Mutations of the p53 gene are associated with a poor prognosis in patients with aggressive B-cell lymphoma.

The buoyant density of hepatitis C virus (HCV), with high in vivo infectivity (strain H) or low in vivo infectivity (strain F), was determined by sucrose gradient equilibrium centrifugation. Viral RNA of strain H was detected in fractions with densities of <1.09 g/ml (principally-1.06 g/ml), while that of strain F was found in fractions with densities of-1.06 and-1.17 g/ml. The observed difference was confirmed by differential flotation centrifugation; in NaCl solution with a density of 1.063 g/ml, most of the HCV RNA of strain H was detected in the top fraction, while that of strain F appeared in the bottom. The same relationship between buoyant density and infectivity was observed in flotation centrifugation experiments with other HCV strains. In immunoprecipitation experiments with anti-human immunoglobulin, HCV (as measured by HCV RNA) was precipitated from the samples with low infectivity and high density but not from those with high infectivity and low density. Examination of serial sera from a chimpanzee infected with HCV revealed parallel changes in the buoyant density and immunoprecipitability of HCV-associated RNA during the course of infection. These data suggest that HCV is bound to anti-HCV antibodies as antigen-antibody complexes in chronic hepatitis C.

A new tissue-equivalent MRI phantom based on carrageenan gel was developed. Carrageenan gel is an ideal solidifying agent for making large, strong phantoms in a wide variety of shapes. GdCl 3 was added as a T 1 modifier and agarose as a T 2 modifier. The relaxation times of a very large number of samples were estimated using 1.5-T clinical MRI equipment. The developed phantom was found to have a T 1 value of 202-1904 ms and a T 2 value of 38 -423 ms when the GdCl 3 concentration was varied from 0 -140 mol/kg and the agarose concentration was varied from 0 -1.6% in a carrageenan concentration that was fixed at 3%. The range of measured relaxation times covered those of all types of human tissue. Empirical formulas linking the relaxation time with the concentration of the modifier were established to enable the accurate and easy calculation of the modifier concentration needed to achieve the required relaxation times. This enables the creation of a phantom having an arbitrary combination of MRI phantoms are useful for calibrating and checking imaging equipment, developing new systems and pulse sequences, and training MRI operators. To be useful in these roles, the material used to make MRI phantoms should 1) have relaxation times similar to those of human tissue; 2) provide uniform relaxation times throughout the phantom itself; 3) be strong enough to enable the fabrication of a "torso" without the use of physical reinforcements; 4) allow the production of phantoms in the shapes and sizes of human organs; 5) be easy to handle; and, 6) remain chemically and physically stable over extended periods.There have been several attempts to create solid materials for MRI phantoms. Former candidates have included agarose (1-5), agar (6,7), polyvinyl alcohol (PVA) (8), gelatin (9,10), TX-150 (11), TX-151 (12), and polyacrylamide (13). These gel phantoms usually contained additives such as paramagnetic ions to control the T 1 relaxation times. The most versatile phantoms are probably the paramagnetically doped gels that are based on agarose (1-5) or agar (6,7). In these systems, the T 1 relaxation times can be easily modulated by varying the concentrations of the paramagnetic ions, whereas the T 2 relaxation times are primarily a function of the gelling agent concentration. In a phantom that is based on polyacrylamide gel (13), both the T 1 and T 2 relaxation times can be modulated simultaneously by varying the concentration of the gel without the paramagnetic ions. These phantoms are easy to prepare and can be made with a wide range of T 1 and T 2 relaxation times including those of human tissue. To create a phantom with a human-like T 2 relaxation time of about 40 -150 ms, however, the concentration of agar, agarose, and polyacrylamide must be about 1.5-3.0, 0.8 -4.0, and 17-30%, respectively. To create a phantom having a long T 2 relaxation time, the concentration would be so low that the gel would not solidify sufficiently. A PVA gel phantom can offer the appropriate physical characteristics because it is as hard as the st...

By adjustments to the concentrations of agarose, GdCl3, and NaCl, the relaxation times and conductivity of almost all types of human tissues can be simulated by CAGN-3.0T phantoms. The phantoms have T1 values of 395-2601 ms, T2 values of 29-334 ms, and conductivity of 0.27-1.26 S/m when concentrations of agarose, GdCl3, and NaCl are varied from 0 to 2.0 w/w%, 0 to 180 μmol/kg, and 0 to 0.7 w/w%, respectively. The CAGN-3.0T phantom has sufficient strength to replicate the torso without using reinforcing agents, and can be cut with a knife into any shape.

We have developed temperature-pulse microscopy in which the temperature of a microscopic sample is raised reversibly in a square-wave fashion with rise and fall times of several ms, and locally in a region of approximately 10 m in diameter with a temperature gradient up to 2°C͞m. Temperature distribution was imaged pixel by pixel by image processing of the f luorescence intensity of rhodamine phalloidin attached to (single) actin filaments. With short pulses, actomyosin motors could be activated above physiological temperatures (higher than 60°C at the peak) before thermally induced protein damage began to occur. When a sliding actin filament was heated to 40-45°C, the sliding velocity reached 30 m͞s at 25 mM KCl and 50 m͞s at 50 mM KCl, the highest velocities reported for skeletal myosin in usual in vitro assay systems. Both the sliding velocity and force increased by an order of magnitude when heated from 18°C to 40-45°C. Temperature-pulse microscopy is expected to be useful for studies of biomolecules and cells requiring temporal and͞or spatial thermal modulation.Recent advances in optical microscopic techniques have made it possible to image single protein molecules in solution (1, 2) and investigate the dynamic nature of molecular motors (3-8).To introduce an additional dimension to this technology, we have developed temperature-pulse microscopy (TPM), in which a microscopic sample(s) in aqueous solution is heated reversibly.There have been several reports on the effects of temperature jumps under an optical microscope: for example, on physiological functions of muscle fibers (9-12) and on phase transition phenomena in membranes of phospholipid vesicles and cells (13). To prevent thermal deterioration of biological samples, and to confirm the absence of the deterioration, it is highly desirable to restore the starting temperature as soon as the measurement is finished. In our TPM, temperature is elevated spatially and temporally by illuminating a lump of metal particles by IR laser; a concentric temperature gradient is created around the lump of metal particles. When the laser beam is shut off, the heat is rapidly dissipated into the surrounding medium. Thus, a square-wave temperature pulse with rise and fall times of less than 10 ms is generated. Exposure to high temperature is minimized, and repetitive thermal cycling is easily programmed. The local heating also permits simultaneous observation of the sample behaviors at various temperatures.In the microscopic temperature-imaging techniques reported so far, the temperature was estimated either from the thermal quenching of fluorescence (14-16) or from the thermal shift of the fluorescence spectrum (13). Here, we applied the former technique. In our TPM, a concentric temperature gradient is formed around the metal aggregate, as assessed from thermal quenching of a fluorescent dye bound to actin filaments with a slope of 1-2°C͞m and extension out to 10-20 m. The temperature distribution on single actin filaments also could be imaged.We have applied ...