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Biomedical subjects

J A Morgan

Publications and source records attributed to J A Morgan.

At least 19 recordsLinked to original sources
PubMed1999

Inhibitor studies of tabersonine metabolism in C. roseus hairy roots.

The conversion of tabersonine to lochnericine and hörhammericine was investigated in C. roseus hairy root cultures. The accumulation of lochnericine and hörhammericine, like tabersonine, was associated with growth. Through the use of oxygenase inhibitors, 1-aminobenzotriazole (ABT), clotrimazole (CLOT), and 2.5-pyridinedicarboxylic acid (PCA), details of the metabolic pathway around tabersonine in hairy roots of C. roseus were elucidated. ABT specifically inhibited the formation of hörhammericine, while CLOT inhibited the accumulation of lochnericine. Using jasmonic acid in combination with the inhibitors suggests an inducible P-450 enzyme responsible for the formation of hörhammericine. The inhibitor study also revealed that both lochnericine and hörhammericine are 'turned over' in hairy root cultures.

Alkaloids↗
PubMed1999

Comparison of flagellin genes from clinical and environmental Pseudomonas aeruginosa isolates.

Pseudomonas aeruginosa, an important opportunistic pathogen, was isolated from environmental samples and compared to clinically derived strains. While P. aeruginosa was isolated readily from an experimental mushroom-growing unit, it was found only rarely in other environmental samples. A flagellin gene PCR-restriction fragment length polymorphism analysis of the isolates revealed that environmental and clinical P. aeruginosa strains are not readily distinguishable. The variation in the central regions of the flagellin genes of seven of the isolates was investigated further. The strains used included two strains with type a genes (998 bp), four strains with type b genes (1,258 bp), and one strain, K979, with a novel flagellin gene (2,199 bp). The route by which flagellin gene variation has occurred in P. aeruginosa is discussed.

Agaricales↗
PubMed1998

Transient studies of light-adapted cultures of hairy roots of Catharanthus roseus: growth and indole alkaloid accumulation.

Cultures of C. roseus transgenic ("hairy") root clones LBE-6-1 and LBE-4-2 were adapted with periodic daily illumination to investigate the effect of light on growth and nutrient utilization, and the accumulation of the indole alkaloids. Light-adapted roots appeared green and had radially thickened morphology compared with dark-grown controls. Their growth rates were higher than dark-grown controls, with 45% lower doubling times: LBE-6-1, 3.6 days; LBE-4-2, 2.8 days. Relative to dark-grown controls, light-adapted growth increased the biomass (DW) of LBE-6-1 by 25%, but had no effect on the DW of LBE-4-2. The macronutrients NH4+, NO3-, Pi, and sugars, were depleted completely by light-adapted root cultures in that order. The specific and total levels of the indole alkaloid serpentine was enhanced and of tabersonine was lowered in both root clones, while the overall trends of growth and non-growth association of tabersonine and serpentine, respectively, remained unaltered by light adaptation. Ajmalicine accumulation was enhanced in LBE-6-1, but lowered in LBE-4-2; its accumulation was growth-associated in dark-grown LBE-6-1, but appeared non-growth associated in light-adapted cultures. The accumulation of tabersonine-related compounds, lochnericine, and hörhammericine exhibited growth-associated trends, and were either negatively affected or unaffected by light adaptation of LBE-6-1. Neither vindoline nor its precursor, deacetylvindoline, was detected.

Adaptation, Physiological↗
PubMed1998

Trematode and monogenean rRNA ITS2 secondary structures support a four-domain model.

The secondary structure of rRNA internal transcribed spacer 2 is important in the process of ribosomal biogenesis. Trematode ITS sequences are poorly conserved and difficult to align for phylogenetic comparisons above a family level. If a conserved secondary structure can be identified, it can be used to guide primary sequence alignments. ITS2 sequences from 39 species were compared. These species span four orders of trematodes (Echinostomiformes, Plagiorchiformes, Strigeiformes, and Paramphistomiformes) and one monogenean (Gyrodactyliformes). The sequences vary in length from 251 to 431 bases, with an average GC content of 48%. The monogenean sequence could not be aligned with confidence to the trematodes. Above the family level trematode sequences were alignable from the 5' end for 139 bases. Secondary structure foldings predicted a four-domain model. Three folding patterns were required for the apex of domain B. The folding pattern of domains C and D varies for each family. The structures display a high GC content within stems. Bases A and U are favored in unpaired regions and variable sites cluster. This produces a mosaic of conserved and variable regions with a structural conformation resistant to change. Two conserved strings were identified, one in domain B and the other in domain C. The first site can be aligned to a processing site identified in yeast and rat. The second site has been found in plants, and structural location appears to be important. A phylogenetic tree of the trematode sequences, aligned with the aid of secondary structures, distinguishes the four recognized orders.

Animals↗
PubMed1998

Mitochondrial ND1 gene sequences used to identify echinostome isolates from Australia and New Zealand.

Echinostomes were collected in Australia and New Zealand as cercariae, metacercariae or adults. Using DNA sequences from the mitochondrial ND1 gene Echinostoma revolutum and Echinostoma paraensei were discovered in Australia. The presence of a further five, as yet unidentified, echinostome species was inferred in Northern Australia and a further isolate, closely allied to E. revolutum, occurs in New Zealand. ND1 sequences of species within the genus diverge from each other by 9.6-30.8%. Sequence divergence levels among strains within a single species are 0-3.6%. The phylogenetic tree produced from the Australasian isolates, in addition to species described previously, identifies the 37-collar-spine species as a well supported monophyletic group. The five unidentified Australian species cluster away from the 37-collar-spine group. These unidentified species appear to divide further into > 37-collar-spine and < 37-collar-spine clusters. Three strains of E. revolutum, collected as metacercariae from snails, were identified from two ponds located 6 km apart. Two of these strains may be cycling through a planorbid snail, Glyptophysa sp., as first intermediate host; however, this hypothesis could not be confirmed as specimens could not be obtained to match sequences between larvae and adults.

Animals↗
PubMed1998

Relative merits of nuclear ribosomal internal transcribed spacers and mitochondrial CO1 and ND1 genes for distinguishing among Echinostoma species (Trematoda).

Cryptic species, belonging to the 37 collar-spine Echinostoma group, were distinguished using nuclear rDNA ITS (884 bases) and mtDNA CO1 (257 bases) and ND1 (530 bases) sequences. Sequences were obtained from five 37 collar-spine species, Echinostoma trivolvis, E. paraensei, E. caproni, E. revolutum and E. sp.I, a parthenogenetic isolate from Africa. Three geographic isolates of E. caproni were compared. Average sequence divergence among the 37 collar-spine species range from 2.2% in the rDNA ITS through 8% for the CO1 and 14% for the ND1. In addition, genes were sequenced from 2 non 37 collar-spine species, E. hortense and an undescribed Australian species, E. sp. (Aus). For each gene, distances of terminals from a predicted ancestral sequence were calculated. These indicated that ND1 is diverging significantly faster than the other 2 regions. In the CO1 gene most substitutions are synonymous and saturation has been reached for the majority of pairwise comparisons. The ND1 gene exhibits greater pairwise divergence but less evidence of saturation due to weaker conservation of first and second codon positions. The ITS has no amino acid coding constraints and displays no evidence of saturation. Although all 3 regions successfully distinguished the nominal species, ND1 appears to be the most informative region for investigating relationships within the 37 collar-spine group.

Animals↗
PubMed1998

Variation in flagellin genes and proteins of Burkholderia cepacia.

The majority of isolates of Burkholderia cepacia, an important opportunistic pathogen associated with cystic fibrosis, can be classified into two types on the basis of flagellin protein size. Electron microscopic analysis indicates that the flagella of strains with the larger flagellin type (type I) are wider in diameter. Flagellin genes representative of both types were cloned and sequenced to design oligonucleotide primers for PCR amplification of the central variable domain of B. cepacia flagellin genes. PCR-restriction fragment length polymorphism analysis of amplified B. cepacia flagellin gene products from 16 strains enabled flagellin type classification on the basis of product size and revealed considerable differences in sequence, indicating that the flagellin gene is a useful biomarker for epidemiological and phylogenetic studies of this organism.

Amino Acid Sequence↗
PubMed1998

Recovery of cellular functions following oxidant injury.

This study investigated the recovery of renal proximal tubule cellular (RPTC) functions following oxidant-induced sublethal injury. tert-Butylhydroperoxide (TBHP) treatment resulted in 24% cell death and loss 4 h following the exposure. The remaining sublethally injured RPTC proliferated, and monolayer DNA content returned to control values on day 4 following TBHP exposure. Basal oxygen consumption (Qo2) and ATP content in sublethally injured RPTC were decreased 64 and 63%, respectively, at 4 h and returned to control values on day 6. Net lactate consumption decreased 71% at 4 h and returned to control values on day 4. In contrast, net glutamine consumption increased 2.7-fold at 4 h and returned to control values on day 6. Ouabain-sensitive Qo2, Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) activity, and Na(+)-coupled glucose transport were inhibited 77, 88, and 83%, respectively, at 4 h and recovered to control values on day 6. These data show that 1) mitochondrial function, Na(+)-K(+)-ATPase activity, active Na+ transport, and Na(+)-coupled glucose transport are decreased in sublethally injured RPTC following oxidant exposure and are repaired over time; 2) monolayer regeneration precedes the recovery of mitochondrial and transport functions, and 3) sublethal injury and subsequent regeneration are associated with alterations in metabolic substrate utilization. These results suggest that oxidant-induced sublethal injury to RPTC may contribute to renal dysfunction and that RPTC can repair and regain cellular functions following oxidant injury.

Animals↗
PubMed1997

The flagellin gene as a stable marker for detection of Pseudomonas fluorescens SBW25.

Flagellin gene central regions from 111 isolates of Pseudomonas fluorescens SBW25 obtained from soil during a field release experiment were analysed using a combined PCR/RFLP technique to look for variation. In addition, a 858 bp flagellin gene sequence from the original strain and the last isolate obtained from the release site were compared. There was no variation in flagellin gene sequences indicating that the gene was stable over the period of the release, and that the flagellin gene is a suitable marker for use in the detection of bacteria in release experiments. A comparison of Ps. fluorescens SBW25 flagellin with other sequenced flagellins revealed closest homology to the flagellin of Ps. putida PRS2000.

Base Sequence↗
PubMed1996

Flagellin gene and protein variation amongst clinical isolates of Pseudomonas aeruginosa.

Flagellin gene sequences from 64 clinical isolates of the opportunistic pathogen Pseudomonas aeruginosa were amplified by PCR and subjected to RFLP analysis by using seven restriction enzymes to digest the amplified products. Using this approach the isolates were assigned to one of 13 groups. The method was rapid, reproducible and applicable to all isolates. In contrast, serotyping failed to satisfactorily resolve 49% of the strains tested. The vast majority of clinical isolates generated amplified products of 1.02 kb (type a) or 1.25 kb (type b). Electron microscopical analysis revealed evidence fax some. flagellar structural variation between P. aeruginosa strains. This study provides further evidence that the flagellin gene is a widely applicable and useful genetic marker for studying genetic variation within populations of closely related bacteria.

Base Sequence↗
PubMed1996

Association of p300 and CBP with simian virus 40 large T antigen.

p300 and the CREB-binding protein CBP are two large nuclear phosphoproteins that are structurally highly related. Both function, in part, as transcriptional adapters and are targeted by the adenovirus E1A oncoprotein. We show here that p300 and CBP interact with another transforming protein, the simian virus 40 large T antigen (T). This interaction depends on the integrity of a region of T which is critical for its transforming and mitogenic properties and includes its LXCXE Rb-binding motif. T interferes with normal p300 and CBP function on at least two different levels. The presence of T alters the phosphorylation states of both proteins and inhibits their transcriptional activities on certain promoters. Although E1A and T show little sequence similarity, they interact with the same domain of p300 and CBP, suggesting that this region exhibits considerable flexibility in accommodating diverse protein ligands.

Amino Acid Sequence↗
PubMed1995

Nuclear rDNA ITS sequence variation in the trematode genus Echinostoma: an aid to establishing relationships within the 37-collar-spine group.

The taxonomic history of members of the 37-collar-spine group within the genus. Echinostoma has been very confused. We obtained DNA sequence data from the nuclear rDNA ITS1, 5.8S and ITS2 of 7 nominal species belonging to this group, Echinostoma trivolvis (Cort, 1914), E. revolutum (Frölich, 1802), E. caproni Richard, 1964, E. liei Jeyarasasingam et al. 1972, E. paransei Lie & Basch, 1967, two African isolates, E. sp.I and E. sp.II, and of one 28-collar-spined echinostome, E. hortense (Asada, 1926). Five of the eight species were clearly distinguishable using ITS data. Sequences from the remaining three taxa, E. caproni, E. sp.II and E. liei were identical to one another and the group containing these taxa was distant from other 37-collar-spine species on a phylogenetic tree. E. trivolvis and E. paraensei form a second, but less distinct group within the 37-collar-spine group. The resolution obtained using DNA sequencing will assist in the current reclassification of the group. It also provides a model for future work on sibling species.

Animals↗
PubMed1995

Advances in the use of ancillary diagnostic testing in the emergency department evaluation of chest pain.

This article discusses the advances of ancillary studies used to evaluate the emergency department patient with chest pain caused by acute myocardial infarction (AMI) or ischemia. This article examines how these studies have improved the early detection of patients with AMI, improved differentiation of acute ischemic coronary events from nonischemic causes of chest pain, more accurately stratified patients for adverse outcome, and decreased the number of patients with AMI inadvertently discharged from the emergency department. Ancillary studies discussed include nonstandard ECGs, nuclear imaging, serum markers, and emergency department observation units. Emergency department echocardiography is discussed elsewhere in the issue.

Chest Pain↗
PubMed1994

Molecular cloning of two Pseudomonas flagellin genes and basal body structural genes.

Pseudomonas putida strains PaW8 and PRS2000 produce flagellins with apparent molecular masses of 81 kDa and 50 kDa respectively. Two Tn5 insertion mutants of P. putida PaW8 lacking the ability to bind the flagellin-specific monoclonal antibody MLV1 were isolated. Mutant PaW8-flg2 contained a Tn5 insertion within a 2.6 kb EcoRI fragment of the P. putida chromosome carrying putative basal body genes. DNA and deduced protein sequences suggested the presence on this fragment of two complete genes homologous to flgH and flgI from Salmonella typhimurium. The insertion of Tn5 occurred in the flgI locus and appeared severely to reduce expression of the P. putida flagellin gene. A Tn5-containing fragment of DNA from a second mutant, PaW8-flg1, was cloned and found to contain sequences that hybridized strongly with the Pseudomonas aeruginosa flagellin gene. A 2.3 kb HindIII fragment containing all but 62 bp of the P. putida PaW8 flagellin gene was cloned and used as a probe to identify clones carrying the equivalent gene from P. putida PRS2000. Flagellin genes from both P. putida strains were sequenced and their amino acid sequences deduced. Both flagellins were found to contain conserved amino- and carboxy-terminal regions when compared to other flagellins, with the central region being more variable. The epitope for MLV1 is likely to lie within this central region of P. putida PaW8 flagellin. The deduced molecular mass of P. putida PaW8 flagellin (68 kDa) differed significantly from its apparent molecular mass estimated by PAGE, possibly as a consequence of post-translational modification.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Elimination of glutathione-induced protection from hyperbaric hyperoxia by acivicin.

Glutathione (GSH) administered intraperitoneally significantly prolongs the time to initial seizure and survival time of rats exposed to hyperbaric hyperoxia (HBO). Acivicin is an antitumor antibiotic that is an inhibitor of gamma-glutamyl transpeptidase (GGT), an enzyme necessary for the breakdown and transport across cell membranes of GSH. To determine whether acivicin treatment alters GSH-induced protection from HBO, rats were dosed with 25 mg/kg of acivicin or vehicle 1 h before O2 exposure at an inspired O2 fraction of 1.0 at 4 ATA. Immediately before exposure, rats received GSH (1 mmol/kg) or vehicle. Time to seizure and time to death were recorded during exposure by direct observation. In separate groups of rats on the same dosing schedule, plasma GSH, renal GGT, and brain GGT were measured 15 min after the GSH injection without HBO exposure and 100 min after the beginning of HBO exposure. Renal GGT was decreased to 2.5% of control and brain GGT to 37% of control in the acivicin-dosed rats. Plasma GSH increased 3-fold in rats given acivicin alone, 52-fold in rats given GSH alone, and 84-fold in rats receiving both acivicin and GSH. Rats dosed with GSH alone had significantly prolonged times to seizure and death compared with all other groups. Rats dosed with GSH after receiving acivicin were not protected from HBO despite the large increase in plasma GSH that occurred in these animals. GSH treatment did not increase tissue GSH in lung, liver, or brain at 160 or 200 min of exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Protein kinase C and intracellular free Ca++: relationship to human immunodeficiency virus (HIV)-induced cellular hyporesponsiveness.

Protein Kinase C (PKC) and Ca++ are both involved in the chain of events leading to T-cell activation. An impairment of the immune response is characteristic of T cells obtained from patients with HIV infection. In this report, the involvement of PKC and Ca++ in HIV-mediated cellular hyporesponsiveness was examined. Infection of peripheral blood mononuclear cells (PBMC)s from HIV-seronegative normal donors with HIV strain HTLV IIIB, or two fresh patient isolates produced a 1.4-, 10.7-, and 11.4-fold enhancement in PKC activity at 1 hr postinfection (PI) and a 1.8-, 2.3-, and 3.8-fold enhancement at 12 hr PI, respectively. A marked decrease of PKC content, as determined by Western Blot analysis, was observed in HIV-infected cells by Day 4 and 7 PI compared with mock-infected control cells. Furthermore, PKC synthesis was also inhibited in cells from immunosuppressed AIDS patients. PKC activity of PBMCs from HIV-infected patients did not change in response to 1 microM of phorbal myristate acetate (PMA). In contrast, the same dose enhanced the activity by 50%-100% in PBMCs from normal HIV-seronegative donors. A 40%, 50%, and 125% increase in intracellular free Ca++ in response to HIV infection was observed 12 hr PI in MT4, JURKAT, and PBMCs, respectively. However, the increase in intracellular free Ca++ in HIV-infected PBMCs obtained from normal donors in response to PHA was 56% and 17% compared with an increase of 100% and 120% in mock infected cells at 12 hr and 1 week PI, respectively. Comparing the Ca++ response to PHA in PBMCs from HIV-infected patients showed that patients with < 250 absolute T4 cells/mm3 had an impaired Ca++ response. These data suggest that there is a relationship between intracellular free Ca++ and PKC and HIV-induced T-cell hyporesponsiveness.

Calcium↗
PubMed1993

The role of ultrasound assisted thoracoscopy in the diagnosis of pleural disease. Clinical experience in 687 cases.

Ultrasonic examination is an established method used to differentiate between solid and liquid structures in the pleural space. It can estimate the volume of a pleural effusion and demonstrate whether the effusion is associated with loculations or adhesions. It is complementary to thoracoscopy. In the diagnosis of pleural disease ultrasonic-assisted thoracoscopy should only be used when the less invasive methods of diagnosis such as pleural aspiration for cytological, bacteriological and chemical examinations and needle biopsy of the pleura have not yielded a diagnosis. Although thoracoscopy is a relatively invasive procedure, it has the advantages of speed and accuracy in the diagnosis of pleural disease. This procedure is not widely used as it requires specialized instruments and equipment and may be time-consuming. The latter disadvantage may be minimized by the use of prior pleural sonography. The ultrasonic examination will indicate the optimal point of entry of the thoracoscopy to avoid adhesions. In order to evaluate feasibility, complications and clinical results in ultrasonic-assisted thoracoscopy, we investigated 687 patients with pleural diseases from 1987 to 1990. As prior induction of a pneumothorax under X-ray control was not necessary, the 20-30 min required for this procedure was saved in all patients. Very few complications were attributable to ultrasonic-assisted thoracoscopy as it could normally be performed under local anesthesia. A macroscopic diagnosis was made in 80% of malignant diseases and 77% of inflammatory diseases in our total of 687 thoracoscopies. The diagnosis of a malignant pleural effusion was confirmed histologically and cytologically in 95% of those 190 patients in whom it was present.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗