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Radiotracer kinetic modeling in small animals with Positron Emission Tomography (PET) requires the determination of the blood tracer concentration as a function of time. A continuous blood counting system was designed to measure the input function from rats and mice in real time. The system consists of a flow-through [beta] counter made of silicon PIN photodiodes and a [micro]I syringe pump. The latter draws blood continuously from an implanted venous or arterial catheter, at a user selected rate. The direct/3 detection by photodiodes minimizes the shield footprint next to the animal and reduces the counter sensitivity to ambient gamma radiation. The device is entirely remote controlled for sampling protocol selection, tuning, and real time monitoring of measured parameters. It can be hooked to a computer or fully integrated with the LabPET[TM] scanner for blood counting during dynamic PET imaging experiments. The counter sensitivity to the most popular PET radioisotopes ([sup.18]F,[sup.84]Cu,[sup.13]N, [sup.11]C) ranges from 7.1 to 46.8 Bq/[micro]. Its linearity is better than 98% up to 46 kBq/[micro]l for [sup.18]F, and a 1.4 s dispersion constant was measured at a rate of 250 [micro]1/min with rat whole blood in a PE10 catheter. Due to its optimized mechanical design and compact shielding, the counter sensitivity to radioactive background is only 5 counts per second (cps) for a 37 MBq [sup.18]F source 10 cm away from the detector. Accurate time-activity curves have been obtained from rats and mice in dynamic PET imaging studies. Index Terms--Beta [beta] detector, blood sampling, pharmacokinetic modeling, small animal PET.

Methicillin-resistant Staphylococcus aureus (MRSA) infection was identified in 2 horses treated at a veterinary hospital in 2000, prompting a study of colonization rates of horses and associated persons. Seventy-nine horses [...]

The rat heart is an excellent model for the investigation of cardiac physiology and metabolism. It has been used extensively for ex vivo studies of the normal heart as well as for the study of various heart diseases. With the advent of dedicated high-resolution small animal PET scanners, it is now possible to transpose many of the cardiac studies routinely used in humans to the rat. These include the in vivo measurement of myocardial blood flow, metabolism, and function. Because these techniques are noninvasive, the same animal can be imaged repetitively, thus allowing for follow-up studies of disease progression and for the assessment of new therapeutic methods. In this work, we report on cardiac studies performed in normal and diseased rats using the Sherbrooke avalanche photodiode PET scanner, a small animal PET imaging device achieving 14 [micro]l volumetric spatial resolution with excellent image signal-to-noise ratio. The system also features flexible fist-mode data acquisition, which allows dynamic studies to be resampled as desired for kinetic modeling. These cardiac PET imaging methods were used for the follow-up of infarcted rats submitted to experimental intramyocardial revascniarization therapy. Index Terms--Avalanche photodiodes, cardiovascular system, pharmacokinetic modeling, positron emission tomography (PET), small animal imaging.

This paper describes an experimental study on the seismic performance of concentrically braced steel frames made with cold-formed rectangular tubular bracing members. A total of 24 quasistatic cyclic tests were performed on full size X bracing and single diagonal bracing systems. Two loading sequences were considered: a symmetrical stepwise increasing deformation sequence and a displacement history obtained from nonlinear dynamic analyses of typical braced steel frames. All specimens buckled out-of the plane of the frame and the tests were interrupted when fracture of the braces occurred in the region of highest curvature. For X bracing, the results clearly show that the effective length of the braces can be used to determine their compression strength and to characterize their hysteretic response, including energy dissipation capability. Simplified models are proposed to predict the out-of-plane deformation of the braces as a function of the ductility level. These models are then used to develop an empirical expression to assess the inelastic deformation capacity before fracture of bracing members made of rectangular hollow sections. CE Database subject headings: Steel frames; Seismic response; Bracing; Buckling; Fractures.

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Radiotracer kinetic modeling in small animals with Positron Emission Tomography (PET) requires the determination of the blood tracer concentration as a function of time. A continuous blood counting system was designed to measure the input function from rats and mice in real time. The system consists of a flow-through β counter made of silicon PIN photodiodes and a μl syringe pump. The latter draws blood continuously from an implanted venous or arterial catheter, at a user selected rate. The direct β detection by photodiodes minimizes the shield footprint next to the animal and reduces the counter sensitivity to ambient gamma radiation. The device is entirely remote controlled for sampling protocol selection, tuning, and real time monitoring of measured parameters. It can be hooked to a computer or fully integrated with the LabPET™ scanner for blood counting during dynamic PET imaging experiments. The counter sensitivity to the most popular PET radioisotopes (18F, 64Cu, 13N, 11C) ranges from 7.1 to 46.8 Bq/μl. Its linearity is better than 98% up to 46 kBq/μl for 18F, and a 1.4 s dispersion constant was measured at a rate of 250 μl/min with rat whole blood in a PE1O catheter. Due to its optimized mechanical design and compact shielding, the counter sensitivity to radioactive background is only 5 counts per second (cps) for a 37 MBq 18F source 10 cm away from the detector. Accurate time-activity curves have been obtained from rats and mice in dynamic PET imaging studies. [ABSTRACT FROM AUTHOR]

Normative data are provided to measure the effect of the size of a bite of food on the chewing time and number of chewing cycles of children undergoing the transition from a mode of ingestion by suckling to that of chewing. In a cross-sectional study, children aged 6 to 24 months were fed groups of five large and five small bites of a flavored gelatin, in random order. The feeding was videotaped to permit recording of the chewing time and cycles for each child. Older children chewed more efficiently than younger ones by decreasing both chewing time and number of cycles, and all children chewed more efficiently in the fifth than in the first trial. The order in which the two sizes of gelatin was administered had no influence on chewing time or cycles, an important consideration for clinicians. Central and peripheral changes of the oral region that occur in normal development are discussed as possible reasons for the increase in eating efficiency. [ABSTRACT FROM AUTHOR]

Binding of pig hemoglobin (Hb) to Actinobacillus pleuropneumoniae lipopolysaccharide (LPS), either extracted or present at the surface of whole cells, was studied. After a short incubation period, pig Hb seemed to cover the bacterial cell surface and enhanced the cells' contrast when examined by transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy analysis showed that the amount of elemental iron detected was increased when cells of A. pleuropneumoniae were incubated with pig Hb. Coating with pig Hb, however, did not interfere with the accessibility of O- and capsular antigens to antibodies on the bacterial cell surface. Binding of pig Hb and polymyxin B to lipid A of A. pleuropneumoniae was confirmed with a fluorescent probe (dansylcadaverine) displacement assay. The binding of pig Hb to extracted LPS resulted in a disaggregation of LPS as observed by TEM after negative staining. Additional evidence for a direct physical interaction between pig Hb and A. pleuropneumoniae LPS was demonstrated by a shift in the sedimentation velocity of LPS-Hb complexes determined by sucrose gradient centrifugation. Pig Hb binding to extracted LPS or to bacterial cells resulted in a significant decrease of chromogenic Limulus amebocyte lysate activation. Finally, the capacity of extracted LPS to induce NO2- in the presence of pig Hb was tested by using cell line J774 and determined by the Greiss' reaction. LPS alone induced, as expected, NO2- production, whereas the presence of pig Hb significantly reduced NO2- production by murine macrophages. Taken together, our results indicate that binding of pig Hb affected some physical and biological properties of A. pleuropneumoniae LPS. [ABSTRACT FROM PUBLISHER]