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Biomedical subjects

G Whittaker

Publications and source records attributed to G Whittaker.

14 recordsLinked to original sources
PubMed2006

Quantitative analysis of residual protein contamination on reprocessed surgical instruments.

'Ready-for-use' instruments from surgical instrument trays were examined after routine cleaning and sterilization in a blinded study. These reprocessed instruments originated from five National Health Service hospital trust sterile service departments in England and Wales. Determination of residual protein and peptide contamination was carried out by acid stripping of the instrument surfaces, hydrolysis of the constituent amino acids and quantitative total amino acid analysis. One hundred and twenty instruments were analysed, and the median levels of residual protein contamination per instrument for the individual trays were 267, 260, 163, 456 and 756 microg. Scanning electron microscopy and energy dispersive X-ray spectroscopic analyses of the instruments showed that tissue deposits were localized on surfaces, but there was no significant correlation between overall protein soiling and instrument complexity. The highest levels of residual contamination were found on instruments used for tonsillectomy and adenoid surgery.

Amino Acids↗
PubMed2001

A phenoxyl radical complex of copper(II).

A new N,O-bidentate pro-ligand (HL), [ML2] (M = Cu, Zn) and [CuL2][BF4] have been synthesised; [CuL2].4DMF and [CuL2][BF4].2CH2Cl2 have been crystallographically and spectroscopically characterised; these data indicate that [CuL2]+ cations are constituted as [Cu2+(L.)(L-)]+ and involve the phenoxyl radical L..

Journal Article↗
PubMed1999

1918 and all that

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Journal Article↗
PubMed1996

The role of nuclear import and export in influenza virus infection.

Infection with influenza virus involves a complex series of nuclear import and export events. Early in infection, incoming viral ribonucleoproteins (vRNPs) are imported into the nucleus. Later, viral transcripts are exported from the nucleus, newly synthesized structural proteins are transported back into the nucleus and, finally, newly assembled vRNPs are exported. All these import and export steps, and, in particular, the bidirectional traffic of vRNPs rely on the transport machinery of the cell, but are regulated both by viral and cellular factors. The viral MI protein serves as the master organizer in determining the directionality of vRNP transport.

Journal Article↗
PubMed1996

Effect of M1 protein and low pH on nuclear transport of influenza virus ribonucleoproteins.

Influenza virus enters its host cell by receptor-mediated endocytosis followed by acid-activated membrane fusion in endosomes. The viral ribonucleoprotein particles (vRNPs) delivered into the cytosol then dissociate from the matrix protein, M1, and from each other, after which they are individually imported into the nucleus via the nuclear pores. For some time, it has been believed that the low pH in endosomes may, in some way, trigger the capsid disassembly events necessary for nuclear transport. This report provides direct evidence that the association of M1 with vRNPs is sensitive to mildly acidic pH within the infected cell. Recombinant M1, expressed in cultured cells, was found to associate with vRNPs and inhibit their nuclear import. Brief acidification of the cytosolic compartment eliminated the interfering activity and allowed the incoming vRNPs to enter the nucleus. Newly assembled progeny M1-vRNP complexes in the cytosol of infected cells were also dissociated by brief acidification. Acidic pH was thus found to serve as a switch that allowed M1 to carry out its multiple functions in the uncoating, nuclear transport, and assembly of vRNPs.

Animals↗
PubMed1996

Nuclear trafficking of influenza virus ribonuleoproteins in heterokaryons.

The influenza virus nucleoprotein (NP), matrix protein (M1), and ribonucleoproteins (vRNPs) undergo regulated nuclear import and export during infection. Their trafficking was analyzed by using interspecies heterokaryons containing nuclei from infected and uninfected cells. Under normal conditions, it was demonstrated that the vRNPs which were assembled in the nucleus and transported to the cytosol were prevented from reimport into the nucleus. To be import competent, they must first assemble into virions and enter by the endosomal entry pathway. In influenza virus mutant ts51, in which M1 is defective, direct reimport took place but was inhibited by heterologous expression of wild-type M1. These data confirm M1's role as the inhibitor of premature nuclear import and as the main regulator of nuclear transport of vRNPs. In addition to this vRNP shuttling, M1 also shuttled between the nucleus and the cytoplasm in ts51-infected cells. When NP was expressed in the absence of virus infection, it was also found to be a shuttling protein.

Animals↗
PubMed1995

Hyperphosphorylation of mutant influenza virus matrix protein, M1, causes its retention in the nucleus.

The matrix (M1) protein of influenza virus is a major structural component, involved in regulation of viral ribonucleoprotein transport into and out of the nucleus. Early in infection, M1 is distributed in the nucleus, whereas later, it is localized predominantly in the cytoplasm. Using immunofluorescence microscopy and the influenza virus mutant ts51, we found that at the nonpermissive temperature M1 was retained in the nucleus, even at late times after infection. In contrast, the viral nucleoprotein (NP), after a temporary retention in the nucleus, was distributed in the cytoplasm. Therefore, mutant M1 supported the release of the viral ribonucleoproteins from the nucleus, but not the formation of infectious virions. The point mutation in the ts51 M1 gene was predicted to encode an additional phosphorylation site. We observed a substantial increase in the incorporation of 32Pi into M1 at the nonpermissive temperature. The critical role of this phosphorylation site was demonstrated by using H89, a protein kinase inhibitor; it inhibited the expression of the mutant phenotype, as judged by M1 distribution in the cell. Immunofluorescence analysis of ts51-infected cells after treatment with H89 showed a wild-type phenotype. In summary, the data indicated that the ts51 M1 protein was hyperphosphorylated at the nonpermissive temperature and that this phosphorylation was responsible for its aberrant nuclear retention.

Amino Acid Sequence↗
PubMed1994

Nuclear import of microinjected influenza virus ribonucleoproteins.

Influenza virus ribonucleoproteins (vRNPs) devoid of the matrix protein (M1) were isolated and introduced into the cytoplasm of CHO and MDCK cells by microinjection. The injected vRNPs were found to be imported into the nucleus, and the RNA was transcribed. Their uptake into the nucleus was ATP-dependent, inhibited by antibodies to the nuclear pore complex, unaffected by the prior acidification of the vRNPs, and not inhibited by amantadine. The results showed that for productive infection, all the early stages of the viral entry pathway (receptor interaction, endocytosis, acid exposure, and membrane fusion) can be bypassed. Once the vRNPs are stripped of M1 and separated from each other, they are competent for import into the nucleus by constitutive cellular processes. Second, the results showed that while the amantadine block for incoming virus is manifested at the level of nuclear entry of the vRNPs, the actual import event per se is not affected. The results are consistent with a recent hypothesis that amantadine inhibits a step needed to prime the core for uncoating, which takes place before the virus has reached the cytosol.

Amantadine↗
PubMed1989

Kinetics of rapid 45Ca uptake into chick skeleton in vivo: effects of microwave fixation.

We have investigated uptake kinetics for 45Ca labels acutely administered as single intravenous injections into twelve-day-old chicks in vivo. Effects of microwave fixation on this process have also been studied. Rapid uptake of 45Ca was demonstrated into the skeleton with approximately 40% of injected label being found in the skeleton within the first 15 min. By 45 min tissue 45Ca levels had stabilized and showed little change during the following 90 min. Soft tissue isotope levels declined during the period from 3 to 135 min following injection. These data were obtained from animals in which tissue isotope levels were stabilized by fixation with microwaves at the point of killing by cervical dislocation. In animals where the microwave fixation step was omitted and tissues were dissected for counting at least 1 h after killing, 45Ca levels in both skeletal and soft tissues were 15-20% higher than in those from microwave groups during the period 3-15 min after injection. In a separate experiment, groups of chicks killed by cervical dislocation 3 min after isotope injection were fixed with microwaves at time intervals ranging from 0 to 45 min post-mortem. Isotope levels in femur increased with time and were significantly higher in groups in which fixation was carried out 12 and 45 min after death when compared with those fixed at the point of death. Data in calvarium reflected those in femur but were not statistically significant at the time intervals tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗