Search PubMed⌕ Search

Biomedical subjects

P Andersen

Publications and source records attributed to P Andersen.

At least 109 records · Page 6Linked to original sources
PubMed1999

T-cell recognition of Mycobacterium tuberculosis culture filtrate fractions in tuberculosis patients and their household contacts.

We examined the immune responses of patients with active pulmonary tuberculosis (TB) and their healthy household contacts to short-term culture filtrate (ST-CF) of Mycobacterium tuberculosis or molecular mass fractions derived from it. Our goal was to identify fractions strongly recognized by donors and differences among the donor groups of possible relevance for vaccine development. The study population consisted of 65 human immunodeficiency virus-negative donors from the Hossana Regional Hospital, Hossana, Ethiopia. Peripheral blood leukocytes from the donors were stimulated with different antigens and immune responses were determined. Household contacts produced significantly higher levels of gamma interferon (IFN-gamma) than the TB patients in response to antigens present in ST-CF and the 10 narrow-molecular-mass fractions. A similar difference in leukocyte proliferative responses to the antigens between the two groups was also found. In general, while all fractions stimulated immune responses, the highest activity was seen with the low-molecular-mass fractions, which include well-defined TB antigens such as ESAT-6. Leukocytes from contacts of TB patients with severe disease produced higher levels of antigen-specific IFN-gamma than those from contacts of patients with minimal disease. Both groups of contacts exhibited higher cell-mediated responses than the patients themselves. The enhanced immune response of healthy contacts, especially those of patients with severe disease, to secreted mycobacterial antigens is suggestive of an early stage of infection by M. tuberculosis, which could in time result in overt disease or containment of the infection. This possibility is currently being investigated by follow-up studies of the household contacts.

Antigens, Bacterial↗
PubMed1998

[Organization and substrate of memory].

Recently, we have witnessed considerable progress in the field of memory research. New approaches and techniques have allowed the fractionation of memory in several subentities. Working memory, in which sensory information is manipulated for 10-20 seconds, is served by an area laterally in the frontal lobes. Long-lasting memories are either of the explicit or implicit variety. Contents of explicit memory stores can be accessed by conscious processes and depend upon medial temporal lobe structures, in particular the hippocampal formation. Implicit memories can not be consciously accessed and have its many substrates distributed to different parts of the brain, depending upon the material or procedures involved. Long-term memories are reconstructive and thus amenable to forgetting, alteration and, in some cases, even repression.

Animals↗
PubMed1998

Importance of the intracellular domain of NR2 subunits for NMDA receptor function in vivo.

NMDA receptors, a class of glutamate-gated cation channels with high Ca2+ conductance, mediate fast transmission and plasticity of central excitatory synapses. We show here that gene-targeted mice expressing NMDA receptors without the large intracellular C-terminal domain of any one of three NR2 subunits phenotypically resemble mice made deficient in that particular subunit. Mice expressing the NR2B subunit in a C-terminally truncated form (NR2B(deltaC/deltaC) mice) die perinatally. NR2A(deltaC/deltaC) mice are viable but exhibit impaired synaptic plasticity and contextual memory. These and NR2C(deltaC/deltaC) mice display deficits in motor coordination. C-terminal truncation of NR2 subunits does not interfere with the formation of gateable receptor channels that can be synaptically activated. Thus, the phenotypes of our mutants appear to reflect defective intracellular signaling.

Amino Acid Sequence↗
PubMed1998

Human cytolytic and interferon gamma-secreting CD8+ T lymphocytes specific for Mycobacterium tuberculosis.

Protective immunity to Mycobacterium tuberculosis is poorly understood, but mounting evidence, at least in animal models, implicates major histocompatibility complex class I-restricted CD8+ T cells as an essential component. By using a highly sensitive assay for single cell interferon gamma release, we screened an array of M. tuberculosis antigen-derived peptides congruent with HLA class I allele-specific motifs. We identified CD8+ T cells specific for epitopes in the early secretory antigenic target 6 during active tuberculosis, after clinical recovery and in healthy contacts. Unrestimulated cells exhibited peptide-specific interferon gamma secretion, whereas lines or clones recognized endogenously processed antigen and showed cytolytic activity. These results provide direct evidence for the involvement of CD8+ cytotoxic T lymphocytes in host defense against M. tuberculosis in humans and support current attempts to generate protective cytotoxic T lymphocyte responses against M. tuberculosis by vaccination.

Adult↗
PubMed1998

Spatial and temporal differentiation of fMRI BOLD response in primary visual cortex of human brain during sustained visual simulation.

The blood oxygenation level dependent (BOLD) response during sustained visual stimulation has been studied by several groups using fMRI with controversial conclusions. This issue was investigated for the human brain at high (4 Tesla) magnetic field strength using a flashing goggle at 8 Hz. The results demonstrate that the overall BOLD response in the primary visual cortex has an initial overshoot after the onset of visual stimulation and an undershoot after the termination of visual stimulation. A significant and positive BOLD response, however, remains constant between the initial and terminal transient responses. The temporal BOLD responses in the primary visual cortex were spatially dependent. The regions identified as draining veins in images displayed proportionately larger initial and terminal transient responses, whereas regions devoid of such vessels and associated mainly with parenchyma exhibited a more time-independent BOLD response. These results reveal that the BOLD effect and, presumably, the uncoupling between cerebral blood flow and cerebral metabolic rate of oxygen consumption, are maintained in the primary visual cortex during sustained visual stimulation, and the temporal characteristics of the BOLD effect are spatially dependent.

Humans↗
PubMed1998

Simultaneous oxygenation and perfusion imaging study of functional activity in primary visual cortex at different visual stimulation frequency: quantitative correlation between BOLD and CBF changes.

A relationship between regional cerebral blood flow (CBF) and blood oxygenation level dependent (BOLD) changes in the primary visual cortex (V1) at varied visual stimulation frequency has been examined quantitatively using the multislice FAIR technique. A linear correlation in the common activation areas between functional BOLD and CBF maps was observed. This supports the hypothesis that the task-stimulated BOLD changes in microvasculature are correlated with the CBF changes that presumably reflect the degree of neuronal activity. The linear correlation coefficients for intrasubject comparisons are more significant than those for intersubject comparisons. This suggests that using intrasubject comparisons for quantitative studies of neuronal activity related to different task stimuli and task performances should be more reliable than using intersubject comparisons.

Brain Mapping↗
PubMed1998

Appropriate timing and velocity of infusion for the selective staining of parathyroid glands by intravenous methylene blue.

BACKGROUND: Intraoperative parathyroid gland (PTG) identification by selective staining using methylene blue dye (MB) infusion has been shown effective but the degree of gland staining is inconsistent. METHODS: The effect of timing and rate of MB infusion on gland uptake was investigated in a canine model by infusing MB either rapidly over 3 to 5 minutes (n = 8) or slowly over 30 minutes (n = 4). The pattern of dye uptake in an exposed PTG was determined by standardized serial photography. RESULTS: Earliest uptake occurred between 10 and 20 minutes after infusion, and maximum uptake averaged 21 minutes, earlier than previously described. Rate of infusion did not affect staining. CONCLUSIONS: This rapid uptake of methylene blue by the parathyroid glands suggests that its selective intraoperative use when glands are difficult to locate intraoperatively, rather than a routine preoperative infusion, is possible without significant operative delay. Clinical experience has confirmed this impression.

Animals↗
PubMed1998

Failure to demonstrate Chlamydia pneumoniae in symptomatic abdominal aortic aneurysms by a nested polymerase chain reaction (PCR).

OBJECTIVE: To investigate whether Chlamydia pneumoniae is present in symptomatic abdominal aortic aneurysms (AAA). METHOD AND MATERIALS: After optimisation of DNA extraction procedures an inhibitor-controlled nested polymerase chain reaction (PCR) amplifying fragments of the gene encoding the C. pneumoniae specific major outer membrane protein was performed on 124 wall-specimens from 20 patients with symptomatic AAA. RESULTS: None of the specimens contained C. pneumoniae-specific DNA. Minor inhibition of the PCR was noticed especially in media specimens. CONCLUSION: Using a sensitive and specific nested PCR, we were not able to detect C. pneumoniae in symptomatic AAA. The failure to detect C. pneumoniae in symptomatic AAA, combined with previously reported positive findings in atherosclerotic lesions, supports the hypothesis that AAA and atherosclerosis might be two different disease entities.

Aortic Aneurysm, Abdominal↗
PubMed1998

Analysis of T cells recruited during delayed-type hypersensitivity to purified protein derivative (PPD) versus challenge with tuberculosis infection.

The delayed-type hypersensitivity (DTH) to purified protein derivative (PPD) test has been used to infer about protective immunity to Mycobacterium tuberculosis and to diagnose tuberculosis. We showed that in memory tuberculosis-immune mice both DTH to PPD and resistance to M. tuberculosis could be effectively elicited in the footpad and both reactions led to the accumulation of reactive T cells in the regional lymph nodes with a CD4+ phenotype and characterized by the secretion of high levels of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) and no IL-4. By adoptive transfer into nude mice of highly purified CD4+ T cells harvested during the recall of protective immunity it was confirmed that this population mediated both manifestations. However, the specificity of the T cells recruited during these processes were found to differ markedly; T cells involved in protection to a challenge with live tuberculosis bacilli recognized predominantly low-mass culture filtrate antigens below 15 000 MW, while cells recruited during DTH to PPD were directed to molecular mass fractions between 15 000 and 31 000. Using single purified antigens we showed that the latter cells recognized the secreted mycobacterial protein Ag85B and the heat-shock proteins, DnaK and GroEL. Protective T cells, in contrast, were characterized by a very high frequency of T cells directed to the ESAT-6 peptide 1-20.

Acyltransferases↗
PubMed1998

Comparison of antigen-specific T-cell responses of tuberculosis patients using complex or single antigens of Mycobacterium tuberculosis.

We have screened peripheral blood mononuclear cells (PBMC) from tuberculosis (TB) patients for proliferative reactivity and interferon-gamma (IFN-gamma) secretion against a panel of purified recombinant (r) and natural (n) culture filtrate (rESAT-6, nMPT59, nMPT64 and nMPB70) and somatic-derived (rGroES, rPstS, rGroEL and rDnaK) antigens of Mycobacterium tuberculosis. The responses of PBMC to these defined antigens were compared with the corresponding results obtained with complex antigens, such as whole-cell M. tuberculosis, M. tuberculosis culture filtrate (MT-CF) and cell wall antigens, as well as the vaccine strain, Mycobacterium bovis bacillus Calmette-Guerin (BCG). In addition, M. tuberculosis and MT-CF-induced T-cell lines were tested in the same assays against the panel of purified and complex antigens. The compiled data from PBMC and T-cell lines tested for antigen-induced proliferation and IFN-gamma secretion showed that the most frequently recognized antigen was ESAT-6, followed by MPT59, GroES, MPB70, MPT64, DnaK, GroEL and PstS. The frequency of ESAT-6 responders, as measured both by proliferation (18/19) and secretion of IFN-gamma (16/19) was comparable to the results obtained with whole-cell M. tuberculosis, MT-CF and M. bovis BCG. We also observed that most of the high responders to complex antigens recognized all of the antigens tested (covariation), demonstrating that the repertoire of human T-cell specificities induced by natural infection is directed towards several unrelated culture filtrate as well as somatic-derived protein antigens. In conclusion, the results obtained suggest that the cellular immune response in humans is directed against several important target antigens of M. tuberculosis and that some antigens, such as ESAT-6, are recognized by a high number of individuals. Such antigens represent candidates to be used for development of specific diagnostic reagents or in subunit vaccines.

Antigens, Bacterial↗
PubMed1998

Effects of doxazosin and atenolol on atherothrombogenic risk profile in hypertensive middle-aged men.

The alpha-blockers prazosin and doxazosin reduce hypertriglyceridemia (HTG) and increase serum levels of high-density lipoprotein (HDL)-cholesterol, whereas beta-blockers such as atenolol have the opposite effect. As HTG is associated with reduced fibrinolysis and hypercoagulability, we investigated the effects of doxazosin and atenolol on serum lipids and hemostatic factors in hypertensive men with an atherothrombogenic risk profile. The study was randomized and open, but blinded to investigator of biochemical results. Forty-five men (mean age, 44.5 years) with central obesity [median body-mass index (BMI), 28 kg/m2] and moderate hypertension [median diastolic blood pressure (DBP), 104.5 mm Hg] were treated with atenolol (n = 22) or doxazosin (n = 23) for 22 weeks, after which changes in between-group differences from baseline were estimated. After intervention, significant between-group differences in favor of doxazosin were found: lower triglycerides (p = 0.008) and higher HDL cholesterol (p = 0.036); furthermore, improvement of fibrinolysis: lower plasminogen activator inhibitor-1 (PAI-1) activity (p = 0.012), higher tissue plasminogen activator (tPA) activity after venous occlusion (VO); and higher levels of serum D-dimer, both unstimulated (p = 0.0016) and after VO (p = 0.0032). In addition, lower levels of serum testosterone were found in the atenolol group (p = 0.0016). A profile with reduced HTG, increased HDL cholesterol, and improved fibrinolysis was obtained with doxazosin when compared with atenolol. Furthermore, the observed decrease in serum testosterone on atenolol treatment would rather favor long-term treatment with doxazosin in this study population.

Adult↗
PubMed1998

Early postoperative calcium levels as predictors of hypocalcemia.

OBJECTIVE: Early, safe postoperative hospital discharge has become a priority in the current environment of cost containment and managed care. One determinant for this following operations of the thyroid or parathyroid glands is a stable postoperative calcium level. This study sought to determine whether early postoperative calcium levels could safely predict hypocalcemia following operations of the thyroid or parathyroid glands. STUDY DESIGN: A retrospective chart review of 197 patients undergoing such operations was undertaken. METHODS: The study population was divided into patients undergoing parathyroid exploration with removal of one or more glands for parathyroid disease ("parathyroid" group) and patients undergoing bilateral thyroid operations ("nonparathyroid" group). Postoperative calcium levels were plotted as a function of time, and the slope between the first two postoperative calcium levels examined. RESULTS: A positive slope predicted normocalcemia in 100% of "nonparathyroid" and 90% of "parathyroid" surgeries. A negative slope was predictive in its magnitude. The nonparathyroid patients who developed postoperative hypocalcemia had an average slope significantly more negative (-0.84% change/h) than patients remaining normocalcemic (-0.49% change/h) (P = .03). Similarly, the parathyroid patients who became hypocalcemic had an average initial slope nearly twice as negative (-1.4% change/h) as patients remaining normocalcemic (-0.78% change/h) (P = .005). CONCLUSIONS: These results indicate that an initial upsloping postoperative calcium curve based on two early postoperative calcium measurements is strongly predictive of a stable postoperative calcium level, and a steeply downsloping initial calcium curve is worrisome for eventual hypocalcemia.

Calcium↗
PubMed1998

B-cell epitopes and quantification of the ESAT-6 protein of Mycobacterium tuberculosis.

ESAT-6 is an important T-cell antigen recognized by protective T cells in animal models of infection with Mycobacterium tuberculosis. In an enzyme-linked immunosorbent assay (ELISA) with overlapping peptides spanning the sequence of ESAT-6, monoclonal antibody HYB76-8 reacted with two peptides in the N-terminal region of the molecule. Assays with synthetic truncated peptides allowed a precise mapping of the epitope to the residues EQQWNFAGIEAAA at positions 3 to 15. Hydrophilicity plots revealed one hydrophilic area at the N terminus and two additional areas further along the polypeptide chain. Antipeptide antibodies were generated by immunization with synthetic 8-mer peptides corresponding to these two regions coupled to keyhole limpet hemocyanin. Prolonged immunization with a 23-mer peptide (positions 40 to 62) resulted in the formation of antibodies reacting with the peptide as well as native ESAT-6. A double-antibody ELISA was then developed with monoclonal antibody HYB76-8 as a capture antibody, antigen for testing in the second layer, and antipeptide antibody in the third layer. The assay was suitable for quantification of ESAT-6 in M. tuberculosis antigen preparations, showing no reactivity with M. bovis BCG Tokyo culture fluid, used as a negative control, or with MPT64 or antigen 85B, previously shown to cross-react with HYB76-8. This capture ELISA permitted the identification of ESAT-6 expression from vaccinia virus constructs containing the esat-6 gene; this expression could not be identified by standard immunoblotting.

Amino Acid Sequence↗
PubMed1998

Identification and characterization of a 29-kilodalton protein from Mycobacterium tuberculosis culture filtrate recognized by mouse memory effector cells.

Culture filtrate proteins from Mycobacterium tuberculosis induce protective immunity in various animal models of tuberculosis. Two molecular mass regions (6 to 10 kDa and 24 to 36 kDa) of short-term culture filtrate are preferentially recognized by Th1 cells in animal models as well as by patients with minimal disease. In the present study, the 24- to 36-kDa region has been studied, and the T-cell reactivity has been mapped in detail. Monoclonal antibodies were generated, and one monoclonal antibody, HYB 71-2, with reactivity against a 29-kDa antigen located in the highly reactive region below the antigen 85 complex was selected. The 29-kDa antigen (CFP29) was purified from M. tuberculosis short-term culture filtrate by thiophilic adsorption chromatography, anion-exchange chromatography, and gel filtration. In its native form, CFP29 forms a polymer with a high molecular mass. CFP29 was mapped in two-dimensional electrophoresis gels as three distinct spots just below the antigen 85 complex component MPT59. CFP29 is present in both culture filtrate and the membrane fraction from M. tuberculosis, suggesting that this antigen is released from the envelope to culture filtrate during growth. Determination of the N-terminal amino acid sequence allowed cloning and sequencing of the cfp29 gene. The nucleotide sequence showed 62% identity to the bacteriocin Linocin from Brevibacterium linens. Purified recombinant histidine-tagged CFP29 and native CFP29 had similar T-cell stimulatory properties, and they both elicited the release of high levels of gamma interferon from mouse memory effector cells isolated during the recall of protective immunity to tuberculosis. Interspecies analysis by immunoblotting and PCR demonstrated that CFP29 is widely distributed in mycobacterial species.

Amino Acid Sequence↗
PubMed1998

Delayed-type hypersensitivity responses to ESAT-6 and MPT64 from Mycobacterium tuberculosis in the guinea pig.

Two antigens from Mycobacterium tuberculosis, ESAT-6 and MPT64, elicited delayed-type hypersensitivity (DTH) skin responses in outbred guinea pigs infected with M. tuberculosis by the aerosol and intravenous routes but not those sensitized with M. bovis BCG or M. avium. The DTH epitope of ESAT-6 was mapped to the C terminus. Nonresponders to the individual antigens were found, but all animals responded to a combination of ESAT-6 and MPT64 or their respective minimal target peptides. Correspondingly, these molecules could form the basis of a new skin test for tuberculosis.

Animals↗
PubMed1998

Two-dimensional electrophoresis for analysis of Mycobacterium tuberculosis culture filtrate and purification and characterization of six novel proteins.

Culture filtrate from Mycobacterium tuberculosis contains molecules which promote high levels of protective immunity in animal models of subunit vaccination against tuberculosis. We have used two-dimensional electrophoresis for analysis and purification of six novel M. tuberculosis culture filtrate proteins (CFPs): CFP17, CFP20, CFP21, CFP22, CFP25, and CFP28. The proteins were tested for recognition by M. tuberculosis-reactive memory cells from different strains of inbred mice and for their capacity to induce a skin test response in M. tuberculosis-infected guinea pigs. CFP17, CFP20, CFP21 and CFP25 induced both a high gamma interferon release and a strong delayed-type hypersensitivity response, and CFP21 was broadly recognized by different strains of inbred mice. N-terminal sequences were obtained for the six proteins, and the corresponding genes were identified in the Sanger M. tuberculosis genome database. In parallel we established a two-dimensional electrophoresis reference map of short-term culture filtrate components and mapped novel proteins as well as already-known CFP.

Amino Acid Sequence↗