An approach for the identification of exemplar sites for scaling up targeted field observations of benthic biogeochemistry in heterogeneous environments.

Continental shelf sediments are globally important for biogeochemical activity. Quantification of shelf-scale stocks and fluxes of carbon and nutrients requires the extrapolation of observations made at limited points in space and time. The procedure for selecting exemplar sites to form the basis of this up-scaling is discussed in relation to a UK-funded research programme investigating biogeochemistry in shelf seas. A three-step selection process is proposed in which (1) a target area representative of UK shelf sediment heterogeneity is selected, (2) the target area is assessed for spatial heterogeneity in sediment and habitat type, bed and water column structure and hydrodynamic forcing, and (3) study sites are selected within this target area encompassing the range of spatial heterogeneity required to address key scientific questions regarding shelf scale biogeochemistry, and minimise confounding variables. This led to the selection of four sites within the Celtic Sea that are significantly different in terms of their sediment, bed structure, and macrofaunal, meiofaunal and microbial community structures and diversity, but have minimal variations in water depth, tidal and wave magnitudes and directions, temperature and salinity. They form the basis of a research cruise programme of observation, sampling and experimentation encompassing the spring bloom cycle. Typical variation in key biogeochemical, sediment, biological and hydrodynamic parameters over a pre to post bloom period are presented, with a discussion of anthropogenic influences in the region. This methodology ensures the best likelihood of site-specific work being useful for up-scaling activities, increasing our understanding of benthic biogeochemistry at the UK-shelf scale.

High resolution study of the spatial distributions of abyssal fishes by autonomous underwater vehicle.

On abyssal plains, demersal fish are believed to play an important role in transferring energy across the seafloor and between the pelagic and benthic realms. However, little is known about their spatial distributions, making it difficult to quantify their ecological significance. To address this, we employed an autonomous underwater vehicle to conduct an exceptionally large photographic survey of fish distributions on the Porcupine Abyssal Plain (NE Atlantic, 4850 m water depth) encompassing two spatial scales (1-10 km(2)) on and adjacent to a small abyssal hill (240 m elevation). The spatial distributions of the total fish fauna and that of the two dominant morphotypes (Coryphaenoides sp. 1 and C. profundicolus) appeared to be random, a result contrary to common expectation but consistent with previous predictions for these fishes. We estimated total fish density on the abyssal plain to be 723 individuals km(-2) (95% CI: 601-844). This estimate is higher, and likely more precise, than prior estimates from trawl catch and baited camera techniques (152 and 188 individuals km(-2) respectively). We detected no significant difference in fish density between abyssal hill and plain, nor did we detect any evidence for the existence of fish aggregations at any spatial scale assessed.

Cerebral emboli during cardiac surgery in children.

BACKGROUND: Microemboli occur commonly during cardiac surgery in adults, and, when present, increase the risk of neuropsychological deficits. Their incidence and significance during correction of congenital heart disease is unknown. The authors hypothesized that microemboli would occur before bypass with right-to-left cardiac shunts and would also occur in large numbers when the aortic crossclamp was released in children during repair of congenital heart defects. METHODS: In 25 children studied with carotid artery Doppler, embolic signals were counted and timed in relation to 13 intraoperative events. Patients were classified as either at high risk (obligate right-to-left shunt or uncorrected transposition of the great arteries) or at low risk (net left-to-right shunt or simple obstructive lesions) for paradoxical (venous to arterial) emboli. RESULTS: The median number of emboli detected was 122 (range, 2-2,664). Forty-two percent of all emboli were detected within 3 min of release of the aortic crossclamp. The high-risk group had significantly more emboli (median, 66; range, 0-116) during the time interval before cardiopulmonary bypass than did the low-risk group (median, 8; range, 0-73), with P < 0.01. There was no significant difference between the high- and low-risk groups in the total number of emboli detected. There was no apparent association between number of emboli and gross neurologic deficits. CONCLUSIONS: Microemboli can be detected in the carotid arteries of children undergoing repair of congenital heart disease and are especially prevalent immediately after release of the aortic crossclamp. The role of emboli in causing neurologic injury in children undergoing repair of congenital heart disease remains to be determined.

Comparison of biopersistence of experimental glass fibres in the lung and peritoneal cavity.

Thirty three female Fischer-344 rats were intra-peritoneally (IP) injected with 5 mg of an experimental glass fibre designated X7753. This fibre type had an in vitro dissolution rate of 600 ng cm-2h-1. Groups of three rats were killed at various times up to one year after injection. The diaphragm and any fibre nodules were removed from the carcass and separately digested using hypochlorite solution, to recover the fibres. The number and morphometry of the fibres was measured using phase contrast optical microscopy (PCOM) and semi-automatic image analysis. The data obtained were compared to the previous studies of the durability of the X7753 fibres in the lung.

The durability and distribution of glass fibres in the rat following intra-peritoneal injection.

Intra-peritoneal (IP) injection is being recommended as a means of assessing potential carcinogenicity of MMF following inhalation. Little is known of the behaviour of fibres in the peritoneal cavity or its relevance to the lung. This study considered both the biopersistence and the distribution of dose following IP injection of fibres. Biopersistence of fibres in the peritoneal cavity has been compared with that observed previously in the lung. Marked differences were found, with long fibres (> 20 microns) being more durable in the peritoneal cavity than in the lung. Breakage could not account for this finding, whereas differences in dissolution could. The behaviour of fibres and powders and their distribution in the peritoneal cavity following injection of different masses is reported. Distribution of dose depended on injection mass, with masses of < 1.5 mg showing even uptake onto the surfaces of the peritoneal organs, and higher masses resulting in the development of nodules of injection material, free in the peritoneal cavity, or loosely bound to the peritoneum. With fine powder, some clearance was observed over the first 48 h after IP injection, but not with fibres. The findings on both durability and distribution of dose following IP injection have implications on the justification for the use of IP injections in assessment of potential carcinogenicity of fibres following inhalation.

Preliminary data from investigations of the in vivo biopersistence of three experimental glass fibres of varying chemical composition.

The durability of three experimental glass fibres (X7753, X7484, and X7779) was investigated in vivo. These fibres had in vitro dissolution rates of 600, 150, and 2 ng cm-2 hour-1, respectively. Three groups of female Fischer-344 rats were intratracheally instilled with a 1.2 mg suspension of one of each of the fibre types. All fibres had previously been neutron activated, to produce radioactive 24Na within the glass, which served as a radiotracer. At 2 days post instillation (PI) about 1 x 10(6) glass fibres were within the pulmonary region of the lung. Animals were killed at various time points from 2 to 360 days PI. Fibres were recovered from the animal lungs by hypochlorite digestion. The retention and morphometry of these fibres was investigated, and preliminary results are presented. After 360 days in the lung, the number of X7753 and X7484 fibres fell respectively to 10% and 50% of those present at 2 days PI. There was no detectable reduction in the number of X7779 fibres in the lung over this period. Morphometric analyses demonstrated a 53% and 22% reduction in the mean length of the X7753 and X7484 fibres, after 360 days in the lung. Reduction in diameter was apparent after only 28 days for the these fibre types. No change in the mean size of the X7779 fibres was observed during the study. The fibre morphometry data suggested that short fibres dissolved at a slower rate than long fibres. In general the in vivo fibre retention and morphometry data reflected the measured in vitro dissolution rate.

The behavior of glass fibers in the rat following intraperitoneal injection.

Potential carcinogenicity of fibers is believed to be determined by three factors: the dose, dimensions and durability of the fibers concerned. Currently there is considerable debate on the appropriateness of using results from intraperitoneal (i.p.) injection studies to predict the potential carcinogenicity of airborne fibers following inhalation. For ip results to have any significance to potential inhalation hazards, there should be some relation between the biopersistence, dose, and dose distribution of fibers in the serosal cavity and in the lung. Preliminary results on the durability of one experimental glass fiber in the peritoneal cavity suggest differences in dissolution when compared with durability in the lung. In the lung, the diameters of the long fibers (> 20 microns) were observed to decline at a rate consistent with their exposure to a neutral pH environment. The diameter of shorter fibers declined much more slowly, consistent with exposure to a more acidic environment such as is found in the phagolysosomes of alveolar macrophages. In the peritoneal cavity all fibers, regardless of length, dissolved at the same rate as short fibers in the lung. The effect of dose on the distribution of fibers in the peritoneal cavity was investigated using similar experimental glass fibers and compared with that of a powder made from ground fibers. For both materials at doses up to 1.5 mg, material was taken up by the peritoneal organs roughly in proportion to their surface area. This uptake was complete 1-2 days after injection. At higher doses, the majority of the material in excess of this 1.5 mg formed clumps of fibers (nodules) which were either free in the peritoneal cavity or loosely bound to peritoneal organs. These nodules displayed classic foreign body reactions with an associated granulomatous inflammatory response. The findings on both durability in the peritoneal cavity and the presence of two distinct populations of material following i.p. injection have implications for the justification of the use of i.p. injections to assess potential carcinogenicity of fibers following inhalation.

A radioactive tracer technique to determine in vivo the number of fibers in the lungs of rats following their administration by intratracheal instillation.

A radioactive tracer technique is described which enables the total number of fibers present in the lungs of rats to be estimated following administration of the fibers by intratracheal instillation. The glass fiber used in the study was irradiated with thermal neutrons to induce radioactive 24Na. A suspension of the radioactive fiber was administered to eight rats by intratracheal instillation and to two additional rats by intraesophageal instillation. The 24Na radioactivity in the rats was counted in vivo at 24 and 48 hr after administration, after which they were killed. The amounts of fiber in the lungs, in the gastrointestinal tracts, and excreted in feces were estimated radiometrically. On average 93% of the administered fiber was accounted for. The lungs were digested with sodium hypochlorite solution and aliquots of the resulting digest filtered through membrane filters which were clear for examination by phase-contrast optical microscopy (PCOM). The numbers of fibers in the lungs, estimated by PCOM, were well correlated with the in vivo counting rates at 48 hr, indicating that the latter can be used to provide an accurate index of the number of fibers retained in the lung at that time.

Conventional screening for enteropathogenic Escherichia coli in the UK. Is it appropriate or necessary?

Enteropathogenic Escherichia coli (EPEC) is a well-recognized cause of infantile diarrhoea in the developing countries. In the developed countries, however, the incidence of EPEC associated outbreaks has dramatically declined. The last major outbreak in the UK was reported in 1980. This paper reviews the recent advances in the field of pathogenesis of diarrhoea caused by EPEC and questions the need to screen routinely for EPEC by conventional serological methods used in clinical microbiology laboratories in the UK.

Dosimetric implications of pulmonary macrophage clusters observed within lungs of rats that have inhaled enriched UO2 particles.

Twenty-four Fischer 344 rats were exposed to enriched uranium dioxide (UO2) aerosols to give a mean initial lung burden of 291 +/- 89 (SD) micrograms. Groups of rats were killed at 1, 7, 180, 360, 540, and 720 days post-inhalation (PI). Their lungs were fixed and inflated. Sections cut from all five lung lobes were used to prepare CR-39 neutron-induced 235U fission fragment autoradiographs. A single traverse across a CR-39 autoradiograph of a tissue section, from the left lung of all the rats, was made using a motorized microscopic stage. The traverse was divided into 10 fields. The track counts per field were used to test for homogeneity of track distribution and to assess if there was any tendency for tracks to be related to the peripheral region of the lung. Full raster scans across the entire tissue image were made on left lung autoradiographs from two animals killed at each time point to assess the homogeneity of fission fragment track distribution throughout the entire section. There was no evidence of any temporal change in the proportion of tracks associated with the lung periphery. At all time points PI, the track distribution was significantly nonhomogeneous, suggesting a nonuniform pattern of tissue irradiation from the 234U alpha particles. At time points from 180 to 720 days PI, large clusters of macrophages were observed in some of the sections taken from all five lung lobes. The total number of macrophage clusters increased with time PI. These macrophage clusters produced many 235U fission fragment tracks within the CR-39 autoradiographs.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term clearance of inhaled UO2 particles from the pulmonary region of the rat.

This paper reports on an enriched uranium dioxide (UO2) mass clearance study undertaken with Fischer-344 rats. The UO2 had a uranium (U) isotopic composition of 0.79% 234U, 92.8% 235U, 0.34% 236U and 6.06% 238U, by mass, with an alpha-particle activity of 1.91 Bq micrograms-1. Forty-six rats were exposed to an enriched UO2 aerosol that had an activity median particle aerodynamic diameter ranging from 2.7 to 3.2 microns. The rats were killed from 1 to 720 d post-inhalation (PI). The mass of enriched UO2 present in the trachea, lung lobes, thoracic lymph nodes, kidneys, liver, spleen, gut, and the remainder of the carcass was assessed at death. At 720 d after exposure, 82% of the total body burden of enriched UO2 was in the lung, with a further 10% in the thoracic lymph nodes. This represented 17% and 2% of the original (5 d PI) lung burden. The mass clearance of enriched UO2 from the lung was fitted to a single exponential function, normalized to 100% at 5 d PI. The rate constant (k) was 2.8 X 10(-3) d-1, giving a clearance half-time of 247 d. Although statistical comparisons with the majority of published data were not possible, it appeared that both enriched UO2 and natural UO2 particles cleared at rates that were broadly similar, with a t1/2 in the rat lung of 150 to 300 d over the 5- to 720-d PI period. As a consequence of the 234U component in the inhaled UO2 particles, the rats killed at 720 d PI received a total mean accumulated alpha-particle dose averaged over the whole lung of 5.7 Gy. Histologic investigations of the rat lungs found that widespread lung disease was only observed in animals killed at 720 d PI.

Studies of alveolar cell morphometry and mass clearance in the rat lung following inhalation of an enriched uranium dioxide aerosol.

Seventy-three rats were exposed to an aerosol of enriched uranium dioxide (UO2), giving initial lung burdens of 26 to 447 micrograms at 6 days post-inhalation (PI). At 7 days PI 35 of these rats were further exposed to thermalised neutrons at a fluence of 1 x 10(12) neutrons cm-2. There was no significant difference between the two groups in the clearance rate of the UO2 particles from the lung, up to 590 days PI. The particles cleared relatively slowly over this period with a retention half-time in the lung of 160 to 176 days. Transmission electron microscope (TEM) studies of tissue from the alveolar region at 8 days PI showed that inhalation of UO2 particles significantly increased the sizes of macrophage and type II cells, and the number of macrophage and type I cells. There was also a significant increase in the size of lysosomal granules within the macrophages after exposure to the UO2 particles. The exposure to UO2, neutrons and 235U fission fragments had no significant effect on any of the cells above that observed in the animals exposed to UO2 alone. Additional rats were exposed to the same neutron fluence without prior UO2 inhalation. The alveolar cells of neutron-only exposed rats were, in size and number, typically no different from those in the completely unexposed control rats.

Critical analysis of radiologist-patient interaction.

A critical incident interview technique was used to identify features of radiologist-patient interactions considered effective and ineffective by patients. During structured interviews with 35 radiology patients and five patients' parents, three general categories of physician behavior were described: attention to patient comfort, explanation of procedure and results, and interpersonal sensitivity. The findings indicated that patients are sensitive to physicians' interpersonal styles and that they want physicians to explain procedures and results in an understandable manner and to monitor their well-being during procedures. The sample size of the study is small; thus further confirmation is needed. However, the implications for training residents and practicing radiologists in these behaviors are important in the current competitive medical milieu.

Prednisolone inhibits phagocytosis by polymorphonuclear leucocytes via steroid receptor mediated events.

Prednisolone, at concentrations between 2.78 x 10(-6) M (1 mug/ml) and 1.39 x 10(-8) M (5 x 10(-3) mug/ml) exerts an inhibitory effect on the phagocytosis of latex particles by normal human polymorphonuclear leucocytes in vitro as assessed by electron microscopical analysis. This inhibition appears to be receptor-mediated, as it is dependent upon RNA and protein synthesis and is glucocorticoid specific.