Distribution and ecology of lampreys Lethenteron spp. in interior Alaskan rivers.

This study describes phenetic characteristics and examines the life history of anadromous Arctic lamprey Lethenteron camtschaticum and freshwater-resident Alaskan brook lamprey Lethenteron alaskense in two tributaries of the middle Yukon River, Alaska. Larval lampreys could not be identified to species using pigmentation density patterns or trunk myomere counts, but adults could be identified to species based on colouration, body size and oral-disc dentition. Although larvae were patchily distributed in both rivers, there was a greater proportion of sample locations where Lethenteron spp. were absent in upper reaches than in middle and lower reaches. Relative abundance, density and median and maximum total length (LT ) of larvae were highly variable among sampling locations. Current velocity, substratum type and coarse woody debris were most strongly correlated with larval Lethenteron spp. density; velocity and substratum size was negatively correlated, whereas woody debris was positively correlated. Water depth, dissolved oxygen levels and specific conductance did not influence habitat selection. Length-frequency distributions, diet composition (organic detritus ≥ 98%), assimilation efficiency (>70%) and gut fullness (<0·2 mg diet ash-free dry mass) were similar for larvae, regardless of river or sampling location. These results increase understanding of Lethenteron spp. biology and ecology in interior Alaska drainages and add to the existing literature on Lethenteron spp. life history.

Single-blind, randomised, parallel group study of the Bard Biocath catheter and a silicone elastomer coated catheter.

A group of 69 community patients undergoing long-term urethral catheterisation for urinary incontinence took part in this study; 33 patients with a mean age of 70.03 years (+/- 16.6) received the Dow Corning Silastic catheter (16 F 10-ml balloon) and 36 patients with a mean age of 75.61 years (+/- 12.6) received the Bard Biocath catheter (16 F 10-ml balloon). Over a 16-week period catheters were monitored every 2 weeks and changed as necessary. The Bard Biocath catheter remained in situ for an average of 89.61 days (+/- 35.31) and the Silastic catheter remained in situ for an average of 56.7 days (+/- 38.8); this difference was statistically significant. Used catheters were analysed for encrustation using scanning electron microscopy (SEM). The average time in situ for non-encrusted Biocath catheters was 83.7 days and 25.28 days for non-encrusted Silastic catheters. It was found that 70% of patients who received Biocath catheters preferred them to their previous catheters whereas only 30% of patients in the Silastic group preferred the trial catheter. The incidence of bypassing was 28% in the Biocath group and 52.8% in the Silastic group.

Infection of catheterised patients: bacterial colonisation of encrusted Foley catheters shown by scanning electron microscopy.

The surfaces of 32 encrusted urinary catheters were examined by scanning electron microscopy to investigate the association of bacteria with the encrusting deposits. Deposits consisted of struvite crystals surrounded by aggregates of very small crystallites of hydroxyapatite. Underneath these minerals there was a layer of closely packed bacteria. Impressions of bacteria were also observed in hydroxyapatite. Crystals were often engulfed by the bacterial layer, which thus appeared to bind the crystals to each other and to the catheter surface. This thick layer of bacteria associated with crystals may protect both the bacteria from antibiotics and the crystals from acidic bladder washout solutions intended to dissolve them. Furthermore, the existence of this sessile population explains why urease-producing bacteria are not invariably detected in the urine of patients with encrusted catheters. The observation of this bacterial layer (or "biofilm") by scanning electron microscopy provided direct evidence for infection being implicated in catheter encrustation.

Resistance of conformable indwelling urinary catheters to encrustation.

Conformable and conventional indwelling urinary catheters, made of latex coated with Teflon and of the same nominal size, were encrusted in vitro. The extent of encrustation was quantified by dissolving the deposits, determining the concentrations of calcium and magnesium in the resulting solutions (by atomic adsorption spectroscopy), and calculating the surface densities of calcium and magnesium. Surface densities of both elements were significantly less on the conformable than on the conventional catheters. This result can be explained by the pulsed flow of urine through the conformable catheter tending to dislodge deposits adhering to its inner surface. A similar action is expected to occur in vivo.

Resistance of catheters coated with a modified hydrogel to encrustation during an in vitro test.

Mid-shaft specimens were cut from latex catheters coated with a modified hydrogel, latex catheters coated with silicone elastomer, and 100% silicone catheters. These specimens were subjected to controlled in vitro encrustation conditions. During a test period of 11 weeks, there was no significant difference in the quantities of encrusting deposits formed on the three materials.

Comparison of in vitro encrustation on silicone and hydrogel-coated latex catheters.

Mid-shaft sections of 100% silicone (Bardex) and hydrogel-coated latex (Biocath) catheters were subjected to controlled in vitro encrustation conditions for periods of up to 18 weeks. There was no significant difference in the quantities of encrusting deposits formed on these two materials during the course of the experiment.

Calcium phosphate in catheter encrustation.

Encrusted catheters from nine female patients were the source of samples of deposits which were examined by X-ray diffraction, atomic absorption spectroscopy, infra-red spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. In eight samples the only crystalline phase which could be clearly distinguished by X-ray diffraction was ammonium magnesium orthophosphate hexahydrate, NH4MgPO4 X 6H2O, which occurs naturally as the mineral struvite. However, atomic absorption spectroscopy revealed an appreciable concentration of calcium in all samples. Calcium phosphates have previously been detected in catheter deposits. Infra-red and EXAFS spectra were consistent with the calcium phosphate being present as a poorly crystalline hydroxyapatite. Thus the deposits appear to consist of a mixture of crystalline struvite and a form of hydroxyapatite which is not fully crystalline.

Serum levels of creatine phosphokinase and its isoenzymes in normal and stressed neonates.

Twenty-six normal newborns (13 male, 13 female) with normal prenatal histories, no perinatal stress, and normal vaginal deliveries had creatine phosphokinase (CPK) activity and isoenzyme activities assayed in cord blood and in 24-hour postpartum serum. Total CPK activity was high in cord blood when compared with adult control values. Moreover, the total CPK was significantly higher in serum at 24 hours of age compared with cord blood. There was a significant increase in both the skeletal muscle isoenzyme and the cardiac muscle isoenzyme from birth to 24 hours of age. There was a decrease in the brain isoenzyme at 24 hours of age which was not statistically significant. These results were compared with values obtained in a group of 10 neonates with severe cardiac problems. Three of the ill neonates had significant elevation of total serum CPK and the skeletal muscle isoenzyme when compared with the normal newborns. There were no significant differences between the normal infants and the ill neonates for the cardiac isoenzyme and the brain isoenzyme. These data suggest that caution should be used in the diagnosis of certain neonatal cardiac syndromes based on serum CPK levels and isoenzyme alone.