PubMed Health⌕ Search

Biomedical subjects

K Karlsson

Publications and source records attributed to K Karlsson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Polyglycosylceramides recognized by Helicobacter pylori: analysis by matrix-assisted laser desorption/ionization mass spectrometry after degradation with endo-beta-galactosidase and by fast atom bombardment mass spectrometry of permethylated undegraded material.

Human erythrocyte polyglycosylceramides (PGCs) are recognized by the gastric pathogen Helicobacter pylori and are based on a successively extended and highly branched N-acetyllactosamine core linked to ceramide and substituted by fucose and sialic acid. As a step in the identification of the binding epitope we earlier characterized intact PGCs by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, MALDI-TOF MS (Karlsson,H., Johansson,L., Miller-Podraza,H., and Karlsson,K-A. [1999] Glycobiology, 9, 765-778). In the present work, PGCs from human blood group O erythrocytes were digested with endo-ss-galactosidase (Bacterioides fragilis), an enzyme which cleaves the bond 3Galss1-4GlcNAc in linear but not branched poly-N-acetyllactosamine chains. The enzymatic digestion resulted in a mixture of neutral and sialic acid-containing glycolipids together with terminal and internal sequences of mainly neutral oligosaccharides. The products were analyzed by MALDI-TOF MS in both positive and negative ion mode which gave spectra where the ions could be assigned to structures of the neutral and acidic components, respectively. Among glycolipids found were [structure in text] where R could be H, Fuc or NeuAc. Also observed were structures as [structure in text] which indicated linear extension along both branches. Observed at higher masses were fully branched structures obtained by stepwise extension with [structure in text] where R could be H, Fuc or NeuAc. Most probably further branching may occur along both the (1-->3)- and the (1-->6)-linked branches to give a partly dendritic structure. Structures with more than one sialic acid substituted could not be observed in the MALDI spectrum. Complementary information of the terminal sequences was obtained by FAB-MS analysis of permethylated undegraded PGCs. High-temperature gas chromatography/mass spectrometry of reduced and permethylated products from enzyme hydrolysis documented that Fuc was present in a blood group O sequence, Fuc-Hex-HexN-. Fucose may be placed on short (monolactosamine) or longer branches, while sialic acid seems to be restricted to monolactosamine branches. The conclusion is that human erythrocyte PGCs display microheterogeneity within terminal and internal parts of the poly-N-acetyllactosamine chains. The first branch from the ceramide end may be located at the second or third Gal and possibly also on the first Gal. Other branches may occur on every N-acetyllactosamine unit in fully branched domains, or there may be linear extensions between branches resulting in incompletely branched structures. The extended linear sequences may be present in both 3- and 6-linked antennae. Terminal structures are based on one, two or maybe higher number of N-acetyllactosamine units.

Carbohydrate Sequence↗
PubMed1999

Enrichment of human brain proteins by heparin chromatography.

Detection of low-abundance proteins is essential for the identification of novel drug targets by differential protein expression studies. We studied the enrichment of human fetal brain proteins by heparin chromatography. Total soluble brain proteins were fractionated on Heparin-Actigel and the fractions collected were analyzed by two-dimensional electrophoresis. The proteins were identified by matrix-assisted laser desorption ionization mass spectrometry. Approximately 300 protein spots were analyzed, representing 70 different polypeptides, 50 of which were bound to the heparin matrix. Eighteen brain proteins were identified for the first time. The proteins enriched by heparin chromatography include both minor and major components of the brain protein extract. The enriched proteins belong to several classes, including proteasome components, dihydropirimidinase-related proteins, T-complex protein 1 components and enzymes with various catalytic activities. The results include a two-dimensional map of the soluble brain proteins and a list of the proteins enriched by heparin chromatography. These may be useful in the design of protein purification protocols and in studies of neurological disorders.

Brain Chemistry↗
PubMed1999

Transvaginal ultrasonography and endometrial histology in peri- and postmenopausal women on hormone replacement therapy.

OBJECTIVE: To determine the association between endometrial thickness and endometrial histology in a large sample of women using HRT. DESIGN: Results from three multi-centre studies were combined. PARTICIPANTS: Five hundred and sixty-four climacteric women were treated with either sequential, continuous combined or long-cycle therapy. MAIN OUTCOME MEASURES: The women underwent 717 examinations with both transvaginal ultrasonography and histological examination of the endometrium. Endometrial thickness was measured and associated with the histological findings. RESULTS: Eight cases of endometrial hyperplasia were diagnosed. All the hyperplasias were simple without atypia. Two cases had an endometrial thickness < 4 mm and two a thickness > 8 mm. The > 4 mm threshold for abnormal endometrium had a sensitivity of 75%, a specificity of 47%, a positive predictive value of 2% and a negative predictive value of 99%. CONCLUSION: No association could be found between the endometrial thickness measured by transvaginal ultrasonography and endometrial pathology. In six out of eight women with simple hyperplasia the endometrium measured > 4 mm.

Administration, Cutaneous↗
PubMed1999

Cytokine levels in synovial fluid from hips with well-functioning or loose prostheses.

We analysed synovial fluid from 88 hips, 38 with osteoarthritis and 12 with well-functioning and 38 with loose hip prostheses. The levels of TNF-alpha, IL-1beta (71 hips) and IL-6 (45 hips) were measured using the ELISA technique. Joints with well-functioning or loose prostheses had significantly increased levels of TNF-alpha compared with those with osteoarthritis. Hips with aseptic loosening also had higher levels of IL-1beta but not of IL-6 compared with those without an implant. The levels of TNF-alpha and IL-1beta did not differ between hips with stable and loose prostheses. Higher levels of TNF-alpha were found in hips with bone resorption of type II and type III (Gustilo-Pasternak) compared with those with type-I loosening. The level of cytokines in joint fluid was not influenced by the time in situ of the implants or the age, gender or area of the osteolysis as measured on conventional radiographs. Our findings support the theory that macrophages in the joint capsule increase the production of TNF-alpha at an early phase probably because of particle load and in the absence of clinical loosening. Since TNF-alpha has an important role in the osteolytic process, the interfaces should be protected from penetration of joint fluid.

Adult↗
PubMed1998

Sorting of lysosomal membrane glycoproteins lamp-1 and lamp-2 into vesicles distinct from mannose 6-phosphate receptor/gamma-adaptin vesicles at the trans-Golgi network.

Newly synthesized lysosomal membrane glycoproteins lamp-1 and lamp-2 are primarily sorted at the trans-Golgi network (TGN) by recognition of a tyrosine-based signal sequence in their cytoplasmic tails. It is presently unclear how this signal is recognized and what type of vesicle transports lamp-1 and lamp-2. Here, we describe a method to generate transport vesicles containing lamp proteins from the TGN in vitro. The method is based on incorporation of radioactive sialic acid in glycoproteins at the TGN by incubation of membranes with tritiated CMP-sialic acid. The generation of vesicles from labeled membranes required ATP and cytosol, and was temperature-dependent and brefeldin A-sensitive. Analysis on Nycodenz gradients revealed that lamp-vesicles were distinct from vesicles containing gamma-adaptin and mannose 6-phosphate receptor (MPR). Moreover, both these types of vesicles migrated differently than vesicles containing proteins destined for the plasma membrane. The conclusion that lamps and MPRs are sorted into different vesicles was further strengthened by the finding that whereas wortmannin both in vitro and in vivo inhibited the production of gamma-adaptin/MPR-containing vesicles, this drug had no effect on the generation of lamp-vesicles and on the sorting of lamps. The results indicate that membrane proteins containing tyrosine-based motifs for sorting at the TGN are segregated from clathrin-coated vesicles containing MPRs.

Adaptor Protein Complex gamma Subunits↗
PubMed1998

Purification of substance P endopeptidase (SPE) activity in human spinal cord and subsequent comparative studies with SPE in cerebrospinal fluid and with chymotrypsin.

An enzyme activity capable of hydrolysing the neuroactive undecapeptide substance P (SP) between its Phe7-Phe8 residues was purified from the membrane-bound fraction of human spinal cords. The enzyme preparation yielded was compared with a previously described SP-hydrolysing enzyme from human cerebrospinal fluid (CSF) with regard to inhibition profile, protein chemical properties and kinetics. In addition, the results were compared with those of bovine pancreatic chymotrypsin (a serine protease that cleaves the carboxy-terminal side preferentially at hydrophobic amino acids). The SP peptidase activity was extracted from human spinal cords with 1% Triton X-100 in 20 mM Tris-HCI pH 7.8. After ion exchange chromatography (DEAE-Sepharose) where the enzyme activity was separated from other proteins by gradient elution, the pooled enzyme fraction was further purified by molecular sieving (Sephadex G-50). The enzyme activity was finally recovered by HPLC molecular sieving (Superdex 75 HR 10/30) using a new preparative system, AKTA-purifier, controlled by UNICORN software version 2.20.

Animals↗
PubMed1998

Alteration in the brain content of substance P (1-7) during withdrawal in morphine-dependent rats.

Previous studies have shown that substance P (SP) may modulate the abstinence reaction to opioid withdrawal. Its N-terminal fragment SP1-7 may inhibit the intensity of the withdrawal reactions in morphine dependent mice. This study was designed to determine whether the endogenous concentrations of the SP1-7 fragment in the brain are affected during naloxone-precipitated withdrawal in the male rat. The amounts of the peptide was assessed by a specific radioimmunoassay in extracts of discrete brain regions (including the cerebral cortex, hippocampus, hypothalamus, nucleus accumbens, striatum, substantia nigra, ventral tegmental area and the spinal cord) during morphine tolerance and withdrawal. The results indicated that the concentrations of SP1-7 were significantly elevated in the ventral tegmental area both in morphine tolerant rats and during naloxone-precipitated withdrawal. During morphine withdrawal significant increases in the peptide concentration were also observed in the hypothalamus and the spinal cord. It was concluded that the enhanced content of SP1-7 may also indicate the involvement of the SP system during opioid withdrawal in the rat. The enhanced production of SP1-7 may reflect an increased release and/or metabolism of SP, which, in turn, counteracts the withdrawal.

Animals↗
PubMed1998

Empiric monotherapy for febrile neutropenia--a randomized study comparing meropenem with ceftazidime.

In this Swedish multicentre study we compared the efficacy of meropenem with ceftazidime for treatment of febrile neutropenia. 192 patients were randomized and the number of evaluable patients was 92 in the meropenem group and 95 in the ceftazidime group. 40 (43%) patients in the meropenem arm and 49 (52%) in the ceftazidime arm had acute leukaemia. 56 (61%) and 52 (55%) patients respectively had a neutrophil count of < 0.1 x 10(9)/l at randomization and the median duration of neutropenia was 6.5 and 8 d, respectively. Thirty-one (34%) and 28 (29%) patients had a microbiologically defined infection, 14 (15%) and 17 (18%) a clinically defined infection and the remaining 47 (51%) and 50 (53%) had unexplained fever. After 72 h of treatment, 46 (50%) patients in the meropenem arm and 53 (56%) patients in the ceftazidime arm were alive on unmodified monotherapy. 42 (46%) and 47 (49%) of these completed the study on monotherapy alone. Only 2 patients (2%) in each arm had to stop treatment owing to allergic reactions. None of the observed differences were statistically significant and we therefore conclude that meropenem was an effective and safe alternative to ceftazidime for empiric treatment of fever during neutropenia.

Adolescent↗
PubMed1998

Superoxide dismutase isoenzymes in the human eye.

PURPOSE: The authors determined the levels of the secreted, interstitially located extracellular superoxide dismutase (EC-SOD), the cytosolic copper- and zinc-containing SOD (CuZn-SOD), and the mitochondrial manganese-containing SOD (Mn-SOD) in tears, cornea, sclera, aqueous humor, lens, vitreous body, and retina of the human eye. METHODS: SOD enzymatic activity was determined by the direct spectrophotometric method using KO2. The amounts of EC-SOD and CuZn-SOD protein were also determined using enzyme-linked immunosorbent assay. RESULTS: Tears, aqueous humor, and vitreous body contained little SOD activity. Here ascorbate is the major scavenger of superoxide radicals. Of the ocular tissues studied, the lens contained the least SOD activity, 15-fold less than that of the average human tissue. The majority came from CuZn-SOD, but the lens also contained considerable amounts of inactive enzyme. There was some Mn-SOD, but the EC-SOD content was negligible. The cornea and sclera contained several times more SOD activity than the lens, and the EC-SOD contents were equal to or larger than those of CuZn-SOD. The retina contained much CuZn-SOD activity, but the EC-SOD and Mn-SOD activities were low. CONCLUSIONS: Ocular tissues and fluids, except for those in the retina, are less protected against superoxide radicals than extraocular tissues and fluids. The large amounts of EC-SOD in the sclera and cornea may be related to the risk for photochemical production of superoxide in these tissues. If inflammatory reactions occur, ocular tissues are at risk for damage induced by superoxide radicals and peroxynitrite, the reaction product with nitric oxide.

Adult↗
PubMed1997

Induction of protective immunity after escherichia coli bladder infection in primates. Dependence of the globoside-specific P-fimbrial tip adhesin and its cognate receptor.

Clinical observations suggest that immune mechanisms affect etiology and course of recurrent cystitis. A primate infection model was used to show that primary bladder infection with a uropathogenic P-fimbriated strain (binding to globoside present in the bladder wall) protects against rechallenge with homologous as well as heterologous Escherichia coli strains for up to 5-6 mo. In contrast, mutant derivatives producing P-fimbriae either lacking the tip adhesin protein or carrying an adhesin for which no bladder receptor was present, were unable to induce protection, even though they generated bladder infections of similar duration as the wild type. Therefore, the protective effect mediated by the adhesin seemed to depend upon the presence of its cognate receptor. Since the wild strain also mediated protection against mutants that lacked the adhesin, our data suggest that the globoside-binding PapG adhesin acts as an adjuvant during infection to enhance a specific response against other bacterial antigens. In fact, the globoside-binding strain DS17, but not the mutant DS17-1, unable to bind to membrane-bound globoside, elicited a secretory IgA response to LPS in urine. These in vivo findings suggest that bacterial adhesin-ligand interactions may have signaling functions of importance for the immune response.

Adhesins, Escherichia coli↗
PubMed1997

Hypercortisolism after stroke--partly cytokine-mediated?

Increased activity of the hypothalamic-pituitary-adrenal (HPA) axis is common early after stroke. Hypercortisolism is a prominent manifestation. Normally the secretion of cortisol is regulated by adrenocorticotrophic hormone (ACTH), but recently an ACTH/cortisol dissociation after stroke was reported. Cytokines may influence the HPA axis, and plasma IL-6 levels are elevated following stroke. We investigated correlations between cortisol, ACTH, and cytokines, and between blood pressure and blood hormone levels early after stroke in seven stroke patients. All had neurological symptoms secondary to brain infarctions. Blood samples for analysis of cortisol, ACTH, IL-6, TNF alpha, norepinephrine, and epinephrine were collected four times daily, and 24-h blood pressure was measured. Plasma IL-6, but not ACTH, correlated significantly to serum cortisol. Catecholamine levels correlated with cytokine and cortisol levels. This study suggests that several routes for HPA-axis dysregulation is present early after stroke. Cytokine release may play an important role in this situation.

Adrenocorticotropic Hormone↗
PubMed1997

Anabolic androgenic steroids increase beta-endorphin levels in the ventral tegmental area in the male rat brain.

The levels of beta-endorphin and Met-enkephalin-Arg-Phe (MEAP) immunoreactivity in various brain regions (including amygdala, cortex, hippocampus, hypothalmus, nucleus accumbens, pituitary and ventral tegmental area) were studied in male rats subjected to daily intramuscular injections during 14 days of high doses (5 and 15 mg/kg) of the anabolic androgenic steroid (AAS), nandrolone decanoate. At the nandrolone dose of 15 mg/kg a significant (about 20-fold) increase in beta-endorphin levels in the ventral tegmental area (VTA) was observed. The steroid did not significantly affect the concentration of the peptide at any dose in other brain areas examined. The levels of MEAP remained unaltered in all studied regions. A slight increase in serum concentrations of both peptides was also found but this elevation was not statistically significant. The observed increase in beta-endorphin in VTA was suggested to be involved in a mechanism by which the steroid may influence the reward system in the brain. An opioid mediated stimulation of the reward system following injection of AAS supports a previous hypothesis that AAS may induce psychological dependence.

Anabolic Agents↗
PubMed1997

Effects of vitamins E, C and catalase on bromobenzene- and hydrogen peroxide-induced intracellular oxidation and DNA single-strand breakage in Hep G2 cells.

BACKGROUND/AIMS: Water-soluble vitamin E (Trolox C), ascorbic acid and catalase were shown in our previous study to protect isolated rat hepatocytes against bromobenzene-induced toxicity. METHODS: In order to study the mechanisms of this protection and the pathogenesis of bromobenzene-induced hepatocellular injury, a fluorometric assay for the investigation of intracellular oxidation, indicated by conversion of dichlorofluorescein diacetate to dichlorofluorescein, was used. Single-strand DNA breakage was also evaluated in Hep G2 cells by a radio-labelling method. RESULTS: Bromobenzene (2.4 and 4.8 mM) induced a significant increase in dichlorofluorescein fluorescence intensity compared to the controls. Trolox C, ascorbic acid or catalase significantly inhibited bromobenzene-induced enhancement of fluorescence intensity (p<0.05-0.001), as well as reduced auto-intracellular oxidation in untreated Hep G2 cells. Hydrogen peroxide (H2O2) evoked a dose-dependent increase in dichlorofluorescein fluorescence intensity in Hep G2 cells, and the effect was completely blocked by Trolox C (2.0 mM) and catalase (4800 unit/ml). Bromobenzene caused significant single-strand DNA breakage in Hep G2 cells during 2 h suspension incubation and 24 h primary incubation. H2O2 (400 microM) led to marked single-strand DNA breakage in 20 min, and the effect was attenuated by Trolox C. CONCLUSIONS: Metabolism of bromobenzene in Hep G2 cells induces production of H2O2, indicated by enhancement of dichlorofluorescein fluorescence intensity, or other free radicals, which leads to single-strand DNA breakage in the cells. Vitamins E and C and catalase display strong intracellular antioxidative effects. Vitamin E could partially inhibit H2O2-induced single-strand DNA breakage in the cells.

Antioxidants↗
PubMed1997

Purification and characterization of substance P endopeptidase activities in the rat spinal cord.

Two enzymes with substance P degrading activity were purified from the membrane bound fraction of the rat spinal cord. The purified enzymes were characterized with regard to biochemical and kinetic properties. One of the enzymes exhibited close similarity to neutral endopeptidase 24.11 (NEP, EC 3.4.24.11), while the other resembled a substance P converting endopeptidase (SPE), which has previously been identified and purified from human cerebrospinal fluid (CSF). Detergent treated spinal cord homogenates from male Sprague Dawley rats were purified by anion-exchange chromatography (DEAE-sepharose CL-6B), hydrophobic-interaction chromatography (phenyl-sepharose CL-4B) and molecular sieving (Sephadex G-50). Two fractions with enzymes differing in size were recovered and allowed for further purification to apparent homogeneity by ion-exchange chromatography and molecular sieving on a micro-purification system (SMART). The enzyme activities were monitored by following the conversion of synthetic substance P using a radioimmunoassay specific for the heptapeptide product, substance P (1-7). By SDS-polyacrylamide gel electrophoresis of the purified enzymes molecular weights of 43 and 70 kDa were estimated for the SPE-like and NEP-like activity, respectively. A K(m) of 5 microM was determined for the conversion of substance P to its (1-7) fragment by the SPE-like activity. Reversed-phase HPLC together with mass spectrometry permitted identification of all fragments released from substance P by the peptidases. The released fragments were for both enzymes identified as substance P (1-7), substance P (8-11), substance P (1-8), substance P (9-11). The NEP-like enzyme preparation also gave substance P (1-6) as a major product.

Animals↗
PubMed1997

Late postnatal transmission of human immunodeficiency virus type 1 infection from mothers to infants in Dar es Salaam, Tanzania.

OBJECTIVE: To study late postnatal transmission of human immunodeficiency virus type 1 in a cohort of children born to HIV-1-seropositive mothers who delivered at Muhimbili Medical Centre in Dar es Salaam, Tanzania. MATERIALS AND METHODS: Since 1991 a prospective cohort study of mother-to-child transmission of HIV-1 has been conducted at Muhimbili Medical Centre in Dar es Salaam. HIV-1-seropositive mothers and age-matched seronegative controls were recruited into the cohort at delivery together with their newborns. Diagnosis of HIV-1 infection in children was based on polymerase chain reaction, HIV-1 p24 antigen tests and HIV antibody tests. Late postnatal transmission was defined as HIV-1 infection occurring after 6 months of age in a child who was uninfected at 6 months of age and who had an HIV-1-seropositive mother. Children born to HIV-seronegative mothers were used as controls. Breast-feeding was universal in this cohort. CD4 and CD8 T lymphocytes were assayed by flow cytometry in the mothers. RESULTS: Among 139 children born to HIV-1-seropositive mothers and known to be HIV-uninfected at 6 months of age, 8 children became HIV-1-infected at the end of their first year of life or later. No conversions were observed in children younger than 11 months. The 8 conversions were observed during a follow-up covering 1555 child months between 6 and 27 months of age corresponding to a conversion rate of 6.2 per 100 child years. Among 260 children with HIV-seronegative mothers no child became HIV-infected during the follow-up. The percentage of CD4 T lymphocytes was similar in mothers with early and late transmission but was significantly lower in transmitting than in nontransmitting mothers. CONCLUSION: Because no HIV-1 infection occurred in children with HIV-seronegative mothers, we conclude that the observed infections at the end of the first year of life or later among children born to HIV-seropositive women were caused by late transmission from mother to child, most likely through breast-feeding.

AIDS Serodiagnosis↗