Biomedical subjects

J Persson

Publications and source records attributed to J Persson.

At least 19 recordsLinked to original sources

PubMed2006

Streptococcal M protein: structural studies of the hypervariable region, free and bound to human C4BP.

Streptococcus pyogenes is a Gram-positive bacterium that causes several diseases, including acute tonsillitis and toxic shock syndrome. The surface-localized M protein, which is the most extensively studied virulence factor of S. pyogenes, has an approximately 50-residue N-terminal hypervariable region (HVR) that plays a key role in the escape of the host immunity. Despite the extensive sequence variability in this region, many HVRs specifically bind human C4b-binding protein (C4BP), a plasma protein that inhibits complement activation. Although the more conserved parts of M protein are known to have dimeric coiled-coil structure, it is unclear whether the HVR also is a coiled coil. Here, we use nuclear magnetic resonance (NMR) to study the conformational properties of HVRs from M4 and M22 proteins in isolation and in complex with the M protein binding portion of C4BP. We conclude that the HVRs of M4 and M22 are folded as coiled coils and that the folded nucleus of the M4 HVR has a length of approximately 27 residues. Moreover, we demonstrate that the C4BP binding surface of M4-N is found within a region of four heptad repeats. Using molecular modeling, we propose a model for the structure of the M4 HVR that is consistent with our experimental information from NMR spectroscopy.

Amino Acid Sequence↗

PubMed2006

Altered brain white matter integrity in healthy carriers of the APOE epsilon4 allele: a risk for AD?

BACKGROUND: Previous research has shown that polymorphisms of apolipoprotein E (APOE) represent genetic risk factors for dementia and for cognitive impairment in the elderly. The neural mechanisms by which these genetic variations influence behavioral performance or clinical severity are not well understood. METHODS: The authors used diffusion tensor imaging to investigate ultrastructural properties in brain white matter to detect pathologic processes that modify tissue integrity. Sixty participants were included in the study of which 30 were homozygous for the APOE epsilon3 allele, 10 were homozygous for the APOE epsilon4 allele, and 20 had the APOE epsilon34 allele combination. All individuals were non-demented, and the groups were matched on demographic variables and cognitive performance. RESULTS: The results showed a decline in fractional anisotropy, a marker for white matter integrity, in the posterior corpus callosum of epsilon4 carriers compared to non-carriers. Additional sites of altered white matter integrity included the medial temporal lobe. CONCLUSIONS: Although the mechanism underlying vulnerability of white matter tracts in APOE epsilon4 carriers is still unknown, these findings suggest that increased genetic risk for developing Alzheimer disease is associated with changes in microscopic white matter integrity well before the onset of dementia.

Aged↗

PubMed2006

The lectin-like domain of thrombomodulin interferes with complement activation and protects against arthritis.

BACKGROUND: Thrombomodulin (TM) is predominantly a vascular endothelial cell plasma membrane glycoprotein that, via distinct structural domains, interacts with multiple ligands, thereby modulating coagulation, fibrinolysis, complement activation, inflammation and cell proliferation. We previously reported that by mediating signals that interfere with mitogen-activated protein kinase and nuclear factor kappaB pathways, the amino-terminal C-type lectin-like domain of TM has direct anti-inflammatory properties. METHODS: In the current study, we use murine models of acute inflammatory arthritis and biochemical approaches to assess the mechanism by which the lectin-like domain of TM modifies disease progression. RESULTS: Mice lacking the lectin-like domain of TM (TM(LeD/LeD)mice) develop inflammatory arthritis that is more rapid in onset and more severe than that developed in their wildtype counterparts. In two models of arthritis, treatment of mice with recombinant soluble lectin-like domain of TM significantly suppresses clinical evidence of disease and diminishes monocyte/macrophage infiltration into the synovium, with weaker expression of the pro-inflammatory high mobility group box chromosomal protein 1. While thrombin-TM mediated activation of thrombin activatable fibrinolysis inhibitor inactivates complement factors C3a and C5a, we show that TM has a second independent mechanism to regulate complement: the lectin-like domain of TM directly interferes with complement activation via the classical and lectin pathways. CONCLUSIONS: These data extend previous insights into the mechanisms by which TM modulates innate immunity, and highlight its potential as a therapeutic target for inflammatory diseases.

Animals↗

PubMed2005

Development and use of fluorescent nanosensors for metabolite imaging in living cells.

To understand metabolic networks, fluxes and regulation, it is crucial to be able to determine the cellular and subcellular levels of metabolites. Methods such as PET and NMR imaging have provided us with the possibility of studying metabolic processes in living organisms. However, at present these technologies do not permit measuring at the subcellular level. The cameleon, a fluorescence resonance energy transfer (FRET)-based nanosensor uses the ability of the calcium-bound form of calmodulin to interact with calmodulin binding polypeptides to turn the corresponding dramatic conformational change into a change in resonance energy transfer between two fluorescent proteins attached to the fusion protein. The cameleon and its derivatives were successfully used to follow calcium changes in real time not only in isolated cells, but also in living organisms. To provide a set of tools for real-time measurements of metabolite levels with subcellular resolution, protein-based nanosensors for various metabolites were developed. The metabolite nanosensors consist of two variants of the green fluorescent protein fused to bacterial periplasmic binding proteins. Different from the cameleon, a conformational change in the binding protein is directly detected as a change in FRET efficiency. The prototypes are able to detect various carbohydrates such as ribose, glucose and maltose as purified proteins in vitro. The nanosensors can be expressed in yeast and in mammalian cell cultures and were used to determine carbohydrate homeostasis in living cells with subcellular resolution. One future goal is to expand the set of sensors to cover a wider spectrum of metabolites by using the natural spectrum of bacterial periplasmic binding proteins and by computational design of the binding pockets of the prototype sensors.

Cells↗

PubMed2004

Should euthanasia be legal? An international survey of neonatal intensive care units staff.

OBJECTIVE: To present the views of a representative sample of neonatal doctors and nurses in 10 European countries on the moral acceptability of active euthanasia and its legal regulation. DESIGN: A total of 142 neonatal intensive care units were recruited by census (in the Netherlands, Sweden, Hungary, and the Baltic countries) or random sampling (in France, Germany, Italy, Spain, and the United Kingdom); 1391 doctors and 3410 nurses completed an anonymous questionnaire (response rates 89% and 86% respectively). MAIN OUTCOME MEASURE: The staff opinion that the law in their country should be changed to allow active euthanasia "more than now". RESULTS: Active euthanasia appeared to be both acceptable and practiced in the Netherlands, France, and to a lesser extent Lithuania, and less acceptable in Sweden, Hungary, Italy, and Spain. More then half (53%) of the doctors in the Netherlands, but only a quarter (24%) in France felt that the law should be changed to allow active euthanasia "more than now". For 40% of French doctors, end of life issues should not be regulated by law. Being male, regular involvement in research, less than six years professional experience, and having ever participated in a decision of active euthanasia were positively associated with an opinion favouring relaxation of legal constraints. Having had children, religiousness, and believing in the absolute value of human life showed a negative association. Nurses were slightly more likely to consider active euthanasia acceptable in selected circumstances, and to feel that the law should be changed to allow it more than now. CONCLUSIONS: Opinions of health professionals vary widely between countries, and, even where neonatal euthanasia is already practiced, do not uniformly support its legalisation.

Adult↗

PubMed2003

Cardiovascular autonomic neuropathy associated with carotid atherosclerosis in Type 2 diabetic patients.

AIMS: To clarify if cardiovascular autonomic neuropathy is associated with carotid artery atherosclerotic plaques in Type 2 diabetic patients. METHODS: Cardiovascular autonomic nerve function was related to carotid artery ultrasound in 61 Type 2 diabetic patients 5-6 years after diagnosis of diabetes. RESULTS: Cardiovascular autonomic neuropathy [abnormal age corrected expiration/inspiration (E/I) ratio or acceleration index (AI)] was found in 13/61 (21%) patients. Patients with cardiovascular autonomic neuropathy showed increased degree of stenosis in the common carotid artery (24.6 +/- 13.2% vs. 14.7 +/- 9.2%; P = 0.014) and a tendency towards a higher plaque score (4.0 +/- 1.7 vs. 3.2 +/- 1.6; P = 0.064). Controlled for age, AI correlated inversely with degree of stenosis (r = -0.39; P = 0.005), plaque score (r = -0.39; P = 0.005), and mean (r = -0.33; P = 0.018) and maximum (r = -0.39; P = 0.004) intima-media thickness in the common carotid artery. In contrast, E/I ratio correlated only slightly with mean intima-media thickness in the common carotid artery (r = -0.28; P = 0.049). CONCLUSIONS: Cardiovascular autonomic neuropathy was associated with carotid atherosclerosis in Type 2 diabetic patients. Abnormal E/I ratios reflect efferent structural damage to parasympathetic nerves whereas abnormal AI reflects afferent autonomic dysfunction possibly due to impaired baroreceptor sensitivity secondary to carotid atherosclerosis.

Adult↗

PubMed2002

Pharmacokinetics and non-analgesic effects of S- and R-ketamines in healthy volunteers with normal and reduced metabolic capacity.

OBJECTIVE: There is a growing interest in low-dose ketamine as an analgesic agent in different intractable pain conditions. Due to its narrow therapeutic window, well-defined pharmacokinetic parameters are essential for its successful use in these situations. Arterial data for ketamine or its enantiomers have not been reported before. The metabolic pathways involved in the metabolism of S- and R-ketamines are not known. METHODS: Ten healthy male volunteers received 7 mg infusions of R- and S-ketamine-hydrochloride in a randomised order over 30 min on 2 separate days. Six were extensive metabolisers, two were poor metabolisers of debrisoquine (CYP2D6) and two were poor metabolisers of mephenytoin (CYP2C19). Arterial and venous concentrations and non-analgesic side effects were measured. RESULTS: Subjective side effects were mild but more pronounced for S- than for R-ketamine. There were no salient differences between the subjects with reduced and normal metabolic capacity in pharmacokinetic parameters or in side effects. Volumes of distribution and mean residence times were 40% smaller for arterial than for venous data. The mean clearance of R-ketamine, 0.020 l min(-1) kg(-1), was slightly but significantly lower than of S-ketamine, 0.024 l min(-1) kg(-1). CONCLUSIONS: There are large differences between arterial and venous data in the pharmacokinetic parameters that are heavily dependent on distribution processes. Parameters mainly reflecting elimination, such as clearance and area under the concentration time curve, are unchanged. The choice of sampling site could be important when computer-controlled infusions are used.

Adult↗

PubMed2002

Thoracic epidural anesthesia and epidural hematoma.

This report involves a 74-year-old-male who developed a thoracic epidural hematoma with paraparesis on the second postoperative day in conjunction with thoracic epidural anesthesia established before surgery for acute abdominal aortic dissection. The finding indicates that laminectomy can be performed successfully as late as three days after diagnosis of the hematoma, with a complete restitution of neurological function. High-dose steroid treatment may have been a contributing factor for the positive outcome.

Aged↗

PubMed2001

Isolated hypervariable regions derived from streptococcal M proteins specifically bind human C4b-binding protein: implications for antigenic variation.

Antigenic variation in microbial surface proteins represents an apparent paradox, because the variable region must retain an important function, while exhibiting extensive immunological variability. We studied this problem for a group of streptococcal M proteins in which the approximately 50-residue hypervariable regions (HVRs) show essentially no residue identity but nevertheless bind the same ligand, the human complement regulator C4b-binding protein (C4BP). Synthetic peptides derived from different HVRs were found to retain the ability to bind C4BP, implying that the HVR corresponds to a distinct ligand-binding domain that can be studied in isolated form. This finding allowed direct characterization of the ligand-binding properties of isolated HVRs and permitted comparisons between different HVRs in the absence of conserved parts of the M proteins. Affinity chromatography of human serum on immobilized peptides showed that they bound C4BP with high specificity and inhibition experiments indicated that different peptides bound to the same site in C4BP. Different C4BP-binding peptides did not exhibit any immunological cross-reactivity, but structural analysis suggested that they have similar folds. These data show that the HVR of streptococcal M protein can exhibit extreme variability in sequence and immunological properties while retaining a highly specific ligand-binding function.

Amino Acid Sequence↗

PubMed2001

An ultra-short perineal pad-test for evaluation of female stress urinary incontinence treatment.

We assessed the reproducibility and feasibility of a rapid perineal pad-test designed for evaluation of stress urinary incontinence treatment. In an experimental study, we included 34 women with genuine stress incontinence, 13 with urge incontinence and 10 non-incontinent volunteers for a repeated pad-test with a standardized bladder volume (300 mL) and a standardized physical activity during one minute. The pad was weighed before and after the exercise to estimate the volume of any leaked urine. In order to find out the percentage of unselected, incontinent women who had been able to perform a preoperative pad-test, we identified all 120 women operated on for stress incontinence during a one-year period in a separate retrospective analysis. In another retrospective analysis, we compared the subjective outcome of laparoscopic colposuspension with the outcome of the test performed before and after the procedure among 93 women with genuine stress incontinence. Among stress incontinent women, the median of the differences in leakage between the first and the second test was 8.5 mL (range 0-60 mL) and the repeatability coefficient was 33.6 mL. None of the 13 women with urge incontinence leaked during the tests. One of the 10 controls leaked (during both tests). Of the unselected women, 104/120 (87%) were able to perform the test. Reduction of leaking after surgery was significantly associated with subjective report of outcome (P < 0.0001). In conclusion, the described pad-test has an acceptable reproducibility and feasibility making it suitable for follow-up studies.

Bandages↗

PubMed2001

Anaerobic desulfurization of ground rubber with the thermophilic archaeon Pyrococcus furiosus--a new method for rubber recycling.

The anaerobic sulfur-reducing archaeon Pyrococcus furiosus was investigated regarding its capacity to desulfurize rubber material. The microorganism's sensitivity towards common rubber elastomers and additives was tested and several were shown to be toxic to P. furiosus. The microorganism was shown to utilize sulfur in vulcanized natural rubber and an increase in cell density was obtained when cultivated in the presence of spent tire rubber. Ethanol-leached cryo-ground tire rubber treated with P. furiosus for 10 days was vulcanized together with virgin rubber material (15% w/w) and the mechanical properties of the resulting material were determined. The increase in the stress at break value and the decrease in swell ratio and stress relaxation rate obtained for material containing microbially treated rubber (compared to untreated material) show the positive effects of microbial desulfurization on rubber.

Biotechnology↗

PubMed2001

Binding of human C4BP to the hypervariable region of M protein: a molecular mechanism of phagocytosis resistance in Streptococcus pyogenes.

The amino-terminal hypervariable region (HVR) of streptococcal M protein is required for the ability of this virulence factor to confer phagocytosis resistance. The function of the HVR has remained unknown, but the finding that many HVRs with extremely divergent sequences bind the human complement regulator C4b-binding protein (C4BP) has suggested that this ligand may play a role in phagocytosis resistance. We used the M22 system to study the function of bound C4BP and provide several lines of evidence that C4BP indeed contributes to phagocytosis resistance. First, the ability of anti-HVR antibodies to cause opsonization correlated with their ability to inhibit binding of C4BP. Secondly, a short deletion in the HVR eliminated C4BP binding and also reduced the ability of M22 to confer phagocytosis resistance. Thirdly, the addition of an excess of pure C4BP to a phagocytosis system almost completely blocked the effect of opsonizing anti-HVR antibodies. Together, our data indicate that binding of C4BP to the HVR of M22 plays an important role in phagocytosis resistance, but other properties of M22 also contribute. This study provides the first molecular insight into the mechanisms by which the HVR of an M protein confers phagocytosis resistance.

Amino Acid Sequence↗

PubMed2000

Neonatal end-of-life decision making: Physicians' attitudes and relationship with self-reported practices in 10 European countries.

CONTEXT: The ethical issues surrounding end-of-life decision making for infants with adverse prognoses are controversial. Little empirical evidence is available on the attitudes and values that underlie such decisions in different countries and cultures. OBJECTIVE: To explore the variability of neonatal physicians' attitudes among 10 European countries and the relationship between such attitudes and self-reported practice of end-of-life decisions. DESIGN AND SETTING: Survey conducted during 1996-1997 in 10 European countries (France, Germany, Italy, the Netherlands, Spain, Sweden, the United Kingdom, Estonia, Hungary, and Lithuania). PARTICIPANTS: A total of 1391 physicians (response rate, 89%) regularly employed in 142 neonatal intensive care units (NICUs). MAIN OUTCOME MEASURES: Scores on an attitude scale, which measured views regarding absolute value of life (score of 0) vs value of quality of life (score of 10); self-report of having ever set limits to intensive neonatal interventions in cases of poor neurological prognosis. RESULTS: Physicians more likely to agree with statements consistent with preserving life at any cost were from Hungary (mean attitude scores, 5.2 [95% confidence interval ¿CI¿, 4.9-5.5]), Estonia (4.9 [95% CI, 4.3-5.5]), Lithuania (5.5 [95% CI, 4.8-6.1]), and Italy (5.7 [95% CI, 5.3-6.0]), while physicians more likely to agree with the idea that quality of life must be taken into account were from the United Kingdom (attitude scores, 7.4 [95% CI, 7.1-7.7]), the Netherlands (7. 3 [95% CI, 7.1-7.5]), and Sweden (6.8 [95% CI, 6.4-7.3]). Other factors associated with having a pro-quality-of-life view were being female, having had no children, being Protestant or having no religious background, considering religion as not important, and working in an NICU with a high number of very low-birth-weight newborns. Physicians with scores reflecting a more quality-of-life view were more likely to report that in their practice, they had set limits to intensive interventions in cases of poor neurological prognosis, with an adjusted odds ratio of 1.5 (95% CI, 1.3-1.7) per unit change in attitude score. CONCLUSIONS: In our study, physicians' likelihood of reporting setting limits to intensive neonatal interventions in cases of poor neurological prognosis is related to their attitudes. After adjusting for potential confounders, country remained the most important predictor of physicians' attitudes and practices. JAMA. 2000;284:2451-2459.

Adult↗

PubMed2000

Conjunction analysis of cortical activations common to encoding and retrieval.

The notion of overlap between encoding and retrieval processes is central in cognitive theories of episodic memory, but to date most functional neuroimaging studies have emphasized differences between these processes. In the present study, overlap between encoding and retrieval processes was investigated by analyzing data from a positron emission tomography (PET) study of encoding and retrieval of different kinds of event information. Using a conjunction analysis, we specifically aimed at identifying overlap in activation patterns for encoding and retrieval of three classes of event information: item, temporal, and spatial. It was found that both encoding and retrieval of spatial information activated posterior parietal areas bilaterally. In addition, item encoding and retrieval were associated with increased activity in the right temporal pole, and temporal encoding and retrieval with left inferior frontal and left inferior temporal regions. These findings suggest that when specific episodic information is retrieved from memory, regions involved in encoding of the same information are engaged.

Brain Mapping↗

PubMed2000

Activity in motor areas while remembering action events.

Episodic memory for simple commands is better following enacted than verbal encoding. This has been proposed to be due to the possibility to base retrieval on motor information. Here we used PET to test the hypothesis that motor brain areas show increased retrieval-related activity following enacted compared to verbal encoding. Brain activity was also monitored during retrieval after imaginary enactment during encoding. It was found that activity in the right motor cortex was maximal following encoding enactment, intermediate following imaginary encoding enactment, and lowest following verbal encoding. These findings provide support that one basis for the facilitating effect on memory performance of overt, and to a lesser degree covert, encoding enactment is the possibility to base retrieval on motor information.

Adult↗

PubMed2000

Model process for separation based on unfolding and refolding of chymotrypsin inhibitor 2 in thermoseparating polymer two-phase systems.

For the design of a new separation process based on unfolding and refolding of protein, the partitioning behaviour of proteins was studied in thermoseparating polymer two-phase systems with varying pH and temperature. Chymotrypsin inhibitor 2 (CI2), which unfolds reversibly in a simple two-state manner, was partitioned in an aqueous two-phase system (ATPS) composed of a random copolymer of ethylene oxide and propylene oxide (Breox) and dextran T-500. Between 25 and 50 degrees C, the partition coefficients of CI2 in Breox-dextran T-500 systems remain constant at neutral pH. However, there is a drastic increase at pH values below 1.7, 2.1, and 2.7 at 25, 40 and 50 degrees C, respectively. The partitioning behavior of CI2 was also investigated in thermoseparating water-Breox systems at 55-60 degrees C, where CI2 was partitioned to the polymer-rich phase at pH values below 2.4. These results on the CI2 partitioning can be explained by the conformational difference between the folded and the unfolded states of the protein, where the unfolded CI2 with a more hydrophobic surface is partitioned to the relatively hydrophobic Breox phase in both systems. A separation process is presented based on the partitioning behavior of unfolded and refolded CI2 by control of pH and temperature in thermoseparating polymer two-phase systems. The target protein can be recovered through (i) selective separation in Breox-dextran systems, (ii) refolding in Breox phase, and (iii) thermoseparation of primary Breox phase.

Chymotrypsin↗

PubMed2000

Polymer recycling in aqueous two-phase extractions using thermoseparating ethylene oxide--propylene oxide copolymers.

This is a study on the recovery and recycling of copolymer in aqueous two-phase systems containing random copolymers of ethylene oxide (EO) and propylene oxide (PO). The random copolymers separate from water solution when heated above the lower critical solution temperature (LCST). The primary phase systems were composed of EOPO copolymer and hydroxypropyl or hydroxyethyl starch. After phase separation the upper EOPO phase was removed and subjected to temperature induced phase separation. Copolymers with different EO/PO compositions have been investigated, EO50P050 [50% EO and 50% PO (w/w)], EO30PO70 and EO20P080. The temperature required for thermoseparation decreases when the PO content of the copolymer is increased. The effect on the recovery of copolymer after addition of salts, a second polymer or protein was investigated. The added components increased the recovery of copolymer after thermoseparation, e.g., increased the amount copolymer separated from the water phase after thermoseparation. Recycling of copolymer and measurements of polymer concentrations in the primary top and bottom phases after repeated recycling steps was performed. The fluctuation in polymer concentration of the phases was very small after recycling up to four times. Partitioning of the proteins BSA and lysozyme was studied in primary phase systems after recycling of copolymer. The partition coefficients of total protein and lysozyme was not significantly changed during recycling of copolymer. More than 90% of the copolymer could be recovered in the thermoseparation step by optimising the temperature and time for thermoseparation. In repeated phase partitionings in EOPO-starch systems the EO50PO50 copolymer could be recovered to 77% including losses in primary system and thermoseparation, which is equivalent to a total copolymer reuse of 4.3 times.

Polyethylenes↗

PubMed2000

End-of-life decisions in neonatal intensive care: physicians' self-reported practices in seven European countries. EURONIC Study Group.

BACKGROUND: The ethical issue of foregoing life-sustaining treatment for newborn infants at high risk of death or severe disability is extensively debated, but there is little information on how physicians in different countries actually confront this issue to reach end-of-life decisions. The EURONIC project aimed to investigate practices as reported by physicians themselves. METHODS: The study recruited a large, representative sample of 122 neonatal intensive-care units (NICUs) by census (in Luxembourg, the Netherlands, and Sweden) or stratified random sampling (in France, Germany, the UK, Italy, and Spain) with an overall response rate of 86%. Physicians' practices of end-of-life decision-making were investigated through an anonymous, self-administered questionnaire. 1235 completed questionnaires were returned (response rate 89%). FINDINGS: In all countries, most physicians reported having been involved at least once in setting limits to intensive care because of incurable conditions (61-96%); smaller proportions reported such involvement because of a baby's poor neurological prognosis (46-90%). Practices such as continuation of current treatment without intensification and withholding of emergency manoeuvres were widespread, but withdrawal of mechanical ventilation was reported by variable proportions (28-90%). Only in France (73%) and the Netherlands (47%) was the administration of drugs with the aim of ending life reported with substantial frequency. Age, length of professional experience, and the importance of religion in the physician's life affected the likelihood of reporting of non-treatment decisions. INTERPRETATION: A vast majority of neonatologists in European NICUs have been involved in end-of-life limitation of treatments, but type of decision-making varies among countries. Culture-related and other country-specific factors are more relevant than characteristics of individual physicians or units in explaining such variability.

Adult↗