The mechanism of Ptychodiscus brevis toxin-induced rat vas deferens contraction

Ptychodiscus brevis, which causes Florida red tide, produces Ptychodiscus brevis toxin (PBTX) known to contain neurotoxins and to induce rhinorrhea, tearing, and cough in normal humans and wheezing in asthmatic subjects. It was previously reported (J Allergy Clin Immunol 69:418, 1982; 73:824, 1984) that PBTX causes canine tracheal smooth muscle contraction via stimulation of sodium channels in the axons of parasympathetic postganglionic nerves and the release of acetylcholine from these nerve endings. This was postulated to be an asthma-triggering mechanism. In this article the toxins were evaluated to determine if they also stimulate sodium channels on adrenergic nerve endings and release norepinephrine. Rat vas deferens was selected as the experimental tissue. Both PBTX and norepinephrine contracted rat vas deferens. Prazosin 10(-6) mol/L blocked the response to PBTX (3 micrograms/ml) (88.3% to 27.3% contraction [n = 6; p less than 0.001]) and the response to norepinephrine (EC50 was shifted from 1.67 X 10(-6) mol/L to 1.25 X 10(-4) mol/L in the presence of prazosin 10(-6) mol/L [n = 6; p less than 0.001]). Phentolamine 10(-6) mol/L also blocked both PBTX and norepinephrine. Tetrodotoxin 10(-7) mol/L, a sodium channel blocker, completely blocked the response to PBTX but not to norepinephrine. The response to PBTX was significantly reduced from 1.53 gm of tension in controls to 0.29 gm of tension (n = 6; p = 0.002) in tissues obtained from rats pretreated with reserpine (2 mg/kg per day for 2 days, injected intraperitoneally). Verapamil 10(-5) mol/L blocked the PBTX response, and PBTX caused no contraction in calcium-free media.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genotoxic changes after low-level solvent and fuel exposure on aircraft maintenance personnel

Individuals may be exposed to solvensudhirt mixtures and fueleither at work or home, through air, water and food contamination.Few studies have addressed the genotoxic effects of mixed, low-levelexposure to fuel and solvent. This was an optimally designedstudy where each subject was sampled prior to exposure and after15 and 30 weeks while exposed, in a repeated measures designwith each subject serving as his own control. Fifty men agedbetween 18 and 50, working on aircraft equipment operation andmaintenance at a military installation were included. Eightunexposed men were concurrently sampled. Sisterchromatid exchanges(SCE) and micronuclei (MN) frequency were measured in conjunctionwith air sampling and expired breath analysis for jet fuel (JP-4),1,1,1-trichloroethane, methyl ethyl ketone, xylenes, tolueneand methylene chloride. Exposure levels measured by industrialhygiene were very low (all means <6 p.p.m.), <10% of theOSHA standard. Expired breath levels were also low, <25 p.p.b.A small but statistically significant increase in the frequencyof SCE occurred after 30 weeks of exposure for sheet metal workers(P = 0.003) and for painters (P = 0.05). The MN frequency inthe sheet metal workers initially showed a statistically significantincrease, but by 30 weeks had decreased. Cigarette smoking,alcohol and caffeine use were not associated with changes frombaseline for either MN or SCE. Smokers, however, had significantlyhigher values of SCEs at baseline than did nonsmokers. In summary,these findings suggest that small increases in SCEs in particular,may serve as a sensitive biologic indicator of low level hydrocarbonexposure in as much as statistically significant changes occurredin the highest exposed groups but not in the low or no exposuregroups. Chance occurrence or exposures to other occupationalor non-occupational agents cannot be eliminated as a cause ofthe study findings. ¹To whom correspondence should be addressed     

Allergens of the imported fire ant

A whole body extact (WBE) was prepared by saline extraction of ground imported fire ants (IFA). A serum pool from rabbits immunized with the WBE elicited 31 precipitates on crossed immunoelectrophoresis. Crossed radioimmunoelectrophoresis was performed with sera from 26 RAST IFA-positive subjects, 24 of whom were known for clinical hypersensitivity to IFA and two subjects, known to be hypersensitive to yellow jacket. Radiostaining was obtained to 14 precipitates, some of which were judged to be partially identical. Thus, six apparently different allergen groups could be identified. Two of these fulfilled arbitrary criteria of major allergens. Three of the IFA WBE allergens were easily identified in crossed immunoelectrophoresis of a commercially obtained IFA-venom preparation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the IFA WBE demonstrated protein bands with molecular weight ranging from 10,000 to 200,000 daltons. An immunoblotting technique with nitrocellulose paper strips revealed binding of human IgE from hypersensitive subjects to four different bands (either single bands or clusters of proteins of similar molecular weight) with molecular weights ranging from 13,000 to 42,000 daltons. It is a notable finding that these insect allergens thus were of a similar size as important aeroallergens.     

Fiber contamination of vermiculites: a potential occupational and environmental health hazard

Vermiculite ores from Montana, Virginia, and South Africa have been analyzed for the presence of amphibole contamination. Fibrous actinolite was found in unexpanded Montana vermiculite ore at a maximum concentration of 2.0%. The fibers persisted in the expanded ore at a maximum concentration of 0.6%. Actinolite was also found in the Virginia vermiculite ore but at a lower concentration and mostly as cleavage fragments with low length-to-width ratios. South African ore contained rare anthophyllite fibers also with low length-to-width ratios. Vermiculite ores have the potential for amphibole contamination and can represent potential health hazards without proper occupational and environmental control measures.     

Model of Epstein-Barr virus infection of human thymocytes: expression of viral genome and impact on cellular receptor expression in the T- lymphoblastic cell line, HPB-ALL

Infection of B lymphocytes and epithelial tissue by Epstein-Barr virus (EBV) is associated with malignancy and autoimmunity. The cellular receptor for EBV has been identified as CD21 (CR2). A molecule, which is biochemically and immunologically similar to B-cell CD21, has been identified on a subpopulation of immature thymocytes, suggesting a role for this molecule in the regulation of T-cell development and further suggesting that immature T cells might be susceptible to EBV infection. A growing body of literature now documents the presence of EBV in tumors of T-cell origin. We have evaluated the susceptibility of the human immature T cell line, HPB-ALL, to infection by EBV. Electron microscopy studies showed a rapid internalization of virus by HPB cells. Southern blotting showed the intracellular presence of linear EBV genomes, and components of the virus replicative cycle were identified. Expression of the BamHI Z region of the genome, encoding the nuclear protein, ZEBRA, which is strictly associated with productive infection in B cells, was detected in HPB-ALL cells. A spliced variant of Z, RAZ, was also identified. Cell surface expression of EBV late antigens was observed to occur transiently. Infection of HPB cells was also accompanied by altered expression of T-cell surface molecules involved in antigen recognition, a process critical to normal development of the T-cell repertoire. Delineation of the outcome of T- cell infection by EBV may lead to a better understanding of the role of this virus in autoimmune processes and malignancy.     

Environmental risk factors of rhinitis in early infancy

Previous studies of allergic rhinitis in children have not documented the environmental risk factors for infants at age one. We examined the relationship of environmental tobacco smoke (ETS) and visible mold exposures on the development of allergic rhinitis, rhinitis and upper respiratory infection (URI) in a birth cohort where at least one parent was skin prick test (SPT) positive. ETS exposure and upper respiratory symptoms were obtained by questionnaires. Visible mold was classified as none, low or high during home visit. Infants had a SPT at age one. After adjustment for potential confounders, exposure to >20 cigarettes per day was associated with an increased risk of developing allergic rhinitis at age one [odds ratio (OR)=2.7; 95% CI 1.04-6.8] and rhinitis symptoms during the first year (OR=1.9; 95% CI 1.1-3.2). Infants with low (OR=1.5; 95% CI 1.1-2.3) or high (OR=5.1; 95% CI 2.2-12.1) levels of visible mold in their homes were more likely to have more frequent URI during the first year. Older siblings were protective for development of both rhinitis symptoms and allergic rhinitis. This study suggests that ETS exposure, rather than visible mold, is associated with rhinitis and allergic rhinitis in infants. The analysis also suggests that mold may be a stronger risk factor for URI that ETS.     

Fat necks: modification of a standard surgical airway protocol in the pre-hospital environmental

We report two cases of trauma where a surgical airway was required. In both cases soft tissue swelling of the neck made modification of the Advanced Trauma Life Support (ATLS) airway guidelines necessary. A gum elastic bougie was used to guide a standard endotracheal tube into a cricothyroidotomy incision and secure the airway. Slight departure from standard techniques may be required in difficult circumstances to achieve a definitive airway.