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Biomedical subjects

M P Fox

Publications and source records attributed to M P Fox.

15 recordsLinked to original sources
PubMed2001

Identification of candidate genes in ulcerative colitis and Crohn's disease using cDNA array technology.

Inflammatory bowel disease (IBD) follows a multigenic mode of inheritance, encompassing the clinically discrete phenotypes of ulcerative colitis (UC) and Crohn's disease (CD). The risk of malignant transformation of the colon increases with the duration and extent of IBD and is particularly high for patients with a longstanding history of UC. We wished to identify candidate genes that might be involved in disease pathogenesis based on functional plausibility and their putative role in IBD carcinogenesis. Polyadenylated mRNA (PolyA+ mRNA) preparation from inflamed intestinal mucosa of patients with a longstanding history of UC and CD was performed with subsequent hybridization of alpha phosphorus [alpha-32P]-deoxyadenotriphosphate-labeled complementary deoxyribonucleic acid (DNA) populations to nucleic acid arrays. Of 588 different human gene transcripts arrayed, secreted apoptosis-related protein 1 (Sarp1), frizzled (fz) homologues, and disheveled (dvl) were differentially expressed, being elevated in UC as compared to CD. These genes encode proteins involved in the Wingless-type (Wnt)/beta-catenin signaling pathway. The autonomous expression of Sarp1 and Sarp1-compatible fz receptor genes suggests that the Wnt pathway may be involved in UC carcinogenesis.

Colitis, Ulcerative↗
PubMed1999

Effect of the ratio of free to total prostate-specific antigen on interassay variability in proficiency test samples.

BACKGROUND: Up to sevenfold differences were observed between total prostate-specific antigen (PSA) methods for New York State Proficiency Test samples prepared with seminal fluid PSA in human female serum. Because the PSA was mainly in its free form under these conditions, we wanted to determine whether a defined mixture of free and complexed PSA would reduce the interassay differences. METHODS: We prepared a series of five solutions of 60 g/L bovine serum albumin with 10 microgram/L total PSA consisting of varied proportions of free, noncomplexible PSA, and alpha(1)-antichymotrypsin (ACT)-complexed PSA from 0% to 100%. Two hundred seventy laboratories measured the total PSA in these samples, and 16 laboratories also analyzed the samples for free PSA. The results were used to calculate free/total PSA ratios. RESULTS: Interassay CVs for total PSA measurements were approximately 7% at 10-15% free PSA but became gradually larger as the free/total PSA ratio increased. Measured free-PSA concentrations were similar within each sample (mean CV, 12%), and the results were relatively independent of the proportion of free PSA in the samples. Twofold discrepancies between actual and expected ratios were observed with some methods at 100% free PSA and to a lesser degree at 30% free PSA. At 100% free PSA, the relatively higher total-PSA values measured by nonequimolar methods yielded low free/total PSA ratios of 50-60%. In contrast, the lower total PSA values obtained by equimolar methods yielded ratios close to the expected 100%. CONCLUSIONS: Preparing proficiency test samples with a 10:90 mixture of free, noncomplexible PSA:PSA-ACT is a viable alternative to the use of seminal fluid PSA. Furthermore, the method used to measure total PSA may have a substantial impact on the calculated proportion of free PSA and hence may have clinical relevance.

Female↗
PubMed1996

Cyclin E, a redundant cyclin in breast cancer.

Cyclin E is an important regulator of cell cycle progression that together with cyclin-dependent kinase (cdk) 2 is crucial for the G1/S transition during the mammalian cell cycle. Previously, we showed that severe overexpression of cyclin E protein in tumor cells and tissues results in the appearance of lower molecular weight isoforms of cyclin E, which together with cdk2 can form a kinase complex active throughout the cell cycle. In this study, we report that one of the substrates of this constitutively active cyclin E/cdk2 complex is retinoblastoma susceptibility gene product (pRb) in populations of breast cancer cells and tissues that also overexpress p16. In these tumor cells and tissues, we show that the expression of p16 and pRb is not mutually exclusive. Overexpression of p16 in these cells results in sequestering of cdk4 and cdk6, rendering cyclin D1/cdk complexes inactive. However, pRb appears to be phosphorylated throughout the cell cycle following an initial lag, revealing a time course similar to phosphorylation of glutathione S-transferase retinoblastoma by cyclin E immunoprecipitates prepared from these synchronized cells. Hence, cyclin E kinase complexes can function redundantly and replace the loss of cyclin D-dependent kinase complexes that functionally inactivate pRb. In addition, the constitutively overexpressed cyclin E is also the predominant cyclin found in p107/E2F complexes throughout the tumor, but not the normal, cell cycle. These observations suggest that overexpression of cyclin E in tumor cells, which also overexpress p16, can bypass the cyclin D/cdk4-cdk6/p16/pRb feedback loop, providing yet another mechanism by which tumors can gain a growth advantage.

Animals↗
PubMed1995

Deregulation of cyclin E in breast cancer.

Cyclin E, a regulatory subunit of cyclin dependent kinase-2, is thought to be rate limiting for the G1/S transition during the mammalian cell cycle. Previously, we showed severe alterations in cyclin E protein expression in human mammary epithelial cell lines and in surgical material obtained from patients with various malignancies. To understand the functional basis of these alterations we analyse here the regulation of cyclin E in breast cancer cells. We find that while cyclin E protein and its associated kinase activity in normal cells are cell cycle regulated, in tumor cells it remains in an active complex throughout the cell cycle. We also analysed cyclin E for possible deletions which could result in its constitutive function and found two novel truncated variants in its coding region. These variant forms of cyclin E were detected in several normal and tumor cell lines and tissue specimens. However, Western blot analysis indicated that only the multiple isoforms of cyclin E protein were expressed in tumor but not the normal tissue specimen, suggesting post transcriptional regulation of cyclin E. Lastly, in vitro analyses indicated that these truncated variant forms of cyclin E are biochemically active in their ability to phosphorylate histone H1. Collectively these observations suggest the presence of more than one form of cyclin E mRNA in all cells, normal and tumor. Once translated in tumor cells, the protein products of these truncated forms could give rise to a constitutively active form of cyclin E containing complexes.

Base Sequence↗
PubMed1993

Facility reimbursement: a critical comparison between hemodialysis and peritoneal dialysis.

The population of patients on dialysis in the United States is growing at between 8% and 9% annually. The increasing patient load places a burden on existing dialysis facility capacity and creates a challenge for physicians and administrators to meet patient demand in the future. Increasing costs, reductions in reimbursement, and volatile regulatory policy have increased the risks associated with operating and investing in dialysis facilities. It is important that administrators and physicians understand the economics associated with the modalities available to treat patients on dialysis and that they incorporate this understanding into their planning for the future.

Hemodialysis Units, Hospital↗
PubMed1991

Binding affinities of structurally related human rhinovirus capsid-binding compounds are related to their activities against human rhinovirus type 14.

The binding affinities (Kds) and the rates of association and dissociation of members of a chemical class of antiviral compounds at their active sites in human rhinovirus type 14 (HRV-14) were determined. On the basis of analysis by LIGAND, a nonlinear curve-fitting program, of saturation binding experiments with HRV-14, the Kds for Win 52084, Win 56590, disoxaril (Win 51711), and Win 54954 were found to be 0.02, 0.02, 0.08, and 0.22 microM, respectively. The independently determined kinetic rates of association and dissociation resulted in calculated Kd values which were in agreement with the Kd values determined in saturation binding experiments. Scatchard plots of each of four compounds for the binding data indicated that approximately 40 to 60 molecules were bound per HRV-14 virion. Hill plots showed no evidence of cooperativity in binding. Furthermore, the antiviral activities (MICs in plaque reduction assays with HRV-14) for this limited series of compounds (n = 4) correlated well (r = 0.997) with the observed Kds. Likewise, the absence of detectable binding of Win 54954 to the drug-resistant mutant HRV-14 (Leu-1188) corresponded to a lack of antiviral activity. The positive relationship between the antiviral activities and the Kds that were determined may have implications for the molecular design of capsid-binding antirhinovirus drugs.

Antiviral Agents↗
PubMed1986

Prevention of rhinovirus and poliovirus uncoating by WIN 51711, a new antiviral drug.

WIN 51711, a potent new antipicornavirus drug, has been shown to inhibit an early event in the replication cycle of human poliovirus type 2 and human rhinovirus type 2. WIN 51711 was not virucidal and had no measurable effect on the adsorption of [3H]uridine-labeled virions to cells. When virion penetration of the plasma membrane was determined through loss of sensitivity to neutralizing antisera, WIN 51711 had no effect on poliovirus penetration, but inhibited rhinovirus penetration by 40%. In the presence of WIN 51711, exposure of neutral red-encapsidated virus-infected cells to light at 3 h postinfection resulted in a 3-log reduction in the number of infectious centers, indicating that WIN 51711 maintained the viral RNA in the encapsidated state after penetrating the cell membrane. The inhibition of uncoating by WIN 51711 in the neutral red assay was found to be concentration dependent, with a concentration of 0.03 micrograms/ml resulting in a 90% inhibition of uncoating. Sucrose gradient sedimentation of lysates from whole cells infected with [3H]uridine-labeled poliovirus showed that poliovirions remained intact in the presence of WIN 51711, but were uncoated in the absence of drug. WIN 51711 also prevented thermal inactivation of poliovirus infectivity, indicating a direct stabilizing effect of this compound on virion capsid conformation.

Antiviral Agents↗
PubMed1985

In vitro activity of WIN 51711, a new broad-spectrum antipicornavirus drug.

WIN 51711 (5-[7-[4-(4,5-dihydro-2-oxazolyl)phenoxy]heptyl]-3-methylisoxazole), a new antipicornavirus drug, is a potent inhibitor of human entero- and rhinoviruses at concentrations not inhibitory to HeLa cell growth. In plaque reduction assays, WIN 51711 reduced plaque formation by 9 enteroviruses and 33 rhinoviruses, with MICs of 0.004 to 0.17 and 0.004 to 6.2 micrograms/ml, respectively. Addition of WIN 51711 to infected cells at concentrations of 0.02 to 5.0 micrograms/ml reduced the yield of picornaviruses by 90%. Other RNA viruses (nonpicornaviruses) and DNA viruses were unaffected by the compound.

Antiviral Agents↗
PubMed1982

Factors controlling the concentrations of methotrexate in cultured hepatic cells.

The polyglutamate metabolites of methotrexate are as inhibitory to the target enzyme dihydrofolate reductase as is methotrexate. Because of their greater retention they have a longer half-life within the cells and thus a greater potential for cytotoxicity. These metabolites have been found in numerous cells and tissues and are extensively synthesized in cultured hepatic cells. Uptake of methotrexate by primary cultures of rat hepatocytes occurs by a pathway which is independent of the folate coenzymes but appears to be related in some way to cholic acid and organic anion uptake. The evidence for the commonality of these pathways is (a) an instability of both uptake systems in the absence of hormones in the culture medium, (b) nearly equal inhibition of uptake by PCMS and NEM, and (c) cross competition of cholic acid and methotrexate for entry into the cells. Cholic acid and BSP can also selectively inhibit methotrexate polyglutamate formation in hepatocytes. Methotrexate entry into H35 hepatoma cells is mediated by the transport system which is shared by folate coenzymes and is not inhibited by cholic acid, BSP or sulfhydryl reagents. At concentrations of cholic acid or BSP which inhibit methotrexate polyglutamate formation in hepatocytes there is little or no loss of polyglutamate formation in H35 cells, possibly because BSP and cholic acid are taken up less by H35 cells than by hepatocytes.

Animals↗
PubMed1975

Arenavirus inactivation on contact with N-substituted isatin beta-thiosemicarbazones and certain cations.

N-methyl and N-ethyl isatin beta-thiosemicarbazones inactivate cell-free Parana and Pichinde viruses as well as three strains of lymphocytic choriomeningitis virus. This antiviral activity is abolished in the presence of the chelating agent EDTA. The rate of virus inactivation by N-methyl isatin beta-thiosemicarbazone is greatly enhanced and controlled by the addition of cupric sulphate. Divalent cations of other first transition series metals are less effective. A difference exists in the copper requirement for fast inactivation of the prototype arenavirus (lymphocytic choriomeningitis) and the Tacaribe Complex of viruses (Parana and Pichinde). In the presence of 20 muM-N-methyl isatin beta-thiosemicarbazone, LCM and Pichinde viruses can be inactivated at about the same rate if 20 muM-CuSO4 is added to the former and 160 muM-CuSO4 is added to the latter. Using 20 muM-N-methyl isatin beta-semicarbazone and CuSO4 the inactivation of LCM is reduced, but not eliminated, in the presence of an equal amount of infectious Pichinde virus. Crude and highly purified Pichinde virus are inactivated at the same rate when exposed to identical concentrations of N-methyl isatin beta-thiosemicarbazone and cupric sulphate. There is little detectable change in the inactivation rates when Pichinde or LCM viruses are grown in a variety of different cell lines.

Cell Line↗
PubMed1974

Characteristics of the in vitro inhibition of arenavirus synthesis by bis-benzimidazoles.

The dihydrochloride salt of (S,S)-1,2-bis(5-methoxy-2-benzimidazolyl)-1,2-ethandiol (A37536) inhibits the synthesis of lymphocytic choriomeningitis (LCM), Parana, and Pichinde viruses in L-929 cells. The compound has no direct inactivating effect on LCM virus nor does it affect the adsorption of LCM virus to L cells. The drug-cell interaction is slow. Maximal activity is observed only by exposing cells to the drug at least 8 h prior to LCM virus infection, or by concomitant drug treatment and infection at a low multiplicity. Addition of serum-free media to L cells after LCM virus infection diminishes the activity of A37536. Whereas A37536 exhibits its antiviral activity at concentrations that have little or no effect on L cell division rate, a marked change can be noted in the cell's sensitivity to lysis by standard trypsin dispersal procedures. A37536 has no specific antiviral activity in LCM virus-infected BHK, HeLa, or Vero cells. All of the four tested derivatives of A37536 showed antiviral activity against LCM virus but only at concentrations that reduced the growth rate or were toxic to L cells.

Antiviral Agents↗