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P Jordan

Publications and source records attributed to P Jordan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Three-dimensional structure of cyanobacterial photosystem I at 2.5 A resolution.

Life on Earth depends on photosynthesis, the conversion of light energy from the Sun to chemical energy. In plants, green algae and cyanobacteria, this process is driven by the cooperation of two large protein-cofactor complexes, photosystems I and II, which are located in the thylakoid photosynthetic membranes. The crystal structure of photosystem I from the thermophilic cyanobacterium Synechococcus elongatus described here provides a picture at atomic detail of 12 protein subunits and 127 cofactors comprising 96 chlorophylls, 2 phylloquinones, 3 Fe4S4 clusters, 22 carotenoids, 4 lipids, a putative Ca2+ ion and 201 water molecules. The structural information on the proteins and cofactors and their interactions provides a basis for understanding how the high efficiency of photosystem I in light capturing and electron transfer is achieved.

Carotenoids↗
PubMed2001

Modeling diffuse phosphorus loads from land to freshwater using the sedimentary record.

Diffuse phosphorus (P) loads to a small lake, Friary Lough, in a 1 km2 agricultural subcatchment were quantified over 90 years using a palaeolimnological model. The model assumes that lake total phosphorus (TP) is lost to the sediments and to the lake outflow during periods of steady-state or is also stored within the water column during periods of non-steady-state behavior. Reconstructed TP loads during the 1991-1995 time interval of 2.05-2.53 g m-2 yr-1 are verified by hydrochemical monitoring results from the lake inflow during 1997-1998. This provides evidence for the accuracy of the palaeolomnological model and also that TP loads to the lake can be accounted for from external catchment runoff. An analysis of the TP load data in terms of catchment exports shows that there was a linear rate of increase from ca. 1946 to 1995 of 1.20-1.56 kg km-2 yr-1. The rate of increase is similar to river P load data in the larger 1480 km2 catchment taken over 17 years. The rate of TP increase to the lake is interpreted with regard to current soil P models that propose increasing and threshold soil P concentrations as the cause for increasing diffuse P loss in runoff.

Agriculture↗
PubMed2001

Glucocorticoids and IL-10, but not 6-MP, 5-ASA or sulfasalazine block endothelial expression of MAdCAM-1: implications for inflammatory bowel disease therapy.

BACKGROUND: Enhanced MAdCAM-1 (mucosal addressin cell adhesion molecule-1) expression is associated with the aetiology of inflammatory bowel disease, but little is known about MAdCAM-1: regulation, or how inflammatory bowel disease therapies modulate MAdCAM-1. AIM: To examine how agents currently used to treat inflammatory bowel disease affect MAdCAM-1: induced by tnf-alpha in an in vitro model of inflammatory bowel disease. METHODS: Endothelial monolayers were pretreated with dexamethasone (DEX): 5-aminosalicylic acid (5-ASA), 6-mercaptopurine (6-MP), sulfasalazine or interleukin-10: (IL-10: prior to TNF-alpha (20 ng/mL), and MAdCAM-1: measured by Western blotting, RT-PCR, EMSA and lymphocyte adhesion assays. RESULTS: MAdCAM-1: was induced dose- and time-dependently by TNF-alpha on endothelial cells. Either dexamethasone or IL-10: reduced TNF-alpha-induced MAdCAM-1: protein, mRNA and lymphocyte adhesion. However, neither 5-ASA, sulfasalazine nor 6-MP blocked MAdCAM-1 induction. CONCLUSIONS: Our data indicate that dexamethasone or IL-10 can exert therapeutic activity in inflammatory bowel disease through MAdCAM-1 inhibition. 5-ASA, sulfasalazine and 6-MP, while beneficial in inflammatory bowel disease, do not directly control MAdCAM-1, and are beneficial through inhibition of other inflammatory processes.

Animals↗
PubMed2001

Assessment of gait irregularities in the horse: eye vs. gait analysis.

The purpose of this study was to verify the sensitivity of 2 gait analysis methods in detecting subtle lameness and to compare the results to the traditional orthopaedic evaluation. Twenty-two horses were evaluated (1) subjectively by 3 different experienced clinicians and (2) objectively with synchronised ground reaction force and accelerometric gait measurements on a treadmill. The horses were assigned for each of the 3 methods independently to one of 3 groups (GR): sound, lameness front limb, lameness hindlimb. Additionally, for each horse, the affected limb (AL) and degree of lameness (DL) were defined. The accordance between the 3 assessment methods for the categorical variables was tested with a Spearman correlation analysis. The relationship between vertical ground reaction forces and dorsoventral as well as mediolateral accelerations were studied using a Pearson correlation matrix. Significant correlation was found between the clinical GR and GR based on force (r = 0.51, P < 0.05) and acceleration data (r = 0.47, P < 0.05), respectively, and between AL based on clinical and ground reaction force (r = 0.65, P < 0.05) assessment. No significant correlation was found, neither for GR between the 2 measuring methods, nor for DL between the 3 assessment methods. The Pearson correlation matrix revealed significant correlations between peak vertical forces and dorsoventral acceleration in the hindlimbs. We conclude that the measurement of kinetic parameters represents a helpful complementary tool in the assessment of subtle gait alterations. However, this information needs to be interpreted carefully and always related to the clinical observation.

Analysis of Variance↗
PubMed2001

PCR amplification introduces errors into mononucleotide and dinucleotide repeat sequences.

The polymerase chain reaction (PCR) is used universally for accurate exponential amplification of DNA. We describe a high error rate at mononucleotide and dinucleotide repeat sequence motifs. Subcloning of PCR products allowed sequence analysis of individual DNA molecules from the product pool and revealed that: (1) monothymidine repeats longer than 11 bp are amplified with decreasing accuracy, (2) repeats generally contract during PCR because of the loss of repeat units, (3) Taq and proofreading polymerase Pfu generate similar errors at mononucleotide and dinucleotide repeats, and (4) unlike the parent PCR product pool, individual clones containing a single repeat length produce no "shadow bands". These data demonstrate that routine PCR amplification alters mononucleotide and dinucleotide repeat lengths. Such sequences are common components of genetic markers, disease genes, and intronic splicing motifs, and the amplification errors described here can be mistaken for polymorphisms or mutations.

Dinucleotide Repeats↗
PubMed2001

Regulation and distribution of MAdCAM-1 in endothelial cells in vitro.

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is a 60-kDa endothelial cell adhesion glycoprotein that regulates lymphocyte trafficking to Peyer's patches and lymph nodes. Although it is widely agreed that MAdCAM-1 induction is involved in chronic gut inflammation, few studies have investigated regulation of MAdCAM-1 expression. We used two endothelial lines [bEND.3 (brain) and SVEC (high endothelium)] to study the signal paths that regulate MAdCAM-1 expression in response to tumor necrosis factor (TNF)-alpha using RT-PCR, blotting, adhesion, and immunofluorescence. TNF-alpha induced both MAdCAM-1 mRNA and protein in a dose- and time-dependent manner. This induction was tyrosine kinase (TK), p42/44, p38 mitogen-activated protein kinase (MAPK), and nuclear factor (NF)-kappa B/poly-ADP ribose polymerase (PARP) dependent. Because MAdCAM-1 is regulated via MAPKs, we examined mitogen/extracellular signal-regulated kinase (MEK)-1/2 activation in SVEC. We found that MEK-1/2 is activated by TNF-alpha within minutes and is dependent on TK and p42/44 MAPKs. Similarly, TNF-alpha activated NF-kappa B through TK, p42/44, p38 MAPKs, and PARP pathways in SVEC cells. MAdCAM-1 was also shown to be frequently distributed to endothelial junctions both in vitro and in vivo. Cytokines like TNF-alpha stimulate MAdCAM-1 in high endothelium via TK, p38, p42/22 MAPKs, and NF-kappa B/PARP. MAdCAM-1 expression requires NF-kappa B translocation through both direct p42/44 and indirect p38 MAPK pathways in high endothelial cells.

Alkaloids↗
PubMed2001

Decreasing process variation in the care of carotid endarterectomy patients.

Avoidable complications after successful carotid endarterectomy surgery typically occur in the immediate postoperative period; most of these complications are related to hemodynamic instability. At Saint Agnes Medical Center, process variation resulted from 22 anesthesiologists and 11 surgeons doing the same process 242 ways. We introduced a Post-Anesthesia Care Unit Carotid Order Set to standardize the process, drug sequence, and drug choices for postoperative carotid endarterectomy patients. Ongoing monitoring demonstrated that this reduction in process variability resulted in a lower complication rate for stroke and wound hematoma.

Algorithms↗
PubMed2000

Small GTPase Rac1: structure, localization, and expression of the human gene.

Rac1 is a member of the Rho family of small GTPases involved in signal transduction pathways that control proliferation, adhesion, and migration of cells during embryonic development and invasiveness of tumor cells. Here we present the complete structure of the human RAC1 gene and characterize its expression. The gene comprises 7 exons over a length of 29 kb and is localized to chromosome 7p22. The GC-rich gene promoter shows characteristics of a housekeeping gene and Northern blot studies revealed ubiquitous expression of two rac1 transcripts, 1.2 and 2.5 kb in size. The two transcripts are expressed in tissue-specific ratios, reflecting competition between two alternative polyadenylation sites. The RAC1 but not RAC2 gene contains an additional exon 3b that is included by alternative splicing into the variant Rac1b, a constitutively active mutant which induces the formation of lamellipodia in fibroblasts. These data indicate that the RAC1 gene encodes two signaling GTPases. The gene structure reported here will enable studies on the regulation of RAC1 expression during tumorigenesis and development.

5' Untranslated Regions↗
PubMed2000

From katayama to the Dakhla Oasis: the beginning of epidemiology and control of bilharzia.

Treatment of schistosomiasis is now simple and control protects millions in Brazil, China and Egypt and many thousands in other countries. It is difficult, therefore, to visualise the frustration and despair of scientists and clinicians in Africa, and in Egypt in particular, at the beginning of the century faced with a disease described as 'perhaps the most dreadful of the remaining plagues of Egypt' (Madden, P.C., 1910). It was known to be caused by a trematode worm (discovered by Bilharz in 1852), but apparently with a life-cycle atypical of other parasites of that class in that the worms are unisexual and that no intermediate host had been identified. The cause of the disease was known but there was no treatment, and the question 'How are people infected?' remained unanswered. Rational preventive and control measures would be possible only when this question was answered. Investigations to answer it, and early attempts at control, constitute the basis of the following historical review. The controversies, theories and fertile imaginations of the eminent scientists, that preceded the unravelling of the schistosome life-cycle, are discussed and observations, techniques and ideas of the early researchers that were forgotten only to be rediscovered many years later, are highlighted.

Africa↗
PubMed2000

Molecular mechanisms involved in cisplatin cytotoxicity.

cis-diamminedichloroplatinum(II) or cisplatin is a DNA-damaging agent that is widely used in cancer chemotherapy. Cisplatin cross-links to DNA, forming intra- and interstrand adducts, which bend and unwind the duplex and attract high-mobility-group domain and other proteins. Presumably due to a shielding effect caused by these proteins, the cisplatin-modified DNA is poorly repaired. The resulting DNA damage triggers cell-cycle arrest and apoptosis. Although it is still debatable whether the clinical success of cisplatin relies primarily on its ability to trigger apoptosis, at least two distinct pathways have been proposed to contribute to cisplatin-induced apoptosis in vitro. One involves the tumour-suppressor protein p53, the other is mediated by the p53-related protein p73. Coupling cisplatin damage to apoptosis requires mismatch repair activity, and recent observations further suggest involvement of the homologous recombinatorial repair system. At present it is generally accepted that abortive attempts to repair the DNA lesions play a key role in the cytotoxicity of the drug, and loss of the mismatch repair activity is known to cause cisplatin resistance, a major problem in antineoplastic therapy. Clearly, a better understanding of the signalling networks involved in cisplatin toxicity should provide a rational basis for the development of new therapeutic strategies.

Animals↗
PubMed2000

Vitamin C concentrations in plasma as a function of intake: a meta-analysis.

The purpose of this study was to estimate the intake-plasma relationship for vitamin C by means of a meta-analysis. A MEDLINE search revealed 30 publications matching our inclusion criteria. We completed the set with 5 older papers and with one monograph. The proposed statistical model corrects for inconsistencies with regard to methodological differences between the various studies. Therefore, the contribution of a particular study to the estimation is independent of the number of data points. The estimations were performed for the complete data set as well as for different subgroups: "adult" aged 15-65 years, "elderly" aged 60-96 years, "nonsmokers" and "smokers". The 50th percentile of the plasma concentration for a daily vitamin C intake of 60 mg was 42.4 mumol/L. The corresponding values for the different subgroups were: "adult" 44.1 mumol/L, "elderly" 31.0 mumol/L, "nonsmokers" 42.4 mumol/L, and "smokers" 33.6 mumol/L. Thus, this meta-analysis confirms earlier results that the requirements of vitamin C is higher in "elderly" and "smokers" compared to "adult" and "nonsmokers" and it can be used for the estimation of the vitamin C intake in order to achieve a desired plasma level within a target population. In the general population the assumed optimal plasma concentration of 50 mumol/L, as proposed by a consensus conference, can be achieved by the intake of 100 mg per day, which is the new recommendation of the Austrian, German, and Swiss Nutrition Societies.

Adolescent↗
PubMed2000

Cell type specificity in alternative splicing of the human mismatch repair gene hMSH2.

Human non-polyposis colorectal cancer is caused by germline mutations in the DNA mismatch repair genes hMSH2 and hMHL1. Several alternatively spliced mRNA species of these genes are present in peripheral blood lymphocytes of normal individuals, which can confound RT-PCR based techniques of mutation detection. Using RT-PCR, we compared the pattern of alternative splicing in whole peripheral blood lymphocytes (PBLs), separated T and B cells, lymphoblastoid cell lines (LCLs) from the same individuals, and a variety of tissues. Alternatively spliced forms of hMLH1 lacking exons 9/10, 10/11 and 9/10/11 were found to have similar patterns of expression in T cells, B cells, and LCLs. By contrast, a subset of hMSH2 transcripts, some of which were produced by utilisation of novel splicing motifs, were generally expressed in T but not in B cells. LCLs derived from the same blood samples showed no expression of any hMSH2 splicing variants. The hMSH2 delta ex13 transcript, while absent from LCLs, was expressed in whole PBLs and both T and B cell fractions. This transcript was furthermore largely undetectable in tissues other than mononuclear blood cells. These data provide evidence for tissue specificity in the regulation of alternative splicing in hMSH2. In particular we show that LCLs generally do not express alternatively spliced forms of hMSH2 mRNA and are thus suited for RT-PCR based mutation screening in that gene.

Alternative Splicing↗
PubMed2000

Pathological exon skipping in an HNPCC proband with MLH1 splice acceptor site mutation.

One of the most commonly mutated mismatch repair genes in human nonpolyposis colorectal cancer (HNPCC) is MLH1. We identified a splice site mutation in MLH1 in a colorectal cancer proband (T-to-A at position -11 of intron 1 splice acceptor) and investigated its functional consequences by RT-PCR, using lymphocyte mRNA from the proband, two noncarrying siblings, and one unrelated individual. Subcloning of PCR products followed by sequencing of individual clones revealed increased transcript heterogeneity in the mutation carrier, attributable to the presence of a variety of mRNA forms lacking exon 2, or combinations of exons 2, 4, 6, 9, and 10. The full-length transcript subcloned from the mutation carrier was detected with a much reduced frequency, suggesting that only the wild-type allele produced functional MLH1 mRNA. The three noncarriers expressed some previously described transcripts and several novel variants, but none that lacked exon 2. The results are consistent with the hypothesis that this splice site mutation causes skipping of MLH1 exon 2 in a large proportion of mRNA transcripts derived from the mutated allele. Such an observation strengthens the case for identifying the mutation as pathogenic in this HNPCC family, which is of interest given the rarity of exon skipping defects resulting from splice acceptor site mutations outside the invariant AG dinucleotide.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Cloning of a novel human Rac1b splice variant with increased expression in colorectal tumors.

Rac1 is a member of the Ras superfamily of small GTPases involved in signal transduction pathways that induce the formation of lamellipodia, stimulate cell proliferation and activate the JNK/SAPK protein kinase cascade. Here we describe that amplification by RT-PCR of the entire Rac1 coding sequence from a series of human adult and fetal tissues revealed beside the expected Rac1 cDNA, a variant product which contained additional 57 nucleotides between codons 75 and 76. This variant resulted in an in-frame insertion of 19 new amino acids immediately behind the switch II region, including two potential threonine phosphorylation sites for casein kinase II and protein kinase C. Primers designed within and downstream of the inserted nucleotide sequence allowed isolation of a genomic clone with intronic consensus sequences demonstrating that the insertion corresponds to a novel, yet undescribed exon 3b. This Rac1 splice variant, designated Rac1b, was predominantly identified in skin and epithelial tissues from the intestinal tract. Most notably, the expression of rac1b versus rac1 was found to be elevated in colorectal tumors at various stages of neoplastic progression, as compared to their respective adjacent tissues. We suggest that the 19 amino acid-insertion following the switch II region may create a novel effector binding site in rac1b, and thus participate in signaling pathways related to the normal or neoplastic growth of the intestinal mucosa.

Adult↗
PubMed1999

Photosystem I, an improved model of the stromal subunits PsaC, PsaD, and PsaE.

An improved electron density map of photosystem I (PSI) calculated at 4-A resolution yields a more detailed structural model of the stromal subunits PsaC, PsaD, and PsaE than previously reported. The NMR structure of the subunit PsaE of PSI from Synechococcus sp. PCC7002 (Falzone, C. J., Kao, Y.-H., Zhao, J., Bryant, D. A., and Lecomte, J. T. J. (1994) Biochemistry 33, 6052-6062) has been used as a model to interpret the region of the electron density map corresponding to this subunit. The spatial orientation with respect to other subunits is described as well as the possible interactions between the stromal subunits. A first model of PsaD consisting of a four-stranded beta-sheet and an alpha-helix is suggested, indicating that this subunit partly shields PsaC from the stromal side. In addition to the improvements on the stromal subunits, the structural model of the membrane-integral region of PSI is also extended. The current electron density map allows the identification of the N and C termini of the subunits PsaA and PsaB. The 11-transmembrane alpha-helices of these subunits can now be assigned uniquely to the hydrophobic segments identified by hydrophobicity analyses.

Amino Acid Sequence↗
PubMed1999

Localization of two phylloquinones, QK and QK', in an improved electron density map of photosystem I at 4-A resolution.

An improved electron density map of photosystem I from Synechococcus elongatus calculated at 4-A resolution for the first time reveals a second phylloquinone molecule and thereby completes the set of cofactors constituting the electron transfer system of this iron-sulfur type photosynthetic reaction center: six chlorophyll a, two phylloquinones, and three Fe4S4 clusters. The location of the newly identified phylloquinone pair, the individual plane orientations of these molecules, and the resulting distances to other cofactors of the electron transfer system are discussed and compared with those determined by magnetic resonance techniques.

Cyanobacteria↗