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Biomedical subjects

J D Williamson

Publications and source records attributed to J D Williamson.

At least 19 recordsLinked to original sources
PubMed1992

Differential response of maize catalases to abscisic acid: Vp1 transcriptional activator is not required for abscisic acid-regulated Cat1 expression.

In this paper we describe the distinctive responses of the maize catalases to the plant growth regulator abscisic acid (ABA). We analyzed RNA and enzyme accumulation in excised maize embryos and found that each catalase responded differently to exogenously applied ABA. Levels of Cat1 transcript and enzyme activity rapidly increased. In contrast, levels of Cat2 transcript and protein decreased, while Cat3 transcript levels were not affected. In developing kernels of the ABA-deficient/biosynthetic viviparous mutant vp5, lower levels of Cat1 RNA correlated with lower endogenous ABA levels when compared to measured levels in comparably aged wild-type siblings from the same ear. The maize vp1 mutant line is morphologically insensitive to normal endogenous levels of ABA. Analysis of the response of Cat1 to exogenously applied ABA in mutant and wild-type vp1 sibling embryos suggests that, unlike other ABA-responsive genes analyzed to date, the Vp1 gene product is not essential for the ABA-mediated regulation of Cat1. The significance of these responses to ABA in defining the roles of the various CATs in maize is discussed.

Abscisic Acid↗
PubMed1992

Differential response of maize catalases and superoxide dismutases to the photoactivated fungal toxin cercosporin.

Many fungi of the genus Cercospora produce a light-induced, photoactivated polyketide toxin called cercosporin. In the presence of light an excited form (triplet state) of the toxin molecule is produced which, depending on the reducing potential of the environment, reacts with molecular oxygen to produce singlet oxygen and/or superoxide radicals. In this paper a system is presented for analysis of antioxidant defense gene response using purified cercosporin under conditions demonstrated to favor superoxide formation. Under the assay conditions employed, changes in total catalase activity, as well as individual isozyme protein levels generally mirrored the changes observed in corresponding steady-state RNA levels in response to applied cercosporin. In contrast, while transcript accumulation for most maize superoxide dismutases increased dramatically, both total superoxide dismutase activity and individual isozyme protein levels remained constant in all toxin treatments. In one case, the analyses indicated that there are two distinct transcripts that hybridize with a gene-specific probe for Sod3. These two transcripts responded differentially to applied toxin (levels of the larger transcript increased while the smaller decreased), whereas corresponding steady-state levels for the SOD-3 isozyme proteins remained constant. This suggests that protein turnover might play a role in the response of these SODs to activated oxygen species.

Catalase↗
PubMed1991

Dealing with extracontractual referrals.

OBJECTIVE: To describe the mechanism established by Richmond, Twickenham, and Roehampton Health Authority to manage extracontractual referral requests made on behalf of its resident population and to examine its working in the first three months of the new arrangements. DESIGN: Description of the procedures for managing extracontractual referrals and the decisions made on requests submitted to the district health authority between 1 April and 30 June 1991. RESULTS: 235 requests were submitted, 79 for emergency care. 156 requests were clearly for elective treatments and, of these, 61 were ultimately refused, 20 because the district health authority was not liable to pay. Of the remaining 41, 17 were appealed successfully and three unsuccessfullly. More than half of the elective extracontractual referrals correctly submitted were to either orthopaedics, general surgery, oral surgery, gynaecology, or plastic surgery. Overall, the district health authority approved three quarters of the requests for which it would be financially liable; this was the predicted workload for the period. CONCLUSIONS: The management of extracontractual referral requests is complex and time consuming for clinicians and managers alike. Patient choice is clearly being limited to some extent, but this is necessary if the number of requests is not to exceed the levels on which funding is based.

Budgets↗
PubMed1991

Photoregulation of the Cat2 and Cat3 catalase genes in pigmented and pigment-deficient maize: the circadian regulation of Cat3 is superimposed on its quasi-constitutive expression in maize leaves.

We have investigated the accumulation of Cat2 and Cat3 catalase transcripts in 6-7-day postimbibition leaves of normally pigmented and pigment-deficient maize seedlings under different light regimes. In seedlings of normal inbred maize lines Cat2 mRNA accumulates to significantly higher levels in either continuous light or a diurnal light/dark cycle than in continuous dark. In contrast to the high levels of the Cat2 message observed in their wild-type siblings, carotenoid-deficient mutants accumulate Cat2 mRNA at barely detectable levels. Mutants deficient in chlorophylls, but having normal carotenoid levels, accumulate normal levels of Cat2 mRNA. This suggests that both light and carotenoids are required for the normal accumulation of the Cat2 message. The steady-state level of Cat3 RNA exhibits a dramatic diurnal variation when seedlings are grown under a 24-hr light/dark cycle. We have previously shown that this variation is at the level of Cat3 gene transcription and is under the control of a novel circadian rhythm. In this study we show that both pigment-deficient mutants and their wild-type siblings exhibit the normal diurnal pattern of Cat3 RNA accumulation. This indicates that photosynthetic pigments, allelic variation, and genetic background do not directly affect the temporal pattern of Cat3 accumulation in leaves. We observed, however, that when normal plants are grown in either continuous light or continuous dark, the Cat3 transcript in leaves is present at uniformly high levels throughout the 24-hr sampling period.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Northern↗
PubMed1991

Effect of HIV-1 and cytomegalovirus in bronchoalveolar lavage cells on the transfer factor for lung carbon monoxide in AIDS patients.

Abnormalities in pulmonary function tests have been observed in AIDS patients with pulmonary disease. In this study, the polymerase chain reaction (PCR) was used to determine if the reductions in transfer factor for lung carbon monoxide (TLCO) were due to the presence of HIV-1 or cytomegalovirus (CMV). HIV-1 was detected in cells from bronchoalveolar lavage (BAL) in 35 out of 60 (58%) of patients. The detection of HIV-1 had no significant effect on pulmonary function. CMV was detected in the BAL of 58% of patients in this study but CMV was the sole viral pathogen in the lung of only two out of 60 (3.3%) individuals. A significant reduction in TLCO was observed in individuals with PCP where CMV was also detected in the BAL. This study shows that reduction in TLCO in HIV-seropositive patients is not due to the presence of HIV-1 or CMV alone in BAL cells.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Biological characterization of recombinant vaccinia viruses in mice infected by the respiratory route.

A murine model based on infection by the respiratory route has been used to study the pathogenesis of recombinant vaccinia viruses. The neurovirulent Western Reserve (WR) strain and the Wyeth smallpox vaccine strain were used as vectors. Recombinant viruses were constructed by insertion of the Epstein-Barr virus membrane glycoprotein 340 gene into the thymidine kinase (TK) gene of each vaccinia virus. Intranasal inoculation of DBA/2 mice with 10(6) pock-forming units (pk.f.u.) of the WR strain was lethal but mice survived similar infection with the WR recombinant virus. Each virus was recovered from lung, blood and brain but, unlike wild-type virus, the recombinant virus was subsequently cleared. No deaths occurred after similar infection with the Wyeth strain or the Wyeth recombinant virus. There was limited growth of the Wyeth strain in the respiratory tract, low levels of virus in the blood and only sporadic recovery in brain extracts. The Wyeth recombinant virus was cleared rapidly with little viraemia or detectable infection of the central nervous system. No phenotypic character determined in vitro could be related consistently to the virulence of wild-type and recombinant viruses. Although the lethal character of the WR strain was affected by its TK+ phenotype, mice survived infection by intranasal inoculation with 10(6) pk.f.u. of WR TK+ recombinant viruses which either expressed the human interleukin 2 gene or had a deficient vaccinia virus growth factor gene.

Animals↗
PubMed1990

Inflammatory responses and the generation of chemoattractant activity in cowpox virus-infected tissues.

Histological examination of the lesions produced on the chick chorioallantois infected with cowpox virus shows extensive haemorrhage but there are few inflammatory cells. However, infection with a deletion mutant, white cowpox virus, results in little haemorrhage but there is massive polymophonuclear cell infiltration. Extracts from tissues infected with the parental, red cowpox virus contained little or no chemoattractant activity detectable in micropore filter assays. However, white cowpox virus-infected tissue extracts, including cellular extracts from infected tissue cultures, had a marked effect in vitro on the migration of both neutrophils and monocytes. The chemoattractant activity induced in ovo by white cowpox virus infection has sedimentation characteristics in sucrose density gradients that are similar to leukotactic factors shown previously to be present in the allantoic fluid of chick embryos infected with paramyxoviruses. Induction of chemoattractant activity did not occur after infection of chick chorioallantois with a recombinant white cowpox virus constructed to express a protein that is responsible for the haemorrhagic character of red cowpox virus. This gene product has been shown previously to have homology with various serine protease inhibitors. The significance of these studies to the immunogenicity and pathogenicity of vaccinia recombinant viruses is discussed.

Allantois↗
PubMed1989

Comparison of antigen capture assays against HIV-1 in evaluating antiviral compounds.

Five antigen capture enzyme-linked immunosorbent assays (ELISAs) have been assessed for detecting HIV-1 in tissue culture supernatants of cell cultures used routinely to investigate antiviral activity. Although all the ELISAs are very sensitive to low levels of antigens they have different characteristics when used for titrating virus antigens.

Enzyme-Linked Immunosorbent Assay↗
PubMed1977

Healthward care.

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Allied Health Personnel↗
PubMed1977

Digoxin measurements in general practice.

1 As part of a prospective study on the use of digoxin in a general practice, plasma digoxin concentrations were measured in all patients receiving the drug. 2 A low mean plasma digoxin concentration was observed, suggesting a cautious approach to digitalization. 3 The correlation between plasma digoxin concentration and signs or symptoms commonly used in the assessment of digoxin effect was poor. 4 It was concluded that the measurement of plasma digoxin could be of assistance in a variety of clinical settings within a general practice.

Aged↗
PubMed1977

A conversion code from the RCGP to the ICHPPC classification system.

Faculty members from four family medicine training programs participated in the production of a definitive conversion of the Royal College of General Practitioners Classification of Diseases as modified for use with problem-oriented medical records (RCGP) to the International Classification of Health Problems for Primary Care (ICHPPC). The method used to produce the conversion and the several problems encountered are described. A detailed translation with the appropriate ICHPPC equivalent for each RCGP diagnostic title and code number is provided.

Disease↗
PubMed1976

The effect of canaline on some events in vaccinia virus replication.

Canaline, a pyridoxal phosphate antagonist, is shown to inhibit two distinct events in the replication of vaccinia virus in HeLa cells. Initial events proceed in the presence of the inhibitor leading to the formation of DNA-containing, cytoplasmic inclusions. However, further DNA synthesis is required for the subsequent production of infectious progeny following the reversal of canaline inhibition by pyridoxal phosphate. Inhibition of a separate, maturation event is shown by the delayed addition of canaline resulting in the failure to coat virus-specific DNA synthesized previously in the absence of the inhibitor. Thus, the replication of vaccinia virus is sensitive to inhibition by canaline at an early and a late stage in the replication cycle. Reversal is accomplished alternatively by the addition of 'non-essential' amino acids suggesting that the effects of canaline result from inhibition of specific protein functions.

Amino Acids↗