Occupational asthma in newly employed workers in intensive swine confinement facilities.

Respiratory symptoms, reductions in pulmonary function and increased bronchial responsiveness have been described in exposed workers and in naïve volunteers exposed to intensive swine production facilities. Typically, this occurs in persons who have been employed for a long duration or in previously unexposed, naïve volunteers. The current authors describe four cases, all female, who developed acute onset of wheezing and cough suggestive of asthma within weeks of commencing full-time employment in intensive swine production facilities. None of the workers were aware of any previous asthma, allergies or hay fever. All four employees reported improvement of symptoms on cessation of work in the facilities and consequent withdrawal from exposure. However, when seen at the respiratory clinic, cases 1 and 3 continued to be either mildly symptomatic or were taking medications with continued borderline airways responsiveness, as measured by methacholine challenge test up to 4 and 5 months, respectively, following work cessation. Case 2 continued to have symptoms for > or =3 months after work cessation. Only case 1, however, was seen at repeated visits in the respiratory clinic. One worker participated in a work re-entry trial and experienced profound coughing and chest tightness within an hour of entry, after which, the trial had to be terminated. Provocative concentration causing a 20% fall in forced expiratory volume in one second (PC20) measured 5 h later was lower than pre-trial PC20. No acute exposure event was recorded in the workers prior to the onset of symptoms. To the current authors' knowledge, this is the first report of occupational asthma occurring in newly employed full-time intensive swine production workers after a short-term exposure and should raise awareness that previously unexposed workers may be at risk of developing what would appear to be long-term asthma after relatively short-term exposure.

Pharmacological characterization of a serotonin receptor involved in an early embryonic behavior of Helisoma trivolvis.

In contrast to the abundance of information on the many physiological and developmental actions of serotonin in molluscan nervous systems, comparatively little is known about the serotonin receptors involved in these responses. Embryos of the pulmonate gastropod, Helisoma trivolvis, display a cilia-driven rotational behavior that is regulated by endogenous serotonin. In the present study, two functional assays were used to determine some of the pharmacological properties of the receptors that mediate the cilio-excitatory action of serotonin. Time-lapse video microscopy was used to measure whole embryo rotation rate and cilia beat frequency in isolated cells. In dose-response experiments, serotonin was approximately 10 times more potent in stimulating cilia beat frequency over embryo rotation. In rotation experiments, 5-carboxyamidotryptamine and methysergide had effective agonist activity in dose ranges similar to that of serotonin (1 to 100 microM). In contrast, 8-hydroxydipropylaminotetralin HBr (8-OH-DPAT) displayed agonist activity of lower potency and effectiveness. Several compounds displayed antagonist activity in the 1 to 100 microM dose range, including mianserin, spiperone, ritanserin, 1-(1-naphthyl)piperazine, and propranolol. alpha-Methylserotonin had mixed agonist-antagonist activity, and metoclopramide, MDL-72222, and ketanserin were inactive. Experiments on isolated cells suggested that the extremely effective antagonism displayed by mianserin in the embryo rotation assay was due to its specific activity at ciliary serotonin receptors. These results implicate the presence of a novel serotonin receptor on embryonic ciliated cells that is pharmacologically distinct from those previously characterized in vertebrate or invertebrate systems.

Cloning and sequence analysis of the Chlamydia trachomatis spc ribosomal protein gene cluster.

We identified and sequenced a segment of Chlamydia trachomatis chromosomal DNA that shows homology to the Escherichia coli spc and distal region of the S10 ribosomal protein (r-protein) operons. Its sequence revealed a high degree of nucleotide and operon context conservation with the E. coli r-protein genes. The C. trachomatis spec operon contains the r-protein genes for L14, L24, L5, S8, L6, L18, S5, L15, and Sec Y along with the genes for r-proteins L16, L29, and S17 of the S10 operon. The two operons are separated by a 16-bp intragenic region which contains no transcription signals. However, a putative promoter for the transcription of the spc operon was found 162 nucleotides upstream of the CtrL14e start site; it revealed significant homology to the E. coli consensus promoter sequences. Interestingly, our results indicate the absence of any structure resembling an EcoS8 regulatory target site on C. trachomatis spc mRNA in spite of significant amino acid identity between E. coli and C. trachomatis r-proteins. Also, the intrinsic aminoglycoside resistance in C. trachomatis is unlikely to be mediated by CtrL6e since E. coli expressing CtrL6e remained susceptible to gentamicin (MIC less than 0.5 micrograms/ml).

Characterization and development of rotational behavior in Helisoma embryos: role of endogenous serotonin.

Cilia-driven rotational behavior displayed by embryos of the pond snail Helisoma trivolvis was characterized in terms of its behavioral subcomponents, developmental changes, and response to exogenous serotonin. Rotation was found to be a complex behavior characterized by four parameters; rotational direction, rotation rate, rotational surges, and periods of inactivity. These parameters all exhibited characteristic developmental changes from embryonic stage E15 through stage E30. Notably, both rotation rate and frequency of rotational surges increased from stage E15 to E25 and declined to an intermediate level by stage E30. It appeared that the developmental increase in overall rotation rate was caused primarily by an increase in surge frequency, rather than an increase in the rate of nonsurge rotation. Immersion of embryos inserotonin-containing pond water resulted in a dose-dependent, reversible increase in rotation rate as well as a dose-dependent, reversible decrease in surge frequency. The serotonin antagonist, mianserin, abolished the excitatory effect of exogenous serotonin. Furthermore, application of mianserin alone reduced rotation rate and virtually abolished rotational surges. Taken together, these pharmacological results suggest that endogenous serotonin is responsible for generating rotational surges. Given that early embryos contain only a single pair of serotonergic neurons (Goldberg and Kater, 1989) during the stages when rotational surges are expressed, these results also prompt the hypothesis that these neurons, embryonic neurons C1, act as cilioexcitatory motor neurons during embryonic development.