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P Andersen

Publications and source records attributed to P Andersen.

At least 163 records · Page 9Linked to original sources
PubMed1995

Purification and characterization of a low-molecular-mass T-cell antigen secreted by Mycobacterium tuberculosis.

A novel immunogenic antigen, the 6-kDa early secretory antigenic target (ESAT-6), from short-term culture filtrates of Mycobacterium tuberculosis was purified by hydrophobic interaction chromatography and anion-exchange chromatography by use of fast protein liquid chromatography. The antigen focused at two different pIs of 4.0 and 4.5 during isoelectric focusing, and each of these components separated into three spots ranging from 4 to 6 kDa during two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The apparent differences in molecular masses or pIs of these isoforms were not due to posttranslational glycosylation. The molecular weight of the purified native protein was determined by applying gel filtration and nondenaturing polyacrylamide gel electrophoresis and found to be 24 kDa. ESAT-6 is recognized by the murine monoclonal antibody HYB 76-8, which was used to screen a recombinant lambda gt11 M. tuberculosis DNA library. A phage expressing a gene product recognized by HYB 76-8 was isolated, and a 1.7-kbp fragment of the mycobacterial DNA insert was sequenced. The structural gene of ESAT-6 was identified as the sequence encoding a polypeptide of 95 amino acids. The N terminus of the deduced sequence could be aligned with the 10 amino-terminal amino acids derived from sequence analyses of the native protein. N-terminal sequence analysis showed that the purified antigen was essentially free from contaminants, and the amino acid analysis of the antigen was in good agreement with the DNA sequence-deduced amino acid composition. Thus, the heterogeneities observed in the pI and molecular weight of the purified antigen do not derive from contaminating proteins but are most likely due to heterogeneity of the antigen itself. Native and recombinant ESAT-6 are immunologically active in that both elicited a high release of gamma interferon from T cells isolated from memory-immune mice challenged with M. tuberculosis. Analyses of subcellular fractions of M. tuberculosis showed the presence of ESAT-6 in cytosol- and cell wall-containing fractions. Interspecies analyses showed the presence of ESAT-6 in filtrates from M. tuberculosis complex species. Among filtrates from mycobacteria not belonging to the M. tuberculosis complex, reactivity was observed in Mycobacterium kansasii, Mycobacterium szulgai, and Mycobacterium marinum.

Amino Acid Sequence↗
PubMed1994

An increase in dendritic spine density on hippocampal CA1 pyramidal cells following spatial learning in adult rats suggests the formation of new synapses.

The search for cellular correlates of learning is a major challenge in neurobiology. The hippocampal formation is important for learning spatial relations. A possible long-lasting consequence of such spatial learning is alteration of the size, shape, or number of excitatory synapses. The dendritic spine density is a good index for the number of hippocampal excitatory synapses. By using laser-scanning confocal microscopy, we observed a significantly increased spine density in CA1 basal dendrites of spatially trained rats when compared to nontrained controls. With unchanged dendritic length, the higher spine density reflects an increased number of excitatory synapses per neuron associated with spatial learning.

Animals↗
PubMed1994

Global fibrinolytic capacity assessed by the serum D-dimer test. Correlation between basal and stimulated values.

Evaluation of fibrinolytic capacity is mostly done after stimulation by venous occlusion (VO) or 1-desamino-8-d-arginine vasopressin (DDAVP), either with global tests or with measurements of the specific fibrinolytic components. The serum D-dimer test has recently been described as a global fibrinolytic test in unstimulated individuals, and related to different levels of fibrinolytic activity. In the present study, we have compared the levels of serum D-dimer and t-PA before and after VO in order to see if the unstimulated values reflect the fibrinolytic capacity after stimulation. Twenty-eight healthy individuals and 126 patients with different metabolic disorders and/or coronary heart disease were included. Blood was drawn in a fasting state between 8 and 10 a.m. before and after VO for determinations of serum D-dimer after standardized coagulation, and of t-PA activity and antigen. There was a 7-fold increase in the median levels obtained after VO both for serum D-dimer and t-PA activity, whereas the increase in t-PA antigen was about 2.5 fold. The correlation coefficients between the levels of serum D-dimer, t-PA activity and t-PA antigen before and after VO were 0.63 (p < 0.001), 0.72 (p < 0.001) and 0.23 (p < 0.05), respectively. We conclude that the basal levels of t-PA and serum D-dimer to a certain degree reflect the fibrinolytic capacity after stimulation. Thus, the unstimulated serum D-dimer test, which reflects both t-PA and PAI-1, could be recommended as a global screening method for evaluation of the fibrinolytic potential.

Adult↗
PubMed1994

Specificity of protein kinase inhibitor peptides and induction of long-term potentiation.

Previous studies have used synthetic peptide analogs, corresponding to sequences within the pseudosubstrate domain of protein kinase C (PKC) or the autoregulatory domain of Ca2+/calmodulin-dependent protein kinase II (CaMKII), in attempts to define the contribution of each of these protein kinases to induction of long-term potentiation (LTP). However, the specificity of these inhibitor peptides is not absolute. Using intracellular delivery to rat CA1 hippocampal neurons, we have determined the relative potency of two protein kinase inhibitor peptides, PKC-(19-36) and [Ala286]CaMKII-(281-302), as inhibitors of the induction of LTP. Both peptides blocked the induction of LTP; however, PKC-(19-36) was 30-fold more potent than [Ala286]CaMKII-(281-302). The relative specificity of PKC-(19-36), [Ala286]CaMKII-(281-302), and several other CaMKII peptide analogs for protein kinase inhibition in vitro was also determined. A comparison of the potencies of PKC-(19-36) and [Ala286]CaMKII-(281-302) in the physiological assay with their Ki values for protein kinase inhibition in vitro indicates that the blockade of induction of LTP observed for each peptide is attributable to inhibition of PKC.

Amino Acid Sequence↗
PubMed1994

The T cell response to secreted antigens of Mycobacterium tuberculosis.

Recent information from several laboratories points to proteins secreted from live Mycobacterium tuberculosis as being involved in protective immunity. We have studied protein release from M. tuberculosis during growth and have defined 3 different groups of proteins: excreted proteins, secreted proteins of the outer cell wall and cytoplasmic proteins released at late culture timepoints. These findings have lead to the definition of a short-term culture filtrate (ST-CF) enriched in excreted/secreted proteins and with a minimal content of autolytic products. ST-CF was tested as antigen in experimental vaccines against tuberculosis. A vaccine based on the adjuvant dimethyldioctadecylammonium chloride (DDA) was constructed and demonstrated to induce a potent cell mediated immune response of the Th-1 type. The vaccine was tested in parallel with a BCG standard vaccine and both vaccines induced a highly significant protection of the same magnitude. Molecules within the Ag85 complex and a 6-kDA secreted protein were mapped as the major antigenic targets for long-lived T cells involved in protective immunity against M. tuberculosis.

Animals↗
PubMed1994

Effective vaccination of mice against Mycobacterium tuberculosis infection with a soluble mixture of secreted mycobacterial proteins.

An experimental vaccine that was based on secreted proteins of Mycobacterium tuberculosis was investigated in a mouse model of tuberculosis. I used a short-term culture filtrate (ST-CF) containing proteins secreted from actively replicating bacteria grown under defined culture conditions. The immunogenicity of the ST-CF was investigated in combination with different adjuvants, and peak proliferative responses were observed when ST-CF was administered with the surface-active agent dimethyldioctadecylammonium chloride. The immunity induced by this vaccine was dose dependent, and, in the optimal concentration, the vaccine induced a potent T-helper 1 response which efficiently protected the animals against a subsequent challenge with virulent M. tuberculosis. Antigenic targets for the T cells generated were mapped by employing narrow-molecular-weight fractions of ST-CF. The experimental vaccine primed a broadly defined T-cell repertoire directed to multiple secreted antigens present in ST-CF. A vaccination with viable Mycobacterium bovis bacillus Calmette-Guérin (BCG), in contrast, induced a restricted T-cell reactivity directed to two secreted protein fractions with molecular masses of 5 to 12 and 25 to 35 kDa. The protective efficacy of the ST-CF vaccine was compared with that of a BCG standard vaccine, and both induced a highly significant protection of equal magnitude. The vaccination with ST-CF gave rise to a population of long-lived CD4 cells which could be isolated 22 weeks after the vaccination and could adoptively transfer acquired resistance to T-cell-deficient recipients. My results confirm the hypothesis that M. tuberculosis cells release protective antigens during growth. The high efficacy of a subunit vaccine observed in the present study is discussed as a possible alternative to a live recombinant vaccine carrier.

Animals↗
PubMed1994

Conserved spatial learning in cooled rats in spite of slowing of dentate field potentials.

Behaviorally induced brain temperature changes have significant effects on field potentials recorded in the hippocampal formation. All components of the field potential are slowed during cooling. Field excitatory postsynaptic potentials (f-EPSPs) are often reduced, while the population spike is increased in this state. To investigate whether such synaptic alterations affect hippocampus-dependent learning, we have compared the effects of reduced brain temperature on dentate field potentials and spatial learning in a Morris water maze. Rats were implanted with thermistors in the brain. A subset of the rats received electrodes for field potential recording in the perforant path-granule cell synapses of the dentate gyrus. After recovery, the rats were cooled by swimming in a pool of water. This invariably led to a brain temperature reduction of several degrees centigrade and a delay of the extracellular response. In addition, the field potential changed as described above. The effect of these changes on spatial learning in a second pool, the water maze, was determined by first cooling and then reheating each rat to a given level of brain temperature prior to each spatial training session. In spite of marked changes in dentate field potentials, all rats trained at brain temperatures above 30 degrees C learned to find the submerged platform similarly well. The speed of acquisition and the final precision of search behavior were also similar in these rats. Only rats that had been cooled below 30 degrees C failed to locate the hidden target. These animals also showed clear evidence of motor impairment.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1993

Synaptic potentiation in the rat dentate gyrus during exploratory learning.

To investigate whether hippocampal synaptic transmission is enhanced during learning, we recorded synaptic field potentials in the dentate gyrus in response to stimulation of the perforant path in rats exploring a novel environment. Because these signals rapidly grow during brain temperature elevation, caused by any motor activity, the potentials were compared with signals sampled at similar brain temperatures after passive warming. Both the field excitatory postsynaptic potential (f-EPSP) and the population spike increased significantly early in the exploration, relative to temperature-matched control potentials. The effect decayed within 15-30 minutes. This is the first demonstration of a temperature-independent synaptic potentiation in the hippocampus during learning about the environment. The time course is similar to that of short-term potentiation.

Animals↗
PubMed1993

Simultaneous electroelution of whole SDS-polyacrylamide gels for the direct cellular analysis of complex protein mixtures.

A novel procedure which allow the rapid screening of complex protein mixtures in cellular assays is described. A device has been developed which allows a convenient, simultaneous electroelution of separated proteins from whole SDS polyacrylamide gels into narrow chambers each containing single or a few protein bands. We have optimized the conditions of the procedure and have obtained an efficient removal of SDS, leading to non-toxic protein fractions in a physiological buffer suited for direct testing in cell cultures. The responses generated by stimulating lymphocytes with the purified products have been compared to the native protein and a corresponding preparation of protein transferred to nitrocellulose particles. The method was used to investigate murine T cell responses to secreted mycobacterial antigens during infection with M. tuberculosis. A immunodominant secreted protein fraction was purified in a semipreparative scale by the procedure and used to immunize mice. The specificity of and lymphokine production by T cells generated in these animals were investigated. The device developed has various applications and provides a tool for the possible identification of new T cell antigens of importance for protective immunity.

Animals↗
PubMed1993

Association between brain temperature and dentate field potentials in exploring and swimming rats.

Attempts to correlate behavioral learning with cellular changes, such as increased synaptic efficacy, have often relied on increased extracellular potentials as an index of enhanced synaptic strength. A recent example is the enlarged excitatory field potentials in the dentate gyrus of rats that are learning spatial relations by exploration. The altered hippocampal field potentials do not reflect learning-specific cellular changes but result from a concomitant rise in brain temperature that is caused by the associated muscular effort. Enhanced dentate field excitatory potentials followed both passive and active heating and were linearly related to the brain temperature. These temperature-related effects may mask any learning-induced changes in field potential.

Animals↗
PubMed1993

Identification of formaldehyde releasers and occurrence of formaldehyde and formaldehyde releasers in registered chemical products.

Substances referred to as formaldehyde releasers were identified on review of the literature. Information on product categories and typical concentrations for chemical products containing formaldehyde and formaldehyde releasers was obtained from the Danish Product Register Data Base (PROBAS). As of February 1992, 62,000 products were registered in PROBAS, 30,900 of these with information on composition and product category. Among the components of these products, 19 of the 22 identified formaldehyde releasers were found. The number of products registered with each formaldehyde releaser varied from 4 to 171, with cleaning agents, soaps, shampoos, paint/lacquers, and cutting fluids as the most frequent product categories. The most frequently registered formaldehyde releasers were bromonitropropanediol, bromonitrodioxane, and chloroallylhexaminium chloride. Formaldehyde itself was registered in 1,781 products, and was found in all product categories included in the study. It is concluded that products for industrial use as well as household and personal care products should be considered as sources of formaldehyde exposure. The use of unsystematic chemical names in literature is discussed.

Chemical Industry↗
PubMed1993

Apolipoprotein(a) and cardiovascular disease in type 2 (non-insulin-dependent) diabetic patients with and without diabetic nephropathy.

The relative mortality from cardiovascular disease is on average increased five-fold in Type 2 (non-insulin-dependent) diabetic patients with diabetic nephropathy compared to non-diabetic subjects. We assessed the possible contribution of dyslipidaemia in general and elevated serum apolipoprotein(a) (apo(a)) in particular. Type 2 diabetic patients with normo-, micro- and macroalbuminuria were compared with healthy subjects. Each group consisted of 37 subjects matched for age, sex and diabetes duration. Serum creatinine in the nephropathy group was 105 (54-740) mumol/l. The prevalence of ischaemic heart disease (resting ECG, Minnesota, Rating Scale) was 57, 35, 19 and 2% in macro-, micro- and normoalbuminuric diabetic patients and healthy subjects, respectively. The prevalence of ischaemic heart disease was higher in all diabetic groups as compared to healthy subjects (p < 0.05), and higher in macroalbuminuric as compared to normoalbuminuric diabetic patients (p < 0.01). There was no significant difference between apo(a) in the four groups: 161 (10-1370), 191 (10-2080), 147 (10-942), 102 (10-1440) U/l (median (range)) in macro-, micro- and normoalbuminuric groups and healthy subjects. Serum total-cholesterol, HDL-cholesterol and LDL-cholesterol were not significantly different when comparing healthy subjects and each diabetic group. Apolipoprotein A-I was lower (p < 0.05) in all diabetic groups as compared to healthy subjects (nephropathy vs healthy subjects): 1.50 +/- 0.25 vs 1.69 +/- 0.32 g/l (mean +/- SD). Triglyceride was higher (p < 0.05) in patients with nephropathy and microalbuminuria as compared to healthy subjects (nephropathy vs healthy subjects): 2.01 (0.66-14.7) vs 1.09 (0.41-2.75) mmol/l (median (range)).(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1993

Proliferative responses to purified and fractionated Bordetella pertussis antigens in mice immunized with whole-cell pertussis vaccine.

The specificity of the cell-mediated immune response to Bordetella pertussis following immunization of C57B1 mice with a whole-cell pertussis vaccine was assessed in a proliferation assay. A proliferative response of lymph node lymphocytes to the filamentous haemagglutinin, the 69 kDa outer membrane protein and the agglutinogens 2 and 3 was demonstrated. The proliferative cells were T cells of the CD4+ phenotype. In addition, several as yet uncharacterized antigens expressed by B. pertussis were shown to induce a proliferative response, also mediated by T cells of the CD4+ phenotype. Although a range of different immunization schedules and preparations of pertussis toxin were used, no specific proliferative responses to pertussis toxin, which is regarded as a protective antigen of major importance from B. pertussis, were found.

Adhesins, Bacterial↗