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Biomedical subjects

K Persson

Publications and source records attributed to K Persson.

At least 55 records · Page 3Linked to original sources
PubMed2000

Purification, crystallization and preliminary crystallographic data for rat cytosolic selenocysteine 498 to cysteine mutant thioredoxin reductase.

Mammalian cytosolic thioredoxin reductase is a homodimer of 55 kDa subunit containing an essential penultimate selenocysteine residue. An active analogue of the rat enzyme in which cysteine replaces selenocysteine has been expressed in Escherichia coli cells at high levels and purified to homogeneity. The pure enzyme contains one FAD per subunit and shows spectral properties identical to that of the wild-type thioredoxin reductase. The isolated enzyme in its oxidized and reduced forms or the enzyme complexed with NADP(+) was crystallized by the hanging-drop vapour-diffusion method. The diffraction pattern extends to 3 A resolution. The crystals are monoclinic, space group P2(1), with unit-cell parameters a = 78.9, b = 140.5, c = 170.8 A, alpha = 94.6 degrees. There are three dimeric molecules in the asymmetric unit.

Crystallization↗
PubMed2000

Assessing the allozyme variation in cultivars and Swedish landraces of rye (Secale cereale L.).

Genetic interpretation and diversity of 9 isozyme loci have been estimated in 7 improved varieties and 19 landraces from Sweden by means of starch gel electrophoresis. The isozyme systems were ACO, DIA, GPI, MDH, PGD and PGM. For the statistic analysis we used the following measures: average number of alleles per locus, percentage of polymorphic loci, average heterozygosity direct count and average heterozygosity Hardy-Weinberg expected unbiased estimate. The measures were made on species and population levels. The distribution of the total genetic diversity among populations was also calculated. To illustrate the genetic relationships among populations, genetic distances were measured and principal component analysis performed. As expected in a cross-pollinated crop we found high genetic diversity and a larger variation within than among the populations. Somewhat unexpectedly, however, we found that the currently used varieties have the same high level of heterozygosity as the landraces but in the dendrogram the two groups are separated. The dendrogram showed three main clusters. The large cluster included 21 populations and the two small clusters were clearly distinguishable from the rest. The landrace spring-type could not be separated from the landraces winter-type, but we did detect a difference between different spring types. A few populations had unique alleles for certain loci.

Aconitate Hydratase↗
PubMed2000

Comparison of five serologic tests for diagnosis of acute infections by Chlamydia pneumoniae.

Serology is often used to diagnose acute infections by Chlamydia pneumoniae. In this study paired sera from patients with acute respiratory tract infection during an epidemic of C. pneumoniae infections were examined by five different antibody tests. These tests were the complement fixation (CF) test, the microimmunofluorescence (MIF) test, a recombinant enzyme immunoassay (rEIA) (Medac) based on a recombinant lipopolysaccharide of chlamydia and measuring antibodies to a common chlamydial antigen, and two tests that utilize preparations of C. pneumoniae organisms, the SeroCp-EIA (Savyon) (with preserved lipopolysaccharide) and the LOY-EIA (Labsystems) (without this antigen). Both of the last two tests should measure specific antibodies to C. pneumoniae, although cross-reacting antibodies may also be detected by the SeroCp-EIA. Acute infection of C. pneumoniae was serologically confirmed in 44% of the cases by at least two different tests. Using an expanded "gold standard," i.e., the presence of significant reactions in at least two tests, the sensitivity of the CF test was 69%, that of the MIF test was 88%, that of the rEIA was 89%, that of the LOY-EIA was 96%, and that of the SeroCp-EIA was 92%. Specificity was high for all methods, but adjustments of diagnostic criteria were made to several of the tests. The basis for these adjustments and supportive data are presented. Infections of C. pneumoniae were detected in patients from 8 to 83 years of age. Two peaks in the incidence of such infections were observed: one among young teenagers and a second in adults 30 to 45 years of age, corresponding to parents of young teen-agers. The tests were equally sensitive in different age groups. Reinfections seemed to be rare.

Acute Disease↗
PubMed2000

Reduced GLP-1 and insulin responses and glucose intolerance after gastric glucose in GRP receptor-deleted mice.

By applying a newly developed ELISA technique for determining biologically active intact glucagon-like peptide [GLP-1, GLP-1-(7-36)amide] in mouse, plasma baseline GLP-1 in normal NMRI mice was found to be normally distributed (4.5 +/- 0.3 pmol/l; n = 72). In anesthetized mice, gastric glucose (50 or 150 mg) increased plasma GLP-1 levels two- to threefold (P < 0.01). The simultaneous increase in plasma insulin correlated to the 10-min GLP-1 levels (r = 0.36, P < 0.001; n = 12). C57BL/6J mice deleted of the gastrin-releasing peptide (GRP) receptor by genetic targeting had impaired glucose tolerance (P = 0.030) and reduced early (10 min) insulin response (P = 0.044) to gastric glucose compared with wild-type controls. Also, the GLP-1 response to gastric glucose was significantly lower in the GRP receptor-deleted mice than in the controls (P = 0.045). In conclusion, this study has shown that 1) plasma levels of intact GLP-1 increase dose dependently on gastric glucose challenge in correlation with increased insulin levels in mice, and 2) intact GRP receptors are required for normal GLP-1 and insulin responses and glucose tolerance after gastric glucose in mice.

Animals↗
PubMed2000

Functional characteristics of urinary tract smooth muscles in mice lacking cGMP protein kinase type I.

Nitric oxide (NO)-mediated smooth muscle relaxation is mediated by cGMP through activation of cGMP-dependent protein kinase I (cGKI). We studied the importance of cGKI for lower urinary tract function in mice lacking the gene for cGKI (cGKI-/-) and in litter-matched wild-type mice (cGKI+/+) in vitro and in vivo. cGKI deficiency did not result in any changes in bladder gross morphology or weight. Urethral strips from cGKI-/- mice showed an impaired relaxant response to nerve-derived NO. The cGMP analog 8-bromo-cGMP (8-BrcGMP) and the NO-donor SIN-1 relaxed the wild-type urethra (50-60%) but had only marginal effects in the cGKI-deficient urethra. Bladder strips from cGKI-/- mice responded normally to electrical field stimulation and to carbachol but not to 8-BrcGMP. In vivo, the cGKI-deficient mice showed bladder hyperactivity characterized by decreased intercontraction intervals and nonvoiding bladder contractions. Loss of cGKI abolishes NO-cGMP-dependent relaxations of urethral smooth muscle and results in hyperactive voiding. These data suggest that certain voiding disturbances may be associated with impaired NO-cGKI signaling.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

PAC1 receptor-deficient mice display impaired insulinotropic response to glucose and reduced glucose tolerance.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a ubiquitous neuropeptide of the vasoactive intestinal peptide (VIP) family that potentiates glucose-stimulated insulin secretion. Pancreatic beta cells express two PACAP receptor subtypes, a PACAP-preferring (PAC1) and a VIP-shared (VPAC2) receptor. We have applied a gene targeting approach to create a mouse lacking the PAC1 receptor (PAC1(-/-)). These mice were viable and normoglycemic, but exhibited a slight feeding hyperinsulinemia. In vitro, in the isolated perfused pancreas, the insulin secretory response to PACAP was reduced by 50% in PAC1(-/-) mice, whereas the response to VIP was unaffected. In vivo, the insulinotropic action of PACAP was also acutely reduced, and the peptide induced impairment of glucose tolerance after an intravenous glucose injection. This demonstrates that PAC1 receptor is involved in the insulinotropic action of the peptide. Moreover, PAC1(-/-) mice exhibited reduced glucose-stimulated insulin secretion in vitro and in vivo, showing that the PAC1 receptor is required to maintain normal insulin secretory responsiveness to glucose. The defective insulinotropic action of glucose was associated with marked glucose intolerance after both intravenous and gastric glucose administration. Thus, these results are consistent with a physiological role for the PAC1 receptor in glucose homeostasis, notably during food intake.

Animals↗
PubMed2000

Combined seropositivity for H. pylori and C. pneumoniae is associated with age, obesity and social factors.

BACKGROUND: Manifestations of cardiovascular disease (CVD) have been associated with chronic infection by Helicobacter pylori and Chlamydia pneumoniae both in cross-sectional and in prospective follow-up cohort studies. This association may be partly due to an increase in metabolic risk factors for CVD, secondary to low-grade inflammation caused by infections. OBJECTIVE: To investigate for subjects classified according to serology titres for infection with C. pneumoniae and H. pylori associations between seropositivity and the degree of obesity and fasting insulin levels, as well as social factors. METHODS: Using methods based on those in earlier investigations of hypertensive patients in the Dalby primary-health-care district, southern Sweden, we investigated frozen samples from serum of 310 middle-aged treated hypertensives and 288 age-matched and sex-matched normotensive controls from a defined population. The baseline examination included the measurement of weight, height and blood pressure as a mean of two office readings with the subject supine. The body mass index (BMI) was calculated as kg/m2. Fasting blood samples were drawn for measurements of levels of serum lipids, blood glucose, plasma insulin and serum lipids, including total cholesterol and triglycerides. The serology titres for H. pylori were determined by an enzyme-linked immunosorbent assay. The titres for C. pneumoniae were determined by a micro-immunofluorescence method. Self-reported factors concerning social and lifestyle backgrounds were recorded. RESULTS: The group (n = 245) of subjects with combined positive serology for H. pylori and C. pneumoniae differed from the group without any positive serology (n = 57) in age (61.6 versus 57.4 years, P < 0.05) and BMI (27.3 versus 25.8 kg/m2, P < 0.05). The seropositive group also differed in terms of fasting levels of insulin (12.7 versus 11.6 pmol/l, P < 0.05), but this difference did not remain significant after adjustment for age and BMI. We detected no intergroup difference in blood pressure and levels of glucose and lipids. Members of the group with combined seropositivity reported having a lower social-class position (educational level) than that of members of the seronegative group. CONCLUSION: Subjects with combined positive serology for H. pylori and C. pneumoniae are characterized by greater age, lower social class and higher BMI, as well as higher fasting levels of insulin than those of seronegative subjects. Obesity might be a marker not only for lower social class but also for greater than normal susceptibility to such infections.

Age Factors↗
PubMed2000

Effects of group motor skill intervention on five- to six-year-old children with developmental coordination disorder.

The purpose of this study was to determine whether group motor skill intervention is an effective form of treatment when added to consultative services in 5- to 6-year-old children with developmental coordination disorder (DCD). An experimental group of DCD children (n = 17) was compared with a DCD control group without intervention (n = 20). The intervention was conducted once a week for 10 weeks. No significant differences between the groups in either Movement ABC motor test or the Movement ABC checklist were found before or after this intervention. When subgroups with different categories of motor difficulties were compared, significantly more children with borderline motor difficulties in the experimental group than in the control group had changed (improved) their category after intervention. It is concluded that children with definite motor difficulties do not benefit from this type of intervention. Future research should include comparison of well-defined subgroups of children with DCD.

Journal Article↗
PubMed1999

Nitric oxide modulates captopril-mediated angiotensin-converting enzyme inhibition in porcine iliac arteries.

The influence of the angiotensin-converting enzyme inhibitor captopril on bradykinin-and angiotensin I-induced responses with special regard to nitric oxide (NO) was studied. Auxometric tension and angiotensin-converting enzyme activity was studied in isolated porcine iliac arteries. Captopril potentiated bradykinin-induced contraction of preparations with intact endothelium; this potentiation was not seen with the kininase I inhibitor mergepta or a bradykinin B(1)-receptor antagonist. Captopril did not affect bradykinin-induced relaxation. The captopril-mediated increase of bradykinin-induced contraction was only seen in preparations with intact endothelium, while captopril did not affect arterial strips treated with Nomega-nitro-L-arginine. Angiotensin I-induced contractions was less reduced by captopril when the strips were pretreated with Nomega-nitro-L-arginine. Both captopril and the NO donor S-nitroso-N-acetyl-penicillamine inhibited angiotensin-converting enzyme activity. An additional reduction in angiotensin-converting enzyme activity was seen when S-nitroso-N-acetyl-penicillamine was added to captopril-treated preparations. In conclusion, captopril increased bradykinin-induced contraction in a NO-dependent manner. This potentiation is probably mediated by the increased metabolism of bradykinin by kininase I, and the additive angiotensin-converting enzyme inhibitory effect of captopril and NO.

3-Mercaptopropionic Acid↗
PubMed1999

Localization and activity of nitric oxide synthases in the gastrointestinal tract of Trypanosoma cruzi-infected mice.

Chagas' disease, caused by the protozoan parasite, Trypanosoma cruzi, is associated with gastrointestinal abnormalities. Since nitric oxide (NO) has been shown to be a factor influencing intestinal function we evaluated the distributions and activities of the NO synthase (NOS) isoforms, in the gut of mice infected with T. cruzi. Ca2+-dependent (NOS1/NOS3) activity was decreased, whereas Ca2+-independent (NOS2) activity was increased in infected mice. NOS2-immunoreactivity was demonstrated in cells within the muscle layers and epithelium in infected mice and NOS1 immunoreactivity was seen in nerve structures. These data indicate that alterations in the NO-system may be important in the pathogenesis of the gastrointestinal manifestations in Chagas' disease.

Animals↗
PubMed1999

[Reduced frequency of resistant pneumococci in Southern Sweden. Community based disease control projects to minimize antibiotic resistance].

In an attempt to limit the spread of penicillin non-susceptible pneumococci (PNSP) in southern Sweden, early in 1995 an intervention project was launched, using a combination of traditional communicable disease control measures and actions aimed at reducing antibiotics consumption. Patients carrying PNSP (penicillin G MIC (0.5 mg/L) are monitored with nasopharyngeal cultures until PNSP-negative. Pre-school children are kept home from group day-care facilities. Previous antibiotic consumption was identified as a risk factor for PNSP carriage. Antibiotics sales decreased during the study period, and epidemiological findings suggest the dissemination of PNSP in the area to have been reduced by the intervention project.

Adult↗
PubMed1999

Murine class I major histocompatibility complex H-2Dd: expression, refolding and crystallization.

A truncated soluble form of the murine class I major histocompatibility antigen complex H-2Dd was cloned using an Escherichia coli based system. It was expressed, refolded in vitro and crystallized in a complex with murine beta2 microglobulin and the peptide RGPGRAFVTI from the V3-loop of the gp160 HIV-1 protein. Crystals belonging to the space group P212121 with cell dimensions a = 51.3, b = 92.5, c = 108.8 A were obtained using two different crystallization conditions. The crystals contain one complex per asymmetric unit and diffract to at least 2.4 A resolution.

Animals↗
PubMed1999

The functional intronless S-adenosylmethionine decarboxylase gene of the mouse (Amd-2) is linked to the ornithine decarboxylase gene (Odc) on chromosome 12 and is present in distantly related species of the genus Mus.

S-Adenosylmethionine decarboxylase (AdoMetDC) is a key enzyme in the biosynthesis of polyamines. We have previously identified a mouse AdoMetDC gene that exhibits the hallmarks of a retroposon; that is, it has no introns, is flanked by direct repeats, and has a poly(dA) tract at its 3'-end. This gene, termed Amd-2, is not a processed pseudogene; rather, it is transcribed in a variety of mouse tissues and encodes a functional enzyme. In the current report, we present the sequence of a 6.7-kb genomic segment of the Amd-2 locus. Several sequences of interest, including an intercisternal A particle (IAP) element, a transposon-related sequence, and several expressed sequence tags (ESTs), were found within or near Amd-2. We also show, through analysis of an interspecific backcross, that Amd-2 is located on Chr 12, tightly linked to the gene (Odc) that encodes ornithine decarboxylase, another key enzyme in polyamine synthesis. Finally, we show that Amd-2 is present among several divergent species of the genus Mus. Thus, the integration event that generated Amd-2 may have occurred early during Mus evolution.

Adenosylmethionine Decarboxylase↗
PubMed1999

Amplification and overexpression of p40 subunit of eukaryotic translation initiation factor 3 in breast and prostate cancer.

Amplification at the long arm of chromosome 8 occurs in a large fraction of breast and prostate cancers. To clone the target genes for this amplification, we used suppression subtraction hybridization to identify overexpressed genes in the breast cancer cell line SK-Br-3, which harbors amplification at 8q (8q21 and 8q23-q24). A differentially expressed gene identified by SSH, the p40 subunit of eukaryotic translation initiation factor 3 (eIF3), was localized to 8q23 and found to be highly amplified and overexpressed in the breast and prostate cancer cell lines studied. High-level amplification of eIF3-p40 was found in 30% of hormone-refractory prostate tumors and in 18% of untreated primary breast tumors. In the vast majority of the cases, p40 and c-myc were amplified with equal copy numbers. Tumors with higher copy numbers of p40 than c-myc were also found. Expression of p40 mRNA was analyzed with in situ hybridization. The amplification of eIF3-p40 gene was associated with overexpression of its mRNA, as expected for a functional target gene of the amplification. These results imply that genomic aberrations of translation initiation factors, such as eIF3-p40, may contribute to the pathogenesis of breast and prostate cancer.

Blotting, Northern↗
PubMed1999

Antibodies to Chlamydia trachomatis heat shock proteins in women with tubal factor infertility are associated with prior infection by C. trachomatis but not by C. pneumoniae.

The antibody response to heat shock proteins 60 and 10 were studied in 163 patients with tubal factor infertility and in 163 age-matched pregnant women. The associations of these antibodies with specific antibodies to Chlamydia trachomatis and to Chlamydia pneumoniae as well as with antibodies to the common chlamydial lipopolysaccharide antigen were studied. Patients with tubal factor infertility had significantly higher frequencies and titres of all antibodies except to C. pneumoniae. In a logistic regression model an association was found between the prevalence of antibodies to the heat shock proteins and to C. trachomatis but no independent influence of antibodies to C. pneumoniae. No interaction between C. trachomatis and C. pneumoniae suggesting a synergistic effect was found although the heat shock proteins from these two organisms are immunologically similar. Antibodies to the chlamydial lipopolysaccharide also seemed to be related to C. trachomatis and not to C. pneumoniae in these women.

Adult↗
PubMed1999

Crystal structure analysis of a pentameric fungal and an icosahedral plant lumazine synthase reveals the structural basis for differences in assembly.

Lumazine synthase catalyzes the penultimate step in the synthesis of riboflavin in plants, fungi, and microorganisms. The enzyme displays two quaternary structures, the pentameric forms in yeast and fungi and the 60-meric icosahedral capsids in plants and bacteria. To elucidate the structural features that might be responsible for differences in assembly, we have determined the crystal structures of lumazine synthase, complexed with the inhibitor 5-nitroso-6-ribitylamino-2,4-pyrimidinedione, from spinach and the fungus Magnaporthe grisea to 3.3 and 3.1 A resolution, respectively. The overall structure of the subunit and the mode of inhibitor binding are very similar in these enzyme species. The core of the subunit consists of a four-stranded parallel beta-sheet sandwiched between two helices on one side and three helices on the other. The packing of the five subunits in the pentameric M. grisea lumazine synthase is very similar to the packing in the pentameric substructures in the icosahedral capsid of the plant enzyme. Two structural features can be correlated to the differences in assembly. In the plant enzyme, the N-terminal beta-strand interacts with the beta-sheet of the adjacent subunit, thus extending the sheet from four to five strands. In fungal lumazine synthase, an insertion of two residues after strand beta1 results in a completely different orientation of this part of the polypeptide chain and this conformational difference prevents proper packing of the subunits at the trimer interface in the icosahedron. In the spinach enzyme, the beta-hairpin connecting helices alpha4 and alpha5 participates in the packing at the trimer interface of the icosahedron. Another insertion of two residues at this position of the polypeptide chain in the fungal enzyme disrupts the hydrogen bonding in the hairpin, and the resulting change in conformation of this loop also interferes with proper intrasubunit contacts at the trimer interface.

Amino Acid Sequence↗