The N-terminal region of the gene encoding polyhedrin, the major occlusion protein of the insect baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV), has been fused to DNA encoding Escherichia coli 3-galactosidase. The fused gene was inserted into the AcNPV DNA genome by cotransfection of insect cells with recombinant plasmid DNA and wild-type AcNPV genomic DNA. Recombinant viruses were selected as blue plaques in the presence of a P-galactosidase indicator, 5-bromo-4-chloro-3-indolyl-,-D-galactopyranoside. Studies of one such virus, LlGP-gal3, indicated that the synthesis of P-galactosidase is temporally controlled beginning late (20 h) in infection after the release of infectious virus particles from the cell. By 48 h postinfection, a remarkably high level of expression is achieved. On the basis of these results, AcNPV should be a useful vector for the stable propagation and expression of passenger genes in a lepidopteran cell background. A generalized transplacement vector that facilitates the construction and selection of recombinant viruses carrying passenger genes under their own promoter control has also been developed.The 128-kilobase (kb) circular, supercoiled, doublestranded DNA genome of the insect baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) replicates in the nucleus of the host cell, where it is also assembled into rod-shaped nucleocapsids. By 10 to 12 h postinfection (p.i.), infectious extracellular virus (EV) is produced as the nucleocapsids leave the nucleus and bud through the plasma membrane. By 18 to 24 h p.i., the synthesis of a second form of the virus, occluded virus (OV), begins. Nucleocapsids of OVs acquire a membrane within the nucleus and are then embedded within a crystalline protein matrix composed primarily of a single 33,000-dalton polypeptide known as polyhedrin. OVs only initiate the primary infection of the host organism, whereas EVs are responsible for the secondary infection within the organism and infection in cell cultures. Rapid advances have been made in understanding the molecular biology, biochemistry, and genetics of this interesting virus (for reviews, see references 4, 6, 13, and L. K. Miller, Methods Virol., in press).Many features of AcNPV make this virus a promising candidate as a vector for the propagation and expression of passenger genes (13). First, the rod-shaped capsid apparently extends to accommodate additional DNA sequences with a vector capacity estimated to exceed 100 kb. Second, EV is the infectious form in cell cultures, and the genes for occlusion are nonessential. Third, the gene encoding polyhedrin is an ideal site for passenger gene insertion, since it is abundantly expressed. At between 18 and 72 h p.i., the polyhedrin mRNA transcript constitutes 20% or more of the total polyadenylic acid-containing mRNA (1, 19), and by the time of cell death, the polyhedrin protein constitutes 20% or more of the total protein of the infected cell. Finally, the synthesis of the 1.2-kb polyhedrin mRNA is temporally controll...

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Aside from its more conventional uses as a cardiovascular drug, the calcium channel blocker verapamil has recently been added to chemotherapeutic regimens to reduce drug resistance in B-cell and other neoplasms that express the P-glycoprotein. We recently treated patients with continuous-infusion verapamil (0.15 mg/kg per hour to 0.60 mg/kg per hour) over a 5-day period in combination with continuous-infusion vincristine and doxorubicin plus oral dexamethasone. Seventy-one courses involving 35 hospitalized patients were prospectively studied for cardiovascular and other side effects. Cardiovascular side effects were observed most frequently and consisted of first-degree heart block, hypotension, sinus bradycardia, and junctional rhythms. We observed higher degree heart block, but the QRS interval remained narrow and the ventricular escape rate remained relatively normal. Effects on mean arterial pressure, heart rate, and PR interval were both time and dose related. Severe, symptomatic congestive heart failure was rarely observed. The most common noncardiovascular side effects were constipation, peripheral edema, and weight gain. All systemic toxic effects observed were easily treated or disappeared with either temporary or permanent discontinuation of the verapamil infusion or by a decrease in the dose of verapamil. We conclude that the cardiovascular side effects associated with continuous, high-dose intravenous verapamil therapy are significant and dose limiting but are rapidly reversible. Less cardiotoxic chemosensitizers are needed to reverse multidrug resistance in cancer.

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Rabbits that survive occlusion of the circumflex artery will develop myocardial dysfunction and left ventricular remodeling. Therapy with DITPA, a thyroid hormone analogue, produces improvement in ventricular performance and reduces end-diastolic pressure. The hemodynamic effects of DITPA were not associated with alterations of MHC isoforms. Whether DITPA represents the prototype of a previously undescribed class of agents for the treatment of heart failure will need to be determined by clinical trials.