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Biomedical subjects

T B Knudsen

Publications and source records attributed to T B Knudsen.

At least 19 recordsLinked to original sources
PubMed2006

Gingival epithelial cells heterozygous for Toll-like receptor 4 polymorphisms Asp299Gly and Thr399ile are hypo-responsive to Porphyromonas gingivalis.

The Toll-like receptor (TLR)4 is the major sensor for bacterial lipopolysaccharide and its two common co-segregating polymorphisms, Asp299Gly and Thr399Ile, which occur at a frequency of between 6 and 10%, have been associated with infectious diseases, LPS hypo-responsiveness and cardiovascular disease. Porphyromonas gingivalis is a Gram-negative bacterium implicated in chronic periodontitis and is a known TLR4 and TLR2 agonist. We obtained two gingival epithelial cell primary cultures from subjects heterozygous for the TLR4 polymorphism Asp299Gly and compared response characteristics with similar cells from patients (four) with the wild-type TLR4 genes. Cytokine responses and transcriptome profiles of gingival epithelial cell primary culture cells to TNFalpha challenge were similar for all primary epithelial cell cultures. P. gingivalis challenge, however, gave markedly different responses for Asp299Gly heterozygous and wild-type epithelial cell cultures. The epithelial cells heterozygous for the TLR4 polymorphism Asp299Gly were functionally hypo-responsive, evidenced by differences in BD-2 mRNA expression, mRNA response profile by microarray analysis and by pro-inflammatory and chemokine cytokines at the protein and mRNA level. These findings emphasize variance in human epithelial cell TLRs, linked with Asp299Gly carriage, which results in a hypo-responsive epithelial cell phenotype less susceptible to Gram-negative diseases and associated systemic conditions.

Amino Acid Substitution↗
PubMed2005

Predictive value of soluble haemoglobin scavenger receptor CD163 serum levels for survival in verified tuberculosis patients.

Pre-treatment serum levels of sCD163 were measured in a cohort of 236 suspected tuberculosis (TB) cases from Guinea-Bissau, with a median follow-up period of 3.3 years (range 0-6.4 years). In 113 cases, the diagnosis of TB was verified by positive sputum microscopy and/or culture. Among the verified TB cases, a decreased survival rate was found in 27 patients with sCD163 levels above the upper reference limit (3.95 microg/mL). The difference in survival was significant during TB treatment (log rank, p<0.02) and after long-term follow-up (log rank, p<0.001). The decrease in survival rate during TB treatment remained significant in a multivariate Cox model controlling for human immunodeficiency virus (HIV) status, age and gender, with a mortality increase of 1.19 (95% CI, 1.04-1.36) per microg of sCD163, and a hazard ratio (HR) for sCD163 levels above the upper reference limit of 4.18 (95% CI, 1.06-16.4). The difference was not significant after excluding patients with concomitant HIV-1 and HIV-2 infection in Kaplan-Meier analyses (log rank, p 0.11). In contrast, the difference in survival remained significant in Kaplan-Meier analyses after long-term follow-up, even after excluding patients with concomitant HIV-1 and HIV-2 infection (log rank, p 0.002). In the Cox model, the mortality increase per microg of sCD163 was 1.27 (95% CI, 1.14-1.40), with an HR for elevated sCD163 levels of 2.85 (95% CI, 1.44-5.63). The HRs for concomitant HIV-1 and HIV-2 infection were 6.92 (95% CI, 3.28-14.58) and 2.48 (95% CI, 1.09-5.67), respectively. Thus, sCD163 levels appeared to be an independent predictor of survival in verified TB patients.

Adult↗
PubMed2003

Severe acute respiratory syndrome--a new coronavirus from the Chinese dragon's lair.

The recent identification of a novel clinical entity, the severe acute respiratory syndrome (SARS), the rapid subsequent spread and case fatality rates of 14-15% have prompted a massive international collaborative investigation facilitated by a network of laboratories established by the World Health Organization (WHO). As SARS has the potential of becoming the first pandemic of the new millennium, a global warning by the WHO was issued on 12 March 2003. The disease, which is believed to have its origin in the Chinese Guangdong province, spread from Hong Kong via international airports to its current worldwide distribution. The concerted efforts of a globally united scientific community have led to the independent isolation and identification of a novel coronavirus from SARS patients by several groups. The extraordinarily rapid isolation of a causative agent of this newly emerged infectious disease constitutes an unprecedented scientific achievement. The main scope of the article is to provide the clinician with an overview of the natural history, epidemiology and clinical characteristics of SARS. On the basis of the recently published viral genome and structural features common to the members of the coronavirus family, a model for host cell-virus interaction and possible targets for antiviral drugs are presented. The epidemiological consequences of introducing a novel pathogen in a previously unexposed population and the origin and evolution of a new and more pathogenic strain of coronavirus are discussed.

China↗
PubMed2001

A new multiplex PCR strategy for the simultaneous determination of four genetic polymorphisms affecting HIV-1 disease progression.

The CCR5 Delta32, CCR2 64I, SDF1 3'A, and CCR5 promoter 59029 polymorphisms have been suggested to influence HIV-1 disease progression. Furthermore, the CCR5 Delta32 and the CCR2 64I polymorphisms have been associated with various other diseases. The purpose of the present study was to develop a multiplex assay for the simultaneous determination of these four polymorphisms. Results obtained with the multiplex assay were compared to results obtained by conventional RFLP-PCR and no differences were observed. The multiplex assay offers a quick tool for the determination of the CCR5 Delta32, CCR2 64I, SDF1 3'A, and CCR5 promoter 59029 A/G polymorphisms.

Chemokine CXCL12↗
PubMed2001

Exposure-disease continuum for 2-chloro-2'-deoxyadenosine, a prototype ocular teratogen. 1. Dose-response analysis.

BACKGROUND: Treatment of pregnant mice with 2-chloro-2'-deoxyadenosine (2CdA) on day 8 of gestation induces microphthalmia through a mechanism coupled to the p53 tumor suppressor gene. The present study defines 2CdA dosimetry with respect to exposure (pharmacokinetics), p53 protein induction, and disease (microphthalmia). METHODS: Pregnant CD-1 mice dosed with 0.5-10.0 mg/kg 2CdA on day 8 provided fetuses for teratological evaluation; 2CdA was measured by HPLC in the antimesometrium through 180 min postexposure, and p53 was assessed with immunostaining of the embryo through 270 min. 5'-/3'-RACE was used to sequence the candidate gene for 2CdA bioactivation from target cells. RESULTS: Microphthalmia appeared first in the dose-response curve. The highest 2CdA dose having no observable adverse effect (NOAEL) was 1.5 mg/kg; the benchmark dose that produced an extra 5% risk of microphthalmia (BMD(5)) was 2.5 mg/kg, and the lower confidence limit (BMDL) was 2.0 mg/kg. Pharmacokinetic parameters for doses encompassing the threshold (1.5-2.5 mg/kg) were modeled at 1.0-1.8 microM (C(max)) and 30-80 microM-min (AUC). The p53 response was not detected below the BMDL; however, a low-grade response appeared 4.5 hr after a teratogenic dose (5.0 mg/kg), and high-grade induction followed an embryolethal dose (10.0 mg/kg). RACE identified a novel splice variant of mitochondrial deoxyguanosine kinase, dGK-3, as the likely candidate for 2CdA bioactivation in the embryo. CONCLUSIONS: Microphthalmia represented the critical effect malformation of 2CdA. The findings suggest a mitochondrial mechanism for 2CdA bioactivation, leading to an embryonic p53 response only after 2CdA elimination and implying pharmacodynamic coupling to the exposure-disease continuum. Published 2001 Wiley-Liss, Inc.

Amino Acid Sequence↗
PubMed2001

Direct influence of the p53 tumor suppressor on mitochondrial biogenesis and function.

Mitochondrial localization of p53 has been observed in several cell systems, but an understanding of its organelle-based physiological activity remains incomplete. The purpose of the present study was to investigate the mitochondrial DNA genomic response to dominant-negative p53 mutant miniprotein (p53DD) fused to a mitochondrial import signal. Constructs were generated to express mitochondrial targeted enhanced green fluorescent protein (mEGFP) or dominant-negative mutant p53 miniprotein (m53DD) by in-frame fusion to the signal peptide sequence of murine Cox8l. Control cytosolic vectors (cEGFP, c53DD) had the signal sequence placed in antisense orientation. NIH 3T3 cells were transiently transfected with these vectors in various combinations. Mitochondrial 16S ribosomal RNA (16S rRNA) expression and fluorochrome staining with Mitotracker Red CMXRos (DeltaPsim) were decreased in cells expressing m53DD. Both alterations were specific for mitochondrial import competence (e.g., m53DD vs. c53DD) as well as the passenger protein (e.g., m53DD vs. mEGFP). The normal functional state of mitochondria was restored with PK11195, a specific ligand of the mitochondrial peripheral-type benzodiazepine receptor. Negative dominance of m53DD on 16S rRNA expression and CMXRos staining, and rescue of these parameters with PK11195, imply a direct positive effect of p53 on mitochondrial biogenesis and function.

3T3 Cells↗
PubMed2001

Adverse effect of the CCR5 promoter -2459A allele on HIV-1 disease progression.

HIV positive individuals heterozygous for a 32 basepair deletion in the CCR5 encoding gene (CCR5 Delta32) have a reduced number of CCR5 receptors on the cell surface and a slower progression towards AIDS and death. Other human polymorphisms, such as the CCR2 64I and the CCR5 promoter -2459 A/G transition that has been discovered recently, have also been shown to influence HIV progression. Since genetic linkages make these polymorphisms interdependent variables, the aim of the present study was to isolate and evaluate the effect on HIV disease progression for each of these mutations independently. Genotypes were determined in 119 individuals enrolled in the Copenhagen AIDS Cohort. When including the concurrent effects of the CCR5 Delta32 and CCR2 64I mutations, homozygous carriers of the CCR5 promoter -2459A allele had a significantly faster progression towards death than heterozygous A/G individuals (P = 0.03), whereas this adverse effect was not significant when comparing A/A and G/G individuals. However, independent analysis revealed a significant adverse effect of the CCR5 promoter -2459A allele. Homozygous carriers of the -2459A allele that lack the protective effects of the CCR5 Delta32 and CCR2 64I mutations were found to have a median survival of 6.0 years, whereas carriers of the -2459G allele had a median survival of 9.4 years (P < 0.01).

Alleles↗
PubMed2000

[Spontaneous infrapatellar tendon rupture in a patient with systemic lupus erythematosus].

A case is described of a 33-year old woman with systemic lupus erythematosus (SLE) in longterm treatment with corticosteroids who experienced spontaneous rupture of the left patellar tendon. A comparative study of 28 previously reported cases of SLE patients with spontaneous tendon rupture in weight bearing joints is performed. It is suggested that renal disease may be an etiological factor for spontaneous tendon rupture in patients with systemic lupus erythematosus.

Adult↗
PubMed2000

Evaluation of biologically based dose-response modeling for developmental toxicity: a workshop report.

Biologically based dose-response (BBDR) modeling represents a novel approach for quantitative assessment of health risk by incorporating pharmacokinetic and pharmacodynamic characteristics of a chemical and by relating the immediate cellular responses to a cascade of aberrant biological actions that leads to detectable adverse outcomes. The quantitative relationship of each of the intervening events can be described in mathematical forms that are amenable for adjustment and extrapolation over a range of doses and across species. A team of investigators at the Reproductive Toxicology Division of the U.S. Environmental Protection Agency has explored the feasibility of BBDR modeling by examining the developmental toxicity of a known teratogen, 5-fluorouracil. A panel of researchers from academic and industrial laboratories, biomathematical modelers, and risk assessment scientists was convened in a workshop to evaluate the approaches undertaken by the EPA team and to discuss the future prospects of BBDR modeling. This report summarizes the lessons learned from one approach to BBDR modeling and comments from the panelists: while it is possible to incorporate mechanistic information into quantitative dose-response models for the assessment of health risks, the process is enormously data-intensive and costly; in addition, the confidence of the model is directly proportional to our current understanding of basic biology and can be enhanced only through the ongoing novel discoveries. More importantly, the extent of "uncertainty" (inherent with the default assumptions associated with the NOAEL or benchmark approach) reducible by BBDR modeling requires further scrutiny and comparison.

Abnormalities, Drug-Induced↗
PubMed1999

Transitory expression of the A2b adenosine receptor during implantation chamber development.

Adenosine is a short-range signal molecule that surges in the mouse uterus immediately after blastocyst implantation (Blackburn et al. [1992] Dev. Dyn. 194:155-168). The present study has investigated patterns of uterine adenosine receptor expression during early post-implantation development. Strong expression of the A2b adenosine receptor was observed. Utilizing northern blot analysis, in situ hybridization, and immunostaining, the source of expression was mapped to the primary and secondary decidua of the antimesometrial region, between days 4-8 of gestation. Distribution of the A2b receptor protein followed that of the corresponding transcript by about one gestational day and reflected the dynamics of antimesometrial tissue organization during implantation chamber development. Uterine adenosine surges to levels sufficient for A2b receptor engagement during a defined period (i.e., days 4-6) after blastocyst implantation. Decidual A2b receptor expression thus defines a transitory window of murine gestation that corresponds to a period of human gestation encompassing most spontaneous pregnancy losses. Because adenosine receptors are sensitive to metabolically stable adenosine analogues, their differential expression during implantation chamber development may hold therapeutic potential in the prevention of early pregnancy loss. Dev Dyn 1999;216:127-136.

Adenosine-5'-(N-ethylcarboxamide)↗
PubMed1998

Altered expression of mitochondrial 16S ribosomal RNA in p53-deficient mouse embryos revealed by differential display.

Inactivation of the tumor suppressor p53 is associated with neural tube defects and altered teratogenicity in early embryos. To gain insight into the function of p53 during early embryogenesis, RNA profiles of wild-type p53(+/+) and p53(-/-) null mutant mouse embryos were compared at the head-fold stage (day 8 post coitum) using HPLC-based mRNA differential display. The results of this screen revealed a deficiency of mitochondrial 16S ribosomal RNA in p53(-/-) embryos. RT-PCR showed abnormalities in 16S rRNA levels relative to some representative nuclear (COIV, beta-actin) and mitochondrial (COIII) transcripts in p53(-/-) embryos, and that 16S rRNA expression increased with development of p53(+/+) embryos during neurulation. Embryos that lack p53 also displayed weakened cytochrome c oxidase staining and reduced ATP content. During neurulation, the mouse embryo switches from an anaerobic (glycolytic) to an aerobic (oxidative) metabolism. The preliminary results of the present study suggest that p53 may be involved, directly or indirectly, in this transition.

Adenosine Diphosphate↗
PubMed1998

Chemokine receptors and their crucial role in human immunodeficiency virus infection: major breakthroughs in HIV research.

Within the last three years, major progress in the understanding of acquired immune deficiency syndrome pathogenesis has been achieved. The discovery that human immunodeficiency virus (HIV), in addition to the CD4 receptor, requires the presence of a coreceptor in order to infect cells has led to a series of breakthroughs in HIV research and knowledge. These include an increased understanding of viral entry, a connection of viral phenotype to specific coreceptor use, and an unequivocal linkage of a single human gene to host susceptibility. All in all these achievements provide a number of promising new strategies for combating HIV.

HIV Infections↗
PubMed1997

Insights into thymic purine metabolism and adenosine deaminase deficiency revealed by transgenic mice overexpressing ecto-5'-nucleotidase (CD73).

The adenosine producing enzyme ecto-5'-nucleotidase (5'-NT) is not normally expressed during thymocyte development until the medullary stage. To determine whether earlier expression would lead to adenosine accumulation and/or be deleterious for thymocyte maturation, thymic purine metabolism, and T cell differentiation were studied in lckNT transgenic mice overexpressing 5'-NT in cortical thymocytes under the control of the lck proximal promoter. In spite of a 100-fold elevation in thymic 5'-NT activity, transgenic adenosine levels were unchanged and T cell immunity was normal. Inosine, the product of adenosine deamination, was elevated more than twofold, however, indicating that adenosine deaminase (ADA) can prevent the accumulation of adenosine, even with a dramatic increase in 5'-NT activity, and demonstrating the availability of 5'-NT substrates in the thymus for the first time. Thymic adenosine concentrations of mice treated with the ADA inhibitor 2'-deoxycoformycin (dCF) were elevated over 30-fold, suggesting that high ADA activity, rather than an absence of 5'-NT, is mainly responsible for low thymic adenosine levels. The adenosine concentrations in dCF-treated mice are sufficient to cause adenosine receptor-mediated thymocyte apoptosis in vitro, suggesting that adenosine accumulation could play a role in ADA-deficient severe combined immunodeficiency.

5'-Nucleotidase↗
PubMed1997

Genetically engineered mice demonstrate that adenosine deaminase is essential for early postimplantation development.

Adenosine deaminase (ADA) is an essential enzyme of purine metabolism that is enriched at the maternal-fetal interface of mice throughout postimplantation development. During early postimplantation stages Ada is highly expressed in both maternally derived decidual cells and zygotically derived trophoblast cells. For the current study we utilized genetically modified mice to delineate the relative contribution and importance of decidual and trophoblast ADA at the maternal-fetal interface. In females genetically engineered to lack decidual ADA a striking pattern of expression was revealed in giant trophoblast cells that surround the early postimplantation embryo. Embryos within gestation sites lacking both decidual and trophoblast ADA died during the early postimplantation period, whereas expression in trophoblast cells alone was sufficient for survival through this period. Severe disturbances in purine metabolism were observed in gestation sites lacking decidual ADA, including the accumulation of the potentially toxic ADA substrates adenosine and 2'-deoxyadenosine. These experiments provide genetic evidence that Ada expression at the maternal-fetal interface is essential for early postimplantation development in mice.

Adenosine↗
PubMed1996

Teratogen-induced eye defects mediated by p53-dependent apoptosis.

BACKGROUND: Many birth defects are believed to involve gene-environment interactions, although the mechanisms involved are poorly understood. Apoptosis is a common effect of many kinds of environmental stresses on the developing embryo; therefore, mechanisms of teratogenesis may be approached within the context of the cell death program. The p53 tumor suppressor gene encodes a transcription factor which functions as a critical regulator of apoptosis in response to environmental stress. RESULTS: To investigate the relationship between p53-dependent apoptosis and teratogenesis, we subjected day 8 mouse embryos with different p53 gene backgrounds to a genotoxic stress, 2-chloro-2'-deoxyadenosine. Treatment rapidly stimulated nuclear p53 accumulation and triggered apoptosis in some (head-fold) but not other (primitive heart) developing structures. Induced cell death was p53 gene-dose dependent, as shown by the intermediate sensitivity of 4-5 somite stage embryos bearing only a single effective p53 allele and the lack of sensitivity of p53-null mutants. Abnormal development was manifested as eye defects by day 11, particularly lens agenesis. Overall the incidences of these defects at term were 73.3% for p53 wild-type fetuses, 52.5% for heterozygous mutants, and 2.2% for p53-null mutants. Statistical analysis indicated that the interaction between teratogen and genotype was highly significant (P < or = 0.001) for cell death on day 8 and eye defects on day 17. CONCLUSIONS: We conclude that teratogen induction of p53-dependent apoptosis in the developing embryo is positively coupled to the determination of congenital eye defects.

Abnormalities, Drug-Induced↗