A longitudinal study of MARS MRI scanning of soft-tissue lesions around metal-on-metal total hip arthroplasties and disease progression.

We investigated the changes seen on serial metal artefact reduction magnetic resonance imaging scans (MARS-MRI) of metal-on-metal total hip arthroplasties (MoM THAs). In total 155 THAs, in 35 male and 100 female patients (mean age 70.4 years, 42 to 91), underwent at least two MRI scans at a mean interval of 14.6 months (2.6 to 57.1), at a mean of 48.2 months (3.5 to 93.3) after primary hip surgery. Scans were graded using a modification of the Oxford classification. Progression of disease was defined as an increase in grade or a minimum 10% increase in fluid lesion volume at second scan. A total of 16 hips (30%) initially classified as 'normal' developed an abnormality on the second scan. Of those with 'isolated trochanteric fluid' 9 (47%) underwent disease progression, as did 7 (58%) of 'effusions'. A total of 54 (77%) of hips initially classified as showing adverse reactions to metal debris (ARMD) progressed, with higher rates of progression in higher grades. Disease progression was associated with high blood cobalt levels or an irregular pseudocapsule lining at the initial scan. There was no association with changes in functional scores. Adverse reactions to metal debris in MoM THAs may not be as benign as previous reports have suggested. Close radiological follow-up is recommended, particularly in high-risk groups.

Recovery of arctic tundra from thermal erosion disturbance is constrained by nutrient accumulation: a modeling analysis.

Abstract. We calibrated the Multiple Element Limitation (MEL) model to Alaskan arctic tundra to simulate recovery of thermal erosion features (TEFs) caused by permafrost thaw and mass wasting. TEFs could significantly alter regional carbon (C) and nutrient budgets because permafrost soils contain large stocks of soil organic matter (SOM) and TEFs are expected to become more frequent as the climate warms. We simulated recovery following TEF stabilization and did not address initial, short-term losses of C and nutrients during TEF formation. To capture the variability among and within TEFs, we modeled a range of post-stabilization conditions by varying the initial size of SOM stocks and nutrient supply rates. Simulations indicate that nitrogen (N) losses after the TEF stabilizes are small, but phosphorus (P) losses continue. Vegetation biomass recovered 90% of its undisturbed C, N, and P stocks in 100 years using nutrients mineralized from SOM. Because of low litter inputs but continued decomposition, younger SOM continued to be lost for 10 years after the TEF began to recover, but recovered to about 84% of its undisturbed amount in 100 years. The older recalcitrant SOM in mineral soil continued to be lost throughout the 100-year simulation. Simulations suggest that biomass recovery depended on the amount of SOM remaining after disturbance. Recovery was initially limited by the photosynthetic capacity of vegetation but became co-limited by N and P once a plant canopy developed. Biomass and SOM recovery was enhanced by increasing nutrient supplies, but the magnitude, source, and controls on these supplies are poorly understood. Faster mineralization of nutrients from SOM (e.g., by warming) enhanced vegetation recovery but delayed recovery of SOM. Taken together, these results suggest that although vegetation and surface SOM on TEFs recovered quickly (25 and 100 years, respectively), the recovery of deep, mineral soil SOM took centuries and represented a major ecosystem C loss.

Availability influences initial and continued ingestion of nicotine by adolescent female rats.

BACKGROUND: The availability of tobacco products is associated with the likelihood that adolescents will begin using tobacco. Yet the relationship between nicotine availability and voluntary consumption has not been tested experimentally in developing rats. METHOD: The impact of environmental availability on adolescent female rats' initial reaction to and continued ingestion of a novel solution (nicotine or control) was compared using a standard 2-bottle free-choice method and a multiple-bottle method. RESULTS: Manipulating the ratio of bottles containing novel solution to water directly influenced the amount of both nicotine and control solutions consumed. Although subtle differences emerged in intake patterns with prolonged exposure, overall intake patterns were remarkably similar for nicotine and control solutions. CONCLUSION: The intake of oral nicotine was directly influenced by the availability of nicotine solution relative to water. The results indicate that simply providing the right environment is sufficient, and perhaps necessary, to increase rats' voluntary consumption of a nicotine solution without relying on deprivation or sweetening of the solution. That overall intake patterns were comparable for nicotine and control solutions suggests that this may be a general principle of rodent behavior rather than an effect specific to nicotine.

Experience with an up-flow biological aerated filter (BAF) for tertiary treatment: from pilot trials to full scale implementation.

Biofilters can be added to existing non-nitrifying activated sludge plants for tertiary ammonia removal and effluent polishing. It is a convenient, efficient, and cost effective way of meeting more stringent consents. In order to prove this technology, a biofilter pilot plant was installed in a large activated sludge plant with challenging conditions, since almost half of the load is industrial effluent and the water temperature can be as low as 7 degrees C. Trials were conducted over a two year period, providing the following information: low water temperature does not affect the process; the optimum rise rate at nominal flow is 8.5 m/h for this wastewater; the consent can be achieved for ammonia loads up to 0.94 kgNH4N/M3 media/day; about 50% of the post-secondary TSS and BOD can be removed in the BAF; a large proportion of industrial effluent has not had any noticeable effect on the beads after two years. A full scale plant with a nominal flow of 8257 l/s was then built and commissioned in summer 1998. Seeding was completed within three weeks of starting the filters. Two months later, a 28 day takeover was started. Results obtained on full scale plant during and after this test confirm the results obtained on the pilot.

Development of functional connections between thalamic fibres and the visual cortex of the wallaby revealed by current source density analysis in vivo.

Functional development of thalamic input to the cortex in anaesthetised wallaby pouch young between postnatal day 25 (P25) and P153 has been studied by electrical stimulation of the optic nerve, current source density (CSD) analysis, and histologic identification of recording sites. Conduction in the optic nerve was recorded prior to P39, by which time responses from the superior colliculus appeared. No evoked potential of cortical origin was recorded until P46, even though thalamic fibres grew into the cortical plate from P15. The first cortical synaptic responses were recorded at the margin of the subplate and the developing cortical plate, where cells that later comprise the adult layer 6 settle. At about P66, an additional short-latency, superficial response appeared, coinciding with the formation of layer 4. The deep response was retained in layer 6. Evoked activity in the presumed layer 4 was found progressively deeper in the cortex over the next few weeks, which would be expected from the addition of layer 3 above it. By P113, a new sink was added superficial in the cortex. Thalamocortical connections follow the same deep-to-superficial order in development as the cellular layers of the cortex.

Reconstructing mental object representations: a machine vision approach to human visual recognition.

This paper introduces a new approach to assess visual representations underlying the recognition of objects. Human performance is modeled by CLARET, a machine learning and matching system, based on inductive logic programming and graph matching principles. The model is applied to data of a learning experiment addressing the role of prior experience in the ontogenesis of mental object representations. Prior experience was varied in terms of sensory modality, i.e. visual versus haptic versus visuohaptic. The analysis revealed distinct differences between the representational formats used by subjects with haptic versus those with no prior object experience. These differences suggest that prior haptic exploration stimulates the evolution of object representations which are characterized by an increased differentiation between attribute values and a pronounced structural encoding.

The mechanisms of nonheme iron uptake determined in IEC-6 rat intestinal cells.

The mechanisms of iron absorption, which control total body iron stores, are not fully understood. We have defined an in vitro model using rat small intestinal cells (IEC-6) to study nutrient uptake by the intestine and have characterized the mechanisms of nonheme iron uptake in this model. IEC-6 cells were grown to confluency, and then 59Fe solutions were layered on the cells, allowing iron uptake to occur through the apical surface. Iron uptake increased over time and comparable results were seen with either 59Fe(II) or 59Fe(III). Two types of 59Fe(II) binding sites were detected, a high affinity site with a dissociation constant of 1 x 10(-8) mol/L and 5 x 10(5) sites per cell, and a lower affinity site with a dissociation constant of 2 x 10(-6) mol/L and 2.6 x 10(6) sites per cell. The 59Fe uptake was inhibited by low temperature, low and high pH, prior iron loading of the cells, high osmotic concentrations, and by N,N'-dicyclohexylcarbodiimide, tannic acid, bathophenanthroline and colchicine. Uptake was not inhibited by vinblastine or verapamil. Transferrin mRNA was not detected in IEC-6 cells grown under normal growth conditions but could be induced under some other conditions. IEC-6 cell proteins that bind iron were detected in a subcellular vesicle fraction having estimated molecular weights of 120,000, 95,000, 55,000 and 35,000. These studies confirm iron uptake studies by other models and demonstrate that IEC-6 cells possess iron-binding moieties, a regulated iron uptake process, and little or no transcription of the transferrin gene under normal growth conditions.

Maximal exercise cardiorespiratory responses of men and women during acute exposure to hypoxia.

Three male and four female subjects were acutely exposed to normoxic and hypoxic gas mixtures (FIO2 = 17.39%, 14.40%, 11.81%) in a single-blind randomized fashion during four treadmill runs to volitional exhaustion. Maximal scores for oxygen consumption (VO2), carbon dioxide production and heart rate decreased linearly (p less than 0.01) with increasing hypoxia. Conversely, maximal scores for ventilation, ventilatory equivalent (VE/VO2) and R increased linearly (p less than 0.01) with decreasing FIO2. During hypoxia, no significant differences in work time or respiratory compensation threshold were evident. However, female subjects had significantly higher (p less than 0.05) VE/VO2 scores and showed a relative decrease in VO2max that was significantly less (p less than 0.01) than male subjects. It was concluded that young highly active females, when compared to males of similar age and relative condition, have a stronger adaptive response to acute hypoxia during a maximal treadmill run.