Pathogenesis of reticuloendotheliosis virus infection in ducks

A new isolate of reticuloendotheliosis virus (REV) from ducks, RU-1, was used to experimentally infect white pekin ducks. Embryonal or neonatal infection usually resulted in persistent viremias, no REV antibody development, and inability to mount antibody responses against bovine serum albumin (BSA) or sheep red blood cells (SRBC). In contrast, infection at 21 days of age resulted in transient viremias, which terminated coincident with REV antibody development. These ducks remained persistently infected, however, based on virus isolations from peripheral blood lymphocytes. Ducks infected at that age were immunologically competent against BSA and SRBC unless they had been embryonally bursectomized, in which case they behaved virologically and immunologically like those infected at an early age. Bursectomy by itself did not prevent responses against the antigens. Total mortality during 4- or 6-month experimental periods ranged from 80 to 100% in REV-infected groups, regardless of age at infection, route of exposure, or whether the ducks were intact or bursectomized. Most deaths were from non-neoplastic conditions (stunting, bacterial infections), but 17 of 69 (25%) infected ducks developed a variety of neoplasms, including lymphosarcomas, histiocytic sarcomas, and spindle-cell sarcomas.

Nitrogenase reactivity: cyanide as substrate and inhibitor

We have examined the reduction of cyanide by using the purified component proteins of nitrogenase (Av1 and Av2). The previously reported self-inhibition phenomenon was found to be an artifact. One of the two species present in cyanide solutions, CN-, was shown to be a potent reversible inhibitor (Ki = 27 microM) of total electron flow, apparently uncoupling MgATP hydrolysis and electron transfer. There appears to be no differential effect of CN- on the specific activities of Av1 and Av2 nor is there any apparent irreversible physical damage to Av2. CN- inhibition is completely reversed by low levels of CO, implying a common binding site. Azide partially relieves the inhibitory effect, but other substrates and inhibitors (N2, C2H2, N2O, H2) have no effect. The other species present in cyanide solutions, HCN, was shown to be the substrate (Km = 4.5 mM at Av2/Av1 = 8), and extrapolation of the data indicates that at high enough HCN concentration H2 evolution can be eliminated. The products are methane plus ammonia (six electrons), and methylamine (four electrons). There is an excess (relative to methane) of ammonia formed, which, according to electron balance studies, may arise from a two-electron intermediate. Both nitrous oxide and acetylene (but not N2) influence the distribution of cyanide reduction products, implying simultaneous binding. HCN appears to bind to and be reduced at an enzyme state more oxidized than the one responsible for either H2 evolution or N2 reduction.

The biology of SAA: identification of the inducer, in vitro synthesis, and heterogeneity demonstrated with monoclonal antibodies

Continued studies of the macrophage-derived mediator of SAA synthesis (SAA Stimulating Factor) confirm our previous observations that SAASF copurified with leukocytic pyrogen (LP) and lymphocyte activating factor (LAF). Moreover, new data demonstrate three separate isoelectric points for human LP-LAF-SAASF each of which possess the three biological activities. During the purification of 15,000 MW LP from crude stimulated mononuclear cell supernatants, only those fractions with pyrogenic activity in rabbits caused augmented stimulation of lymphocytes (LAF) and induced SAA synthesis in mice. Purified human LP stimulated isolated mouse hepatocytes in vitro to synthesize SAA in a dose-responsive manner. Colchicine treatment of hepatocytes led to decreased secretion of SAA into the medium and to an intracellular accumulation of SAA. Messenger RNA was isolated from the livers of endotoxin-stimulated mice and translated in a wheat-germ cell-free system. A major product was identified at 13-14,000 MW. Immunoprecipitation with anti-mouse AA identified several bands on autoradiography of polyacrylamide gels. These larger SAA precursors may account for the previously noted heterogeneity of human SAA, comprising at least 6 SAA isomers, of similar molecular weight but different solubility and electrophoretic charge characteristics. Two monoclonal antibodies (IgM-K and IgG1-K) have been prepared using standard cell hybridization techniques. They are directed at the variable COOH terminal region of SAA since they detect differences between the 6 human SAAs but do not react with human, monkey, dog or mouse AA proteins, human AP, C-reactive protein, IgG nor albumin. These antibodies will be useful in examining the origin, structure and function of SAA.

Properties of the N gene transcription antitermination protein of bacteriophage lambda

The product of the N gene of bacteriophage lambda prevents the termination of lambda early transcription. Here we describe the physical properties of pure lambda N protein. N protein is small and very basic. The apparent Mr of N protein during electrophoresis in the presence of sodium dodecyl sulfate is 12,500. It contains 22 mol % (arginine plus lysine) and only one methionine. The methionine residue is at the blocked NH2 terminal since N protein is not detectably shortened by reaction with cyanogen bromide. When use is made of the DNA sequence of the N gene region of lambda DNA (Franklin, N. C., and Bennett, G. N. (1979) Gene 8, 107-119), the lack of an internal methionine residue, the size, and the amino acid composition of N protein can be used to predict that N protein contains 107 amino acids (calculated Mr = 12,241) and that its coding sequence begins at position 223 of the lambda pL operon mRNA. N protein can be assayed by its ability to stimulate endolysin synthesis in vitro in a reaction programmed with lambda N- DNA. N protein activity is heat-stable and trypsin-sensitive. Its sedimentation velocity in a sucrose gradient and its Stokes' radius indicate that N protein is an extremely asymmetric monomer (f/fmin = 1.6). The relationship between this high degree of molecular asymmetry and the sequence which N protein must recognize in lambda nucleic acid is discussed.

Formation of crystalline arrays of chlorophyll a/b - light-harvesting protein by membrane reconstitution

The structure of the major protein constituent of photosynthetic membranes in higher plants, the chlorophyll a/b-light harvesting complex (LHC), was studied by x-ray diffraction and electron microscopy. The LHC was purified from Triton X-100 solubilized thylakoid membranes of the pea, and contained 6 mol of chlorophylls a and b per mole of a polypeptide of 27,000 molecular weight. X-ray diffraction showed that in the presence of 10 mM MgCl2, purified LHC forms planar aggregates that stack with a period of 51 A. Within each layer, LHC molecules pack with a center-to-center distance of 85 A but without long-range order. However, when LHC is incorporated into single-walled vesicles of plant lecithin, the addition of NaCl above 10 mM, or MgCl2 above 2 mM, led to the formation of plaques of hexagonal lattices, with a lattice constant of 125 A. The large domain size and high degree of order in the plane of the membrane are evident from the sharp lattice lines observed to 7 A resolution on the equator of the x-ray pattern. Freeze-fracture electron micrographs demonstrated an aligned stacking of the lattices in adjacent membranes, resulting in crystallinity in the third dimension over short distances. Micrographs of negatively stained membranes revealed a hexagonal lattice of the same lattice constant, formed by surface-exposed parts of the LHC molecules which are probably responsible for the ordered stacking of lattices. In both the LHC aggregates and in the reconstituted membrane lattices the diffracted x-ray intensities at 10-A spacing on the equator indicate that the LHC molecule contains paralled alpha-helices or beta-sheets that are oriented perpendicular to the planar arrays.

Interaction of the sigma factor and the nusA gene protein of E. coli with RNA polymerase in the initiation-termination cycle of transcription

The nusA gene protein of E. coli is involved in regulating termination of transcription in vivo. In vitro it causes termination of transcription in the tR2 region of the PR operon of bacteriophage lambda. We have now used a nusA-Sepharose affinity column and gradient sedimentation experiments to show that the nusA protein binds directly, with great specificity, and with equimolar stoichiometry to the E. coli RNA polymerase core enzyme beta beta' alpha 2. The RNA polymerase sigma subunit is able to displace the nusA protein from a beta beta' alpha 2-nusA complex, regenerating RNA polymerase holoenzyme beta beta alpha 2-sigma able selectively to initiate transcription at promoter sites. It is proposed that beta beta' alpha 2-nusA and beta beta' alpha 2-sigma are complementary forms of RNA polymerase that interchange with one another in the initiation-termination cycle of transcription.

Maternal behavior, pup vocalizations, and pup temperature changes following handling in mice of 2 inbred strains

A cross-fostering design was used to examine maternal behavior, pup vocalizations, and pup temperature changes following an infantile procedure in C57BL/6J (C) and A/J (A) mice. In Experiment I, maternal behavior of C and A mothers after infantile handling differed in a number of ways irrespective of the strain of the foster pups. In addition, A pups were retrieved faster but licked less than were C pups by mothers of both strains. Handling appeared to increase the probability that strain differences would occur in that no differences between the lines, in either the behavior of the mothers or the capacity of the pups to elicit maternal behavior, were found during observations made just prior to daily handling. These observations also revealed that mothers of both strains treated same-strain foster pups differently than they treated foster pups of another strain. In Experiment II, A pups were found to emit more ultrasound following handling than were C pups, suggesting that retrieval but not pup-licking was stimulated by ultrasonic signals. Measurement of pup temperature during and following the handling procedure showed that (1) strain differences in ultrasonic signaling were not related to strain differences in the degree of hypothermia experienced by the pups; (2) recovery of body temperature following handling was slow for pups of both strains, and depended to some degree on the strain of the pups' foster mother; and (3) development of thermoregulation occurred more rapidly in C than A pups.

The nonspecificity of diffuse pulmonary uptake of 67Ga on 24-hour images

Eighteen patients who underwent whole-body scintigraphy 24 and 48 hours after intravenous injection of 67Ga-citrate were evaluated retrospectively. At 24 hours, 7 of the 16 normal patients (44%) and both abnormal patients demonstrated significant pulmonary uptake. However, by 48 hours, only 2 normal patients (12%) remained positive, while both abnormal patients continued to show significant pulmonary activity. The authors conclude that 48-hour 67Ga images offer improved specificity and uncompromised sensitivty in patients with diffuse pulmonary disease.

L factor that is required for beta-galactosidase synthesis is the nusA gene product involved in transcription termination

The DNA-dependent in vitro synthesis of Escherichia coli beta-galactosidase requires the presence of a soluble protein referred to as L factor [Kung, H., Spears, C. & Weissbach, H. (1975) J. Biol. Chem. 250, 1556-1562]. In the present study, comparison of physical, immunological, and biological properties shows that L factor is the product of the E. coli nusA gene. The nusA gene product is known to interact with bacteriophage lambda N gene protein and to prevent premature termination of transcription from the early lambda promoters. Our results suggest that premature transcription termination in the lac operon of E. coli may also be overcome by the nusA protein.