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Biomedical subjects

J D Williamson

Publications and source records attributed to J D Williamson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Plant antioxidant gene responses to fungal pathogens.

Antioxidant defense systems are a prominent element in plant responses to environmental stress. Activated oxygen species have themselves been implicated as both a part of the plant's defense against pathogen attack as well as the phytotoxic component of photosensitizing fungal toxins. Molecular analyses are just beginning to define how plant oxidant and antioxidant genes might integrate with other defense responses to provide effective protection against pathogen attack.

Antioxidants↗
PubMed1993

The epidemiology of HIV-1 infection of the lung in AIDS patients.

OBJECTIVE: To examine the relationship between HIV-1 infection of cells obtained by bronchoalveolar lavage (BAL) from the lung and the pathogenesis of AIDS. DESIGN: Prospective study of 121 consecutive HIV-1-seropositive patients undergoing investigation for respiratory symptoms or abnormal chest radiograph. METHODS: Polymerase chain reaction (PCR) for the detection of HIV-1-specific proviral DNA. Cocultivation of leukocytes obtained from BAL with donor cord blood leukocytes (CBL) to isolate HIV-1. RESULTS: HIV-1 was detected by PCR in the lung cells of 78 out of 121 (65%) patients. It was detected in 55% of patients who had been seropositive for less than 1 year, but in over 80% of patients who had been seropositive for more than 3 years. HIV-1 was isolated from 61 out of 106 (58%) individuals. The ability to detect or isolate HIV-1 from the lung correlated directly to CD4 cell count in peripheral blood. HIV-1 was detected significantly more frequently in the BAL cells of smokers compared with non-smokers (P = 0.01). CONCLUSIONS: HIV-1 was frequently detected and isolated from the lung of AIDS patients undergoing a respiratory episode. HIV-1 infection of the lung became more frequent with time from serodiagnosis. Patients who smoked were more likely to succumb to HIV-1 infiltration into the lung and HIV-1 infection of the lung was associated with progression to death.

Adult↗
PubMed1993

Relation of HIV-I in bronchoalveolar lavage cells to abnormalities of lung function and to the presence of Pneumocystis pneumonia in HIV-I seropositive patients.

BACKGROUND: HIV is present in bronchoalveolar lavage cells of some but not all HIV seropositive patients. Abnormalities of lung function have been described in such patients in the absence of clinically overt pneumonia or other respiratory infections. It is possible that the presence of HIV in alveolar macrophages could account for these abnormalities. It is also possible that the presence of HIV in alveolar macrophages contributes to immunosuppression and an increased incidence of opportunistic infections. METHODS: This was a prospective study of 157 HIV seropositive patients requiring diagnostic bronchoscopy for investigation of new respiratory symptoms, chest radiograph abnormality, or pneumonic illness. Presence of HIV in bronchoalveolar lavage cells obtained at diagnostic bronchoscopy was determined by polymerase chain reaction to detect proviral DNA and in vitro cocultivation to detect productive virus infection. With these two techniques the presence or absence of HIV in bronchoalveolar lavage was compared with the presence of abnormalities of lung function or presence of Pneumocystis pneumonia. RESULTS: HIV was detected in bronchoalveolar lavage cells in 65% of patients by means of the polymerase chain reaction and 59% with cocultivation. With both methods of detection there was no association between the presence or absence of HIV and the presence of Pneumocystis pneumonia; nor was there a relation between the presence of HIV and abnormalities of lung function. CONCLUSION: The presence of HIV in bronchoalveolar lavage cells does not predispose to an increased incidence of Pneumocystis pneumonia; nor does it contribute to abnormalities of lung function.

Bronchoalveolar Lavage Fluid↗
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↗
PubMed1989

Differential Accumulation of a Transcript Driven by the CaMV 35S Promoter in Transgenic Tobacco.

A transcriptional fusion composed of the CaMV 35S promoter, a 19 kD zein cDNA, and the 3' flanking regions from the 0' to 1' T(R) T-DNA genes was introduced into tobacco (Nicotiana tabacum) by Agrobacterium-mediated transformation. The accumulation of RNA generated from this transcriptional fusion varied both temporally and spatially in all tissues examined in greenhouse-grown tobacco plants, suggesting that the CaMV 35S promoter is not constitutive. Younger, actively dividing leaf, stem, root, and flower tissues contained higher steady state levels of zein RNA than did older, more quiescent tissues. Zein RNA levels greatly decreased during seed development and were undetectable in the mature seed. In addition, the two RNA termination or processing signals present in our construct were differentially utilized during seed development.

Journal Article↗
PubMed1988

ABA-Regulation of Two Classes of Embryo-Specific Sequences in Mature Wheat Embryos.

We have previously described the isolation and characterization of ABA-enhanced sequences from developing wheat embryos. Here we use in vivo RNA labeling and the inhibitors alpha-amanitin and cycloheximide to determine the level at which ABA acts to modulate these sequences in cultured mature embryos. Sequences fell into two classes: one, represented by the 7S globulin clone, p511, appears to be regulated at the level of transcription, while the other, represented by the early methionine-labeled polypeptide (E(m))-protein clone, p1015, has an additional posttranscriptional component. In mature embryos cultured in the absence of ABA, mRNA levels of p511 and p1015 declined rapidly until neither was detected at 3 days postimbibition. Levels of p511 increased in mature embryos cultured in the presence of ABA, but remained low in the presence of ABA + alpha-amanitin, suggesting p511 RNA is regulated at the level of transcription. Levels of p1015, in contrast, remained high not only in the presence of ABA, but also in the presence of ABA + alpha-amanitin or alpha-amanitin alone. This suggests p1015 regulation might be at the level of selective RNA stability. Cycloheximide had no detectable effect on ABA-mediated stabilization of p1015, suggesting that newly synthesized proteins are not involved. E(m)-protein synthesis rates closely paralleled E(m) RNA levels, suggesting E(m) expression is not controlled at the level of translation.

Journal Article↗
PubMed1988

The synthesis of a 19 kilodalton zein protein in transgenic petunia plants.

Transcriptional fusions composed of a 19 kilodalton zein cDNA, the 5' flanking region from a beta-phaseolin gene, and 3' flanking regions from either the phaseolin or a 15-kilodalton zein gene were introduced into Petunia by Agrobacterium-mediated transformation. The expression of both zein mRNA and protein in these transgenic plants was seed-specific and developmentally regulated. Both monocot (zein) and dicot (phaseolin) polyadenylation consensus sequences were recognized in Petunia. Analysis by immunoblotting showed that the M(r) of the zein protein corresponded to that of the mature protein, suggesting that recognition and cleavage of the signal sequence had occurred. While zein mRNA accumulated to approximately 1% of the total poly(A)(+) RNA in seeds of the transformed plants, zein protein was present at a much lower concentration than expected, at most being 0.005% of the total seed protein. These results suggest that the 19 kilodalton zein gene, in addition to lacking specific sequences required for efficient transcription in dicots, might also lack sequences required for the efficient synthesis, targeting, transport, or stabilization of the protein.

Journal Article↗
PubMed1985

Em polypeptide and its messenger RNA levels are modulated by abscisic acid during embryogenesis in wheat.

The effect of abscisic acid (ABA) on the expression of the 'early-methionine-labeled' (Em) polypeptide was examined in cultured, immature wheat (Triticum aestivum, L.) embryos and in developing embryos in planta. A complementary DNA (cDNA) library was constructed from poly(A)-rich RNA from immature embryos cultured in the presence of ABA. ABA-enhanced sequences were first identified by differential colony-blot hybridization, and then verified using RNA slot-blot analysis. Dot-blot hybridization showed that one clone, p1015, was homologous to the previously isolated Em cDNA, pWG432. Electrophoretic analysis of the hybrid-select translation product of p1015 confirmed its identity as an Em sequence. Comparison of the p1015 cDNA insert size and the Em message size, from northern blot analysis, showed that p1015 contained about 87% of the Em sequence. RNA slot-blot analysis and protein electrophoresis showed that Em message, but not Em protein, accumulated at a low, basal level in immature embryos in the absence of ABA. Neither Em message nor Em protein was seen in three-day germinated seedlings. Steady-state levels of Em message and protein increased in immature embryos in the presence of ABA, both in culture and in planta. Regulation appeared to be primarily at the level of transcription or specific message stability. Regulation may also involve specific protein stability, since synthesis of Em protein continued in immature embryos in the absence of ABA, but Em protein did not accumulate in detectable amounts. We conclude that ABA specifically modulates Em message and protein levels in immature embryos, but is probably not responsible for the embryogenic specificity of Em expression.

Abscisic Acid↗