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B Samuelsson

Publications and source records attributed to B Samuelsson.

At least 109 records · Page 6Linked to original sources
PubMed1990

Leukotriene A4 hydrolase: an epoxide hydrolase with peptidase activity.

Purified leukotriene A4 hydrolase from human leukocytes is shown to exhibit peptidase activity towards the synthetic substrates alanine-4-nitroanilide and leucine-4-nitroanilide. The enzymatic activity is abolished after heat treatment (70 degrees C, 30 min). At 37 degrees C these substrates are hydrolyzed at a rate of 380 and 130 nmol/mg/min, respectively, and there is no enzyme inhibition during catalysis. Apo-leukotriene A4 hydrolase, obtained by removal of the intrinsic zinc atom, exhibits only a low peptidase activity which can be restored by the addition of stoichiometric amounts of zinc. Reconstitution of the apoenzyme with cobalt results in a peptidase activity which exceeds that of enzyme reactivated with zinc. Preincubation of the native enzyme with leukotriene A4 reduces the peptidase activity. Semipurified preparations of bovine intestinal aminopeptidase and porcine kidney aminopeptidase do not hydrolyze leukotriene A4 into leukotriene B4.

Aminopeptidases↗
PubMed1990

Leukotriene A4 hydrolase: a zinc metalloenzyme.

Purified human leukotriene A4 hydrolase is shown to contain 1 mol of zinc per mol of enzyme, as determined by atomic absorption spectrometry. The enzyme is inhibited dose-dependently by the chelating agents 8-hydroxy-quinoline-5-sulfonic acid, and 1,10-phenanthroline with KI values of about 2 and 8 x 10(-4) M, respectively, whereas dipicolinic acid and EDTA are ineffective in this respect. The inhibition by 1,10-phenanthroline is time-dependent, and at a concentration of 5 mM, 50% inhibition of enzyme (3 x 10(-7) M) occurs after about 15 min. The zinc atom of leukotriene A4 hydrolase can be removed by dialysis against 1,10-phenanthroline which results in loss of enzyme activity. The catalytic activity is almost completely restored by the addition of stoichiometric amounts of Zn2+ or Co2+.

Amino Acid Sequence↗
PubMed1990

Nomenclature.

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Arachidonic Acids↗
PubMed1990

Cloning of the cDNA for human 12-lipoxygenase.

A full-length cDNA clone encoding 12-lipoxygenase (arachidonate:oxygen 12-oxidoreductase, EC 1.13.11.31) was isolated from a human platelet cDNA library by using a cDNA for human reticulocyte 15-lipoxygenase as probe for the initial screening. The cDNA had an open reading frame encoding 662 amino acid residues with a calculated molecular weight of 75,590. Three independent clones revealed minor heterogeneities in their DNA sequences. Thus, in three positions of the deduced amino acid sequence, there is a choice between two different amino acids. The deduced sequence from the clone plT3 showed 65% identity with human reticulocyte 15-lipoxygenase and 42% identity with human leukocyte 5-lipoxygenase. The 12-lipoxygenase cDNA recognized a 3.0-kilobase mRNA species in platelets and human erythroleukemia cells (HEL cells). Phorbol 12-tetradecanoyl 13-acetate induced megakaryocytic differentiation of HEL cells and 12-lipoxygenase activity and increased mRNA for 12-lipoxygenase. The identity of the cloned 12-lipoxygenase was assured by expression in a mammalian cell line (COS cells). Human platelet 12-lipoxygenase has been difficult to purify to homogeneity. The cloning of this cDNA will increase the possibilities to elucidate the structure and function of this enzyme.

Amino Acid Sequence↗
PubMed1990

Characterization of the human 5-lipoxygenase gene promoter.

Nucleotide sequences that direct transcription of the human 5-lipoxygenase gene have been examined by ligation to the chloramphenicol acetyltransferase gene and determination of chloramphenicol acetyltransferase activity in transfected HeLa and HL-60 cells. Various lengths of 5'-flanking sequences up to 5.9 kilobase pairs 5' of the transcriptional initiation sites were tested. Two positive and two negative apparent regulatory regions were seen. Part of the promoter sequence (-179 to -56 from ATG), which includes five repeated GC boxes (the putative Sp1 binding sequence) was essential for transcription in both HeLa and HL-60 cells. Gel-shift assays (using the DNA fragment -212 to -88) revealed that the transcriptional factor Sp1 could bind to this region of the 5-lipoxygenase promoter. Furthermore, HL-60 nuclear extracts contained specific nuclear factor(s) binding to 5-lipoxygenase promoter DNA, which could not be detected in HeLa cell nuclear extracts.

Amino Acid Sequence↗
PubMed1989

Identification of a novel 7-cis-11-trans-lipoxin A4 generated by human neutrophils: total synthesis, spasmogenic activities and comparison with other geometric isomers of lipoxins A4 and B4.

Addition of (15S)-hydroxy-5,8,11-cis-13-trans-eicosatetraenoic acid (15-HETE) and the ionophore A23187 (2.5 microM) to human neutrophils led to the formation of both lipoxin A4 and lipoxin B4 as well as a novel 5,6,15-trihydroxyeicosatetraenoic acid. The new compound was identified using an improved isolation and detection system and its basic structure was determined by physical methods. On the basis of biosynthetic considerations, geometric isomers of lipoxin A4 and lipoxin B4 were prepared by total synthesis. Comparison of these synthetic materials with the neutrophil-derived product showed that the new compound is (5S,6R,15S)-trihydroxy-9,11,13-trans-7-cis-eicosatetraenoic acid or the 7-cis-11-trans-isomer of LXA4 (7-cis-11-trans-LXA4). LXA4, 11-trans-LXA4, 7-cis-LXA4 and 7-cis-11-trans-LXA4 all evoked dose-dependent (0.1-10 microM) contractions of the guinea pig lung strip, whereas 6-cis-LXB4 and 6-cis-8-trans-LXB4 relaxed this preparation. LXA4 and 7-cis-LXA4 were approx. 10-times more potent than the compounds with 11-trans geometry. However, all four double-bond isomers of LXA4 caused contractions which, based upon pharmacological evidence, appeared to involve specific activation of the same site as cysteinyl-containing leukotrienes. In conclusion, 7-cis-11-trans-LXA4 was isolated and identified as a novel biologically active eicosanoid formed by human neutrophils.

Airway Resistance↗
PubMed1989

Characterization of the human 5-lipoxygenase gene.

The gene for human 5-lipoxygenase has been isolated from three different bacteriophage genomic libraries and a genomic cosmid library. The gene spans greater than 82 kilobases and consists of 14 exons. The size range for the exons is 82-613 base pairs, whereas that for the introns is approximately 200 bp to greater than 26 kb. A major site of transcription initiation in leukocytes was mapped to a thymidine residue 65 base pairs upstream of the ATG initiation codon by nuclease S1 protection and primer extension experiments. Other potential minor initiation sites were found. The putative promoter region contains no TATA and CCAAT sequences in the expected positions upstream of the major transcription initiation site but contains multiple GC boxes within a (G + C)-rich region, as does the immediate 5' region of the first intron. Characteristics common to the 5' end of the human 5-lipoxygenase gene and the promoter regions of the housekeeping genes raise important questions concerning the regulation of 5-lipoxygenase gene expression.

Amino Acid Sequence↗
PubMed1989

Native and mutant 5-lipoxygenase expression in a baculovirus/insect cell system.

Human 5-lipoxygenase (EC 1.13.11.34), the key enzyme involved in the transformation of arachidonic acid to the potent biologically active leukotrienes, has been overexpressed in insect cells using a baculovirus expression system. A recombinant baculovirus (3B6) carrying the human 5-lipoxygenase coding sequence downstream of the strong polyhedrin protein promoter was isolated. Approximately 48 hr after infection of Spodoptera frugiperda cells with the recombinant baculovirus, maximal intracellular enzyme activity and protein levels were detected. The recombinant 5-lipoxygenase in 10,000 x g supernatant fractions was able to synthesize large amounts of 5-hydroperoxy-6,8,10,14-icosatetraenoic acid, together with smaller amounts of the nonenzymatic hydrolysis products of leukotriene A4, and exhibited a dependence on Ca2+ and ATP for maximal activity. Immunoblot analysis of supernatant proteins from human leukocytes and recombinant virus-infected cells indicated the presence of indistinguishable approximately 80-kDa bands. However, 5-lipoxygenase protein in recombinant-infected cells was found to be present in amounts 50-200 times that present in leukocytes on a per-cell basis. Histidine-362 and histidine-372, potential iron-atom ligands within a putative iron-binding domain, were changed to serine residues. Recombinant baculoviruses carrying the mutations were isolated and used to infect insect cells. Although infected cells were able to express mutant 5-lipoxygenase protein, enzyme activity was not substantially altered, suggesting the nonessential nature of these histidines in binding iron at the putative ferric catalytic site.

Arachidonate 5-Lipoxygenase↗
PubMed1989

Neurofibromatosis in Gothenburg, Sweden. IV. Genetic analyses.

The genetic analysis undertaken here shows that the direct (i.e. proband) method for calculating risk figures is not readily applicable to von Recklinghausen neurofibromatosis (NF-1); the selection of available sibling groups for analysis becomes biased in various ways, primarily because of the wide phenotypic variation of the disease. However, indirect methods of analysis confirm that NF-1 shows autosomal dominant inheritance with full penetrance. The existence of an unusually high mutation frequency is also confirmed. In this study it is estimated to be between 4.3 x 10(-5) and 6.5 x 10(-5). However, in contrast to the findings of others, among sporadic cases, both their distribution within sibships and parental ages at delivery did not differ from random distributions. An assessment of the degree of severity of NF-1 and comparisons of the sporadic cases with the familial cases produced no evidence of any clinical somatic differences between the two groups, likewise for psychiatric evaluations of the two groups. Apart from 2 cases with non-NF-1 segmental forms of NF, it was not possible to distinguish alternative forms of NF among the sporadic cases. A pair of monozygotic twins with NF-1 is discussed with reference to the nature and localization of their respective tumours, which are not identical, indicating the influence of factors beyond the mutant NF-1 gene itself on the manifestations of the disease. In a genealogical study involving about 3,000 ancestors of patients from Gothenburg with known NF-1, families with common ancestors were not found, nor was it possible to demonstrate a tendency to clustering in one geographical area or isolated locality.

Adult↗
PubMed1989

Neurofibromatosis in Gothenburg, Sweden. II. Intellectual compromise.

The literature is replete with suggestions that patients with neurofibromatosis (NF) in general and von Recklinghausen NF (NF-1) in specific often manifest mild mental retardation. However, intellectual performance in NF-1 has only rarely been the subject of study in a comparatively uniform population; it has been reported mainly in the setting of case histories. In the present material, representing a population-based cohort of Gothenburg, Sweden, it was possible to assess intelligence levels in 71 of the 74 patients originally identified [Samuelsson B, Samuelsson S: Neurofibromatosis 1989;2:6-22]. Thirty-two of the seventy-one patients (45%) showed slight mental retardation and 2 of these were somewhat more retarded than the remainder. This slight mental retardation was usually recognized during the early school years; it did not appear to be progressive. While patients affected with this problem were placed in remedial or special classes in school, these patients generally did not acquire any vocational training. There is reason to suspect that NF-1 itself leads to some impairment of intellectual development in all patients, for the intellectual achievements of those whose intelligence was judged to be within the normal range appeared to fall short of the average. Non of the patients with normal intelligence had passed any academic examination and many showed achievements less than expected based on the achievements of their healthy relatives. In certain families, the NF appeared to be associated with mild mental retardation more than in other families. Mental retardation of a more severe degree, corresponding to special school level or lower, is not typical of NF-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Cohort Studies↗
PubMed1989

Neurofibromatosis in Gothenburg, Sweden. III. Psychiatric and social aspects.

Mental illness affected 23 (33%) of the 69 patients with von Recklinghausen neurofibromatosis (NF-1) who were the primary subjects of this report. Moderately severe or severe mental illness, that is, grade 2 and 3 according to the Comprehensive Psychopathological Rating Scale (CPRS), was found in 15 of the 69 patients (22%). The 23 mentally ill patients did not show any uniform clinical psychiatric syndrome. The most commonly occurring psychiatric diagnoses were depressive syndrome, anxiety state with vegetative dysfunction and organic brain syndrome. There was a significant positive relation between depressive syndrome and organic brain syndrome according to the CPRS rating. Half of the 69 patients complained of mental symptoms in the form of hostile feelings and autonomic disturbances and these were the most frequent psychiatric symptoms; they were also frequent among patients without mental illness. Other common symptoms were sleep difficulties, tiredness, and aches and pains. Among patients with NF-1 there was a significantly positive relation between mental illness and mental retardation, but no significant positive relation between mental illness and physical severity of NF-1. Patients with mental illness also showed a significantly increased frequency of positive neurological findings indicating central nervous manifestations of NF-1.

Adult↗
PubMed1989

Neurofibromatosis in Gothenburg, Sweden. I. Background, study design and epidemiology.

In this study, a clinical evaluation was carried out for all patients who were at or beyond 20 years of age and known to the health services as cases of neurofibromatosis (NF) and who were resident in Gothenburg, Sweden, as of January 1, 1978. The approach of the study was clinical, with emphasis on the general somatic, psychiatric and genetic aspects of NF. The patients included in the study were ascertained by scrutiny of all available archives of medical records in the area, and by requests to every doctor in the city of Gothenburg to report any possible case of NF known to him or her. This search identified 74 patients with NF living in Gothenburg on the census day. All but 3 of these patients had definite von Recklinghausen NF (NF-1). This represents a prevalence of 1 case of NF in 4,600 adults, which must be considered a minimum frequency estimate. The 74 patients included 35 women with a mean age of 46 (+/- 17) years and 39 men with a mean age of 43 (+/- 14) years. The prevalence of NF was highest in the age range of 40-50 years, while it was significantly reduced in the ages above this range, most probably owing to an excess mortality. Sixty-nine of the original seventy-four patients were personally interviewed and examined, including the 3 without definite NF-1. The patients were classified according to the degree of severity of NF into three categories: mild, moderate and severe. The number of patients in each groups was, respectively, 18, 43 and 13. A detailed description of each patient's pigmentary abnormalities and neurofibromas (number, appearance and localization) was recorded. Findings of osseous dysplastic changes (12-16%), endocrine changes (pheochromocytoma, 3%), malignant disease (sarcoma, 4%), epilepsy (3%) and other somatic diseases were also recorded. Mild mental retardation was present in 45% of the patients. The mental retardation did not appear progressive, and severe retardation was not found. Mental illness occurred in 23 (33%) patients, defined as mild in 8, moderate in 7 and severe in 8. No uniform psychiatric syndrome was found. Depressive syndrome, anxiety state with vegetative dysfunction and organic brain syndrome were most frequently observed. Hostile feelings and autonomic disturbances were the most common symptoms, each found in 50% of all patients. The frequency of abnormal neurological findings, presumably indicating manifestations of NF-1 in the central nervous system, was significantly increased among the patients with mental illness.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗