Over one-half billion years of head conservation? Expression of an ems class gene in Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa)

We report the isolation of an empty spiracles class homeodomain-containing gene, Cn-ems, from the hydrozoan Hydractinia symbiolongicarpus, the first gene of this class characterized in a lower metazoan. Cn-ems was found to be expressed in the head of gastrozooids, specifically in endodermal epithelial cells of the taeniolae of the hypostome. Cn-ems is not expressed in gonozooids, which lack taeniolae. Experimental conversion of the posterior region of the planula larva into head structures up-regulates expression of the gene. These findings establish that the association of ems-class genes with head structures preceded the evolution of bilateral symmetry.     

Reactive arthritis in patients attending an urban sexually transmitted diseases clinic

OBJECTIVE: To assess the prevalence, clinical manifestations, associated genital infections, and HLA associations of reactive arthritis (ReA) among patients attending an urban sexually transmitted diseases (STD) clinic. METHODS: Using a standardized questionnaire, 271 consecutive adults, primarily black, with possible or proven Chlamydia trachomatis genital infection were screened for symptoms of ReA. A followup questionnaire was administered 6 weeks later by mail. Patients who reported at least 1 symptom were evaluated by a rheumatologist. HLA-B typing was performed on patients with objective ReA features. RESULTS: Nine of 217 patients (4.1%) with genital infection/inflammation had objective ReA features. Chlamydial or nongonococcal STD syndromes were diagnosed in 8 of these 9 patients (88%). Genital infection/inflammation was asymptomatic in 78% of patients with ReA features. HLA-B27 or other B7-cross-reactive group antigens were not associated with the occurrence of ReA. CONCLUSION: Nongonococcal genital infections, often asymptomatic, can trigger a relatively mild ReA in a larger number of exposed patients than previously thought, irrespective of the individual's HLA status.     

Heterogeneous Nucleation of the Martensite Transformation

Experiments on powders of an Fe-Ni alloy have shown that the martensite trans-formation appears to start on heterogeneous nucleation sites. The nature of these sites is hypothesized and a mechanism for burst phenomenon in Fe-Ni alloys is set forth qualitatively on the basis of these heterogeneous nucleation sites.     

The release of unstable fission products during variable reactor operating histories

A solution to the diffusion equation describing the release of unstable fission products during irradiation has been obtained which may be employed for consecutive periods at different temperatures and ratings. The equations have been used to evaluate the release of species of different half-lives for three idealized irradiation histories which retain the same time-averaged irradiation conditions. The results illustrate the wide spectrum of release characteristics displayed by short-, medium- and long-lived species for these cases. It is concluded that the employment of the present analysis is essential for an accurate assessment of radiological hazard.     

Single-case designs in the modification of smoking

Hepatic echo-angiostructure: echo-anatomical study of the intraparenchymatous canal With a suitable technique (real time, grey scale) hepatic ultrasonography is able to display intraglandular ductal elements: portal veinous network, supra-hepatic veinous network, and, if enlarged intrahepatic biliary tree. A careful echoanatomic study is necessary to identify the enlarged biliary network in case of obstructive jaundice; such a study is also necessary not to confuse normal ductal structures, insufficiently displayed, with pathological reflections - a rather frequent hazard with conventionnal techniques.     

An evaluation of the effects of antimony and tin stabilizer on the fusion characteristics of PVC dryblends

Although the classification of lubricants can be misleading, the classification of their actions is not only possible but very useful. By considering the basic actions which affect PVC dryblend fusion, a better understading of the characteristics and advantages of additives can be realized. The antimony and tin stabilizers used in this study have been characterized by the affects on PVC dryblend fusion. Production extrusion results confirm the laboratory classifications.     

Fish immunology: the utility of immortalized lymphoid cells--a mini review

Long term cell lines can be readily established at high frequency with PBLs from normal channel catfish. Depending upon the mode of stimulation, morphologically and functionally distinct catfish lymphoid cell lines resembling B cells, T cells and monocytes have been developed. These fish cell lines appear unique from their putative mammalian counterparts in that they are immortalized without the need for exogenous factors or overt attempts at transformation.