Biomedical subjects

T Christensen

Publications and source records attributed to T Christensen.

At least 19 recordsLinked to original sources

PubMed2006

A randomized study of two interferon-beta treatments in relapsing-remitting multiple sclerosis.

OBJECTIVE: To investigate whether the efficacy of interferon-beta (IFNbeta) treatment of relapsing-remitting MS (RR-MS) was influenced by type, dose, and frequency of administration. METHODS: From June 1996 through October 1997, the authors offered participation to all Danish RR-MS patients who met the following criteria: definite MS, at least two relapses within 2 years, age 18 to 55, and an Expanded Disability Status Scale (EDSS) score of < or = 5.5. The study was multicenter, controlled, open-label, randomized, head-to-head comparing IFNbeta-1a 22 microg once a week (n = 143) with IFNbeta-1b 250 microg every other day (n = 158), both subcutaneously, for 24 months. Patients who declined randomization were offered treatment with IFNbeta-1b 250 microg every other day (n = 120). The primary end-points were the annualized relapse rate, the time to first relapse, and neutralizing antibody formation. The secondary endpoint was time to sustained progression. RESULTS: The annual relapse rates were virtually equal in the two arms of the randomized study (IFNbeta-1a: 0.70; IFNbeta-1b: 0.71); so were the time to first relapse and the time to sustained progression. In the nonrandomized patients (IFNbeta-1b), the annual relapse rate was not significantly different, but the time to progression was shorter. CONCLUSION: In this study, 250 microg interferon-beta-1b administered every other day did not prove clinically superior to once-a-week administration of 22 microg interferon-beta-1a.

Adjuvants, Immunologic↗

PubMed2006

The role of EBV in MS pathogenesis.

Environmental factors operate on a background of genetic susceptibility in the pathogenesis of MS. Human herpesviruses, notably Epstein-Barr virus (EBV), and human endogenous retroviruses are factors associated with MS. EBV association is found in epidemiological surveys where late EBV infection confers a higher risk of MS, and EBV reactivation also appears to be linked to disease activity in early MS. MS patients have elevated anti-EBV antibody responses, both in serum and cerebrospinal fluid. Molecular mimicry is found between certain EBV and myelin epitopes in the cell-mediated immune response. EBV cannot stand alone as a causal factor of MS, but is likely to play an indirect role as an activator of the underlying disease process.

Antibodies, Viral↗

PubMed2005

Integrated treatment ameliorates negative symptoms in first episode psychosis--results from the Danish OPUS trial.

PURPOSE: To investigate the effect of integrated treatment on negative, psychotic and disorganised symptoms in patients with first episode psychosis. METHOD: A RCT comparing integrated treatment (IT) with standard treatment (ST) was conducted, including 547 patients, aged 18-45, diagnosed with schizophrenia spectrum disorders. All patients were assessed with SCAN, SAPS and SANS at entry and after 1 and 2 years. The IT consisted of assertive community treatment, multifamily groups, psycho-education and social skills training, and the caseload was 1:10 compared with 1:25 in ST. Since attrition was considerable, a mixed model analysis with repeated measurements was used to examine the possible effects of IT statistically. RESULTS: IT reduced both negative and positive symptoms significantly better than ST. Most marked were the results from the negative dimension, where all five global scores from SANS had a significantly better reduction in IT. Sub-analyses did not single out any one element in the integrated treatment that could explain this result. CONCLUSION: Integrated treatment significantly reduced both negative and psychotic symptoms, assumably due to the different psychosocial treatment elements that were provided in the IT. The results indicate that the integrated approach is crucial, since, most likely, many aspects of the integrated treatment have contributed to the reduction of symptoms.

Adolescent↗

PubMed2005

In vivo spectroscopy of jaundiced newborn skin reveals more than a bilirubin index.

AIM: The aims of this study were to improve the algorithms for calculating a transcutaneous bilirubin index (TcB), to follow the bilirubin concentrations during phototherapy and to evaluate possible changes in skin optical parameters such as pigmentation and erythema during phototherapy. METHOD: Reflectance measurements were performed on 51 jaundiced newborns, of which 10 were subjected to phototherapy. The measurements were collected with a diode array spectrophotometer with an integrating sphere accessory, and a TcB was calculated from the measured spectra using algorithms based on diffusion theory. The newborns' birthweights were > or = 2000 g and their gestational age was > or = 35.5 wk. They had no substantial illnesses, and no newborns were submitted to the study until their second day. Heel prick blood samples were analysed for total serum bilirubin (Sbr) by the diazo reaction method. Phototherapy equipment was either an overhead lamp or lightbed. RESULTS: Measurements from the forehead gave the best correlation between TcB and Sbr (r = 0.81, p < 0.05). However, during phototherapy no significant correlation between TcB and Sbr was observed. A correlation (r = 0.45, p < 0.05) was found between phototherapy and melanin index obtained from the patients' back. CONCLUSIONS: Reflectance spectroscopy is useful in assessing bilirubin concentrations before phototherapy, and can also reveal changes in skin parameters such as pigmentation occurring as a result of phototherapy.

Algorithms↗

PubMed2003

Antibodies against a human endogenous retrovirus and the preponderance of env splice variants in multiple sclerosis patients.

The human endogenous retrovirus HERV-H is associated with multiple sclerosis (MS). Previously performed reverse transcriptase-polymerase chain reactions (RT-PCR) on virion-RNA demonstrated sequence variants of the HERV-H family located in the particulate fraction of MS patient plasma samples and not in controls. In this study a significantly elevated level of antibodies towards peptides derived from HERV-H/RGH-2 DNA sequences in serum and cerebrospinal fluid (CSF) from MS patients is demonstrated. Further, Wistar rats immunized with purified virions develop a specific serologic response, indicating that some virion proteins are encoded by HERV-H-related sequences. Also shown is that in RNA from blood cells, a HERV-H protease-env splice variant can be found together with an env splice variant in about 40% of MS patients but only in 10% of controls. The results substantiate the association between activated HERV-H and MS, but a causal relationship is yet to be demonstrated. HERV-H could represent a causal factor either by eliciting an autoimmune response or through the pathogenic potential of the retrovirus itself.

Adult↗

PubMed2002

A randomized, double-blind, placebo-controlled MRI study of anti-herpes virus therapy in MS.

OBJECTIVE: To evaluate the effect of treatment with the antiherpes drug valacyclovir on MRI-evident lesions in patients with relapsing-remitting MS in a phase 2, randomized, double-blind, placebo-controlled study. BACKGROUND: It has been postulated from virologic studies that herpesvirus infection could play a role in the progression of MS. METHODS: Patients were eligible for the study if they had had two or more MS relapses in the 2-year period before enrollment. Seventy patients with Expanded Disability Status Scale scores of 0 to 5.5 were randomly assigned to receive 1 gram of valacyclovir (n = 36) or placebo (n = 34) three times daily for 24 weeks. Patients underwent MRI every fourth week for 32 weeks: twice during pretreatment, six times during treatment, and once after treatment. Scoring of neurologic disability was performed at the start and end of the treatment period. The primary endpoint was the number of new active MRI-evident lesions over 24 weeks of treatment. Secondary endpoints included other MRI measures and clinical endpoints. RESULTS: The mean number of new active lesions +/- SD per patient during 24 weeks of treatment with valacyclovir was 11.9 +/- 17.6 and that during placebo treatment was 14.5 +/- 21.4. A protocol-planned exploratory analysis stratified patients according to baseline activity; this analysis showed that patients with high levels of disease activity in the valacyclovir treatment group (n = 17) developed fewer new active lesions per scan than did those in the placebo treatment group (n = 11). The median number (Q(1), Q(3) range) of active lesions was 2.0 (1.38, 3.96) in the valacyclovir treatment group and 6.5 (2.63, 9.0) in the placebo treatment group. CONCLUSIONS: Valacyclovir treatment did not reduce the formation of active lesions in patients with relapsing-remitting MS who had two or more relapses during the previous 2-year period. In a subgroup of patients with high levels of disease activity who had more than one active MRI-evident lesion during 4 weeks, valacyclovir treatment was associated with a reduced number of new active MRI-evident lesions and with an increase in the number of scans free of new active lesions. The results of the exploratory subgroup analysis provide support for further studies of antiherpes therapy for patients with MS and high levels of MRI-evident disease activity.

Acyclovir↗

PubMed2001

In vivo cellular uptake of glutamate is impaired in the rat hippocampus during and after transient cerebral ischemia: a microdialysis extraction study.

Using microdialysis in CA1 of the rat hippocampus, we studied the effect of transient cerebral ischemia on in vivo uptake and on extracellular levels of glutamate during, and at different time points after ischemia. (3)H-D-aspartate (test substance), and (14)C-mannitol (reference substance), were added to the dialysis perfusate, and the cellular extraction of (3)H-D-aspartate was calculated from scintillation analysis of fractionated dialysate samples. The extraction of (3)H-D-aspartate was studied both in a tracer like condition with a perfusate concentration of 0.2 microM, and in a condition of high saturation level, with 1.0 mM D-aspartate added to the perfusate. In between radioisotope perfusions, dialysate was sampled for analysis of amino acid content by HPLC. During ischemia, extraction of (3)H-D-aspartate (0.2 microM) declined to a maximum reduction of 68%. In the hours after ischemia, extraction of (3)H-D-aspartate (0.2 microM) was decreased by 32%. In the days after ischemia, there was a progressive decline in extraction of (3)H-D-aspartate (1.0 mM), reaching a reduction of 89% on Day 4 after ischemia. Extracellular glutamate remained at control levels at all time points after ischemia. The present study is the first to investigate uptake of glutamate in the intact rat brain in relation to cerebral ischemia. Evidence is provided that uptake of Glu is restrained during ischemia, and that in the hours after ischemia, the extracellular turnover of glutamate is decreased. In the course of the days after ischemia, degeneration of CA1 pyramidal cells occurs concomitantly with a progressive decline in glutamate transport ability, possibly of pathogenetic importance to CA1 pyramidal cell loss.

Animals↗

PubMed2001

[Is visual assessment of MRI adequate in the investigation of patients with temporal lobe epilepsy? Evaluation of the diagnostic accuracy of the visual assessment of MRI in mesial temporal sclerosis].

INTRODUCTION: Is visual assessment of MRI adequate in patients with temporal lobe epilepsy? Visual versus quantitative MRI assessment of mesial temporal sclerosis (hippocampal gliosis (HG) and hippocampal atrophy (HA)). MATERIAL AND METHODS: The MRIs of 25 patients with temporal lobe epilepsy were assessed visually by three radiologists with different levels of neuroradiological MRI experience (expert, trained, and inexperienced). Diagnosis obtained earlier by T2-relaxometry and volume measurements were considered to be the gold standard. RESULTS: The diagnostic accuracy of visual assessment was high for unilateral HA, but low for bilateral HA and unilateral and bilateral HG, and it was not better for the expert eye than for the inexperienced. Interobserver agreement on the visual diagnosis of HG and HA (Cohen's Kappa coefficient): 0.49 (HG) and 0.84 (HA). Intraobserver reliability for the expert/trained/inexperienced observer for visual diagnosis (Kappa): 0.83/0.64/0.47 (HG) and 0.88/0.69/0.73 (HA). DISCUSSION: Reproducibility and diagnostic accuracy of visual assessment varied unacceptably from the quantitative MRI-based diagnosis. Quantitative measurements are recommended in patients suspected of MTS.

Atrophy↗

PubMed2001

Stability and function of interdomain linker variants of glucoamylase 1 from Aspergillus niger.

Several variants of glucoamylase 1 (GA1) from Aspergillus niger were created in which the highly O-glycosylated peptide (aa 468--508) connecting the (alpha/alpha)(6)-barrel catalytic domain and the starch binding domain was substituted at the gene level by equivalent segments of glucoamylases from Hormoconis resinae, Humicola grisea, and Rhizopus oryzae encoding 5, 19, and 36 amino acid residues. Variants were constructed in which the H. resinae linker was elongated by proline-rich sequences as this linker itself apparently was too short to allow formation of the corresponding protein variant. Size and isoelectric point of GA1 variants reflected differences in linker length, posttranslational modification, and net charge. While calculated polypeptide chain molecular masses for wild-type GA1, a nonnatural proline-rich linker variant, H. grisea, and R. oryzae linker variants were 65,784, 63,777, 63,912, and 65,614 Da, respectively, MALDI-TOF-MS gave values of 82,042, 73,800, 73,413, and 90,793 Da, respectively, where the latter value could partly be explained by an N-glycosylation site introduced near the linker C-terminus. The k(cat) and K(m) for hydrolysis of maltooligodextrins and soluble starch, and the rate of hydrolysis of barley starch granules were essentially the same for the variants as for wild-type GA1. beta-Cyclodextrin, acarbose, and two heterobidentate inhibitors were found by isothermal titration calorimetry to bind to the catalytic and starch binding domains of the linker variants, indicating that the function of the active site and the starch binding site was maintained. The stability of GA1 linker variants toward GdnHCl and heat, however, was reduced compared to wild-type.

Amino Acid Sequence↗

PubMed2001

Thermodynamics of metal ion binding. 1. Metal ion binding by wild-type carbonic anhydrase.

Understanding the energetic consequences of molecular structure in aqueous solution is a prerequisite to the rational design of synthetic motifs with predictable properties. Such properties include ligand binding and the collapse of polymer chains into discrete three-dimensional structures. Despite advances in macromolecular structure determination, correlations of structure with high-resolution thermodynamic data remain limited. Here we compare thermodynamic parameters for the binding of Zn(II), Cu(II), and Co(II) to human carbonic anhydrase II. These calorimetrically determined values are interpreted in terms of high-resolution X-ray crystallographic data. While both zinc and cobalt are bound with a 1:1 stoichiometry, CAII binds two copper ions. Considering only the high-affinity site, there is a diminution in the enthalpy of binding through the series Co(II) --> Zn(II) --> Cu(II) that mirrors the enthalpy of hydration; this observation reinforces the notion that the thermodynamics of solute association with water is at least as important as the thermodynamics of solute-solute interaction and that these effects must be considered when interpreting association in aqueous solution. Additionally, DeltaC(p) data suggest that zinc binding to CAII proceeds with a greater contribution from desolvation than does binding of either copper or cobalt, suggesting Nature optimizes binding by optimizing desolvation.

Apoenzymes↗

PubMed2001

Thermodynamics of metal ion binding. 2. Metal ion binding by carbonic anhydrase variants.

The ability to construct molecular motifs with predictable properties in aqueous solution requires an extensive knowledge of the relationships between structure and energetics. The design of metal binding motifs is currently an area of intense interest in the bioorganic community. To date synthetic motifs designed to bind metal ions lack the remarkable affinities observed in biological systems. To better understand the structural basis of metal ion affinity, we report here the thermodynamics of binding of divalent zinc ions to wild-type and mutant carbonic anhydrases and the interpretation of these parameters in terms of structure. Mutations were made both to the direct His ligand at position 94 and to indirect, or second-shell, ligands Gln-92, Glu-117, and Thr-199. The thermodynamics of ligand binding by several mutant proteins is complicated by the development of a second zinc binding site on mutation; such effects must be considered carefully in the interpretation of thermodynamic data. In all instances modification of the protein produces a complex series of changes in both the enthalpy and entropy of ligand binding. In most cases these effects are most readily rationalized in terms of ligand and protein desolvation, rather than in terms of changes in the direct interactions of ligand and protein. Alteration of second-shell ligands, thought to function primarily by orienting the direct ligands, produces profoundly different effects on the enthalpy of binding, depending on the nature of the residue. These results suggest a range of activities for these ligands, contributing both enthalpic and entropic effects to the overall thermodynamics of binding. Together, our results demonstrate the importance of understanding relationships between structure and hydration in the construction of novel ligands and biological polymers.

Asparagine↗

PubMed2001

A powder formulation of measles vaccine for aerosol delivery.

Both the mortality rate for measles and the risks associated with injection continue to be high in the developing world. In response to the need for safe, cost-effective vaccine delivery technologies, a powder formulation of measles vaccine has been developed to test the feasibility of administering measles vaccine as an aerosol. The first challenge in aerosol formulation development is to produce fine particles without damaging the activity of the virus or inducing physical changes. In this study, live attenuated measles vaccine is micronized by jet milling to generate particle sizes appropriate for pulmonary delivery (1-5 microm). Milling does not induce detectable physical changes and significant viral potency is maintained. Potency retention of milled vaccine ranges from 31 to 89%, demonstrating that the standard dose of vaccine can easily be achieved. Following size reduction, particles are blended with an inert carrier to improve handling and aerosol dispersion. The measles vaccine formulation is dispersable, as shown by laser light particle size analysis of vaccine aerosols. Thus, evaluation of both the potency retention and the aerosol characteristics of the current formulation clearly demonstrates the feasibility of delivering measles vaccine as a powder aerosol for immunization.

Aerosols↗

PubMed2001

Time-temperature superposition in viscous liquids.

Dielectric relaxation measurements on supercooled triphenyl phosphite show that time-temperature superposition (TTS) is obeyed for the primary relaxation process at low temperatures. Measurements on other molecular liquids close to the calorimetric glass transition indicate that TTS is linked to an omega(-1/2) high-frequency decay of the loss, while the loss peak width is nonuniversal.

Journal Article↗

PubMed2001

[Endogenous retroviruses in multiple sclerosis].

INTRODUCTION: In recent years, it has been suggested that human endogenous retroviruses (HERVs) may play a role in autoimmune diseases. HERVs represent both putative susceptibility genes and putative pathogenic viruses in multiple sclerosis (MS). Initially, our objective was to characterize a retrovirus produced by MS derived cell lines and to investigate this association in vivo. METHODS: The retrovirus was identified by RT-PCR on virion RNA purified from RT-positive retroviral particles from the MS cell lines, and from blood samples from MS patients. Wistar rats were immunized with purified virions and serological responses analyzed by ELISA. RESULTS: Sequence variants highly homologous to the HERV-H family were found. The same sequences were specifically found in the particulate fraction of a series of MS patient plasma samples and were absent in controls. A database search demonstrated HERV-H copies in several chromosome regions implied in MS susceptibility. Virion-immunized rats developed a specific serological response towards HERV-H peptides indicating that immunogenic virion proteins are encoded by HERV-H. DISCUSSION: Activation of normally replicatively quiescent HERVs may be causally involved in MS.

Animals↗

PubMed2001

Indirect evidence for the potential ability of magnetic resonance imaging to evaluate the myocardial iron content in patients with transfusional iron overload.

The purpose of this study was to evaluate the potential ability of magnetic resonance imaging (MRI) for evaluation of myocardial iron deposits. The applied MRI technique has earlier been validated for quantitative determination of the liver iron concentration. The method involves cardiac gating and may, therefore, also be used for simultaneous evaluation of myocardial iron. The tissue signal intensities were measured from spin echo images and the myocardium/muscle signal intensity ratio was determined. The SI ratio was converted to tissue iron concentration values based on a modified calibration curve from the liver model. The crucial steps of the method were optimized; i.e. recognition and selection of the myocardial slice for analysis and positioning of the regions of interest (ROIs) within the myocardium and the skeletal muscle. This made the myocardial MRI measurements sufficiently reproducible. We applied this method in 41 multiply transfused patients. Our data demonstrate significant positive linear relationships between different iron store parameters and the MRI-derived myocardial iron concentration, which was significantly related to the serum ferritin concentration (rho=0.62, P<0.0001) and to the MRI-determined liver iron concentration (rho=0.36, P=0.02). The myocardial MRI iron concentrations demonstrated also a significant positive correlation with the number of blood units given (rho=0.45, P=0.005) and the aminotransferase serum concentration (rho=0.54, P=0.0008). Our data represents indirect evidence for the ability of MRI techniques based on myocardium/muscle signal intensity ratio measurements to evaluate myocardial iron overload.

Adolescent↗

PubMed2001

Focal cerebral ischemia induces increased myelin basic protein and growth-associated protein-43 gene transcription in peri-infarct areas in the rat brain.

Although oligodendrocytes are vulnerable to focal cerebral ischemia, remyelination of denuded or regenerating axons in the peri-infarct area has been observed in the central nervous system. We studied the expression of myelin basic protein (MBP), a major component of central nervous system myelin, in peri-infarct areas in adult rat brain after transient middle cerebral artery occlusion (MCAO) and correlated it to the expression of the growth-associated protein-43 (GAP-43), a marker for axonal regeneration and sprouting, using non-radioactive in situ hybridization techniques. Within the infarct, MBP messenger RNA (mRNA) had disappeared by 24 h, whereas myelin protein, identified by MBP and myelin oligodendrocyte glycoprotein (MOG) immunohistochemistry, appeared structurally intact until day 3. Peri-infarct oligodendrocytes increased their expression of MBP mRNA from 24 h to maximal levels at day 7, corresponding to the appearance of process-bearing MBP and occasional MOG-immunoreactive oligodendrocytes in parallel sections. Quantitative analysis revealed significant increases in the density of oligodendrocytes (up to 7.6-fold) and in the level of MBP mRNA expressed by individual cells. Parallel sections showed that increased expression of GAP-43 mRNA in neurons was concomitant to MBP mRNA upregulation in oligodendrocytes. While the mechanisms regulating oligodendrocyte survival and myelination signals are not clear at this point, axonal sprouting could putatively serve as a stimulus for the upregulation of oligodendrocyte cell numbers, differentiation state, and/or active myelination in the peri-infarct areas.

Animals↗

PubMed2001

Expression of connexin 37, 40, and 43 mRNA and protein in renal preglomerular arterioles.

Gap junctions allow direct intercellular coupling between many cells including those in the vascular wall. Studies of connexin expression in cells of the microcirculatory system are very few in number. However, cell-to-cell communication between cells of the arteriolar wall may be particularly important in microcirculatory control. We investigated the expression of connexins 43, 40, and 37 (Cx43, Cx40, Cx37) mRNA and proteins in primary cultures of smooth muscle cells (SMC) from rat renal preglomerular arterioles and in the aortic cell line A7r5. Furthermore protein expression in preglomerular arterioles in frozen sections was evaluated. SMC were isolated from kidneys using an iron oxide sieve method and explant technique. Total RNA from these cultures was tested by RT-PCR analysis for the expression of the three connexins mRNA. Using immunofluorescence we examined whether the expression pattern of connexin protein in the cell culture and frozen sections corresponded to the mRNA expression. The data show that A7r5 and preglomerular SMC express mRNA for Cx37 in addition to Cx43 and Cx40. In A7r5 cells the mRNA for Cx43, Cx40, and Cx37 are translated to protein, whereas cultured preglomerular SMC and the media of afferent arterioles in frozen sections only showed Cx40 immunoreactivity.

Animals↗

PubMed2001

MASP-3 and its association with distinct complexes of the mannan-binding lectin complement activation pathway.

The mannan-binding lectin (MBL) pathway of complement activation is part of the innate immune defense. The binding of MBL to microbial carbohydrates activates the MBL-associated serine proteases (MASPs), which recruit the complement factors, C4 and C2, to generate the C3 convertase or directly activate C3. We present a phylogenetically highly conserved member of the MBL complex, MASP-3, which is generated through alternative splicing of the MASP-1/3 gene. The designation of MASP-3 as a protease is based on homology to known MASPs. Different MBL oligomers were found to have distinct MASP composition and biological activities. MASP-1, MAp19, and direct C3-cleaving activity are associated with smaller oligomers whereas MASP-3 is found together with MASP-2 on larger oligomers. MASP-3 downregulate the C4 and C2 cleaving activity of MASP-2.

Alternative Splicing↗