In situ clearance rates of planktonic rotifers

The in situ clearance rates of several rotifer species from a small, temperate eutrophic lake were measured using three radioactive tracer cell-types, a bacterium (Aerobacter), a yeast (Rhodoto-rula), and alga (Chlamydomonas). Rates were below 10 µl/anim/h but varied significantly among species. Keratella cochlearis, Kellicottia bostoniensis, and Conochilus dossuarius ingested all three tracer cells but rates varied substantially with tracer cell-type. Polyarthra dolichoptera and P. euryptera ingested only the algal cells. Co-occurring forms of K. cochlearis and species of Polyarthra differed markedly in size and in tracer cell utilization, indicating niche diversification in food resources.     

The spring-time abundance and feeding ofEurytemora affinis (Poppe) in Volkerak-Zoommeer,a newly-created freshwater lake system in the Rhine delta (The Netherlands)

Eurytemora affinis, a calanoid copepod, has been encountered in Volkerak-Zoommeer (Rhine delta region, S.W. Netherlands) both before this lake system was isolated in 1987 from the estuarine influence, and after. It was the main particle-feeding crustacean at all the 3 sampling stations in March–April 1990 when it reached densities of up to 215 ind.l^–1. Its decline from mid April onwards, and low densities through summer, coincided with increase in cladocerans, especiallyDaphnia spp. (D. pulex andD. galeata), a decrease in seston (<33m) and chlorophyll concentrations and in primary production rates. The clearance rates (CR) ofEurytemora measured in the spring period varied enormously (0.6–24 ml.ind^–1.d^–1) depending mainly on size (0.44–1.06 mm), food concentration (0.8–2.2 mg C.l^–1), and the water temperature which varied only narrowly (8.0–9.0°C). Mean ingestion rates of the animals measuring 0.68±0.02 mm during the study was 6.7±3.2 gC.ind^–1.d^–1; and assimilation efficiency varied between 27 and 53% (mean: 41±9%). The weight specific CR (SCR) varied between 0.96 and 6.4 litre.mg^–1 body C.d^–1. Pooled regression of SCR on the animal's body weight at the 3 study stations revealed a significant inverse relationship. Also daily ration and specific assimilation ofE. affinis varied greatly and inversely with the body weight. This calanoid contributed from about 50 to 100% to the zooplankton community grazing rates and assimilation rates, the former often exceeding the phytoplankton primary production.     

Biological half-time in rats exposed to nickel monosulfide (amorphous) aerosol by inhalation

This study reports the biological half-time of amorphous nickel monosulfide(NiS(A)) aerosol retained in rat lungs. Wistar male rats were exposed to NiS(A) aerosols (mass median aerodynamic diameter: 4.0 μm) for a single 4 h exposure, or for 7 h/d, 5 d/wk for 1 mo. The average exposure concentrations were controlled at 107 mg/m³ for the single exposure and at 8.8 mg/m³ for the repeated exposures by a dust generator consisting of a continuous fluidized bed with an overflow pipe and a screw feeder. After the exposures, the nickel contents in the rat organs, blood, and urine were measured and histopathological examinations were performed. The biological half time of NiS(A) in rat lungs was 20 h, which was extremely shorter than 21 mo of green nickel oxide (NiO(G)). There were no malignant tumors in any of the exposure groups.     

Effect of age on phagocytosis of carbon in the rat

The half-life of intravenously injected colloidal carbon increases with age of the rat if the dose of carbon is in proportion to body weight. An equation was found for the change in half-life as a function of body weight. By the use of the equation of Gompertz we have derived a curve relating half-life of colloidal carbon to age of the rat. A large part of the variation of phagocytic activity with age can be removed by allowing for the change in relative spleen weight that occurs with age, or by the use of a constant dose of carbon instead of a dose proportionate to body weight.     

Plasmodium berghei: Phagocytic activity in two strains of rats

The Wistar and Sprague-Dawley strains of rats differ in their ability to maintain phagocytic hyperactivity toward colloidal carbon during infection with Plasmodium berghei. Both strains were highly stimulated by the 4th day, but on the 7th and 8th days of infection one-third of the Sprague-Dawley rats were not hyperactive while all the Wistar rats remained hyperactive. The course of infection subsequent to the carbon test was similar in hyperactive and in nonhyperactive rats.     

Ex vivo Method for High Resolution Imaging of Cilia Motility in Rodent Airway Epithelia

An ex vivo technique for imaging mouse airway epithelia for quantitative analysis of motile cilia function important for insight into mucociliary clearance function has been established. Freshly harvested mouse trachea is cut longitudinally through the trachealis muscle and mounted in a shallow walled chamber on a glass-bottomed dish. The trachea sample is positioned along its long axis to take advantage of the trachealis muscle to curl longitudinally. This allows imaging of ciliary motion in the profile view along the entire tracheal length. Videos at 200 frames/sec are obtained using differential interference contrast microscopy and a high speed digital camera to allow quantitative analysis of cilia beat frequency and ciliary waveform. With the addition of fluorescent beads during imaging, cilia generated fluid flow also can be determined. The protocol time spans approximately 30 min, with 5 min for chamber preparation, 5-10 min for sample mounting, and 10-15 min for videomicroscopy.     

Modelling of intracranial behaviour on occiput impact in judo

Acute subdural hematoma (ASDH) sometimes occurred in judo because of the bridging veins’ failure by rotation of the brain in the skull. However, the relationship between intracranial behaviour and the motion of the body on occiput impact has not yet been clarified. In this study, we developed an intracranial mechanical model based on multibody dynamics and compared it with experimental results. The results show the importance of modelling bridging veins and cerebral spinal fluid to the relative displacement between brain and skull. The proposed model will contribute to accident analyses or the optimum design of supporting devices.     

Formulating gels for decreased mucociliary transport using rheologic properties: Polyacrylic acids

The purpose of these studies was to identify the rheologic properties of polyacrylic acid gels necessary for optimal reductions in mucociliary clearance. The mucociliary transport of 2 bioadhesive polyacrylic acid polymers, polycarbophil and carbopol, was assessed in vitro by measuring their clerance rates across explants of ciliated bovine tracheal tissue. The viscoelastic properties of polymer gels were measured in the presence of mucus using controlled stress rheometry. Combinations of apparent viscosity (η) and complex modulus (G^*) were found to be the most useful parameters in the identification of polyacrylic acid formulations capable of decreasing mucociliary transport rate (MTR). A narrow range of η and G^* values suitable for reducing mucociliary clearance, while remaining sufficiently fluid for intranasal administration, were identified. The correlations between the rheologic parameters of the polycarbophil gels and their mucociliary transport rates were used to identify other polyacrylic acid gels that also had suitable mucociliary clearance properties, demonstrating that these parameters can be used to direct the optimization of formulations using simple in vitro rheologic testing. Published: April 20, 2007     

Axonal autophagosomes use the ride-on service for retrograde transport toward the soma

Degradation of autophagic vacuoles (AVs) via lysosomes is an important homeostatic process in cells. Neurons are highly polarized cells with long axons, thus facing special challenges to transport AVs generated at distal processes toward the soma where mature acidic lysosomes are relatively enriched. We recently revealed a new motor-adaptor sharing mechanism driving autophagosome transport to the soma. Late endosome (LE)-loaded dynein-SNAPIN motor-adaptor complexes mediate the retrograde transport of autophagosomes upon their fusion with LEs in distal axons. This motor-adaptor sharing mechanism enables neurons to maintain effective autophagic clearance in the soma, thus reducing autophagic stress in axons. Therefore, our study reveals a new cellular mechanism underlying the removal of distal AVs engulfing aggregated misfolded proteins and dysfunctional organelles associated with several major neurodegenerative diseases.