Relating cistrons and functions in bacteriophage PM2

An approach to correlate functions with cistrons in bacteriophage PM2 is presented. Two of the temperature-sensitive mutants obtained differed from the wild type in heat sensitivity and four differed in host range. Comparison of the electrophoretic patterns of DNA from cells infected at the restrictive temperature with those obtained in wildtype infection revealed that viral DNA bands were absent with three additional mutants. Complementation analysis assigned the four host range mutants to cistron I and the three mutants defective in DNA synthesis to cistron IV. Recombination frequencies were used to locate cistrons III and IV on the partial genetic map of PM2.     

Mapping of the influenza virus genome II. Identification of the P1, P2, and P3 genes

Polyacrylamide gel electrophoresis of the RNAs of influenza A viruses was performed under conditions in which each of the eight RNA segments of influenza A/PR/8/34 (H0N1) virus migrates differently from the equivalent segments of influenza A/Hong Kong/8/68 (H3N2) virus. As reported previously [Palese, P. and Schulman, J. L. Proc. Nat. Acad. Sci. USA73, 2142–2146 (1976)], analysis of RNA patterns of recombinant viruses derived from these two parents permitted the identification of the fourth RNA segment (the slowest-moving RNA segment is counted as #1) of each virus as the gene coding for hemagglutinin, and the fifth segment of Hong Kong virus and the sixth segment of PR8 virus as the genes for the respective neuraminidases. Three more genes have been identified by correlating migration patterns of RNAs with protein patterns of recombinant viruses on gradient polyacrylamide gels. The slowest-moving band (RNA 1) is the gene coding for the third largest influenza virus protein (P3). RNA segment 2 codes for the largest protein (Pl), and the P2 protein is coded for by RNA segment 3.     

The dorsal column system: I. Existence of long ascending postsynaptic fibres in the cat's fasciculus gracilis

Summary Microelectrode recordings were made from dorsal column fibres at the 12th thoracic segment in cats. Two kinds of activity were elicited by electric shocks applied on the sciatic nerve in the popliteal fossa: primary afferent activity and trans-synaptically evoked activity. The dorsal column postsynaptic (DCPS) fibres represented 9.3% of the total population of fibres studied in the fasciculus gracilis and 14.5% of those with receptors in the skin. They were found to lie between the primary fibres of cutaneous and those of deep origin. The fastest fibres of the alpha range contributed to their activation and it is likely that C fibres contributed as well. 87% of the DCPS fibres studied at Th 12 were antidromically activated from the first cervical segment, and their conduction velocities measured between cervical and thoracic levels ranged from 16 to 71 m/sec.     

Changes in Hemodynamics and Respiration in Rats with Different Resistance to Acute Hypoxia

Effects of acute hypoxia on hemodynamics and respiration were studied in acute experiments on narcotized rats. The animals were divided into groups characterized by high, low-, and medium- resistance to hypoxia by the time of respiration arrest during inhalation of gas mixture containing 3% O2. Hemodynamic parameters of highly resistant animals were higher than in low-resistant rats throughout the entire hypoxic period. The development of a rare (with prolonged inspiratory phase) respiratory rhythm in highly resistant rats is an adaptive reaction, which allows them longer tolerate hypoxia compared to low-resistant animals.     

Biology of simian virus 40 (SV40) transplantation antigen (TrAg) III. Involvement of SV40 gene A in the expression of TrAg in permissive cells.

Temperature-sensitive (ts) mutants of simian virus (SV40) which map in the early region of the SV40 genome were used to determine the role of the viral genome in the expression of SV40-specific transplantation rejection antigen (TrAg). The results indicated that tsA mutants (1612, 1637, 7, and 28) did not induce the expression of SV40-TrAg at the surface of infected permissive African green monkey kidney cells (TC-7) at 41° but did induce the expression of TrAg at the permissive temperature (33°) in TC-7 cells. Wild-type SV40 and late SV40 temperature-sensitive mutants (tsBC1602, tsBC1606, tsB8, and tsC219) induced SV40-TrAg in TC-7 cells at nonpermissive and permissive temperatures with equal efficiency. One of the mutants belonging to complementation group D (tsD1601) was defective in inducing SV40-TrAg at 41°. Kinetic studies indicated that SV40-TrAg appears by 18 hr after infection at 41° and 38 hr post-infection at 33°, paralleling closely the synthesis of T antigen. The synthesis of immunoreactive T antigen in TC-7 cells infected with tsA mutants at nonpermissive temperature did not correlate with the inability of tsA mutants to express TrAg at nonpermissive temperature. We conclude that the expression of TrAg in SV40-infected cells depends upon normal functioning of the A gene.     

Egg allergy, influenza vaccine, and immunoglobulin E antibody.

In a study of 70 patients with asthma, rhinitis, and eczema, those giving a definite history of allergic reactions to egg more frequently showed positive skin tests to egg extracts (p = less than 0.003), the wheal diameters of which were significantly larger (p = less than 0.01) than in patients with only a possible or no such history. Patients with a definite history of egg allergy had significantly higher levels of specific IgE antibody against egg yolk, egg white, and allantoic fluid than patients in the other two groups (p = less than 0.005). Seven patients, all of whom had given a definite history of allergy to egg, were found to have positive skin prick tests to influenza vaccine, at the concentration used in medical practice. Two of these patients had previously been given influenza vaccine and both had developed adverse reactions. Of the 22 patients giving a definite history of allergy to egg, the 7 (35 per cent) with positive skin tests to influenza vaccine had significantly larger skin tests and higher levels of specific IgE antibody to the egg extracts than the group as a whole (p = less than 0.001). Allergic reactions to influenza vaccine are likely to occur in patients who have a definite history of allergy to egg and large skin prick test reactions or high levels of specific IgE antibody to egg extracts. Those at risk can best be identified by skin prick testing with egg extracts and undiluted influenza vaccine.     

Analysis of thymic epithelial cell proliferation in vitro by combining bromodeoxyuridine and keratin labeling in an immunofluorescence assay

A simple method of analyzing thymic epithelial cell (TEC) proliferation has been developed by combining bromodeoxyuridine (BrDU) and keratin labeling in an immunofluorescence assay. The first reagent specifically visualizes the cells entering the S phase of the cell cycle, whereas the second immunostaining reveals which of the proliferating BrDU-positive cells actually belong to the epithelial lineage. This method, besides being rapid and free of radioactivity, appears to be reliable in view of the minor variations in the percentages of BrDU+ TEC observed in several distinct experiments. Thus, BrDU/keratin immunolabeling appears to represent a useful tool for the analysis of in vitro TEC proliferation.     

Purification and characterization of potyvirus helper component

Helper component (HC) was purified from tobacco vein mottling (TVMV)- and potato virus Y (PVY)- infected tobacco plants by sucrose gradient fractionation followed by affinity chromatography on oligo(dT)-cellulose and by gel electrophoresis. The subunit apparent molecular weights (M(r)) of the purified HCs were 53,000 (53K) and 58K for TVMV and PVY, respectively. Antisera to these purified polypeptides specifically blocked the activity of the homologous HC, as determined by aphid transmission assays, and specifically precipitated 75K products of the cell-free translation of the homologous RNA. The molecular weight of undissociated, biologically active TVMV or PVY HC, as determined by high-pressure liquid chromatography (HPLC)-gel permeation chromatography was found to be between 100K and 150K, suggesting that the active molecule is a dimer.     

Characterization of hepatitis B virus (Dane particle)

Hepatitis B virions (Dane particles) were purified from the sera of chronic HBsAg carriers by consecutive rate-zonal and isopycnic centrifugations in sucrose gradients using HBsAg, HBcAg and endogenous DNA polymerase activities as specific markers. Purified Dane particles, radiolabelled with Na ¹²⁵I by the chloramine-T procedure, had a higher buoyant density in CsCl (1.28 g/cm³) than unlabelled particles (1.26 g/cm³) and an estimated sedimentation coefficient of 280 s. ¹²⁵I-Dane particles were fully precipitated by anti-HBs and not by anti-HBc sera. Heavy and light density core particles were purified from heavy and light density populations of Dane particles and radioiodinated. The iodinated polypeptides of Dane particles and HBcAg were compared with those of the iodinated 22-nm form of HBsAg by SDS-PAGE. Iodinated Dane particles contained seven polypeptides with molecular weights of 18,000, 23,000, 26,000, 34,000, 43,000, 48,000 and 115,000. Heavy and light core particles contained three polypeptides with molecular weights of 18,000, 25,000 and 37,000.     

Systematic isolation of transducing phages for Myxococcus xanthus.

Six new phages active on Myxococcus xanthus have been isolated from cultures of myxobacteria. The six are all capable of transduction, and they fall into three groups. Members of one group have long contractile tails, have a characteristic neutralization antigen, and resemble the previously described M×4. Members of a second group, exemplified by M×8, have very short tails and a characteristic antigen. M×9, the sole member of the third group, has a very short tail and a characteristic antigen. Phage M×8, which is active on fruiting as well as nonfruiting strains of M. xanthus, can transduce auxotrophic, antibiotic resistance and motility markers in M. xanthus. Although crude lysates of M×8 contain 58-nm diameter particles with a tail and 29-nm particles without tail, only 58-nm particles can form plaques and transduce. The plaque-forming particles of M×8 possess a single DNA molecule of 56,000 base pairs with a buoyant density of 1.726 g/cm³, virtually identical to that of the DNA from its host.