PubMed Health⌕ Search

Biomedical subjects

T M Wilson

Publications and source records attributed to T M Wilson.

At least 19 recordsLinked to original sources
PubMed1995

Differential cellular expression of the human MSH2 repair enzyme in small and large intestine.

The human MSH2 (hMSH2) protein is responsible for the initial recognition of mismatched nucleotides during the postreplication mismatch repair process. Loss of hMSH2 function has been demonstrated to lead to the accumulation of replication errors, resulting in a mutator phenotype, which may be responsible for the multiple mutations required for multi-stage carcinogenesis. Alterations of the hMSH2 gene has been linked to approximately 60% of hereditary nonpolyposis colon cancer cases. Colon tumors in hereditary nonpolyposis colon cancer patients originate within benign preneoplastic adenomas and display replication errors in the form of microsatellite instability. The aim of this study was to investigate the cellular expression of the hMSH2 protein in cells of the large and small intestines. Using antibody specific for hMSH2, we have determined that this protein is highly expressed in cells of the crypts of Lieberkühn that are undergoing rapid renewal in both the ileum and colon. Proliferative perifibroblasts in the colon also showed significant presence of the hMSH2 protein. These results confirm the hypothesis that hMSH2 is expressed in highly proliferative cells of the gut, and mutations in this gene could, therefore, be expected to expedite the progression of adenoma to carcinoma in this tissue.

Animals↗
PubMed1995

An analysis of spontaneous deletion sites in soil-borne wheat mosaic virus RNA2.

Plants mechanically inoculated with soil-borne wheat mosaic virus (SBWMV, Oklahoma isolate) generated several deleted forms of RNA2, the smaller genomic RNA (3593 nt). Four naturally deleted forms were cloned by RT-PCR methods and the sequences around each deletion site were compared. SBWMV RNA2 molecules were deleted for 519, 759, 964, or 1030 nt, respectively, each within the coat protein-readthrough domain. No common sequences were found flanking the 5'- and 3'-sites of deletion; however, the 5'-site of each deletion lay in the region between genome coordinates 1417-1465. The delta 759nt clone isolated from virus-infected plants after a single mechanical passage was identical to a clone described previously (J. Chen, S. A. MacFarlane, and T. M. A. Wilson, 1994, Virology 202, 921-929) which became the dominant, stable form of SBWMV RNA2 after five or more serial mechanical transfers. In this study, a total of 33 independent, RT-PCR clones with an apparent deletion of 759 nt, isolated after one to seven mechanical passages, were also sequenced and their precise deletion sites were compared. Twenty-six clones contained the original "stable," 759-nt deletion, whereas 7 clones, which were found only during the first four passages, had deletions at one of four alternative sites. After the fifth mechanical passage the stable 759-nt deletion dominated. The results also show that, in general, the smaller deletions are not intermediates in the larger deletion process. The complete nucleotide sequence of SBWMV RNA2 (Oklahoma) is also reported.

Base Sequence↗
PubMed1995

A conserved, precise RNA encapsidation pattern in Tobamovirus particles.

The bidirectional RNA encapsidation pathway in nine sequenced Type 1 Tobamovirus genomes will result in RNA-coat protein assembly, up to and including the first transcribed G, adjacent to the 5'-cap structure (m7 Gppp). This precision is highly conserved, despite wide interstrain variations in the absolute position of the phase-determining core of the origin-of-assembly sequence (Gxx)n and in overall genome length (6311-6507 nts). A Type 2 Tobamovirus genome did not comply with this pattern. All genomes had a statistically significant bias for G at every third (or 3n) position, resulting in a preponderance of GNN codons and hence a high Val, Ala, Gly, Asp, Glu content, at least in the large (126/183 kDa) and amino-coterminal replicase protein genes. Contrary to predictions from the X-ray fibre diffraction structure of tobacco mosaic virus (TMV, U1 strain), only one (pepper mild mottle virus) of the nine Type 1 Tobamoviruses positioned the preferred G-repeat in the most favourable (5') position of the trinucleotide binding site on each coat protein (CP) subunit. In all but one of the eight remaining Type 1 Tobamovirus genomes, G would predominate in the CP 3'-site. The significance of these observations for TMV particle assembly, disassembly and host cell interactions are discussed.

Base Composition↗
PubMed1995

Expression in Escherichia coli of a rat cDNA encoding an apurinic/apyrimidinic endonuclease.

A rat cDNA (rAPEN) with 85% DNA identity to the major human apurinic/apyrimidinic (AP) endonuclease gene was used to construct a fusion between it and glutathione-S-transferase (GST). The GST-rAPEN fusion was subsequently overexpressed in Escherichia coli, purified on glutathione-agarose affinity columns, and the purified protein tested for AP endonuclease activity. DNA nicks were found to be specifically introduced into AP DNA in a reaction that was dependent upon the time of incubation and the amount of GST-rAPEN added. The DNA scissions produced by GST-rAPEN were determined to be adjacent and 5' to an AP site. The purified fusion protein was also able to efficiently remove 3'-(4 hydroxy-5-phospho-2-pentenal) residues, and to a lesser extent 3'-phosphoglycolate residues. The GST-rAPEN activity failed to exhibit any 3'-5' exonuclease activity, a characteristic shared by the major AP endonuclease in bovine and human.

Animals↗
PubMed1995

Effect of inhA and katG on isoniazid resistance and virulence of Mycobacterium bovis.

Isoniazid (INH) resistance of the Mycobacterium tuberculosis Complex (MtbC) is associated with both loss of catalase activity and mutation of the inhA gene. However, the relative contributions of these changes to resistance and to the loss of virulence for guinea-pigs is unknown. In this study, a virulent strain of Mycobacterium bovis, a member of the MtbC, was exposed to increasing concentrations of INH. Two INH-resistant strains were produced which had lost catalase activity. Strain WAg405, which had a higher resistance to INH, also had a mutation in the inhA gene. This demonstrated that loss of catalase activity and mutation of inhA had a cumulative effect on INH resistance. When a functional katG gene was integrated into the genome of WAg405 the INH resistance was greatly reduced. This indicated that most of the resistance had been caused by loss of catalase activity. While the parent INH-sensitive strain was virulent for guinea-pigs, the INH-resistant strains were significantly less virulent. Integration of a functional katG gene into the most resistant strain restored full virulence. This clearly established that katG is a virulence factor for M. bovis and that mutation of the inhA gene has no effect on virulence.

Animals↗
PubMed1995

Coordinate gene expression of luteinizing hormone-releasing hormone (LHRH) and the LHRH-receptor after prolactin stimulation in the rat Nb2 T-cell line: implications for a role in immunomodulation and cell cycle gene expression.

PRL has been shown to induce a number of genes after the stimulation of quiescent Nb2 T-cells, including c-fos, c-myc, ornithine decarboxylase, interferon regulatory factor-1, and others. One of these genes, LHRH, has not previously been reported to respond in this manner, although we and others have reported its presence in rat and human T- and B-cells. Furthermore, recent evidence suggests that LHRH functions as an immunoregulator in a cytokine-like manner. Using the rat immature T-cell line Nb2, we present data showing for the first time that 1) the LHRH gene is regulated by PRL at various times during the cell cycle; 2) an alternatively spliced LHRH messenger RNA exists in Nb2 cells and may produce a new truncated GnRH-associated peptide (alternatively called PIF for PRL-inhibiting factor); 3) the LHRH receptor is expressed in lymphocytes in a manner similar to the LHRH gene after PRL addition, and its complementary DNA sequence is identical to that of the pituitary receptor; 5) the SH gene, found on the opposite strand of the LHRH gene, is expressed in lymphocytes at the same time and in the same manner as the LHRH gene; 6) the LHRH messenger RNA has a very short half-life in these cells; and 7) the lymphocyte LHRH transcription start site is essentially the same as the hypothalamic site. These data strengthen the relationship between PRL and LHRH expression in the immune system and further support our contention that LHRH is an important immunoregulator, on par with other known cytokines.

Animals↗
PubMed1994

Assembly of tobacco mosaic virus and TMV-like pseudovirus particles in Escherichia coli.

High-level expression of plant viral proteins, including coat protein (CP), is possible in Escherichia coli. Native tobacco mosaic virus (TMV) CP expressed in E. coli remains soluble but has a non-acetylated N-terminal Ser residue and following extraction, is unable to package TMV RNA in vitro under standard assembly conditions. Changing the Ser to Ala or Pro by PCR-mutagenesis did not confer assembly competence in vitro, despite these being non-acetylated N-termini present in two natural strains of TMV. All TMV CPs made in E. coli formed stacked cylindrical aggregates in vitro at pH 5.0 and failed to be immunogold-labelled using a mouse monoclonal antibody specific for helically assembled TMV CP. TMV self-assembly has been studied extensively in vitro, and an origin of assembly sequence (OAS) mapped internally on the 6.4 kb ssRNA genome. Pseudovirus particles can be assembled mono- or bi-directionally in vitro using virus-derived CP and chimeric ssRNAs containing the cognate TMV OAS, but otherwise of unlimited length and sequence. Studies on plant virus assembly in vivo would be facilitated by a model system amenable to site-directed mutagenesis and rapid recovery of progeny particles. When chimeric transcripts containing the TMV OAS were co-expressed with TMV CP in vivo for 2-18 h, helical TMV-like ribonucleoprotein particles of the predicted length were formed in high yield (up to 7.4 micrograms/mg total bacterial protein). In addition to providing a rapid, inexpensive and convenient system to produce, protect and recover chimeric gene transcripts of any length or sequence, this E. coli system also offers a rapid approach for studying the molecular requirements for plant virus "self-assembly" in vivo. Transcription of a full-length cDNA clone of TMV RNA also resulted in high levels of CP expression and assembly of sufficient intact genomic RNA to initiate virus infection of susceptible tobacco plants.

Capsid↗
PubMed1994

Acute ethanol exposure suppresses the repair of O6-methylguanine DNA lesions in castrated adult male rats.

Alcohol has clearly been associated with an increase of cancers in numerous tissue, including the respiratory tract, colon, rectum, liver, but especially the esophagus, larynx, pharynx, and mouth. Alcohol alone has not been shown to be a mutagen until it is converted to acetaldehyde and, therefore, alcohol presumably acts as a cocarcinogen. Previous data has shown that alcohol concentrations of 2% or greater inhibits DNA repair, and in light of the widespread consumption of alcoholic beverages with alcohol contents ranging from 4 to 5% (beer and wine coolers) to 50% (whiskey), interest in determining the mechanism(s) responsible for alcohol-induced carcinogenesis has heightened. Although previous studies, in intact rats, have investigated the effects of chronic alcohol exposure on some aspects of DNA repair, we have begun to address the effects of acute or "binge" alcohol exposure on mammalian DNA repair. Toward this end, we report the inhibition of O6-methylguanine-DNA methyltransferase (MGMT) by a single intraperitoneal injection of 30% ethanol in adult male castrated rats. This inhibition lasted for at least 24 hr. We also observed a dose-response effect of ethanol on MGMT activity, again only in the castrated rats. The finding of ethanol's effect on MGMT activity in castrated and not intact rats implies a hormonal component of MGMT DNA repair response, which has only been alluded to in past research.

Animals↗
PubMed1993

Clinical Stage B0 or T1c prostate cancer: nonpalpable disease identified by elevated serum prostate-specific antigen concentration.

A retrospective study was performed to evaluate the clinical and pathologic characteristics of 60 patients with a palpably benign prostate gland, but with biopsy-proved prostate cancer. All patients underwent prostate biopsy because of elevated serum prostate-specific antigen (PSA) concentration, and subsequently underwent radical retropubic prostatectomy (RRP). Similar analysis was performed for a randomly selected group of 60 clinical Stage B1 prostate cancers from the same period (control cohort). Patients with nonpalpable prostate cancers had a higher preoperative PSA level as compared with the clinical Stage B1 group (median value: 12.3 ng/mL versus 4.6 ng/mL, p < 0.001). There was no significant difference between the two groups with regard to clinical parameters (voiding symptoms, hematuria, age). The nonpalpable prostate cancers exhibited a significant tumor volume (mean: 7.4 cc; range: 0.3-56 cc), and 18 (30%) demonstrated capsular perforation to involve the periprostatic tissues. Of these, three (5%) had seminal vesicle invasion, and one (2%) had pelvic lymph node involvement. There was no difference between these pathologic characteristics and those of the clinical Stage B1 prostate cancers. These findings suggest that nonpalpable prostate cancers identified by an elevated serum PSA level can be of clinical significance and warrant therapeutic consideration. Although nonpalpable, these cancers are peripherally located and were clinically suspected prior to biopsy. Therefore, we propose that these cancers be classified as clinical Stage B0 in the Whitmore-Jewett staging system; in the new TNM staging system, they are designated as clinical Stage T1c.

Adult↗
PubMed1993

Biopsy-proved prostate cancer in 100 consecutive men with benign digital rectal examination and elevated serum prostate-specific antigen level. Prevalence and pathologic characteristics.

To determine whether a significant percentage of patients with a benign digital rectal examination (DRE) and an elevated serum prostate-specific antigen (PSA) level harbor a prostatic malignancy, 100 consecutive patients underwent transrectal ultrasound (TRUS)-guided biopsy of the prostate. The biopsy results were correlated with the pre-biopsy serum PSA level and ultrasound findings. Overall, the cancer detection rate was 35 percent (S.E. 4.8%). When the biopsy results were analyzed according to the PSA level, the rate of cancer detection increased with advancing PSA levels, irrespective of ultrasound findings. In the 60 patients with ultrasound abnormalities, the cancer detection rate was 47 percent compared with 18 percent for those without ultrasound abnormalities. Comparison of TRUS-negative and TRUS-positive biopsy results revealed a more than two-fold increase in cancer detection for the TRUS-positive group in each PSA range. Cancer detection in the TRUS-positive, PSA 4.1-10, 10.1-20.0, and > 20 ng/mL groups was 40 percent, 56 percent, and 67 percent, respectively; in the TRUS-negative group, cancer detection was 12 percent, 27 percent, and 33 percent, respectively. Twenty (57%) of the patients with prostate cancer underwent radical retropubic prostatectomy. The mean tumor volume was 4.7 cc. Seventy percent had organ-confined disease, 30 percent demonstrated capsular penetration only, and no patients had seminal vesicle or pelvic lymph node invasion. These data indicate that a significant percentage of patients with a benign DRE and an elevated serum PSA value harbor a clinically significant, but potentially curable prostatic malignancy.

Adenocarcinoma↗
PubMed1992

The localization, partial purification and regulation of pea plastid HMG-CoA reductase.

HMG-CoA reductase was located to the envelope membranes of pea etioplasts, the first report of the suborganelle localization of this key enzyme in isoprenoid synthesis. The enzyme was purified 156 fold from isolated envelope membranes. Purification was achieved by detergent solubilization, hydroxylapatite chromatography and glycerol gradient centrifugation. Membrane-bound etioplast HMG-CoA reductase was activated 4 to 5 fold by high concentrations of inorganic phosphate, this activation was prevented by arsenate, a structural analog of phosphate.

Arsenates↗
PubMed1992

A review and update of animal toxicoses associated with fumonisin-contaminated feeds and production of fumonisins by Fusarium isolates.

During the 1989 corn harvest season, numerous reports of equine leukoencephalomalacia (ELEM) outbreaks and a pulmonary edema (PPE) syndrome in swine from several regions of the United States were received by the National Veterinary Services Laboratories (NVSL), Ames, Iowa. Previous and concurrent research linked Fusarium moniliforme and fumonisin-contaminated feeds to both diseases. Chemical and mycological investigations revealed fumonisin B1 (FB1) concentrations of 20 to 360 ppm in suspect swine feeds and 8 to 117 ppm in suspect equine feeds. Nonproblem feeds contained concentrations below 8 ppm. Fusarium moniliforme and Fusarium proliferatum were isolated from both problem and nonproblem equine and swine feeds. When cultured on autoclaved corn, the F. moniliforme and F. proliferatum isolated produced respective FB1 and fumonisin B2 (FB2) that range from less than 5 to more than 2450 ppm and less than 5 to more than 1000 ppm, respectively. Isolates from both problem and nonproblem feeds produces high levels (greater than 500 ppm) in culture. Reported here is a review of chemical and mycological data resulting from the study of several cases of PPE and ELEM.

Animal Feed↗
PubMed1992

Experimental reproduction of ELEM. A study to determine the minimum toxic dose in ponies.

An experiment to gain insight into the minimum toxic dose of fumonisins was conducted by feeding ponies rations with known fumonisin concentrations. Naturally contaminated corn screenings (CS) were blended with pellets, corn, and molasses to formulate individual daily diets. One group of 4 ponies was fed a ration with fumonisin B1 (FB1) varying from less than 1 ppm to 22 ppm. A second group of 5 ponies was fed a ration at varying rates containing 8 ppm FB1 for 180 days. A panel of clinical chemistry parameters was evaluated twice weekly for both groups. One pony in the first group died of equine leukoencephalomalacia (ELEM) after 225 days of which the final 55 days' diet contained 22 ppm FB1. Approximately 9 days prior to death, this animal experienced elevated liver chemistry values. All 5 ponies in the second group experienced mild, transient, clinical signs; were euthanized at 180 days; and had mild, histopathological brain lesions.

Animal Feed↗
PubMed1992

Increases in serum sphingosine and sphinganine and decreases in complex sphingolipids in ponies given feed containing fumonisins, mycotoxins produced by Fusarium moniliforme.

Consumption of food contaminated with Fusarium moniliforme causes leucoencephalomalacia and hepatotoxicity in horses, pulmonary edema in pigs and liver cancer in rats, and has been correlated with esophageal cancer in humans. The causative agents are thought to be a family of compounds called fumonisins, which have recently been shown to be potent inhibitors of sphingosine (sphinganine) N-acyltransferase. Because inhibition at this step blocks the formation of complex sphingolipids while leading to accumulation of sphinganine, we hypothesized that exposure of animals to fumonisin-contaminated feed might be detected by analyses of serum sphingolipids. Within days of giving ponies feed contaminated with 15 to 44 micrograms/g fumonisin B1, there was an increase in the amount of free sphinganine (and sometimes sphingosine) and a reduction in complex sphingolipids. Free sphinganine and sphingosine decreased when ponies consumed less of the contaminated feed, and increased again when they consumed more fumonisin. When toxicosis was evident as indicated by other serum markers, complex sphingolipids as well as free sphingosine and sphinganine were elevated, probably due to loss of sphingolipids from dying cells. These findings establish that consumption of fumonisin-contaminated feed disrupts sphingolipid metabolism. Because the changes in sphinganine and sphingosine were seen before liver enzymes were noticeably elevated, they may be an early marker of exposure to fumonisins.

Animal Feed↗
PubMed1992

Characterization of an epizootic of pulmonary edema in swine associated with fumonisin in corn screenings.

In 1989, corn screenings were associated with acute interstitial pulmonary edema, hydrothorax, and death in swine. Attack rate was 5-50%, case fatality rate was 50-90%, and clinical course was 1-2 days. Screenings from farms with pigs affected with pulmonary edema contained 20-330 micrograms fumonisin B1 per gram. Screenings containing 92 micrograms fumonisin B1 per gram fed to weanling pigs caused pulmonary edema and death. Sterilized corn inoculated with Fusarium moniliforme and diluted 1:1 with clean corn contained fumonisin B1 (17 micrograms/g) and caused acute pulmonary edema when fed for 5 days. Survivors developed subacute hepatotoxicosis with individual hepatocellular necrosis, hepatomegalocytosis, and increased numbers of mitotic figures. Similar liver lesions occurred in pigs given fumonisin B1 intravenously at 0.8 mg/kg body weight for 14 days.

Animal Feed↗