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P Kristensen

Publications and source records attributed to P Kristensen.

At least 37 records · Page 2Linked to original sources
PubMed1999

Properties of thiol-specific anti-oxidant protein or calpromotin in solution.

We have isolated calpromotin, a protein reported abundant in human red cells and shown to be of significance for KCl transport. We show that calpromotin is identical to a radical scavenger protein, thiol-specific antioxidant protein (TSA). Calpromotin is known to exist partially as a large complex of identical subunits and partially as dimers probably held together by disulfide bridges. The stability of the high-molecular-weight form was studied by variations of pH and urea concentration. It is shown that the equilibrium between the large complex and the dimeric subunit is governed by the dissociation of a group with a pK value of about 7.5. Dissociation of the complex was also complete at 2.5 M urea, where no unfolding of the peptide chains was detectable.

Amino Acid Sequence↗
PubMed1999

Neurochemical characterization of hypothalamic cocaine- amphetamine-regulated transcript neurons.

The novel neuropeptide cocaine-amphetamine-regulated transcript (CART) is expressed in several hypothalamic regions and has recently been shown to be involved in the central control of food intake. To characterize the hypothalamic CART neurons and understand the physiological functions they might serve, we undertook an in situ hybridization and immunohistochemical study to examine distribution and neurochemical phenotype of these neurons. In situ hybridization studies showed abundant CART mRNA in the periventricular nucleus (PeV), the paraventricular nucleus of the hypothalamus (PVN), the supraoptic nucleus (SON), the arcuate nucleus (Arc), the zona incerta, and the lateral hypothalamic area. The distribution of CART-immunoreactive neurons as revealed by a monoclonal antibody raised against CART(41-89) displayed complete overlap with CART mRNA. Double immunohistochemistry showed co-existence of CART immunoreactivity (CART-IR) and somatostatin in some neurons of the PeV. In the magnocellular division of the PVN as well as the SON, CART-IR was demonstrated in both oxytocinergic and vasopressinergic perikarya. In the medial parvicellular region of the PVN a few CART-IR neurons co-localized galanin, but none was found to co-localize corticotropin-releasing hormone. In the Arc, almost all pro-opiomelanocortinergic neurons were shown to contain CART, whereas no co-localization of CART with NPY was found. In the lateral hypothalamic area nearly all CART neurons were found to contain melanin-concentrating hormone. The present data support a role for CART in neuroendocrine regulation. Most interestingly, CART is co-stored with neurotransmitters having both positive (melanin-concentrating hormone) as well as a negative (pro-opiomelanocortin) effect on food intake and energy balance.

Animals↗
PubMed1999

The hypothalamic satiety peptide CART is expressed in anorectic and non-anorectic pancreatic islet tumors and in the normal islet of Langerhans.

The hypothalamic satiety peptide CART (cocaine and amphetamine regulated transcript) is expressed at high levels in anorectic rat glucagonomas but not in hypoglycemic insulinomas. However, a non-anorectic metastasis derived from the glucagonoma retained high CART expression levels and produced circulating CART levels comparable to that of the anorectic tumors. Moreover, distinct glucagonoma lines derived by stable HES-1 transfection of the insulinoma caused severe anorexia but retained low circulating levels of CART comparable to that of insulinoma bearing or control rats. Islet tumor associated anorexia and circulating CART levels are thus not correlated, and in line with this peripheral administration of CART (5-50 mg/kg) produced no effect on feeding behavior. In the rat two alternatively spliced forms of CART mRNA exist and quantitative PCR revealed expression of both forms in the hypothalamus, in the different islet tumors, and in the islets of Langerhans. Immunocytochemistry as well as in situ hybridization localized CART expression to the somatostatin producing islet D cell. A potential endocrine/paracrine role of islet CART remains to be clarified.

Adenoma, Islet Cell↗
PubMed1999

Tissue-specific processing of cocaine- and amphetamine-regulated transcript peptides in the rat.

Cocaine- and amphetamine-regulated transcript (CART) is a recently discovered hypothalamic peptide regulated by leptin and with a potent appetite-suppressing activity. In the rat, the CART gene encodes a peptide of 116 amino acid residues (or a splice variant 13 residues longer). The predicted signal sequence is 27 amino acid residues, resulting in a prohormone of 89 residues. The CART prohormone contains several potential posttranslational processing sites in the form of mono- and dibasic sequences. In the present study we have purified CART peptides from extracts of adrenal gland, hypothalamus, nucleus accumbens, and pituitary gland (anterior and neurointermediate lobe) of the rat and determined the peptide structures by using microsequencing and mass spectrometry. In none of the tissues examined the long splice variant was found. From the adrenal gland, the CART(1-89) and CART(10-89) peptides were isolated, in contrast to the hypothalamus and nucleus accumbens, from which the shorter form peptides CART(42-89) and CART(49-89) were purified. From the anterior lobe of the pituitary gland, CART(42-89) was isolated, in contrast to the neurointermediate lobe, which contains only CART(49-89). This tissue-specific processing indicates that CART peptides may have different biological functions in the periphery and in the central nervous system.

Animals↗
PubMed1999

Identical subunit topographies of human and yeast 20S proteasomes.

The arrangement of subunits in human 20S proteasomes was recently determined by us by immunoelectron microscopy and chemical cross-linking. The positions of 4 of the 14 subunits differed from those found in the yeast proteasome by X-ray crystallography. Double labeling of human 20S proteasomes with antibodies to subunits C2 and C5 has now shown that these subunits are nearest neighbors. The result contradicts our published model for the human proteasome but is in accordance with the subunit arrangement in yeast proteasomes, suggesting that yeast and human proteasomes most probably have identical subunit arrangements. Immunoelectron microscopy also showed that the C-terminal extension at the human C2 subunit is flexible but takes up a well-defined position in the proteasome.

Antibody Specificity↗
PubMed1999

Recombinant CART peptide induces c-Fos expression in central areas involved in control of feeding behaviour.

We have recently shown that the hypothalamic neuropeptide CART (cocaine-amphetamine-regulated-transcript) is a leptin dependent endogenous satiety factor in the rat. In the present study we confirm and extend our previous observations by showing that intracerebroventricular (i.c.v.) administered CART(42-89) dose-dependently inhibits 3-h food intake in food restricted rats with a lowest effective dose of 0.5 microgram. CART also potently inhibits NPY-induced food intake in satiated rats as well as nighttime food intake in free feeding animals. To identify brain areas potentially involved in mediating the anorectic effects of CART, the temporal expression pattern of the immediate early gene c-fos was examined in the central nervous system by immunohistochemistry in rats receiving recombinant CART. Compared to vehicle, CART induced c-Fos expression in several hypothalamic and brainstem structures implicated in the central control of food intake. In the hypothalamus, high numbers of c-Fos immunoreactive (-ir) cells were observed in the medial parvocellular part of the paraventricular nucleus and in the posterior part of the dorsomedial nucleus. Lower numbers of c-Fos positive nuclei were found in the supraoptic and arcuate nuclei. A relatively high number of c-Fos-ir cells was found in the central nucleus of the amygdala. In the brainstem, c-Fos-positive nuclei were found in the parabrachial nucleus, and in the nucleus of the solitary tract. Notably both the area postrema and the dorsal motor nucleus of the vagus were virtually devoid of c-Fos-ir cells. The present experiments suggest that CART peptide exerts its inhibitory effects on appetite by activating hypothalamic and brainstem neurones implicated in the central control of feeding behaviour and metabolism.

Amphetamine↗
PubMed1999

Exposure scenarios and guidance values for urban soil pollutants.

In general, risk assessments of urban soil pollution are prepared by comparing the levels of pollutants with soil quality criteria. However, large urban areas are contaminated with concentrations of pollutants far exceeding the existing soil quality criteria and would consequently be considered to be of potential risk to humans. This is, however, a rather rigid approach, and for risk management purposes it would be desirable to have more than just one level of soil quality criteria. Therefore, a generic risk assessment model was developed for five different use scenarios: child-care centers, kitchen gardens, ornamental gardens, parks, and sports grounds. In each of the scenarios, three different types of expected behavior are described for children and adults, respectively, resulting in different levels of exposure to the pollutants. For risk management purposes, various guidance values can then be derived for each use scenario. Below a lower guidance value, a free use of the area according to the defined use is possible without an unacceptable risk to the public. Above an upper value, a cutoff of the exposure is necessary. In between, the use may be regulated by different types of advice. The model is still preliminary but was, however, used for derivation of guidance values for five commonly found soil pollutants, of which the results for benzo[a]pyrene and lead are presented.

Adult↗
PubMed1999

Co-localization of growth hormone secretagogue receptor and NPY mRNA in the arcuate nucleus of the rat.

Growth hormone secretagogues (GHS) are small, synthetic compounds which have the potential of releasing growth hormone (GH) from the pituitary. The mechanism of action of GHS has not been fully elucidated. A specific GHS receptor (GHS-R) is expressed in the pituitary gland and in several areas of the brain including the hypothalamus. We have characterized the GHS-R-mRNA-expressing neurons with respect to co-expression of selected neurotransmitters in the hypothalamus. This was done by dual chromogenic and autoradiographic in situ hybridization with riboprobes for GHS-R mRNA and neuropeptide Y (NPY), pro-opiomelanocortin (POMC), somatostatin (SRIH) or GH-releasing hormone (GHRH) mRNA. In the arcuate nucleus, GHS-R mRNA was expressed in 94 +/- 1% of the neurons expressing NPY, 8 +/- 2% of those expressing POMC and 30 +/- 6% expressing SRIH mRNA. 20-25% of the GHRH- mRNA-expressing neurons contained GHS-R mRNA, whereas the vast majority of the arcuate GHS-R-mRNA-containing cells did not contain GHRH mRNA. The finding of a significant co-expression of GHS-R and NPY mRNA in the arcuate nucleus is in accordance with the previous demonstration by Dickson et al. that c-Fos is induced in NPY neurons following GHS administration. These results indicate that GHS have other effects on neuroendocrine regulation than GH release via GHRH neurons. Stimulation of the arcuate NPY neurons via GHS-R may explain the increased appetite and the cortisol release seen after administration of some GHS compounds.

Animals↗
PubMed1999

Parental exposure, adverse pregnancy and offspring effects--perspectives in developmental epidemiology.

Developmental health is governed by biology and the societal culture that shapes family planning. This context should not be ignored in epidemiologic studies that address the effect of parental exposure from environmental and occupational agents on prenatal development, growth and survival, on adverse birth effects, or on postnatal events. It is important to have a thorough basic knowledge of developmental health in the population under study and to consider this basis in study design and performance. One way of accomplishing this task is to combine strengths of population-based cohort studies and nested case-control studies. Sibship-based cohorts and case-control studies that make use of biomarkers may provide particular advantages. Future research on the impact of parental exposure should be more strongly based on biological knowledge about the genetic, immune, and endocrine regulation of prenatal growth and development.

Environmental Exposure↗
PubMed1998

Muscarinic agonists exhibit functional dopamine antagonism in unilaterally 6-OHDA lesioned rats.

(5R,6R) 6-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]oc tane (PTAC) is a selective muscarinic ligand with high affinity for central muscarinic receptors, agonist mode of action at the muscarinic M2 and M4 receptor subtypes and substantially less or no affinity for central dopamine receptors. In the present study PTAC, as well as the muscarinic agonists oxotremorine, RS86 and pilocarpine, inhibited dopamine D1 and D2 receptor agonist induced contralateral rotation in unilaterally 6-OHDA lesioned rats. The dose of SKF 38393 used to induce contralateral rotation also caused an intense Fos protein immunoreactivity in the rat dorsolateral striatum on the lesioned site which was inhibited by PTAC indicating that the inhibition of rotation by PTAC was not due to non-specific peripheral side effects.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1998

Distribution of neuropeptide Y receptor expression in the rat suprachiasmatic nucleus.

Neurones of the suprachiasmatic nucleus constitute the mammalian circadian clock which receives photic information via the retino-hypothalamic tract and to some extent non-photic information via the geniculo-hypothalamic tract. The majority of neurones in the geniculo-hypothalamic tract contains neuropeptide Y and both in vitro and in vivo physiological experiments have demonstrated that neuropeptide Y administered directly into the suprachiasmatic nucleus has the capacity to phase-shift the endogenous circadian rhythm of these neurones. The recent cloning of multiple mammalian neuropeptide Y receptors enabled us to perform an in situ hybridization histochemical study identifying expression of distinct neuropeptide Y receptor encoding mRNAs in the suprachiasmatic nucleus. It was seen that Y1 and Y5 receptor mRNA is highly expressed in neurones of the ventrolateral portion of the suprachiasmatic nucleus while neither Y2 nor Y4 receptor mRNA could be detected in the nucleus. These experiments demonstrate that post-synaptic neuropeptide Y mediated events in the suprachiasmatic nucleus are likely to be mediated by either of these receptors.

Animals↗
PubMed1998

Hypothalamic CART is a new anorectic peptide regulated by leptin.

The mammalian hypothalamus strongly influences ingestive behaviour through several different signalling molecules and receptor systems. Here we show that CART (cocaine- and amphetamine-regulated transcript), a brain-located peptide, is a satiety factor and is closely associated with the actions of two important regulators of food intake, leptin and neuropeptide Y. Food-deprived animals show a pronounced decrease in expression of CART messenger RNA in the arcuate nucleus. In animal models of obesity with disrupted leptin signalling, CART mRNA is almost absent from the arcuate nucleus. Peripheral administration of leptin to obese mice stimulates CART mRNA expression. When injected intracerebroventricularly into rats, recombinant CART peptide inhibits both normal and starvation-induced feeding, and completely blocks the feeding response induced by neuropeptide Y. An antiserum against CART increases feeding in normal rats, indicating that CART may be an endogenous inhibitor of food intake in normal animals.

Animals↗
PubMed1998

Purification and characterisation of a tissue specific elongation factor 1 alpha (EF-1 alpha 2) from rabbit muscle.

The peptide elongation factor 1 alpha (EF-1 alpha) has been isolated and characterised from a number of species. Recently we and others have reported the existence of an isoform of the ubiquitously expressed EF-1 alpha mRNA in higher eukaryotes, including human cells. This isoform has a tissue specific expression pattern, confining it primarily to muscle, heart, and brain. In the present study we have purified the isoform of EF-1 alpha from rabbit muscle. Using partial amino acid analysis, we can conclude that in rabbit muscle essentially only the isoform of elongation factor 1 alpha, designated EF-1 alpha 2, is translated. Preliminary activity assays show that the isoform has the same functional activities as the normal EF-1 alpha, designated EF-1 alpha 1, in relation to protein synthesis, but may behave differently in the ability to bind nucleotides. Based on the availability of the isoforms of EF-1 alpha purified from a mammalian species, it will be possible to conduct further comparative studies in order to elucidate the different functions of EF-1 alpha 1 and EF-1 alpha 2 proteins.

Amino Acid Sequence↗
PubMed1998

The elongation factor 1 A-2 isoform from rabbit: cloning of the cDNA and characterization of the protein.

Eukaryotic elongation factor 1 A (eEF1A, formerly elongation factor-1 alpha) is an important component of the protein synthesis apparatus. Here we report the isolation and characterization of the cDNA sequence encoding rabbit eEF1A-2, an isoform of eEF1A, as well as a structural and functional comparison of the two rabbit isoforms. Northern analysis of the expression pattern of eEF1A-2 showed that this isoform is expressed in skeletal muscle, heart, brain and aorta, while transcripts are not detected in liver, kidney, spleen and lung. In contrast, the previously characterized eEF1A-1 isoform is expressed in all tissues examined except skeletal muscle. We have recently purified eEF1A-2 from rabbit skeletal muscle. By partial amino acid sequencing and determination of the post-translational modifications of eEF1A-2 we found that both of the glycerylphosphorylethanolamine modifications observed in eEF1A-1 appear to be present in eEF1A-2. However, two of the residues found dimethylated in eEF1A-1 appeared to be trimethylated in eEF1A-2. A comparison of the enzymatic activity showed that eEF1A-1 and eEF1A-2 have indistinguishable activity in an in vitro translation system. In contrast, the GDP dissociation rate constant is approximately 7 times higher for eEF1A-1 than for eEF1A-2. The nucleotide preference ratio (GDP/GTP) for eEF1A-1 was 0.82, while the preference ratio for eEF1A-2 was 1.50.

Amino Acid Sequence↗
PubMed1998

CART, a new anorectic peptide.

Cocaine and amphetamine regulated transcript peptide (CART), is a recently discovered hypothalamic peptide with a potent appetite suppressing activity. In the rat the CART gene encodes a peptide of either 129 or 116 amino acid residues whereas only the short form exists in humans. The predicted signal sequence is 27 amino acid residues resulting in a prohormone of 102 or 89 residues. The C-terminal end of CART, consisting of 48 amino acid residues and 3 disulphide bonds, is thought to constitute a biologically active part of the molecule. In the central nervous system CART is highly expressed in many hypothalamic nuclei, some of which are involved in regulating feeding behaviour. The CART mRNA is regulated by leptin, and the expressed CART is a potent inhibitor of feeding that even overrides the feeding response induced by neuropeptide Y. The putative CART receptor is therefore a potential therapeutic target for an anti-obesity drug.

Amino Acid Sequence↗
PubMed1998

Proteolytic selection for protein folding using filamentous bacteriophages.

BACKGROUND: Filamentous bacteriophages have been used for the selection of folded peptide and protein 'ligands' by binding the phage to 'receptor'-coated solid phase. Here, using proteolysis, we have developed a technique for the selection of folded and stable proteins that is independent of their binding activities. RESULTS: When a 21-residue peptide comprising a protease cleavage site was introduced into the flexible linker between the second and third domains of the minor coat protein p3 of filamentous bacteriophage, the phages could be cleaved by trypsin and were rendered non-infective. By contrast, phages displaying mutant barnases at this site were resistant to proteolysis, but were cleaved and their infectivity was destroyed as the temperature was raised. By mixing phages bearing two barnase mutants of differing stability, and adding protease at a temperature at which one mutant was resistant and the other was sensitive, we were able to enrich by 1.6 x 10(4)-fold for phages bearing the more stable barnase. CONCLUSIONS: The approach provides a means for the selection of folded and stable proteins, and may be applicable to the selection of de novo proteins.

Amino Acid Sequence↗
PubMed1998

Implementing clinical guidelines in the treatment of hypertension in general practice.

Discrepancies between clinical guidelines and clinical practice call for practical implementation strategies. This study evaluates the implementation of clinical guidelines for hypertension in general practice with a specific computer-based clinical decision support system (CDSS) as part of the intervention. We carried out a randomized study of general practice health centres in Sør- and Nord-Trøndelag counties in Norway (population 380000). A total of 17 health centres were included, with 24 doctors and 984 patients in the intervention group. Data from 887 patients was used in the analyses. There were 12 health centres with 29 doctors and 1255 patients in the control group. Data from 1127 control patients was used in the analyses. The main outcome measures were doctor's behaviour, measured by adherence to registration of recommended variables in the Norwegian clinical guidelines for hypertension. The aim of the intervention was to lower the fractions of patients without registrations. However, there were no clinically significant differences between the intervention group and the control group for fractions of patients without registration of blood pressure (intervention group 14.3%, control group 14.2%) or serum cholesterol (62.3% vs. 56.8%) during 12 months, nor, during 18 months, for fractions of patients without a registration of cigarette smoking (82.9% vs. 87.1%), cardiovascular inheritance (79.5% vs. 73.4%) and body mass index (81.5% vs. 89.2%). One or several variables necessary for calculation of risk score for myocardial infarction were missing in 91.7% of patients in the intervention group and 91.9% of patients in the control group. Large centre variations were shown for all variables. Implementation of clinical guidelines in the treatment of hypertensive patients in general practice, by means of a CDSS and several procedures for implementation did not result in clinically significant changes in the doctors' behaviour. Of importance are both the lack of user-friendliness of the specific CDSS and problems in performing time-consuming multidimensional procedures.

Adult↗