Suppression of B cell differentiation by ligation of membrane-bound IgM

Using B cells from the transgenic mouse line B6-Sp6 and control littermates, stimulated by lipopolysaccharide (LPS) under novel culture conditions that provide for the response of all B cells, we show here that specific ligation of the surface IgM molecules always results in inhibition of terminal differentiation and immunoglobulin secretion by activated cells, regardless of the ligand. Thus, monoclonal antibodies to (a) the CH region of Ig (anti-μ. and anti-allotype), (b) the Cx region, (c) the V region (anti-idiotype) of surface IgM, as well as (d) multivalent antigen (2,4,6-trinitrophenyl-bovine serum albumin), all show similar effects and dose-response curves. IgD-negative transgenic B cells are equally sensitive to IgM ligation-dependent inhibition, as control (IgD-positive) B cells. The allotype specificity of this inhibition, assessed by using anti-u, allotype reagents to inhibit and assay the responses, suggests that B cells expressing transgenic or endogenous IgM in transgenic B6-Sp6 mice are largely independent populations. These observations establish that anti-IgM antibodies in conjunction with appropriate LPS stimulation, provide a universal model system for functional characterization of B cell responses.     

Neural classifier construction using regularization, pruning and test error estimation

In this paper we propose a method for construction of feed-forward neural classifiers based on regularization and adaptive architectures. Using a penalized maximum likelihood scheme, we derive a modified form of the entropic error measure and an algebraic estimate of the test error. In conjunction with optimal brain damage pruning, a test error estimate is used to select the network architecture. The scheme is evaluated on four classification problems.     

The Maillard reaction in demineralized dentin in vitro

The Maillard reaction between carbohydrate and protein has been proposed as a cause of the browning of carious lesions. The aim of the present investigation was to determine the occurrence of this reaction in bovine dentin collagen in vitro and to establish the effect of the reaction on the proteolytic degradation of bovine dentin collagen in vitro. Slices of demineralized bovine dentin were incubated with 0.2 M glucose or buffer for 10 weeks at 37°C. The formation of initial (furosine) and advanced (pentosidine) products of the Maillard reaction in dentin exposed to glucose was confirmed by HPLC. After reduction with NaBH₄ to prevent intermediate Maillard products from further reaction, slices were either degraded with collagenase for fluorescence measurement or incubated with trypsin or pepsin to assess enzymatic degradation. Fluorescence characteristic for the Maillard reaction increased in glucose-exposed slices. Degradation of collagen by pepsin, but not by trypsin, was greatly depressed following glucose pretreatment. This may indicate an altered sensitivity to proteolytic degradation; the Maillard reaction thus has a potential role in caries arrestment.     

PHARMACOLOGIC MANAGEMENT OF COMMON MUSCULOSKELETAL DISORDERS IN WOMEN

The range of musculoskeletal disorders encountered in primary care settings is broad, extending from simple injuries to complex chronic diseases. Assessment, management, referral, and pharmacologic intervention for many of these conditions may fall to certified nurse-midwives who increasingly are assuming primary care responsibilities.     

Assessment of the invasive potential of human gynecological tumor cell lines with the in vitro Boyden chamber assay: influences of the ability of cells to migrate through the filter membrane

The Boyden chamber assay is widely used for in vitro measurement of the invasive capacity of cells. However, results can be affected significantly if certain precautions are not taken. Using the Boyden chamber assay we investigated in vitro the invasive potential of a variety of human gynecological tumor cell lines to degrade and migrate through the artificial basement membrane matrix Matrigel. However, in the absence of this Matrigel layer large differences were observed in the ability of cells to adhere to, migrate through and attach to the lower side of the filter membranes. These differences were influenced by cell density, degree of directional locomotion, and the size of the filter pores. To adjust for these influences (which are not directly correlated to the capacity of cells to traverse the Matrigel layer), invasion results were corrected for the ability of cells to migrate through the filter membrane. In addition, the invasion of MDA-MB-231 cells was used as an internal standard to compensate for variations in the Matrigel layer between different experiments. Overall, in our experimental set up, the five human breast cancer cell lines were the most invasive (mean invasion ± SEM relative to MDA-MB-231 invasion: 104.7 ± 6.1%), the five human ovarian cancer cell lines the least invasive (60.2 ± 2.2%) and the six human endometrial cancer cell lines showed an intermediate capacity (79.1 ± 3.5%). In conclusion, the Boyden chamber assay can be used reliably for studying the invasive potential of cells in vitro, if the ability of the cells to migrate through the filter is taken into account, and a reference cell line is included to enable comparison of the data obtained from independently performed experiments on different cell lines.     

Exploring the nature of the relationship between child sexual abuse and substance use among women

Aims. This study investigated whether child sexual abuse (CSA) was associated with earlier substance use and greater severity of substance dependence and what aspects of CSA might predict substance abuse. Design. The study compared (a) drug and alcohol treatment clients with and without a history of CSA and (b) CSA survivors outside drug and alcohol treatment who did or did not have current substance abuse. Settings. Semi-structured interviews took place at participants' homes, treatment agencies or the research centre. Participants. Volunteer participants included 100 women recruited from drug and alcohol treatment programmes and 80 CSA survivors recruited through CSA counselling services and media advertising. Measurements. The results focus on data from the Opiate Treatment Index, Severity of Alcohol Dependence Questionnaire, Substance Dependence Scale, Self-Esteem Inventory and self-reported histories of CSA. Findings. There were no differences between CSA survivors and other drug and alcohol treatment clients in their severity of dependence. Women with a history of CSA more frequently identified stimulants as their main problem drug and reported an earlier age of first intoxication and earlier use of inhalants. Among CSA survivors outside drug and alcohol treatment, women with current substance abuse had typically been abused during adolescence by someone outside the family, whereas those without current substance abuse were typically abused by family members before adolescence. Conclusions. The results suggest that adolescence is a crucial time for the influence of CSA experiences on substance abuse.     

Mycobacterial infection and atopy in childhood: A systematic review

The epidemiological relation between mycobacterial infection and the prevalence of atopic disease in humans is still unclear. This is in contrast to studies in murine models in which a clear suppression of atopic symptoms was observed after exposure to mycobacteria or mycobacterial products. We therefore wanted to provide a systematic overview of the published literature on the relationship between mycobacterial infection and atopic disease and to evaluate the causal relationship in a meta-analysis. The EMBASE and MEDLINE databases were searched systematically for papers published in the English literature (1966-2005) on the relation between mycobacterial infection and atopic disease. Original observational or interventional studies involving the paediatric population were included. Two authors independently reviewed articles for data on mycobacterial exposure and atopic disease outcome. Any differences were resolved by discussion. Of a total of 1201 hits, 23 studies (19 cross-sectionals, three case-controls and one prospective cohort) met the inclusion criteria. Only a minority of studies (40%) observed an association between mycobacterial infection and the prevalence of atopic disease outcome. In the meta-analysis, only studies containing data on mycobacterial exposure and atopic disease outcome variables were included. Only cross-sectional studies, in which the relation between a positive tuberculin skin test and allergic symptoms was studied, observed statistically significant negative correlation (odds ratio 0.63; 95% confidence interval: 0.51-0.79). The results of this review show that the evidence of the relationship of mycobacterial infection and atopic disease is based on observations of cross-sectional studies. In a meta-analysis, calculations showed a high level of heterogeneity (I(2)) within studies with similar design making it difficult to pool effects. This may partly be explained by differences in the type and definition of mycobacterial infection and lack of uniformity in the definition of atopy. The results show that only a minority of studies in the literature shows any evidence of inverse relationship between mycobacterial exposure and atopic disease outcome. The fact that the present epidemiological evidence on the relationship between mycobacterial infection and the development of atopic disease is based mainly on cross-sectional observational studies indicates the need for population-based prospective studies to address this issue. This issue needs to be addressed in view of recent suggestions to developing mycobacterial-based vaccines against atopic disease in the future.