta-treated than in placebo-treated patients both after one year (pooled OR 0.53; 95% CI, 0.40 to 0.71; p <0.0001) as well as after two years of follow-up (pooled OR 0.52; 95% CI, 0.38 to 0.70; p <0.0001). Early treatment with IFN beta was associated with the side effect profile reported by the randomised controlled trials with this drug. Since side effects were reported with some heterogeneity in the three studies the metanalysis was possible only for the frequency of serious adverse events, not significantly different in IFN beta-treated or placebo-treated patients.

AUTHORS' CONCLUSIONS

The efficacy of IFN beta treatment on preventing the conversion from CIS to CDMS was confirmed over two years of follow-up. Since patients had some clinical heterogeneity (length of follow-up, clinical findings of initial attack), it could be useful for the clinical practice to further analyse the efficacy of IFN beta treatment in different patient subgroups.

Advanced techniques in placental biology -- workshop report

Major advances in placental biology have been realized as new technologies have been developed and existing methods have been refined in many areas of biological research. Classical anatomy and whole-organ physiology tools once used to analyze placental structure and function have been supplanted by more sophisticated techniques adapted from molecular biology, proteomics, and computational biology and bioinformatics. In addition, significant refinements in morphological study of the placenta and its constituent cell types have improved our ability to assess form and function in highly integrated manner. To offer an overview of modern technologies used by investigators to study the placenta, this workshop: Advanced techniques in placental biology, assembled experts who discussed fundamental principles and real time examples of four separate methodologies. Y. Sadovsky presented the principles of microRNA function as an endogenous mechanism of gene regulation. J. Robinson demonstrated the utility of correlative microscopy in which light-level and transmission electron microscopy are combined to provide cellular and subcellular views of placental cells. A. Croy provided a lecture on the use of microdissection techniques which are invaluable for isolating very small subsets of cell types for molecular analysis. Finally, G. Rice presented an overview methods on profiling of complex protein mixtures within tissue and/or fluid samples that, when refined, will offer databases that will underpin a systems approach to modern trophoblast biology.

Activation of NF-κB transcription factor in the preterm ovine brain and placenta after acute LPS exposure

Intrauterine infection may be causally related to inflammation and injury of the fetal brain, however the mechanisms by which this occurs are unclear. We have investigated whether nuclear factor (NF)-kappaB, a transcription factor for proinflammatory cytokines, is activated in the fetal brain after acute LPS-exposure. At 95 days of gestation (term = approximately 147 days), 5 fetuses received a single intravenous bolus dose of LPS (1 microg/kg); 6 fetuses served as controls. Fetal blood samples were taken hourly for 6 hr post LPS-exposure to assess physiological status. Ewes and fetuses were then euthanased, placental and brain tissue examined histologically, and NF-kappaB activation assessed in several regions of the fetal brain using an electromobility shift assay (EMSA). Oxidative stress was measured using lipid peroxidation and 8-isoprostane biochemical assays and brain cytokine concentrations analysed by enzyme linked immunosorbent assay (ELISA). LPS-exposed fetuses (relative to controls) were hypoxemic and the haematocrit and lactate levels had increased. In the brains of LPS-exposed fetuses compared to controls, NF-kappaB binding activity was elevated in the hippocampus and the thalamus/basal ganglia; 8-isoprostane levels were elevated overall (P < 0.05) in the parietal/occipital/temporal lobes and thalamus/basal ganglia. TNF-alpha and IL-6 concentrations were not elevated, however, there was a tendency for an elevation of IFN-gamma concentrations in the thalamus/basal ganglia. IFN-gamma concentration was elevated (P < 0.05) in the plasma 4 hr after LPS-exposure. In the placenta, NF-kappaB binding activity was increased (P < 0.05). We conclude that acute systemic administration of LPS leads to increased binding activity of NF-kappaB subunits in specific regions of the fetal brain and in the placenta, but that there is no clear-cut relationship between this elevation and vulnerability to endotoxic damage.

Ascites induces modulation of alpha6beta1 integrin and urokinase plasminogen activator receptor expression and associated functions in ovarian carcinoma

Interactions between cancer cells and the surrounding medium are not fully understood. In this study, we demonstrate that ascites induces selective changes in the expression of integrins and urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) in ovarian cancer cells. We hypothesise that this change of integrin and uPA/uPAR expression triggers signalling pathways responsible for modulating phenotype-dependent functional changes in ovarian cancer cells. Human ovarian surface epithelial (HOSE) cell lines and epithelial ovarian cancer cell lines were treated with ascites for 48 h. Ascites induced upregulation of alpha6 integrin, without any change in the expression of alphav, beta1 and beta4 integrin subunits. Out of the four ovarian cancer cell lines studied, ascites induced enhancement in the expression of uPA/uPAR in the more invasive OVCA 433 and HEY cell lines without any change in the noninvasive OVHS1 and moderately invasive PEO.36 cell lines. On the other hand, no change in the expression of alpha6 integrin or uPAR, in response to ascites, was observed in HOSE cells. In response to ascites, enhancement in proliferation and in adhesion was observed in all four ovarian cancer cell lines studied. In contrast, no significant increase in proliferation or adhesion by ascites was observed in HOSE cells. Ascites-induced expression of uPA/uPAR correlated with the increased invasiveness of HEY and OVCA 433 cell lines but was not seen in OVHS1, PEO.36 and HOSE cell lines. Upregulation of alpha6 integrin and uPA/uPAR correlated with the activation of Ras and downstream Erk pathways. Ascites-induced activation of Ras and downstream Erk can be inhibited by using inhibitory antibodies against alpha6 and beta1 integrin and uPAR, consistent with the inhibition of proliferation, adhesion and invasive functions of ovarian cancer cell lines. Based on these findings, we conclude that ascites can induce selective upregulation of integrin and uPA/uPAR in ovarian cancer cells and these changes may modulate the functions of ovarian carcinomas.

Ascites induces modulation of alpha6beta1 integrin and urokinase plasminogen activator receptor expression and associated functions in ovarian carcinoma

Interactions between cancer cells and the surrounding medium are not fully understood. In this study, we demonstrate that ascites induces selective changes in the expression of integrins and urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) in ovarian cancer cells. We hypothesise that this change of integrin and uPA/uPAR expression triggers signalling pathways responsible for modulating phenotype-dependent functional changes in ovarian cancer cells. Human ovarian surface epithelial (HOSE) cell lines and epithelial ovarian cancer cell lines were treated with ascites for 48 h. Ascites induced upregulation of alpha6 integrin, without any change in the expression of alphav, beta1 and beta4 integrin subunits. Out of the four ovarian cancer cell lines studied, ascites induced enhancement in the expression of uPA/uPAR in the more invasive OVCA 433 and HEY cell lines without any change in the noninvasive OVHS1 and moderately invasive PEO.36 cell lines. On the other hand, no change in the expression of alpha6 integrin or uPAR, in response to ascites, was observed in HOSE cells. In response to ascites, enhancement in proliferation and in adhesion was observed in all four ovarian cancer cell lines studied. In contrast, no significant increase in proliferation or adhesion by ascites was observed in HOSE cells. Ascites-induced expression of uPA/uPAR correlated with the increased invasiveness of HEY and OVCA 433 cell lines but was not seen in OVHS1, PEO.36 and HOSE cell lines. Upregulation of alpha6 integrin and uPA/uPAR correlated with the activation of Ras and downstream Erk pathways. Ascites-induced activation of Ras and downstream Erk can be inhibited by using inhibitory antibodies against alpha6 and beta1 integrin and uPAR, consistent with the inhibition of proliferation, adhesion and invasive functions of ovarian cancer cell lines. Based on these findings, we conclude that ascites can induce selective upregulation of integrin and uPA/uPAR in ovarian cancer cells and these changes may modulate the functions of ovarian carcinomas.

Ascites induces modulation of alpha6beta1 integrin and urokinase plasminogen activator receptor expression and associated functions in ovarian carcinoma

Interactions between cancer cells and the surrounding medium are not fully understood. In this study, we demonstrate that ascites induces selective changes in the expression of integrins and urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) in ovarian cancer cells. We hypothesise that this change of integrin and uPA/uPAR expression triggers signalling pathways responsible for modulating phenotype-dependent functional changes in ovarian cancer cells. Human ovarian surface epithelial (HOSE) cell lines and epithelial ovarian cancer cell lines were treated with ascites for 48 h. Ascites induced upregulation of alpha6 integrin, without any change in the expression of alphav, beta1 and beta4 integrin subunits. Out of the four ovarian cancer cell lines studied, ascites induced enhancement in the expression of uPA/uPAR in the more invasive OVCA 433 and HEY cell lines without any change in the noninvasive OVHS1 and moderately invasive PEO.36 cell lines. On the other hand, no change in the expression of alpha6 integrin or uPAR, in response to ascites, was observed in HOSE cells. In response to ascites, enhancement in proliferation and in adhesion was observed in all four ovarian cancer cell lines studied. In contrast, no significant increase in proliferation or adhesion by ascites was observed in HOSE cells. Ascites-induced expression of uPA/uPAR correlated with the increased invasiveness of HEY and OVCA 433 cell lines but was not seen in OVHS1, PEO.36 and HOSE cell lines. Upregulation of alpha6 integrin and uPA/uPAR correlated with the activation of Ras and downstream Erk pathways. Ascites-induced activation of Ras and downstream Erk can be inhibited by using inhibitory antibodies against alpha6 and beta1 integrin and uPAR, consistent with the inhibition of proliferation, adhesion and invasive functions of ovarian cancer cell lines. Based on these findings, we conclude that ascites can induce selective upregulation of integrin and uPA/uPAR in ovarian cancer cells and these changes may modulate the functions of ovarian carcinomas.

Changes in the expression of prostaglandin E and F synthases at induced and spontaneous labour onset in the sheep

The differential production of prostaglandin (PG) F(2 alpha) and PGE(2) within the uterine compartment may play a role in controlling myometrial contraction. We hypothesized that the enzymes downstream of PG endoperoxide synthase-2 (PGHS-2) determine the ratio of PGF(2 alpha) and PGE(2) in the utero-ovarian vein plasma and the time of normal and preterm labour onset. The aim of this study was to simultaneously determine the expression of PGF and PGE synthases (PGFS and PGES) in gestational tissues at spontaneous and induced-preterm labour in sheep. Myometrial, endometrial and placental tissue were obtained from ewes in dexamethasone-induced preterm labour, age-matched control ewes, and ewes in spontaneous term labour for analysis of mRNA expression by real-time PCR. PGFS mRNA expression was significantly increased following dexamethasone-induced and spontaneous labour onset in placentome (P<0.01) but was unchanged in the myometrium and endometrium. In contrast, PGES mRNA expression remained unchanged or decreased. PGHS-2 mRNA expression was increased in all tissues examined in both dexamethasone-induced and spontaneous labour (P<0.001). Plasma PGE(2) and PGF(2 alpha) concentrations rose in both dexamethasone-induced and spontaneous labour with the ratio of PGF(2 alpha):PGE(2) increased with labour onset (P<0.05). These results are consistent with the hypothesis that the increased expression, of PGFS is responsible for the increased PGF(2 alpha):PGE(2) ratio and this, together with increased PGHS-2 expression, accounts for myometrial activity at labour onset. The findings point to PGFS expression as a key factor in regulating the uterotonic process in the sheep.

Downregulation of urokinase plasminogen activator receptor expression inhibits Erk signalling with concomitant suppression of invasiveness due to loss of uPAR-beta1 integrin complex in colon cancer cells

Cancer invasion is regulated by cell surface proteinases and adhesion molecules. Interaction between specific cell surface molecules such as urokinase plasminogen activator receptor (uPAR) and integrins is crucial for tumour invasion and metastasis. In this study, we examined whether uPAR and beta1 integrin form a functional complex to mediate signalling required for tumour invasion. We assessed the expression of uPAR/beta1 integrin complex, Erk signalling pathway, adhesion, uPA and matrix metalloproteinase (MMP) expression, migration/invasion and matrix degradation in a colon cancer cell line in which uPAR expression was modified. Antisense inhibition of the cell surface expression of uPAR by 50% in human colon carcinoma HCT116 cells (A/S) suppressed Erk-MAP kinase activity by two-fold. Urokinase plasminogen activator receptor antisense treatment of HCT116 cells was associated with a 1.3-fold inhibition of adhesion, approximately four-fold suppression of HMW-uPA secretion and inhibition of pro-MMP-9 secretion. At a functional level, uPAR antisense resulted in a four-fold decline in migration/invasion and abatement of plasmin-mediated matrix degradation. In empty vector-transfected cells (mock), uPA strongly elevated basal Erk activation. In contrast, in A/S cells, uPA induction of Erk activation was not observed. Urokinase plasminogen activator receptor associated with beta1 integrin in mock-transfected cells. Disruption of uPAR-beta1 integrin complex in mock-transfected cells with a specific peptide (P25) inhibited uPA-mediated Erk-MAP kinase pathway and inhibited migration/invasion and plasmin-dependent matrix degradation through suppression of pro-MMP-9/MMP-2 expression. This novel paradigm of uPAR-integrin signalling may afford opportunities for alternative therapeutic strategies for the treatment of cancer.

Viruses from extreme thermal environments

Viruses of extreme thermophiles are of great interest because they serve as model systems for understanding the biochemistry and molecular biology required for life at high temperatures. In this work, we report the discovery, isolation, and preliminary characterization of viruses and virus-like particles from extreme thermal acidic environments (70-92 degrees C, pH 1.0-4.5) found in Yellowstone National Park. Six unique particle morphologies were found in Sulfolobus enrichment cultures. Three of the particle morphologies are similar to viruses previously isolated from Sulfolobus species from Iceland and/or Japan. Sequence analysis of their viral genomes suggests that they are related to the Icelandic and Japanese isolates. In addition, three virus particle morphologies that had not been previously observed from thermal environments were found. These viruses appear to be completely novel in nature.

Using dose addition to estimate cumulative risks from exposures to multiple chemicals

The Food Quality Protection Act (FQPA) of 1996 requires the EPA to consider the cumulative risk from exposure to multiple chemicals that have a common mechanism of toxicity. Three methods, hazard index (HI), point-of-departure index (PODI), and toxicity equivalence factor (TEF), have commonly been considered to estimate the cumulative risk. These methods are based on estimates of ED(10) (point of departure) and reference doses from the dose-response functions of individual chemicals. They do not incorporate the actual dose-response function of the mixture from multiple chemical exposures. Dose addition is considered to be an appropriate approach to cumulative risk assessment because it assumes that the chemicals of interest act in accordance with a common mode of action (a similar action). This paper proposes a formal statistical procedure to estimate the cumulative risk by fitting the dose-response model of the mixture under dose addition. The relative potency between two chemicals is estimated directly from the joint dose response model of the mixture. An example data set of four drugs representing four chemicals is used to illustrate the proposed procedure and compare it to the HI, PODI, and TEF methods.

Genetic susceptibility to MS: a second stage analysis in Canadian MS families

Four published genome screens have identified a number of markers with increased sharing in multiple sclerosis (MS) families, although none has reached statistical significance. One hundred and five markers previously identified as showing increased sharing in Canadian, British, Finnish, and American genome screens were genotyped in 219 sibling pairs ascertained from the database of the Canadian Collaborative Project on Genetic Susceptibility to MS (CCPGSMS). No markers examined met criteria for significant linkage. Markers located at 5p14 and 17q22 were analyzed in a total of 333 sibling pairs and attained mlod scores of 2.27 and 1.14, respectively. The known HLA Class II DRB1 association with MS was confirmed (P<0.0001). Significant transmission disequilibrium was also observed for D17S789 at 17q22 (P=0.0015). This study highlights the difficulty of searching for genes with only mild-to-moderate effects on susceptibility, although large effects of specific loci may still be present in individual families. Future progress in the genetics of this complex trait may be helped by (1) focussing on more ethnically homogeneous samples, (2) using an increased number of MS families, and (3) using transmission disequilibrium analysis in candidate regions rather than the affected relative pair linkage analysis.

Elevated interleukin-8 concentrations in cervical secretions are associated with preterm labour

The aim of this study was to assess the potential clinical utility of interleukin-8 (IL-8) present in cervical secretions as a marker of preterm labour and delivery. Samples of cervical mucus from 91 pregnant women were assessed for the presence and concentration of IL-8. Two samples were collected (at 18 +/- 2 and 28 +/- 2.5 weeks of gestation) and correlated with cervicovaginal microbiology and cervical length, as measured by transvaginal ultrasound. The IL-8 concentration at 28/40 was significantly higher in women who went on to deliver preterm (p < 0.01), and there was a greater than five-fold increase from 18 to 28 weeks in 6/7 of these women.

Bone marrow transplantation in multiple sclerosis

There is strong circumstantial evidence that multiple sclerosis (MS) is an autoimmune disease. Nonspecific immunosuppressive therapy has not been successful in altering the natural course of the illness. Bone marrow transplantation has heretofore been a radical therapy used in patients with life-threatening malignancies but has potential as a treatment for human autoimmunity. In MS there have been no controlled studies. We report here four patients with MS undergoing bone marrow transplantation with 6-48 months of follow-up. In three this was carried out for co-existing malignancy and in one as an experimental treatment for MS using the patient's unaffected identical twin as a donor. The limited outcome that can be evaluated in these patients supports further experimentation into this treatment modality in MS patients with poor prognostic indications.

Cost and health related quality of life consequences of multiple sclerosis

OBJECTIVES

To (i) quantify the cost of multiple sclerosis (MS) to the Canadian health care system and society; (ii) measure health utility in MS patients, and (iii) examine the influence of disability on patient utility and health care costs.

MATERIALS AND METHODS

A comprehensive patient survey and chart review of relapsing MS patients in remission, relapse and recalling a relapse.

RESULTS

Annual remission costs increased with EDSS level ($7596 at EDSS 1, $33 206 at EDSS 6). At all EDSS levels the largest costs were due to inability to work, which increased with EDSS. The average relapse cost for all EDSS levels was $1367. An inverse correlation was found between EDSS level and patient utility for patients in remission and relapse. The decrease in remission health utility from EDSS 1 to 6 was 0.24, which is 25% greater than the difference in health status between an average 25 and 85 year-old.

CONCLUSIONS

This study demonstrates that MS produces substantial health care costs and reductions in patient quality of life and ability to work, losses that can be avoided or delayed if disease progression is slowed. These data provide health-care decision-makers with the opportunity to consider the full impact of MS when faced with budget allocation decisions.

Derivation of U.S. EPA's oral Reference Dose (RfD) for methylmercury

Mercury (Hg) cycles in the environment through a series of complex chemical and physical transformations that occur in air, soils, and water bodies. One component of the environmental mercury cycle is the formation of methylmercury (MHg) primarily by aquatic and marine microorganisms and the accumulation of MHg in foodwebs, particularly in piscivorous species. Human consumption of piscivorous fish and other piscivorus animals is the most common pathway of exposure to MHg. For non-carcinogenic toxic endpoints, the U.S. EPA typically develops a Reference Dose (RfD). This is generally interpreted to be a concentration of a chemical which can be consumed on a daily basis over a lifetime without expectation of adverse effect. There is substantial evidence in both animal and humans that MHg is a neurotoxicant in the adult and the child as well as a developmental neurotoxicant for the fetus. Epidemics of MHg poisoning in Japan and Iraq have resulted from high-dose exposures to MHg. In these epidemics adults, children, nursing infants and fetuses were affected by MHg. The epidemics demonstrate that neurotoxicity is the health effect of greatest concern and that effects on the developing human nervous system apparently occur at lower exposures than those affecting the adult nervous system. We describe how the data from the Iraqi MHg epidemic were used to derive the current RfD of 0.1 microgram/Kgbw/day (U.S. EPA, 1995;).

Uncertainty analysis of the estimated ingestion rates used to derive the methylmercury reference dose

The U.S. EPA's Reference Dose (RfD) for methylmercury (MeHg) uses a simple one-compartment toxicokinetic model to estimate ingestion doses in mg/kg-day from measured concentrations of mercury in hair. The model includes a number of input variables for which point estimates are made. Uncertainty in the inputs is addressed by the use of a 3-fold uncertainty factor. There are, however, published ranges for each variable which are used to develop distributions for each of the inputs. Monte Carlo output of the model is generated. The 90% confidence interval spans a 3-fold to 5-fold range of ingestion doses for any given concentration of mercury in hair. The hair:blood mercury concentration ratio contributes most to the variance of the output. The results indicate that the uncertainty factor of three is appropriate.

The natural history of multiple sclerosis: a geographically based study. 7. Progressive-relapsing and relapsing-progressive multiple sclerosis: a re-evaluation

Classifications of multiple sclerosis subtypes have been largely based on clinical phenomenology. Nevertheless, definitions of relapse, remission and progression have been imprecise. Recently an international consensus group, as part of a reclassification of disease subtypes, recommended dropping the term 'relapsing-progressive' (RP) and retaining the term 'progressive-relapsing' (PR) multiple sclerosis. The term 'RP' multiple sclerosis had been applied when the early course combined both relapses and progression and was believed to identify some patients with a worse than average outcome. The PR group consisted of patients with primary progressive disease who later in their course developed relapses. Since the terminology has been largely arbitrary, we have evaluated the validity of the terms 'RP' and 'PR' multiple sclerosis in the context of long-term outcome within a large population-based cohort of progressive multiple sclerosis patients seen at the London Multiple Sclerosis Clinic (Canada) between 1972 and 1984. Mean follow-up of the entire cohort was 25 years. Designation of RP multiple sclerosis did identify a more rapidly progressive subgroup. To realign these natural history data with consensus recommendations, these patients were reassigned to secondary progressive (SP) or to primary progressive (PP) multiple sclerosis, with progression defined as at least 1 year of progressive deterioration. PP multiple sclerosis patients with relapses after a year were designated as having PR multiple sclerosis. Relapses in primary progressive multiple sclerosis occurred in 27.8% of patients at some point even two to three decades after onset. In general these relapses were mild and remitting, but served to blur the distinction between progressive and relapsing-remitting disease. The long-term outcomes of time to Kurtzke disability scores (DSS) of 3, 6, 8 and 10 were compared among the progressive subtypes. Times to these disability end-points and to death were not different between PR and PP multiple sclerosis. Survival curves for progressive patients have been amended to incorporate the reassignment of PR multiple sclerosis patients into the PP group and the RP multiple sclerosis patients into the PP and SP subgroups. The time to reach DDS 3, 6, 8 and 10 for a population-based cohort of primary and secondary progressive patients resulting from the elimination of the categories of RP multiple sclerosis and PR multiple sclerosis has been established. These results provide justification for retaining only PP and SP multiple sclerosis as the subgroups of progressive disease.

Heat transfer through penguin feathers

Morphological measurements of penguin feathers are used to construct a thermal model of heat transfer through the coat. Assuming uniform distribution of the feathers and their associated afterfeathers, it is possible to model heat transfer through the coat of the penguin using standard theory. It is shown that convection does not occur in the coat of the penguin and that radiative heat loss is minimized. The theory predicts a thermal conductivity of 2.38 W m(-2)K(-1)which compares well with an empirically measured value of 1.93 W m(-2)K(-1). Copyright 1999 Academic Press.

A randomized controlled trial of a smoking cessation intervention during pregnancy

This study was a randomized controlled trial of a smoking cessation intervention for pregnant smokers. Women who reported smoking at their first antenatal visit and satisfied the inclusion criteria were asked to participate in the trial. Analysis was restricted to 393 evaluable women in the control group (received usual antenatal care) and 339 women to the study group (received usual antenatal care plus the intervention). The primary hypotheses were that the intervention would result in a higher proportion of quitters and that the mean birth-weight of babies born to women receiving the intervention would be greater than that of babies born to women in the control group. The outcome measures were smoking status based on self-report combined with a urinary cotinine level of <115 ng/mL, and birth-weight. There was no significant difference in quit rate between women receiving the intervention and women in the control group (11.9% versus 9.8% p=0.41). Babies born to women receiving the intervention were on average 84 g heavier than babies born to controls (p=0.04). The factors that contribute to the lack of a significant increase in smoking cessation in the intervention group and the possible explanation for the changes in birth-weight are discussed.

Reduced visual evoked responses in multiple sclerosis patients with optic neuritis: comparison of functional magnetic resonance imaging and visual evoked potentials

The limited application of functional magnetic resonance imaging (fMRI) for investigations of multiple sclerosis (MS) patients has already shown that deficits of the motor, cognitive and visual systems may be identified by differences in the patterns of activation in response to a suitable stimulus. In MS patients with unilateral optic neuritis, the area of activation in the primary visual cortex, measured by fMRI techniques, is dramatically reduced in response to stimulation of the affected eye. The latency of the major positive component of the visual evoked potential (VEP) recorded upon stimulation of the affected eye is significantly increased in these patients, as compared to the unaffected eye and normal volunteers. We have found a correlation between the neural response measured using fMRI and the latency of the VEP. fMRI signal responses have the potential to provide more detailed topographic information relating to functional deficits in MS.