Increased susceptibility to bacterial infection as a sequela of exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The effects of subclinical levels of 2,3,7,8-tetrachloridibenzo-p-dioxin (TCDD) on the response of mice to infection with either Salmonella bern or Herpesvirus suis, also known as pseudorabies virus, are reported. TCDD is a contaminant of certain commercially useful chemicals, such as chlorinated phenols or herbicides. It has been shown to cause thymic atrophy and to suppress cell-mediated immunity in laboratory animals. Sublethal levels of TCDD were used: 0.5, 1,5, 10, or 20 mug/kg, given through a gastric tube once weekly for 4 weeks. A significant decrease in weight gain compared with control mice occurred at the 20-mug dosage. Dose schedules of 1 mug or more, followed by salmonella infection, resulted in significant increases in mortality and decreases in the time from infection to dealth. However, TCDD had no significant effect on mortality in the pseudorabies-infected mice. The most important finding in this study is that extremely low levels of TCDD, which do not produce clinical or pathological change, still have the capacity to affect host defense.     

Association study of dopamine D3 receptor gene and schizophrenia

Several groups have reported an association between schizophrenia and the MscI polymorphism in the first exon of the dopamine D3 receptor gene (DRD3). We studied this polymorphism using a North American sample (117 patients plus 188 controls) and an Italian sample (97 patients plus 64 controls). In the first part of the study, we compared allele frequencies of schizophrenia patients and unmatched controls and observed a significant difference in the total sample (P = 0.01). The second part of the study involved a case control approach in which each schizophrenia patient was matched to a control of the same sex, and of similar age and ethnic background. The DRD3 allele frequencies of patients and controls revealed no significant difference between the two groups in the Italian (N = 53) or the North American (N = 54) matched populations; however, when these two matched samples were combined, a significant difference was observed (P = 0.026). Our results suggest that the MscI polymorphism may be associated with schizophrenia in the populations studied. © 1995 Wiley-Liss, Inc.     

Use of an antigen-capture assay for characterisation of monoclonal antibodies to mycobacterial lipoarabinomannan

Monoclonal antibodies directed to six separate antigen molecules of Mycobacterium leprae have been tested in an antigen-capture assay based on combined use of polyclonal ("capture") and monoclonal ("detector") antibody reagents. This approach provides a potentially versatile, sensitive and specific assay for detection and relative quantitation of M. leprae antigens. Characterisation of monoclonal antibodies to mycobacterial lipoarabinomannan (LAM-B) by the antigen-capture assay indicates that some of the antigenic determinants present on LAM-B from M. leprae may be either absent altogether or present at much lower concentrations on the corresponding LAM-B structure form M. tuberculosis.     

A549 lung epithelial cells grown as three-dimensional aggregates: alternative tissue culture model for Pseudomonas aeruginosa pathogenesis

A three-dimensional (3-D) lung aggregate model was developed from A549 human lung epithelial cells by using a rotating-wall vessel bioreactor to study the interactions between Pseudomonas aeruginosa and lung epithelial cells. The suitability of the 3-D aggregates as an infection model was examined by immunohistochemistry, adherence and invasion assays, scanning electron microscopy, and cytokine and mucoglycoprotein production. Immunohistochemical characterization of the 3-D A549 aggregates showed increased expression of epithelial cell-specific markers and decreased expression of cancer-specific markers compared to their monolayer counterparts. Immunohistochemistry of junctional markers on A549 3-D cells revealed that these cells formed tight junctions and polarity, in contrast to the cells grown as monolayers. Additionally, the 3-D aggregates stained positively for the production of mucoglycoprotein while the monolayers showed no indication of staining. Moreover, mucin-specific antibodies to MUC1 and MUC5A bound with greater affinity to 3-D aggregates than to the monolayers. P. aeruginosa attached to and penetrated A549 monolayers significantly more than the same cells grown as 3-D aggregates. Scanning electron microscopy of A549 cells grown as monolayers and 3-D aggregates infected with P. aeruginosa showed that monolayers detached from the surface of the culture plate postinfection, in contrast to the 3-D aggregates, which remained attached to the microcarrier beads. In response to infection, proinflammatory cytokine levels were elevated for the 3-D A549 aggregates compared to monolayer controls. These findings suggest that A549 lung cells grown as 3-D aggregates may represent a more physiologically relevant model to examine the interactions between P. aeruginosa and the lung epithelium during infection.     

A comparison of two techniques for the detection of an antibody in human serum to Chang liver cell surface antigens

The antibody-dependent cell-mediated cytotoxicity technique (ADCC) and an isotopic antiglobulin technique have been compared for their abilities to detect human serum antibodies to Chang liver cell membrane antigens. The optimal conditions were established for the latter technique, which was found to be superior with respect to reproducibility and sensitivity. Also, unlike ADCC, the isotopic antiglobulin technique was unaffected by other factors, such as immune complexes present in pathological sera.     

Selective enrichment broth culture for detection of Clostridium difficile and associated cytotoxin

A procedure was devised for routine examination of feces for Clostridium difficile with selective enrichment broth culture containing increased levels of carbohydrates and antibiotics to detect cytotoxin and volatile acids in broths inoculated with fecal samples. C. difficile was detected and identified with a rapidity comparable to that of conventional culture on selective cycloserine-cefoxitin fructose agar. Detection rates for C. difficile in inoculated broths (111/401 or 27%) were significantly higher than for culture on cycloserine-cefoxitin fructose agar (47/401 or 11%, P greater than 0.001). All fecal samples containing C. difficile and cytotoxin were correctly identified by the procedure. Isocaproic acid peak heights greater than 2 mm in selective enrichment broths inoculated with fecal samples indicated that C. difficile was present in the fecal sample examined. Of the positive specimens examined, 58% (64/111) produced peak heights greater than 10 mm. Peak heights less than 2 mm were not associated with C. difficile in the fecal sample. The investigated procedure provided a reliable alternative to the routine processing of feces for detecting C. difficile and associated cytotoxin in feces. Inoculated broths with isocaproic acid peak heights greater than 2 mm, after 24 to 48 h of incubation, and in which cytotoxin was detected, were subcultured to blood agar to obtain isolates of the organism as required. Broths which showed isocaproic acid peak heights less than 2 mm, and in which cytotoxin was not detected, were discarded as negative for C. difficile. The procedure was deemed potentially useful for epidemiological surveys of C. difficile.     

Vitamin A Levels and Immunity in Humans

In animal studies, vitamin A deficiency induces a shift from type 2 (humoral) to type 1 (cellular) cytokines; there are no similar data for humans. Control of human immunodeficiency virus (HIV) and Mycobacterium tuberculosis infections requires type 1 cytokine (cellular) immunity. These infections and vitamin A deficiency are highly prevalent in Africa. We therefore examined the interactions among serum vitamin A levels, immune parameters, HIV infection status, Mycobacterium bovis BCG vaccine scarring (as an indicator of a type 1 cytokine profile), and clinical findings for 70 hospitalized children in Malawi, Africa. Directly conjugated monoclonal antibodies and flow cytometry were used to assess cell-specific cytokine production by peripheral blood monocytes and lymphocyte subpopulations. The statistical techniques employed included nonparametric statistics and logistic regression analyses. Thirty percent of the participants had severe vitamin A deficiency (<10 μg/dl), 34% had moderate deficiency (10 to <20 μg/dl), and 36% had normal levels (≥20 μg/dl). Vitamin A levels were lower for HIV-positive than for HIV-negative children (median, 10 and 17 μg/dl, respectively). Vitamin A-deficient children (<20 μg/dl) were more likely than non-vitamin A-deficient children to have higher proportions of natural killer (NK) cells (median, 8.3 and 5.2%, respectively) and lower ratios of interleukin-10-producing monocytes to tumor necrosis factor alpha-producing monocytes after induction (median, 1.0 and 2.3, respectively). Vitamin A-deficient children were also more likely than non-vitamin A-deficient children to exhibit respiratory symptoms (47% versus 12%) and visible BCG vaccine scars (83% versus 48%), which are indicative of a type 1 response to vaccination. Vitamin A status did not vary with gender, age, incidence of malaria parasitemia, blood culture positivity, or rates of mortality (6% of vitamin A-deficient children died versus 20% of non-vitamin A-deficient children). Lower vitamin A levels were associated with a relative type 1 cytokine dominance and proportionately more NK cells, both of which may be somewhat beneficial to persons who are exposed to HIV, M. tuberculosis, or other type 1 pathogens.     

Characterization of diethylstilbestrol‐induced hypospadias in female mice

The urethral duct and vagina are formed from the urogenital sinus (UGS) during the early neonatal period in mice. Neonatal estrogen exposure results in hypospadias, or the malpositioning of vaginal and urethral openings, with wide cleft clitoris. We sought to characterize diethylstilbestrol (DES) influence on UGS morphogenesis and hypospadias formation. Newborn (day 0) and 1–4‐day‐old female mice (ICR/Jcl) were given (s.c.) oil or 3.0 μg DES. Animals were killed 24 hr later; then hypospadias formation and epithelial apoptosis and proliferation within the developing UGS were assessed. DES did not alter normal UGS morphogenesis by day 1, in comparison with controls. However, hypospadias formation was observed in DES‐treated mice by day 3. In these mice, the distal dorsal urethral duct appeared to fuse with and open into the lower vaginal solid cord region. Further, DES treatment produced a gradual significant increase in dorsal urethral epithelial apoptosis (P < 0.05) just prior to and during fusion and hypospadias formation. DES‐induced urethral epithelial and sinus cord proliferation appeared significantly increased (P < 0.05) and unchanged, respectively, just prior to fusion. By day 5, DES‐treated mice exhibited wide cleft clitoris. In addition, if DES was given on day 3 or 5, a gradual, distinct caudal shift in the vaginal‐urethral junction was observed compared to mice treated on days 0–2. Although hypospadias was not induced when neonates were given DES on day 7, these mice continued to display early vaginal opening. Dose‐response analysis indicated that 0.03 μg DES for 5 days is the lowest known critical dose for hypospadias induction. We have shown for the first time that DES‐induced hypospadias onset may primarily be the result of changes in developing dorsal urethral epithelial cell apoptotic and proliferative activity, and that the location of DES‐induced hypospadias formation is dependent on age at time of exposure. Anat Rec 266:43–50, 2002. © 2002 Wiley‐Liss, Inc.     

Plasma immunoglobulin concentrations in twins

A study has been made of the similarity of concentrations of IgG, IgA and IgM in twins. The results provide evidence for the genetic control of all three immunoglobulins in adolescence, but in adults genetic control was demonstrable only for IgG in males. The findings suggest that although genetic factors regulating all classes of immunoglobulin levels in adults cannot be excluded by this study, if such factors do exist their effects are relatively small or are confined to certain individuals. This conclusion suggests that immunoglobulin concentrations in healthy adults will not form useful indices of future susceptibility to genetically determined diseases of immunity.