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P Jensen

Publications and source records attributed to P Jensen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Positive selection of CD4(+) T cells is induced in vivo by agonist and inhibited by antagonist peptides.

The nature of peptides that positively select T cells in the thymus remains poorly defined. Here we report an in vivo model to study the mechanisms of positive selection of CD4(+) T cells. We have restored positive selection of TCR transgenic CD4(+) thymocytes, arrested at the CD4(+)CD8(+) stage, due to the lack of the endogenously selecting peptide(s), in mice deficient for H2-M and invariant chain. A single injection of soluble agonist peptide(s) initiated positive selection of CD4(+) transgenic T cells that lasted for up to 14 days. Positively selected CD4(+) T cells repopulated peripheral lymphoid organs and could respond to the antigenic peptide. Furthermore, coinjection of the antagonist peptide significantly inhibited agonist-driven positive selection. Hence, contrary to the prevailing view, positive selection of CD4(+) thymocytes can be induced in vivo by agonist peptides and may be a result of accumulation of signals from TCR engaged by different peptides bound to major histocompatibility complex class II molecules. We have also identified a candidate natural agonist peptide that induces positive selection of CD4(+) TCR transgenic thymocytes.

Amino Acid Sequence↗
PubMed2001

Domestication effects on foraging strategies in fowl.

Birds of two different breeds differing in degree of domestication were studied to reveal any differences in foraging strategies between them. The breeds were wild-type birds (crossing between red jungle fowl (Gallus gallus) and Swedish bantam (Gallus gallus domesticus) and domestic birds (Swedish bantam), breeds representing an increasing level of domestication. Bantam birds have not been selected for any specific characteristics. The birds were allowed to forage in an experimental pen containing two separate food patches, which depleted as a function of being exploited, to see how well the different breeds were able to assess costs and benefits as the distance between patches were changed (short distance between patches compared to long distance between patches). Both breeds behaved in accordance with some general predictions of optimal foraging theory, i.e. moved between patches, left patches before these were empty and stayed for a shorter time in more depleted patches. Wild-type birds responded more than domestic birds to an increase of distance between patches, by spending longer average time in patch when there was a long distance between them compared to when there was a short distance. The wild-type birds adopted what seemed to be a more costly foraging strategy, moving more between patches than the domestic birds without ingesting more feed. During domestication, in the protected environment provided by man, individuals using less costly behavioural strategies may have gained increased fitness over those spending more energy on foraging. Although domestic birds still possessed the ability to respond adaptively to environmental conditions, the differences between the wild-type and the domestic breed might be a result of the reduction of the natural selection pressure which accompanies domestication.

Journal Article↗
PubMed2001

Autoantibodies to pancreatic hsp60 precede the development of glucose intolerance in patients with cystic fibrosis.

Persons expressing the genetic disease cystic fibrosis (CF) suffer from a high risk of developing impaired glucose tolerance and diabetes. The development of diabetes in CF has been attributed, in the past, to the destruction of pancreatic islets and their resident beta-cells secondary to the destruction of the surrounding tissue by mechanical clogging of the pancreatic exocrine ducts. However, the discovery that autoimmunity to the 60-kDa heat shock protein (hsp60) may cause type I diabetes in NOD mice raises the possibility that hsp60 autoimmunity may be involved in CF diabetes too; could the hyperimmunization to bacterial hsp60 characteristic of CF spread to self-hsp60 and hence to autoimmune diabetes? We now report that rising levels of IgG autoantibodies to hsp60 do indeed precede the appearance of glucose intolerance and diabetes in CF patients. We produced a recombinant human pancreatic hsp60 protein and investigated the IgG antibody response to hsp60 in prediabetic and non-diabetic patients with CF. To detect hsp60 autoantibodies in the presence of high levels of antibodies to bacterial hsp60, we absorbed test sera with the 60-kDa GroEL of Pseudomonas aeruginosa and used an immunostaining technique. Using this technique, 32 prediabetic CF patients were evaluated over a five-year period, three years, on the average, before the onset of glucose intolerance. We found that a significant increase in hsp60 autoantibody preceded impaired glucose tolerance (P=0.042, n=17), diabetes (P=0.011, n=15) and glucose intolerance (P=0.005, n=32). As has been observed in NOD mice and in type I diabetic patients, the hsp60 autoantibodies decline at the outbreak of glucose intolerance in the CF patients. The association of CF diabetes with the rise and fall of hsp60 autoimmunity suggests that the pathogenesis of the diabetes may not be merely mechanical, but arise in the wake of bacterial hyperimmunisation.

Adolescent↗
PubMed2001

Freunds adjuvant alone is antiatherogenic in apoE-deficient mice and specific immunization against TNFalpha confers no additional benefit.

TNFalpha participates in the pathogenesis of atherosclerosis. The effect of immunization against TNFalpha on development of advanced vascular lesions in atherosclerosis-susceptible apoE-deficient mice was investigated. At 5-7 weeks of age, animals received immunization with either Freunds adjuvant and a recombinant antigenic TNFalpha molecule (TNF106), Freunds adjuvant alone, or no immunization. All mice received a Western-type high-fat diet for 12 weeks. Aortic sinus lesion area was determined by microscopic morphometry, the total aortic arch cholesterol content was determined by gas chromatography, and antibodies against TNFalpha, malondialdehyde-modified low density lipoprotein, or heat shock protein 60, were assessed by ELISAs. Immunization with TNF106 induced high-titered circulating antibodies against TNFalpha (n=23), and these antibodies were not detected in mice immunized with Freunds adjuvant alone (n=22), or in non-immunized control animals (n=25). After 12 weeks, the atherosclerotic lesion size was significantly reduced in immunized animals, whether they had been immunized with TNF106 or Freunds adjuvant alone, and the total lesional cholesterol content was decreased in mice immunized with TNF106. There were no correlations between circulating antibody titers and plaque size, total aortic arch cholesterol content, or plasma lipid levels, respectively. Administration of Freunds adjuvant alone can thus reduce formation of mature atherosclerotic lesions in apoE-deficient mice and this response is not modified by specific immunization against TNFalpha.

Animals↗
PubMed2001

Relative increase in IgG antibodies to Pseudomonas aeruginosa 60-kDa GroEL in prediabetic patients with cystic fibrosis.

In recent years research has focused on a possible connection between bacterial infection and development of diabetes mellitus. In this study, serum antibody responses against bacterial antigens in diabetic and nondiabetic patients with cystic fibrosis (CF) were evaluated. The first part of the study included 252 CF patients of whom 46 (18 %) had diabetes. This study showed that precipitating antibodies (precipitins) against Pseudomonas aeruginosa and other bacteria in crossed immunoelectrophoresis, and IgG antibodies against a 60-kD GroEL of P. aeruginosa, were highly variable and positively correlated with age. Patient material matched for age and sex showed no significant difference between diabetic and nondiabetic CF patients in precipitins or IgG antibodies to P. aeruginosa GroEL. Two longitudinal studies of 9 and 5 y using retrospectively selected sera from 29 prediabetic and 29 cross-matched nondiabetic CF patients were performed. As to precipitins against P. aeruginosa, we found no difference between the prediabetic and the nondiabetic group of patients during the study period. The study revealed, however, a significant increase of 24.6 % (p = 0.008) of IgG antibodies against P. aeruginosa 60-kD GroEL, 3-12 mo before the onset of diabetes in patients with CF, compared with an overall increase of 5 % to 6 % per year in both groups during the observation period. This study shows that diabetes in CF appears after a peak of serum IgG antibodies against GroEL and indicates that development of diabetes in CF patients may not only be caused by a progressive fibrosis of the pancreatic tissue, but may be augmented by a short-term specific immunologic reaction, initially triggered by an ongoing and progressive pulmonary infection.

Adolescent↗
PubMed2000

Dimensions of maternal behaviour characteristics in domestic and wildxdomestic crossbred sows.

We examined the maternal behaviour of seven domestic and seven wildxdomestic primiparous sows during 10 days post partum to investigate two questions: (1) Did maternal behaviour change during domestication? (2) Can the interindividual variability of maternal behaviour be subsumed into a few dimensions of maternal temperament? We recorded: (a) willingness to leave the nest for food on Day 2; (b) reaction to a playback of squeezed piglet distress vocalisation on Day 2; (c) spontaneous nursing behaviour and spontaneous lying-down behaviour on Day 5 (from an overnight video recording); (d) reactions to playbacks of various piglet distress vocalisations on Day 6 and (e) reactions to a human in the 'nest' with piglets on Day 9. Moreover, data on baseline cortisol saliva concentration and its increase during a brief transportation period and novel environment challenge at the age of 5 months were available. Crossbred sows did not differ from domestic ones in any aspect of maternal behaviour except for a higher tendency to terminate final massage during nursings and a higher frequency of changing posture from lying to standing and back during the night. Factor analysis (based on correlation matrix of 11 behaviour and cortisol variables calculated for all 14 sows after removing the effect of breed) indicated that 82% of the variability in the data could be explained by three factors: first, 'calmness' on which low night time frequency of major posture changes, carefulness of lying-down behaviour and high propensity to remain in nursing position after milk ejection loaded positively while cortisol concentrations during challenge loaded negatively; second, 'protectiveness' with high loadings of the reaction scores to the playbacks of piglet distress calls and the human presence near the piglets; and third, 'nursing activity' which was strongly positively associated with nursing frequency, and negatively with the proportion of nutritive nursings and baseline cortisol values. The results indicate that most aspects of pig maternal behaviour have not been significantly changed by domestication and that substantial variability in maternal behaviour exists between sows, perhaps in the form of several behaviour characteristics which encompass both behaviour and endocrine profiles of the sows.

Journal Article↗
PubMed2000

Self-penetration--a structural compromise between single networks and interpenetration: magnetic properties and crystal structures of

The three-dimensional coordination polymers [Mn(dca)2(H2O)] (1) and [M(dca)(tcm)], M =Co (2), Ni (3), Cu (4), dca =dicyanamide, N(CN)2-, tcm = tricyanomethanide, C(CN)3-, have isomorphous structures. In 1 half the dca ligands coordinate directly (through all three nitrogen atoms) to three Mn atoms (all metal atoms are six-coordinate), while the other half coordinate to two Mn atoms (through the nitrile nitrogens) and hydrogen bond to water molecules coordinated to a third Mn atom (through the amide nitrogen). This dca. H2O structural moiety is disordered over a mirror plane, and is replaced by the structurally equivalent tcm ligand in compounds 2-4. The resulting structures display a new self-penetrating 3,6-connected (2:1) network topology that can be related to, but is different from, the rutile net. The self-penetrating [M(dca)(tcm)] network can be viewed as a structural compromise between the two interpenetrating rutile-like networks of [M(tcm)2] and the single rutile-like network of alpha-[M(dca)2]. The temperature and field dependence of the DC and AC magnetic susceptibilities and magnetisations has been measured for complexes 1-4. Compounds 1-3 exhibit long-range magnetic order with critical temperatures of 6.3 K for 1, 3.5 K for 2 and 8.0 K for 3. The Cu11 compound 4 does not order and is essentially a paramagnet. Hysteresis measurements of coercive field and remnant magnetisation show that 1, 2 and 3 are soft magnets, 1 being a canted-spin antiferromagnet (weak ferromagnet), while 2 and 3 are ferromagnets that display some unusual features in their high-field magnetisation isotherms in comparison to their related alpha-[M(dca)2] phases.

Journal Article↗
PubMed2000

Changing shapes in the nanoworld

What are the mechanisms leading to the shape relaxation of three-dimensional crystallites? Kinetic Monte Carlo simulations of fcc clusters show that the usual theories of equilibration, via atomic surface diffusion driven by curvature, are verified only at high temperatures. Below the roughening temperature, the relaxation is much slower, kinetics being governed by the nucleation of a critical germ on a facet. We show that the energy barrier for this step linearly increases with the size of the crystallite, leading to an exponential dependence of the relaxation time.

Journal Article↗
PubMed2000

The effects of weight asymmetry and resource distribution on aggression in groups of unacquainted pigs.

The relationship between weight asymmetry and aggression when mixing groups of unacquainted pigs in two different environments was investigated. Ten groups of 4 female (LandracexYorkshire), unacquainted pigs with a weight asymmetry of 3.1+/-0.2 kg (mean weight: 16.6+/-0.6 kg) between each pig, and another 10 groups with a weight asymmetry of 1.2+/-0.1 kg (mean weight: 14.1+/-0.1 kg), were mixed at the age of 7 weeks. Ten of the groups (five of each) were mixed in an experimental pen with a heterogeneous distribution of straw. The pen consisted of two main compartments with straw in one of them, and a passage area with concrete floor in between. The other 10 groups were mixed in the same pen, but with a homogenous distribution of straw (straw spread all over the pen).The results showed that fighting duration was significantly shorter in groups with large weight asymmetry than in groups with small weight asymmetry irrespective of the environment. The number of bites delivered during the fights in the heterogeneous environment was lower in groups with large weight asymmetry than in groups with small weight asymmetry. In the homogenous environment, however, there was no significant difference between groups with large and small weight asymmetries regarding the number of bites. The combination of a limited straw area and a small weight asymmetry resulted in the greatest number of bites. In groups with large weight asymmetry, the largest pig won around 50% of the fights, and 25% of the variation in the percentage of fights won was explained by the weight asymmetry.In groups with small weight asymmetry, less than 10% of the variation in the percentage of fights won could be explained by weight asymmetry. The two largest pigs delivered significantly more bites and spent significantly more time fighting than the smallest pig. The second largest pig received significantly more bites and body lesions than the smallest pig in the groups. Fights between the two largest pigs had a significantly longer duration than when other pigs were involved. The results were discussed in relation to sequential assessment theory and resource defence theory.

Journal Article↗
PubMed2000

[From psychiatric hospital to residential home for younger psychiatric patients. A cross-over study of residents in Sundbygaard in Copenhagen]].

Along with the implementation of community psychiatry, an increasing number of younger psychiatric patients live in social institutions, with psychiatric treatment offered on a consultation basis. On the basis of hospital records and interviews with staff members, the study describes two groups of patients in a former psychiatric nursing hospital, group 1 offered time-limited stay with the aim of social rehabilitation, and group 2 offered permanent stay. Patients of group 1 were younger and more frequently treated with atypical antipsychotics. Apart from this, no differences were found. The vast majority of both groups suffered from schizophrenia. The intensity of symptoms was high, despite extensive medication. The two groups might represent the same category of the most severely disabled patients, seen at different ages. More intensive psychiatric consultant service is found necessary, and the process of rehabilitation should be evaluated prospectively.

Adult↗
PubMed2000

No limiting role for glycogenin in determining maximal attainable glycogen levels in rat skeletal muscle.

We examined whether the protein level and/or activity of glycogenin, the protein core upon which glycogen is synthesized, is limiting for maximal attainable glycogen levels in rat skeletal muscle. Glycogenin activity was 27.5 +/- 1.4, 34.7 +/- 1.7, and 39.7 +/- 1.3 mU/mg protein in white gastrocnemius, red gastrocnemius, and soleus muscles, respectively. A similar fiber type dependency of glycogenin protein levels was seen. Neither glycogenin protein level nor the activity of glycogenin correlated with previously determined maximal attainable glycogen levels, which were 69.3 +/- 5.8, 137.4 +/- 10.1, and 80.0 +/- 5.4 micromol/g wet wt in white gastrocnemius, red gastrocnemius, and soleus muscles, respectively. In additional experiments, rats were exercise trained by swimming, which resulted in a significant increase in the maximal attainable glycogen levels in soleus muscles ( approximately 25%). This increase in maximal glycogen levels was not accompanied by an increase in glycogenin protein level or activity. Furthermore, even in the presence of very high glycogen levels ( approximately 170 micromol/g wet wt), approximately 30% of the total glycogen pool continued to be present as unsaturated glycogen molecules (proglycogen). Therefore, it is concluded that glycogenin plays no limiting role for maximal attainable glycogen levels in rat skeletal muscle.

Animals↗
PubMed1999

Rescue of cerebellar granule cells from death in weaver NR1 double mutants.

The weaver mutation results in the extensive death of midline cerebellar granule cells. The mutation consists of a single base pair substitution of the gene encoding the G-protein-activated inwardly rectifying potassium channel protein, GIRK2. The functional consequences of this mutation are still in dispute. In this study we demonstrate the in vivo and in vitro rescue of weaver granule cells when NR1 NMDA subunits are eliminated in weaver NR1 double mutants. This rescue of weaver granule cells provides evidence that wvGIRK2 alone is not sufficient to cause granule cell death.

Aging↗
PubMed1999

[Primary hyperoxaluria type 1 detected by liver biopsy].

PH1 is caused by deficiency of the liver-specific peroxisomal enzyme alanine: glycoxylate aminotransferase (AGT). Early onset with progressive renal failure and systemic oxalosis is typical. We report a case of a 42 year-old man with PH1 in whom liver biopsy and DNA-analysis showed reduced AGT-activity and homozygosity for the polymorphism C154T and the point mutation G630A. The patient seems to respond to pyridoxine treatment. We suggest that clinical suspicion of PH1 be pursued with a diagnostic liver biopsy.

Adult↗
PubMed1999

A Theoretical Investigation of the Renner Interactions and Magnetic Dipole Transitions in the Ã-&Xtilde; Electronic Band System of HO(2).

The Ã(2)A' --> &Xtilde;(2)A" electronic band system of HO(2) has been simulated in emission using an extended version of the program RENNER (P. Jensen, M. Brumm, W. P. Kraemer, and P. R. Bunker, J. Mol. Spectrosc. 171, 31-57 (1995)). The two electronic states involved in this transition have strongly bent equilibrium geometries but they correlate together to form a (2)Pi state at linearity. As a result the energy level pattern in the states is affected by electronic angular momentum effects (i.e., the Renner effect and spin-orbit coupling). To simulate the spectrum, we have calculated ab initio the potential energy surfaces, electric dipole moment surfaces, magnetic dipole moment surfaces, spin-orbit coupling parameter, and the electronic angular momentum matrix elements. Some of the forbidden DeltaK(a) = 0 transitions occurring in the spectrum are induced by the magnetic dipole transition moment, and the others are electric dipole transitions that gain intensity because of the Renner interaction, spin-orbit coupling, or because of rotation-vibration interaction. All of these effects are allowed for in our calculation. The electric dipole transition moment is very small (0.017 D at the ground state equilibrium geometry) and because of this the magnetic dipole transitions are quite visible; the strongest magnetic dipole transitions are calculated to be about 10 times weaker than the strongest electric dipole transitions. In this way previous experimental assignments (E. H. Fink and D. A. Ramsay, J. Mol. Spectrosc. 185, 304-324 (1997)) are confirmed theoretically. Copyright 1999 Academic Press.

Journal Article↗