A Pseudomonas sp. grew with nicotine optimally 3 g l(-1) and at 30 degrees C and pH 7. Nicotine was fully degraded within 10 h. The resting cells degraded nicotine in tobacco solid waste completely within 6 h in 0.02 m sodium phosphate buffer (pH 7) at maximally 56 mg nicotine h(-1) g dry cell(-1).

Swimmer's itch (cercarial dermatitis) affects people engaged in open-water activities. We report incidence and risk factors for a US lake. Water exposures and swimmer's itch experience were reported daily for riparian household residents and guests at Douglas Lake, Michigan, in July 2000. Incidence of swimmer's itch was 6.8 episodes per 100 water exposure days. Positive risks were (1) exposures in shallow water and in areas with onshore winds and (2) more days of lake use in July. Further epidemiological studies will help public health agencies address this bothersome problem at recreational lakes.

Stagnicola emarginata were collected from 3 northern Michigan lakes and examined for larval trematode infections. The structure of the trematode community was then compared with 2 previous studies conducted on Douglas Lake in order to determine what changes had taken place over a period of more than 50 yr and to examine the possibility of using trematodes as bioindicators of environmental quality. Species richness was reduced by half (from 16 to 8 species) from the first study conducted in 1936, along with a decrease in the overall prevalence from 61% to 13%. No new species had colonized the lake, and the same 8 trematodes were also the only species found in 2 other lakes. The decline in prevalence was most severe in trematodes that used gulls as definitive hosts, whereas species that used ducks as hosts increased slightly. The decrease in species richness and prevalence of infection over time may reflect increasing human impacts on lakes. However, because of patchy host distributions, the use of larval trematodes as bioindicators of environmental change requires further investigation.

This epidemiologic study reports incidence, severity, and risk factors of swimmer's itch (cercarial dermatitis). Daily diaries about water exposures and swimmer's itch symptoms were completed by 40 riparian households at Douglas Lake, Michigan, for July 2000. Minutes spent in the water, minutes in shallow water, location, time of day, preventive action, age, and gender were recorded for all residents and guests. Incidence of swimmer's itch was 6.8 episodes per 100 water-exposure days. Probability of an episode increased with more days of water use and at locations with onshore winds. Episode severity increased with more time in the water and at the same locations. Age and gender had no effect on incidence or severity. In sum, onset and severity of swimmer's itch are affected by how people interact with the lake, not by their demographic features. More studies of human incidence and severity are needed to convince public health agencies to address this problem at recreational lakes. Study designs that combine epidemiologic and biological data will simultaneously inform public health education and biological control programs.

Trematode infections have long been associated with specific types of cancer. We investigated the ability of the liver fluke Fasciola hepatica to alter host enzymes in a manner that might provide insight into the phenomenon of biologically associated cancers. Our data demonstrate an increased activity of the CYP2A5 isozyme in male mouse liver infected with F.hepatica. Induction of this enzyme was further assessed immunohistochemically. The infection affected CYP2A5 distribution in hepatic tissue. Inflammation and proliferation in liver tissue were observed at the same time that CYP2A5 activity increased. This enzyme is known to participate in the metabolism of several carcinogens which are common contaminants in environments of developing countries where parasitic infections may be prevalent.

No abstract

The epidermis of D. tigrina was examined using the scanning electron microscope. Both dorsal and ventral surfaces are extremely irregular in contour, as well as being permeated by large numbers of pores. Cilia are restricted to the ventral surface, the auricles and that part of the dorsum adjacent to the auricles. Club-shaped receptors, as well as cilia, were seen in the auricles. The epidermis anteriad to the eyespots is indistinguishable from that covering the remainder of the dorsal surface. Light rays could not enter the eyespot through this rough epidermal surface without becoming diffracted in an irregular fashion. It was therefore concluded that visual image perception is not a function of the planarian eyespot.

A detailed study of the surface topography of the echinostomes Echinostoma revolution and Isthmiophora melis has been carried out using SEM. The tegument of the body surface has a cobblestone-like appearance with interspersed pits. The presence of possible secretory granules is noted. Observations of the anterior end reveal that the collar spines are retractable. An unusual structure is described from the ventral gap of the spiny collar of E. revolutum. The origins of this structure and the possible functions of the spiny collar are discussed. The shape and distribution of body spines is described. Differences in cirrus morphology for the two species are described. The taxonomic position of, I. melis and the significance of cirrus morphology as a useful taxonomic character are discussed. Four types of presumed sensory or secretory structures occur—ciliated, domed, button and bilobed papillae. Their distribution is described and possible functions discussed.