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Biomedical subjects

S John

Publications and source records attributed to S John.

At least 91 records · Page 5Linked to original sources
PubMed1998

Integrated microsatellite markers suitable for genetic studies of cytokine genes.

A panel of 13 highly informative dinucleotide repeats which are genetic markers for 17 cytokine genes and receptors is described. The marker panel is designed for use in fluorescence based semi-automated genotyping, with primers designed and labelled such that all 13 markers can be analysed in a single lane of a gel. Cytokine and cytokine receptors have a potential role in many diseases and pathological processes. Evidence suggests that cytokine production in vivo is influenced by polymorphisms within regulatory sequences of these genes. Genetic investigation of disease genes often requires genotyping of very large numbers of individuals. This panel of markers will, therefore, provide a useful tool to those wishing to undertake family-based linkage analysis studies of cytokine genes or large-scale association studies.

Alleles↗
PubMed1998

Identification and analysis of yeast nucleosomal histone acetyltransferase complexes.

Many studies have linked acetylation of lysine residues on the amino-terminal tails of the core histones to transcriptional activity of cellular chromatin. New insights into this field were gained on the identification of the first nuclear, type A histone acetyltransferase (HAT). The yeast transcriptional adaptor protein Gcn5 was identified as a nuclear HAT and thus provided a direct link between pathways of transcriptional activation and histone acetylation. However, while recombinant Gcn5 can efficiently acetylate free histone H3 and, to a lesser extent, H4 it is unable to acetylate nucleosomal histones. It is therefore very likely that additional proteins are required for Gcn5-mediated acetylation of chromosomal histones. We have recently shown that Gcn5 is the catalytic subunit of two high-molecular-weight histone acetyltransferase complexes in yeast. In addition to the Gcn5-containing ADA and SAGA HAT complexes we have identified two other HAT complexes in yeast. These are called NuA3 and NuA4 for their predominant specificity to acetylate histones H3 and H4, respectively. Here we describe the identification and characterization of four native nuclear high-molecular-weight HAT complexes in Saccharomyces cerevisiae. These purified HATs can be used in a variety of functional assays to further address questions of how acetylation has an impact on transcriptional regulation.

Acetyltransferases↗
PubMed1998

Lipid peroxidation and antioxidant enzymes in isoproterenol induced oxidative stress in rat tissues.

The oxidative metabolism of catecholamines produce quinones which react with oxygen to produce superoxide anions (O2-.) and H2O2. The catecholamines, however, are important under stress conditions but may have damaging effects due to the generation of reactive oxygen species (ROS) and formation of oxidation products. ROS are involved as causative factors in many diseases, therefore, the generation of ROS by catecholamines may also contribute to this process. Isoproterenol (ISO) was administered to rats in two doses so as to evaluate their beta-adrenergic and toxicological actions in terms of lipid peroxidation (LPO) and the changes in the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and glutathione (GSH) content in heart, liver and kidney. ISO treatment caused LPO in tissues, however, the heart initially showed decreased LPO. This is attributed to the condition of hypertrophy by which the heart can protect itself to a limited extent against oxidative stress. The second dose of ISO, administered 24 h after the first treatment, showed toxic effects resulting in a higher increase in LPO. The increased SOD activity in tissues 3 days after a dose of ISO suggests that the ROS may induce SOD activity to dismutate O2-. However, increased amounts of O2-., inhibited SOD activity at 3 and 6 h with recovery towards control values at 12 h of a second dose of ISO treatment. CAT activity in tissues increased at 6 h of a second dose of ISO treatment. The elevated SOD and CAT enzymes in tissues indicate a response due to increased ROS. The increase in GSH content in the heart, liver and kidney at day 2 of ISO treatment and 12 h after the second dose of ISO may also neutralise oxidative stress. The inhibition in GST activity in tissues was observed probably due to increased ROS generation, however, GST activity partially recovered by 12 h after the second dose of ISO, in an attempt to counteract oxidative stress. The result shows that ISO induced oxidative stress and the increase of the antioxidant system in tissues may attenuate oxidative stress. It is suggested that ROS generation in the oxidation of catecholamines may be partially counteracted by the antioxidant system in tissues.

Adrenergic beta-Agonists↗
PubMed1998

Does lipoprotein(a) impair endothelial function?

OBJECTIVES: This study was undertaken to test the hypothesis that lipoprotein(a) [Lp(a)] impairs endothelial function. BACKGROUND: Elevated Lp(a) plasma levels have been demonstrated to be associated with an increased risk of coronary heart disease. In atherosclerosis, endothelial dysfunction is known to be an early indicator of vascular changes. However, the effect of Lp(a) on nitric oxide (NO)-dependent vasodilator response has not yet been determined. We therefore examined the influence of Lp(a) on basal and stimulated NO-mediated vasodilator response in the forearm vascular bed. METHODS: Strain gauge plethysmography was used to measure changes in forearm blood flow produced by intraarterial infusion of increasing doses of acetylcholine (3, 12, 24 and 48 microg/min), sodium nitroprusside (200, 800 and 3,200 ng/min) and N-monomethyl L-arginine (L-NMMA) (1, 2 and 4 micromol/min) in 57 white subjects (mean age +/- SD 37 +/- 14 years). Lp(a) plasma concentrations were determined by rocket immunoelectrophoresis. RESULTS: Endothelium-dependent vasodilation tested by intraarterial acetylcholine and endothelium-independent vascular relaxation tested by intraarterial sodium nitroprusside were not correlated with Lp(a). Similarly, no significant differences in forearm blood flow changes were observed when patients were classified into tertiles according to their individual Lp(a) concentration. In contrast, changes in forearm blood flow after intraarterial L-NMMA indicating basal production and release of NO differed significantly among tertiles. Patients in the highest Lp(a) tertile (49.2 +/- 20.3 mg/dl) had a much greater vasoconstrictive response to L-NMMA than patients in the lowest Lp(a) tertile (4.8 +/- 2.5 mg/dl): 2 micromol/min of L-NMMA, -23.6 +/- 22.5% vs. -10.4 +/- 9.1% (p < 0.02); 4 micromol/min of L-NMMA, -27.8 +/- 10.3% vs. -17.6 +/- 9.9% (p < 0.03). Lp(a) plasma level consistently correlated negatively with the forearm blood flow responses to 4 micromol/min of intraarterial L-NMMA (r = -0.38, p < 0.01). Multiple stepwise regression analysis of variables, including total and high and low density lipoprotein cholesterol, further confirmed that plasma Lp(a) remained a significant independent determinant of forearm blood flow changes in response to L-NMMA (p < 0.02). CONCLUSIONS: The endothelium-dependent vasoconstrictive response to L-NMMA was enhanced in subjects with relatively high Lp(a) plasma levels, suggesting an increased basal production and release of NO. This response seemed to reflect a compensatory mechanism of the endothelium to yet unknown Lp(a)-induced atherosclerotic effects.

Acetylcholine↗
PubMed1998

Two novel biallelic polymorphisms in the IL-2 gene.

We have detected two novel single nucleotide polymorphisms in the IL-2 gene, at positions -330 and +166 relative to the transcription start site. The +166 change occurs within the leader peptide and does not affect amino acid sequence. The -330 polymorphism has two common alleles, making it an ideal marker for genetic association studies.

5' Untranslated Regions↗
PubMed1998

The position and length of the steroid-dependent hypersensitive region in the mouse mammary tumor virus long terminal repeat are invariant despite multiple nucleosome B frames.

Stimulation of the mouse mammary tumor virus with steroids results in the generation of a DNase I-hypersensitive region (HSR) spanning the hormone responsive element (HRE) in the long terminal repeat. Restriction enzymes were used to characterize the accessibility of various sites within the HSR of mouse mammary tumor virus long terminal repeat-reporter constructions in four different cell lines. The glucocorticoid-dependent HSR was found to span minimally 187 bases, a stretch of DNA longer than that associated with histones in the core particle. Although the 5'-most receptor binding site within the HRE is downstream of -190, hypersensitive sites were found further upstream to at least -295. The relationship in the accessibility between pairs of sites in the vicinity of the HSR was further examined in one cell line by a two-enzyme restriction access assay. In the uninduced state, the accessibilities at these sites were found to be independent of each other. In contrast, when stimulated with hormone, the accessibilities at these sites were observed to become linked. That is, once a distinct promoter was activated, all of the sites within the HSR of that molecule became accessible. The HSR formed along an invariant stretch of DNA sequence despite the multiplicity of nucleosome frames in the nucleosome B region, where the HRE is located. The results indicate that the macroscopic length of the HSR does not arise from core length-remodeling events in molecules containing Nuc-B in alternative positions.

Animals↗
PubMed1998

Linkage of cytokine genes to rheumatoid arthritis. Evidence of genetic heterogeneity.

OBJECTIVE: To investigate linkage of candidate disease susceptibility genes to rheumatoid arthritis (RA) in affected sibling pair families stratified for specific clinical features. METHOD: Two hundred RA affected sibling pair families were genotyped for informative microsatellite markers mapping within or less than 3cM from: INF alpha, INF gamma, INF beta, IL1 alpha, IL1 beta, IL1R, IL2, IL6, IL5R, IL8R, BCL2, CD40L, NOS3, NRAMP, alpha 1 anti-trypsin, and alpha 1 anti-chymotrypsin, using fluorescence based automated technology. Linkage was examined by defining allele sharing sibling pairs. This was assessed by maximum likelihood-inheritance by descent methods. RESULTS: An increase in allele sharing was seen for IL5R in female sibling pairs (LOD 0.91, p = 0.03), for INF gamma in sibling pairs with an affected male (LOD 0.96, p = 0.03) and most significantly for IL2 in sibling pairs where one or both were persistently seronegative (LOD 1.05, p = 0.02). CONCLUSION: Weak evidence of linkage of RA to IL5R, IFN gamma, and IL2 has been detected in clinical subsets of sibling pairs suggesting that RA is a genetically heterogeneous disease.

Arthritis, Rheumatoid↗
PubMed1998

Ultrasonic characterisation of malignant melanoma of choroid.

An in-vitro study of wave spectral analysis in 8 enucleated eyes was conducted in order to differentiate histological subtypes of malignant melanoma. To obtain the backscattering coefficient for the tissues, we used a broadband focussed transducer with a frequency range of 7-12 MHz and a centre frequency of 10 MHz. Experimental measurement of backscattering coefficient and attenuation coefficient at various frequencies was done by substitution techniques. The backscattering coefficient, scatterer size, and root mean square velocity fluctuation were derived by the numerical method, while the attenuation coefficient at 1 MHz was derived from attenuation coefficient at different frequencies. This study revealed that backscattering coefficient and attenuation coefficient, over a frequency range of 7-12 MHz, show an increase in the spindle cell type compared to the mixed cell type of malignant melanoma. Particularly, the scatterer size was significantly higher in the spindle cell group (p = 0.013) in contrast to the mixed cell type. Spindle cells have uniform and compact histological pattern which contributes to an increase in scatterer size and root mean square velocity fluctuation. The ultrasonically obtained parameters have been shown to have a good correlation with the histology of malignant melanoma.

Choroid Neoplasms↗
PubMed1997

The human HNP36 gene is localized to chromosome 11q13 and produces alternative transcripts that are not mutated in multiple endocrine neoplasia, type 1 (MEN I) syndrome.

Multiple endocrine neoplasia, type 1 (MEN I), is an autosomal dominant syndrome of selected endocrine neoplasms whose causative gene, a suspected tumor suppressor, has been localized to chromosome 11q13, but has not been identified. Recently, the HNP36 cDNA was identified as a novel growth factor responsive gene of undetermined biological function that is expressed in the pituitary and parathyroid glands. In studies seeking the function of the HNP36 gene product, the gene was localized by fluorescence in situ hybridization within the 11q13 segment. Further analysis of radiation-reduced hybrid DNAs and chromosome 11-specific YAC clones established that the HNP36 gene is within 80 kb of D11S913, a marker tightly linked to the MEN1 gene. Consequently, the HNP36 gene was studied as a candidate for the MEN1 gene. The human HNP36 gene was cloned and determined to consist of 12 exons. Expression of the HNP36 gene from pituitary and parathyroid tissue and four patient tumors or lymphoblasts was confirmed by RT-PCR amplification of the coding sequences, and HNP36 transcripts were analyzed for mutations. All tissues expressed three HNP36 gene transcripts that result from alternative splicing and appear to encode related, but distinct, proteins. However, DNA sequence determination of the RT-PCR products from MEN I-associated tumors found no deletions and identified a single nucleotide difference that may be a polymorphism. Thus, mutations in the coding segments of the HNP36 gene are not the cause of the MEN I syndrome. Nevertheless, the assignment of the HNP36 gene to 11q13 and identification of new potential gene products provides a novel growth-regulated genetic candidate for other disorders whose genes map to this locus.

Alternative Splicing↗
PubMed1997

[The first manifestations of Schönlein-Henoch purpura in a 74-year-old female patient with hyperthyroidism].

HISTORY AND CLINICAL FINDINGS: A 74-year-old woman had for 3 weeks suffered from watery diarrhoea and diffuse abdominal pain. She felt restless, had a subfebrile temperature (37.8 degrees C), tachycardia and a blood pressure of 190/90 mmHg. Shortly after admission petechiae were found over the lower legs and she complained of joint pains. INVESTIGATIONS: Laboratory tests established hyperthyroidism. Skin biopsy showed leukocytoclastic vasculitis. Tests for antinuclear antibodies, antistreptolysin titre, rheumatoid factors, cryoglobulins and TSH-receptor antibodies were negative, immunoglobulin A (IgA) was raised. TREATMENT AND COURSE: As a drug-induced vasculitis was suspected treatment was started with methylprednisolone, 100 mg daily. Proteinuria (5.6 g daily) indicated renal biopsy, which revealed focal glomerulonephritis with deposits of IgA, fibrin/fibrinogen and complement factor 3. Gastroscopic biopsy, performed after an episode of gastrointestinal bleeding, demonstrated necrotizing vasculitis, confirming the diagnosis of Schönlein-Henoch-purpura (SHP). As the patient's condition rapidly worsened, cyclophosphamide was started additionally (2 mg/kg). She died on the 17th hospital day from acute cardiac failure. CONCLUSION: The lethal course of the disease in this elderly patient illustrates a previously not reported close temporal and clinical relationship between SHP and hyperthyroidism.

Abdominal Pain↗
PubMed1997

Multipoint analysis of quantitative traits.

Complete multipoint analysis as implemented by MAPMAKER/SIBS was used to identify the chromosomal regions with the strongest evidence of linkage. Three different quantitative sib-pair methods were compared. For each trait the maximum lod/Z score was used to implicate a chromosomal region. For trait Q5, chromosome 5, the analysis was repeated in a second data set to test for replication of the result from the first data set. The initial screen was carried out using complete parental information and the first sibling pair from each nuclear family. The effect of removing the parental genotypes and the use of multiple independent sibs was examined in the second data set for Q5, chromosome 5.

Chromosome Mapping↗
PubMed1997

Allelic markers close to prolactin are associated with HLA-DRB1 susceptibility alleles among women with rheumatoid arthritis and systemic lupus erythematosus.

OBJECTIVE: To investigate linkage disequilibrium between HLA-DRB1 disease susceptibility alleles and microsatellite markers close to the prolactin gene, among women with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) and normal controls. METHODS: DNA from 89 women with RA, 76 women with SLE, and 94 controls was typed for HLA-DRB1 status and D6S422 and D6S285, 2 highly polymorphic microsatellite markers close to the prolactin gene. RA patients were stratified by DRB1*0401 status, and SLE patients were stratified by *0301 status. RESULTS: There was an excess frequency of D6S422*1 among SLE patients with DRB1*0301 (odds ratio [OR] 3.1). The frequency of this allele was also slightly in excess among RA patients with DRB1*0401 (OR 1.9). D6S285*5 was also in excess among female RA patients with DRB1*0401 (OR 3.5), and was slightly increased among female SLE patients with DRB1*0301. None of these alleles were found to be increased among *0401-positive or *0301-positive controls. CONCLUSION: These data indicate that there may be linkage disequilibrium between HLA-DRB1 alleles and microsatellite marker alleles close to the prolactin gene among women with RA and SLE. This suggests the possibility of extended haplotypes encoding for HLA-DRB1 susceptibility and high prolactin production, which contribute to susceptibility to both RA and SLE.

Alleles↗
PubMed1997

Analysis of transcription factor-mediated remodeling of nucleosomal arrays in a purified system.

An early step in a pathway leading to transcriptional initiation involves the rearrangement of chromatin at gene regulatory sequences. To study this process, we have developed a biochemical system analyzing the interactions between chromatin templates composed of arrays of positioned nucleosomes and sequence-specific transcriptional activators. Here, a procedure is presented for the assembly of nucleosomal arrays on DNA fragments containing synthetic and natural gene sequences inserted within tandem repeats of sea urchin 5S rDNA. We also provide methods for the use of these templates in transcription factor-binding assays, as well as experimental data illustrating the efficacy of such analyses to uncover mechanisms directing factor-mediated nucleosome remodeling.

Cell-Free System↗
PubMed1997

Is endothelial function of the radial artery altered in human essential hypertension?

There is controversy over whether endothelial function is impaired in human essential hypertension. All studies to date have used measurements of forearm blood flow by plethysmography to assess endothelium-dependent vasodilation and endothelial function. In contrast to these studies, which have focused on resistance vessels, we have determined what effects the endothelium has on underlying smooth muscle cells in conduit arteries by measuring arterial compliance of the radial arteries (change in diameter of radial artery over pressure for each arterial pulse). In 13 normotensive healthy subjects and 11 young patients with essential hypertension, arterial compliance of the radial artery was assessed directly with a new high-precision ultrasonic device (NIUS 02) after infusion of acetylcholine (endothelium-dependent response) or sodium nitroprusside (endothelium-independent response). Arterial compliance of the radial artery was similar at baseline and with increasing doses of acetylcholine and sodium nitroprusside in normotensive and in hypertensive subjects. The increase in arterial compliance from baseline at each individual concentration of acetylcholine and sodium nitroprusside was the same in both normotensive and hypertensive subjects. However, after a single oral dose of a combination of the angiotensin converting enzyme inhibitor spirapril and the calcium entry blocker isradipine, the increase in arterial compliance in response to the maximum dose of intraarterial acetylcholine was enhanced in normotensives (0.38 +/- 1.23 to 0.76 +/- 1.01 mm2/mm Hg x 10(-3), P < .05), but not in hypertensives (+0.41 +/- 1.26 to 0.36 +/- 1.31 mm2/mm Hg x 10(-3), not significant), and differed significantly between normotensive and hypertensive subjects (P < .05). Thus, pharmacologic stimulation disclosed a blunted response of endothelium-dependent action in the arterial compliance of the conduit arteries in hypertensive subjects. This suggests an impaired endothelial function reserve in persons with essential hypertension.

Acetylcholine↗
PubMed1997

Elevated serum cyclophilin levels in patients with severe sepsis.

Several cytokines are considered to be important mediators in the pathophysiology of sepsis. Cyclophilins (Cyps), the main binding proteins for the immunosuppressive drug cyclosporine A, have been suggested to function as cytokines. This study was conducted to determine (i) if serum Cyp levels were elevated in critically ill patients suffering from either sepsis or other life-threatening diseases and (ii) if so, whether there was an association between Cyp levels and a certain diagnosis and/or outcome. Serum samples of 45 patients (22 severe sepsis, 23 other diagnoses) and 17 healthy controls were prospectively analyzed by an enzymatic assay using the ability of cyclophilins to catalyze cis/trans isomerisation of peptidylprolyl-peptide bonds (PPIase activity). In addition, western blotting was applied to differentiate both isoforms. PPIase activity was significantly higher in patients with severe sepsis than in patients with other diagnoses (P = 0.004) or in healthy subjects (P = 0.001). There was no difference between healthy subjects and other critically ill patients (P = 0.067). Elevated PPIase activity was associated with high mortality (P = 0.03). It is concluded that Cyps might play a role, probably as mediators in the pathophysiology of sepsis or as symptoms of diagnostic value.

Adult↗