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D M Lambert

Publications and source records attributed to D M Lambert.

At least 91 records · Page 5Linked to original sources

The sensitive period for yellow phenocopy induction in Drosophila melanogaster.

Yellow phenocopies of Drosophila melanogaster were produced by raising larvae on alpha-DMT contaminated media. Using a survivorship test, the sensitive period for phenocopy induction was found to occur during the third larval instar of development, with increased survivorship at 1% alpha-DMT compared with lower concentrations. It was also found that treatment with alpha-DMT significantly slowed development. These findings are related to the relevant morphological and behavioral developmental pathways and to phenocopy induction.

Age Factors↗

Role of oligosaccharides in the structure and function of respiratory syncytial virus glycoproteins.

The contribution of oligosaccharides to the structural and functional make-up of respiratory syncytial (RS) virus G and F proteins was investigated by observing the effects of various oligosaccharide-specific enzymes on their molecular size as well as on virus infectivity. The N-linked oligosaccharides of the F protein were completely removed by endoglycosidase F and N-glycanase. Addition of oligosaccharides to F protein during synthesis was completely inhibited by the drug tunicamycin (TM), an inhibitor of N-linked glycosylation. Glycosylation of the G protein was partially resistant to TM resulting in an 80-kDa form designated GTM. The G protein was estimated to contain approximately 3% N-linked and 55% O-linked carbohydrates, based on migration of G and GTM in polyacrylamide gels. Furthermore, treatment of detergent-extracted G protein with endoglycosidase F and endo-alpha-N-acetylgalactosaminidase, enzymes that specifically cleave N-linked and O-linked oligosaccharides, respectively, generated a variety of partially unglycosylated species, ranging in molecular weight from approximately 80 to 40 kDa. Virus infectivity was sensitive to limited removal of N-linked or O-linked oligosaccharides by endoglycosidases under conditions which did not greatly alter the molecular weight of the G protein. Thus, G and F protein oligosaccharides readily accessible to enzymatic removal are presumed to play an important role in the infectious process.

Capsid↗

Kinetics of synthesis and phosphorylation of respiratory syncytial virus polypeptides.

The kinetics of synthesis of [35S]methionine-labelled respiratory syncytial virus-specific proteins were studied in CV-1 cells infected at high multiplicity. Immunoprecipitated viral proteins resolved by SDS-PAGE were quantified by scanning fluorographs of protein bands. The nucleocapsid (N) protein was detectable by 2 h post-infection (p.i.), whereas the phospho- (P), matrix (M) and fusion (Fo) proteins and Vp24 (a matrix-like protein) were first detected between 4 and 6 h p.i. Synthesis of the glyco- (G) protein was first detected at 6 h p.i. and reached its peak synthesis rate at 10 h p.i. Virus-specific P, M and Vp24 proteins were phosphorylated in infected cells. The P protein was highly phosphorylated in purified virions whereas phosphorylated species of the M and Vp24 proteins were minor components. The phosphorylated form of the P protein was detected by monoclonal antibody precipitation, confirming the identity of this protein. The N protein was not phosphorylated in infected cells or in virions. Synthesis of [35S]methionine-labelled proteins preceded detectable 32Pi labelling by several hours. The putative phosphorylated M protein was detected at 6 h p.i. before phosphorylated forms of P and Vp24 were seen. The timing of appearance of the phosphorylated species of P and Vp24 proteins in infected cells corresponded to the release of infectious virions from infected cell monolayers at 10 to 12 h p.i.

Animals↗

Molecular cloning and sequence analysis of the human parainfluenza 3 virus gene encoding the matrix protein.

The sequence of the matrix (M) protein gene and contiguous intergenic regions of the human parainfluenza 3 virus (PF3) was determined by molecular cloning. The encoded M protein contains 354 amino acids and has a predicted mol wt of 39,506. The M protein amino acid sequence was compared to the homologous proteins from other members of the Paramyxoviridae family. The PF3 protein shared 61% homology with the Sendai virus protein and approximately 35% homology with measles and canine distemper virus proteins. Little homology was observed with respiratory syncytial virus. The M protein appears to be the most highly conserved among the Paramyxoviridae proteins.

Amino Acid Sequence↗

Immediate persistent infection by human parainfluenza virus 3: unique fusion properties of the persistently infected cells.

We describe here a persistently infected cell system with unique properties. Cells infected with human parainfluenza virus type 3 (PF3) at high multiplicities of infection showed little or no cytopathic effects (cell fusion). Unlike other paramyxovirus persistent infections that require a long development time, the majority of the cells survived the initial infection and formed persistently infected cell cultures that were immediately available for study. In addition, unlike other paramyxovirus persistent infections, the PF3 system described here produced high levels of infectious virus and did not undergo periodic crises. Although cells persistently infected with PF3 contained large amounts of the cleaved, active form of the viral fusion protein, F1, the persistently infected cells did not fuse with each other. However, they did fuse with uninfected cells within minutes of cell-to-cell contact. Other persistent paramyxovirus infections do not have this property. Fusion occurred with all cells tested, including red blood cells, and was not dependent on protein synthesis. The unique fusion properties of these PF3 persistently infected cells make this an interesting system for the study of mechanisms of viral fusion and mechanisms of inhibition of viral fusion.

Animals↗

Molecular cloning and sequence analysis of the human parainfluenza 3 virus RNA encoding the nucleocapsid protein.

The sequence of 1690 nucleotides from the 5' end of the viral complementary RNA for the human parainfluenza 3 virus was determined by molecular cloning. One large open reading frame consisting of 1548 nucleotides was demonstrated. The encoded protein, the nucleocapsid protein (NP), consists of 515 amino acids, and has a predicted molecular weight of 57,819. A noncoding 5' sequence of 51 nucleotides is present at the end of the NP-mRNA. Two consensus sequences were identified which are homologous with sequences found in Sendai virus. One of these sequences, AGGATTAAAG, was located at the 5' end of the nucleocapsid mRNA and may function in transcription initiation. The other consensus sequence, GTAAGGGAA, was found in the viral genomic leader sequence. The nucleocapsid protein amino acid sequence was compared to other members of the Paramyxoviridae family. The parainfluenza 3 virus protein nucleocapsid amino acid sequence demonstrated a high degree of homology with the Sendai virus nucleocapsid protein. Seventy percent of the first 387 amino acids from the amino termini were identical. Little homology was observed in the distal carboxy termini.

Amino Acid Sequence↗

Molecular cloning and sequence analysis of the human parainfluenza 3 virus mRNA encoding the P and C proteins.

The sequence of the mRNA encoding the phosphoprotein (P protein) of the human parainfluenza virus 3 (PF3) was determined by molecular cloning. In other Parmyxoviridae the P protein mRNA is functionally bicistronic and encodes an additional smaller nonstructural protein termed C. In this report three open reading frames (ORF) are described. These consist of a single long ORF encoding the P protein, and two shorter ORFs encoding the structural Vp18 protein (analogous to the Sendai C protein) and a putative polypeptide termed D protein. The encoded phosphoprotein consists of 603 amino acids and has a predicted molecular weight of 67,683. The C protein consists of 199 amino acids and has a predicted molecular weight of 23,288. The D protein consists of 140 amino acids and has a predicted molecular weight of 16,270. Although the D protein has not yet been demonstrated in vivo its synthesis could be demonstrated in vitro using a rabbit reticulocyte lysate system. Thus it appears that unlike the other paramyxoviruses, the PF3 P protein mRNA may be functionally tricistronic.

Amino Acid Sequence↗

A simple method for increased recovery of purified paramyxovirus virions.

A simple method involving vigorous agitation of infected cell monolayers prior to collection of culture medium is described to greatly increase the recovery of purified virions of measles virus, respiratory syncytial virus and human parainfluenza virus. Vigorous agitation of the flasks containing monolayers of infected cells increased the recovery of purified virions by at least 3- to 10-fold as judged by the intensity of [35S]methionine labeled viral proteins on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). These protein profiles also indicated that these virions were as clean as those purified from gently collected medium. Analysis of titers of infectious virus recovered from medium of agitated and non-agitated flasks showed similar increases. These results suggest that the cell associated nature of these viruses may be at least partly due to either partially budded virions or mature virions sticking to the cell membrane, since these both might be expected to be freed from the cell by mechanical shearing.

Animals↗

Human parainfluenza virus 3: purification and characterization of subviral components, viral proteins and viral RNA.

A simple method was established that allowed large quantities of human parainfluenza 3 (PF3) virions to be isolated from tissue culture cells. The purity of the virus was sufficient for biochemical analysis of virion proteins. The density of PF3 virions was 1.18-1.20. Purified virions contained seven viral proteins with estimated molecular weights of: L, 180 000; P, 83 000; HN, 69 000; NP, 66 000; F0, 60 000; F1, 51 000; and M, 38 000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. There were three phosphoproteins, P, NP and M, and two glycoproteins, HN and F (includes F0 and F1). F1.2, the activated, cleaved, fusion glycoprotein (60 000 Da), consisting of two disulfide-linked subunits, F1 and F2, was seen only under nonreducing conditions. Because of its small size (approximately 9000 Da) F2 could be seen only on gels with high acrylamide concentrations. As in other enveloped viruses, cellular actin (43 000 Da) was present in purified virions. Several minor bands migrating between NP and M represented breakdown products of NP. Solubilization of the virion membrane in low salt buffer with non-ionic detergent resulted in the loss of HN and F. In high salt buffer, the M protein was also removed. Nucleocapsids isolated by CsCl centrifugation contained L, P, NP and small amounts of M. Nucleocapsids isolated in the presence of the ionic detergent, sarcosyl, contained only the NP protein. The density of nucleocapsids was 1.29-1.30. Genomic 50S RNA isolated from nucleocapsids had an estimated molecular weight of 5 X 10(6).

Animals↗

Intracellular synthesis of human parainfluenza type 3 virus-specified polypeptides.

The intracellular synthesis of human parainfluenza type 3 virus-specified polypeptides was examined by polyacrylamide gel electrophoresis of [35S]methionine-labeled cell extracts under reducing conditions. All of the virion structural proteins were detected in cell extracts, including: L, 180,000 molecular weight (180K); P, 83K; HN, 69K; NP, 66K; F0, 60K; F1, 51K; and M, 38K. P and NP were phosphorylated. HN and F were glycosylated. The kinetics of intracellular viral protein synthesis did not detect any early or late proteins. Pulse-chase experiments failed to detect any precursor-product relationships. No nonstructural proteins were detected.

Cell Line↗

Respiratory syncytial virus glycoproteins.

The proteins of respiratory syncytial (RS) virus were analyzed by SDS-polyacrylamide gel electrophoresis. Eight virion structural proteins with molecular weights of 180,000, 89,000, 48,000, 42,000, 34,000, 28,000, 25,000, and 21,000 were identified. These proteins were given tentative designations of L (180,000), G (89,000), F1 (48,000), NP (42,000), P (34,000), M (28,000), Vp25 (25,000), and F2 (21,000). The 89,000-, 48,000-, and 21,000-dalton polypeptides were glycosylated and could be purified on lentil-lectin sepharose columns. All three glycoproteins could be immunoprecipitated from extracts of infected cells but not from uninfected cells, suggesting that they are viral specified. The host cell affected the apparent molecular weights of the largest and smallest glycosylated polypeptides possibly by differences in glycosylation. The 48,000- and 21,000-dalton glycopolypeptides were disulfide linked subunits of a 68,000-dalton glycoprotein that was seen on unreduced gels. The 68,000-dalton glycoprotein was thus similar to the fusion (F) protein of paramyxoviruses. Treatment of infected cultures with tunicamycin, a drug that blocks glycosylation, inhibited syncytial formation and resulted in over a 1000-fold reduction of extracellular infectious virus. Virions purified from tunicamycin-treated cells had reduced amounts of all three glycosylated proteins. No new forms of these proteins were conclusively identified, suggesting that unglycosylated forms of RS glycoproteins were not incorporated into virion membranes.

Chromatography, Affinity↗

Improvement of respiratory syncytial virus replication in actively growing HEp-2 cells.

The growth of respiratory syncytial (RS) and parainfluenza type III (PI3) viruses has been studied in actively growing versus relatively stationary HEp-2 cells. There was no effect on PI3 virus growth. RS virus synthesis was stimulated from 20- to 60-fold by growth in actively growing cultures when the cell density was approximately 1/3 that of a confluent culture. This stimulation was manifested by a greater yield of virus per cell, more virus-specific mRNA produced per cell, and a 50% decrease in the time before cytopathic changes appeared.

Cell Count↗

Nucleic acids of respiratory syncytial virus.

Analysis of purified respiratory syncytial virus revealed that the virion RNA was composed of 50S, 28S, 18S, and 4S species. The 18S and 28S species were presumed to represent host rRNA since virus grown in actinomycin D-treated cells contained only 50S and 4S RNAs. Actinomycin D treatment stimulated production of infectious respiratory syncytial virus 5- to 10-fold. The 50S virion RNA was shown to hybridize with polyadenylated mRNA's isolated from infected cells, indicating that respiratory syncytial virus RNA is of negative-strand sense. Six mRNA's were identified by polyacrylamide gel electrophoresis.

Cell Line↗

Protection from morbidity and mortality from first infarcts: the case for beta-blockade.

The original concept of alpha and beta sympathetic receptors put forward by Alquist in 1948 suggesting that beta receptors were situated mainly in the heart and alpha receptors peripherally, gave rise to the theory that selective blockade of beta receptors might have the effect of relieving the heart from excessive sympathetic stimulation. This possibility was developed by Black and Stephenson with the birth of the first beta-blocking drugs--pronethalol and propranolol. The importance of such a drug was foreseen by Chamberlain who showed subsequently that propranolol and cervical sympathectomy reduced an exercise tachycardia to the same extent. Pronethalol was not developed for clinical use and propranolol was in any event found to be the more active drug with no demonstrable hazards. Propranolol was marketed for clinical use as 'Inderal' by the Pharmaceuticals Division of Imperial Chemical Industries, UK, where this original work had been done.

Aged↗