A rat hepatoma cell line (Q7) of Morris hepatoma origin was transfected with a construct containing the tandem dimer genome of human hepatitis B virus (HBV) and the neomycin-resistant selection marker. The culture medium of several neomycin-resistant single-cell clones was found to accumulate high levels of secreted HBV surface antigen and core-related e antigen. HBV-specific replication intermediates, including relaxed circular and single-stranded DNA with a minus-strand polarity, could be found in both the intracellular fraction and the extracellular culture medium by the Southern blot procedure. One of these clones, designated Q7 HBV-21, was characterized in further detail. DNA polymerase activity was present in the virus particles produced by Q7 HBV-21 cells. Characteristic transcripts of HBV, including the 3.5-, 2.5-, and 2.1-kilobase mRNA as well as a core-generelated transcript of 2.2 kilobases could be detected. Electron microscopic examination of the conditioned medium from Q7 HBV-21 cells identified 42-nm Dane-like particles as well as 22-nm subviral particles with a spherical or filamentous shape. This Q7 HBV-21 cell line has been maintained in the absence of neomycin for 1 year without losing the properties of HBV DNA replication and Dane-like particle production. Our results strongly suggest that the species barrier of HBV infection is at an early step of viral absorption onto or penetration into the target hepatocytes. This nonhuman system for HBV production in culture could be used to complement the human HepG2 system.Research on human hepatitis B virus (HBV) has been hampered by the slow development of a tissue culture system for HBV propagation (1)(2)(3). It is possible to study HBV production in culture by using human hepatoma cell lines HepG2 (4, 5) or Huh6-c15 (6) and stable transfection techniques. In addition, the human hepatoma cell line Huh7 was used as a recipient for production of HBV through the transient transfection technique (7,8). In all these studies, HBV-specific DNA replication intermediates were identified. Moreover, characteristic subviral and matured viral particles (Dane particles) were observed by electron microscopy. These viral particles produced by HepG2 cells were later shown to be infectious in chimpanzees (9,10).HBV is a member of the so-called hepadnavirus family including hepatitis B viruses of woodchucks, ground squirrels, tree squirrels, Pekin ducks, etc. (1-3). Members of the hepadnavirus family in general exhibit a rather strict host range. For example, HBV is known to replicate only in humans and chimpanzees. It has been reported that infectious particles of duck hepatitis B virus can be generated by transient gene transfer to the established human hepatoma cell lines HepG2 (11,12) and Huh7 (12,13). Although these experiments demonstrated that duck hepatitis B virus can replicate and mature in certain human hepatoma cell lines, it remains unclear if the converse is true-i.e., if HBV can propagate and mature into infectious Dane particles in a nonhuman h...

A Macintosh-based signal processing system has been developed to support simultaneous respiratory and cardiac gating on the ECAT EXACT HR PET scanner. Using the Lab-View real-time software environment, the system reads analog inputs from a pneumatic respiratory bellows and an ECG monitor to compute an appropriate histogram memory location for the PET data. Respiratory state is determined by the bellows signal amplitude; cardiac state is based on the time since the last R-wave. These two states are used in a 2D lookup table to determine a combined respiratory-cardiac state. A 4-bit address encoding the selected histogram is directed from the system to the ECAT scanner, which dynamically switches the destination of tomograph events as respiratory-cardiac state changes. To test the switching efficiency of the combined Macintosh/ECAT system, a rotating emission phantom was built. Acquisitions with 25 msec states while the phantom was rotating at 240 rpm demonstrate the system could effectively stop motion at this rate, with approximately 5 msec switching time between states.

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