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Biomedical subjects

A Ribeiro

Publications and source records attributed to A Ribeiro.

At least 55 records · Page 3Linked to original sources
PubMed1997

Purification, and biochemical and biological characterization of an immunosuppressive and lymphocyte mitogenic protein secreted by Streptococcus sobrinus.

An immunosuppressive/mitogenic (ISM) protein was purified from the supernatants of cultures of Streptococcus sobrinus with an isoelectric point of 4.75 and a relative molecular mass of 38 kDa (p38). Treatment of C57BL/6 mice with p38 induced an increase in the numbers of non-specific splenic Ig-secreting plaque-forming cells (PFC) with peak responses on day 3 for IgM-secreting PFC and on day 5 for IgG-secreting PFC, with an isotype pattern consisting predominantly of IgG2a and IgG2b. This increase was accompanied by a lymphocyte blastogenic response of both T and B lymphocytes. The in vitro effects of p38 on pure B, T and total splenic lymphocytes indicated that this ISM protein was primarily a B cell mitogen, being T cells activated subsequently by the generation of B blasts. Suppression of the murine primary immune response against sheep red blood cells was observed in C57BL/6 mice treated 4 days before with p38. The amino acid sequence of the N-terminus of p38 has a significant similarity with several enolases, particularly with rabbit enolase. However, the biological effects ascribed to p38 have not been detected after in vivo treatment with that enolase. The immunosuppressive effect of p38 was abrogated by depletion of IL-10 but not of IL-4. In agreement with this observation IL-10 was the only cytokine detected in serum of C57BL/6 mice after p38 treatment and the peak of serum levels was observed as soon as 2 h after treatment.

Amino Acid Sequence↗
PubMed1997

Left ventricular function after repeated episodes of ventricular fibrillation and defibrillation assessed by transoesophageal echocardiography.

BACKGROUND: Investigators studying the effects of cardioverter-defibrillators on left ventricular systolic function have given only minor attention to the diastolic effects. OBJECTIVES: The purpose of this study was to investigate the impact of repeated episodes of ventricular fibrillation and defibrillation on systolic function and diastolic filling of the left ventricle during non-thoracotomy implantation of a cardioverter-defibrillator. METHODS: Systolic function and diastolic filling of the left ventricle were assessed peri-operatively on a beat-by-beat basis using a transoesophageal echo-Doppler technique in 12 patients during > or = 4 episodes of ventricular fibrillation and defibrillation. Systolic function was assessed from the fractional area change and diastolic filling from the E/A ratio. Arterial blood pressure and the ECG were recorded continuously. RESULTS: Blood pressure and heart rate did not change significantly throughout the procedure. The systolic function, similarly, was not significantly affected; the only changes were seen in the first two beats after defibrillation when the mean fractional area increased from 0.2 +/- 0.01 to 0.4 +/- 0.02 and 0.3 +/- 0.02, respectively (P < 0.001). Diastolic filling was, however, impaired as reflected by a decrease in the E/A ratio from 2.6 +/- 0.5 before to 1.6 +/- 0.4 (P < 0.01) after repeated threshold tests. CONCLUSIONS: While the combined ischaemic and electrical trauma caused by repeated episodes of ventricular fibrillation and defibrillation during the implantation of a cardioverter-defibrillator did not cause any systolic dysfunction, diastolic filling was significantly impaired.

Adult↗
PubMed1997

Long-term effects of dual chamber pacing in patients with hypertrophic cardiomyopathy without outflow tract obstruction at rest.

BACKGROUND: Atrioventricular-synchronous pacing is beneficial in patients with hypertrophic obstructive cardiomyopathy. The effects of pacing in patients without significant left ventricular outflow tract obstruction at rest are, however, less well explored. This study compares the long-term outcome of pacing patients with and without significant left ventricular outflow tract obstruction at rest. METHODS: Forty-one patients with hypertrophic obstructive cardiomyopathy were studied, 19 with a left ventricular outflow tract gradient < 40 mmHg at rest, but exceeding 50 mmHg during provocation with isoproterenol (group A), and 22 with a left ventricular outflow tract obstruction > 40 mmHg at rest (group B). Before the implantation of a permanent pacemaker, the patients were studied according to a temporary pacing protocol. This included graded isoproterenol provocation of the left ventricular outflow tract obstruction, which was assessed by echo Doppler. Following permanent pacemaker implantation, the patients were regularly followed up with echo Doppler, exercise testing and monitoring of the clinical condition. RESULTS: Isoproterenol provocation was reproducible and the technique did not cause any clinically important side effects. Left ventricular outflow tract gradient reduction after chronic pacing did not differ between the two groups. In group A, it decreased from 98 +/- 30 mmHg in sinus rhythm to 42 +/- 26 mmHg during pacing. The corresponding values in group B were 87 +/- 40 mmHg to 36 +/- 24 mmHg. The clinical condition improved similarly in the two groups. Exercise capacity increased significantly and perceived dyspnoea and angina pectoris were significantly lower at submaximal levels of exercise after 6 months of pacing. CONCLUSION: Hypertrophic obstructive cardiomyopathy patients who only exhibit significant left ventricular outflow tract obstruction during provocation benefit as much from pacemaker treatment as do patients who already have significant obstruction at rest. Isoproterenol is a safe and reproducible method for pre-pacing evaluation of hypertrophic obstructive cardiomyopathy patients.

Adult↗
PubMed1997

CO2 provocation of panic: symptomatic and manometric evaluation in patients with noncardiac chest pain.

OBJECTIVES: Occult panic disorder (PD) may underlie 10-43% of chest pain syndromes in patients with normal coronary arteries. A variety of agents, such as intravenous lactate, oral caffeine, and inhaled CO2, has been identified that may provoke panic attacks in susceptible patients. The aims of this study were (1) to better define the relationship between noncardiac chest pain syndromes and panic disorder; and (2) to assess the diagnostic utility of PD provocative testing with inhaled CO2 in eliciting chest pain and/or esophageal manometric disturbances. METHODS: Fourteen patients with chest pain syndromes and negative coronary angiograms or stress thallium tests were evaluated for PD and underwent (1) standard esophageal manometry followed by continuous manometric recording; (2) inhalation by face mask of room air or 35% CO2, single blinded, in random order; (3) a previously validated Acute Panic Inventory questionnaire administered before and immediately after each inhalation; and (4) Tensilon 10 mg i.v. administration. RESULTS: Of 14 patients, 8 met DSM-IIIR criteria for panic disorder. Mean Acute Panic Inventory scores (reflecting panic symptoms) increased significantly after CO2 inhalation relative to room air in all patients. Of 14 patients, 8 (4 PD, 4 non-PD) experienced chest pain after CO2 inhalation, whereas no patient had chest pain after room air inhalation. Of 14 patients, 5 had pain with Tensilon (4 of 5 whom responded to CO2). No specific manometric abnormalities occurred during any chest pain episode. CONCLUSION: CO2 inhalation is as effective as Tensilon in provoking chest pain in patients with noncardiac chest pain. The high prevalence of PD in such patients suggests that CO2 inhalation, a known panicogen, may be useful in evaluating such patients. The mechanism of CO2 induced chest pain remains unknown, but does not appear to be attributable to demonstrable esophageal motility abnormalities.

Administration, Inhalation↗
PubMed1996

The proximal element of the human apolipoprotein A-II promoter increases the enhancer activity of the distal region.

We have previously shown that human apolipoprotein A-II (apoA-II) transcription is controlled by a complex set of regulatory elements. In this study, we demonstrate that the distal region of the apoA-II promoter (-911/-614) acts as an enhancer and results in a 6-fold increase in activity when the proximal AB element is inserted between this enhancer and a TATA box. The AB element alone does not display any transcriptional activity. The combination of the proximal AB element and the enhancer is sufficient to activate transcription to the same level as that achieved with the full-length promoter. DNA binding and competition assays, and binding interference experiments allowed us to identify two adjacent binding sites within the AB element. These bind activities designated CIIIB1 and AIIAB3/4, respectively. Mutation on each of these sites showed that the binding site of CIIIB1 within the AB element played a major role in the interaction with the enhancer. Whereas transcriptional activation of other apolipoprotein genes involves the binding of the liver-enriched hepatocyte nuclear factor 4 (HNF4) on their proximal promoter, the present study demonstrates that neither HNF4 nor ApoA-I regulatory protein 1, its antagonistic orphan receptor, was able to bind the AB element. Instead, apoA-II transcription was driven by the interaction of apoA-II enhancer with proximal AB element, which involves an unidentified activity, CIIIB1.

Animals↗
PubMed1996

Sucrose synthase and enolase expression in actinorhizal nodules of Alnus glutinosa: comparison with legume nodules.

Two different types of nitrogen-fixing root nodules are known- actinorhizal nodules induced by Frankia and legume nodules induced by rhizobia. While legume nodules show a stem-like structure with peripheral vascular bundles, actinorhizal nodule lobes resemble modified lateral roots with a central vascular bundle. To compare carbon metabolism in legume and actinorhizal nodules, sucrose synthase and enolase cDNA clones were isolated from a cDNA library, obtained from actinorhizal nodules of Alnus glutinosa. The expression of the corresponding genes was markedly enhanced in nodules compared to roots. in situ hybridization showed that, in nodules, both sucrose synthase and enolase were expressed at high levels in the infected cortical cells as well as in the pericycle of the central vascular bundle of a nodule lobe. Legume sucrose synthase expression was studied in indeterminate nodules from pea and determinate nodules from Phaseolus vulgaris by using in situ hybridization.

Actinomycetaceae↗
PubMed1996

Nitrogen metabolism in actinorhizal nodules of Alnus glutinosa: expression of glutamine synthetase and acetylornithine transaminase.

Two nodule cDNA clones representing genes involved in Alnus glutinosa nitrogen metabolism were analysed. ag11 encoded glutamine synthetase (GS), the enzyme responsible for ammonium assimilation, while ag118 encoded acetylornithine transaminase (AOTA), an enzyme involved in the biosynthesis of citrulline, the nitrogen transport form in Alnus. GS mRNA was found at highest levels in root nodules, where it was present in the infected cells as well as in the cells of the pericycle of the vascular system. AOTA transcripts were found at high levels in nodules, confined to the infected cells, suggesting that in nodules of A. glutinosa, citrulline biosynthesis takes place mainly in the infected cells.

Actinomycetales↗
PubMed1996

Surviving resuscitation: successful repair of cardiac rupture.

An 83-year-old man was found unconscious and was successfully resuscitated. Progressive cardiac failure developed. After 42 hours of observation echocardiography revealed cardiac tamponade and a discontinuity in the left atrial wall. Exploration showed a laceration of the left atrium at the junction of the left pulmonary veins, which was closed with a direct suture on cardiopulmonary bypass. The postoperative course was uneventful.

Aged↗
PubMed1996

Influence of right ventricular pacing site on left ventricular outflow tract obstruction in patients with hypertrophic obstructive cardiomyopathy.

OBJECTIVES: This study was designed to show the influence of right ventricular pacing site on left ventricular outflow tract obstruction during pacing treatment of patients with hypertrophic obstructive cardiomyopathy. BACKGROUND: Atrioventricular synchronous pacing has been reported to reduce left ventricular outflow obstruction and symptoms in patients with hypertrophic obstructive cardiomyopathy. A paradoxic septal movement induced by right ventricular pacing has been implicated as the mechanism behind the reduced left ventricular outflow tract obstruction; however, the importance of pacing site has not been clarified. METHODS: Cardiac output, measured invasively, and left ventricular outflow tract gradient, estimated by Doppler echocardiography, were studied in 15 patients with hypertrophic obstructive cardiomyopathy. Measurements were made with the right ventricular electrode in the septal and apical positions during temporary pacing and during sinus rhythm. RESULTS: Right ventricular apical pacing reduced the outflow tract gradient in all 15 patients to a mean +/- SD of 38 +/- 24 mm Hg from 96 +/- 33 mm Hg during sinus rhythm. During high septal pacing the outflow tract gradient was not reduced, remaining at 93 +/- 44 mm Hg. No significant changes in cardiac output were seen when levels during sinus rhythm (6.4 liters/min), apical pacing (6.4 liters/min) and high septal pacing (5.6 liters/min) were compared. CONCLUSIONS: The right ventricular pacing site is of crucial importance for reducing left ventricular outflow tract obstruction when patients with hypertrophic obstructive cardiomyopathy are treated with pacing. Cardiac output is not reduced by apical pacing.

Adult↗
PubMed1996

Identification of agthi1, whose product is involved in biosynthesis of the thiamine precursor thiazole, in actinorhizal nodules of Alnus glutinosa.

A cDNA clone, pAgthi1, encoding a homologue of yeast Thi4, which is involved in thiazole biosynthesis, was isolated from a library made from poly(A) RNA from actinorhizal nodules of Alnus glutinosa by differential screening with nodule and root cDNA, respectively. The corresponding gene, agthi1, was shown to be expressed at high levels in nodules and shoot tips of A. glutinosa, while having low expression levels in roots, flowers, and developing fruits. The function of AgThi1 was demonstrated by yeast complementation studies, in which AgThi1 was able to rescue a yeast thi4 mutant when fused to the yeast Thi4 signal peptide. In A. glutinosa nodules, high levels of agthi1 mRNA were detected in the infected cortical cells and in the pericycle of the nodule vascular system. A homologue of this cDNA, ara6/tz, was identified in Arabidopsis thaliana. ara6 maps in a region of chromosome 5 of Arabidopsis containing the tz locus which is consistent with the fact that ara6 transcription is disturbed in two tz mutant lines. ara6/tz is expressed at high levels in chloroplast-containing parenchymatic cells of leaves, inflorescence shoots and flowers of Arabidopsis, and at lower levels in the vascular system.

Arabidopsis↗
PubMed1996

Effect of blood donation on the establishment of normal ranges of lymphocyte subsets.

BACKGROUND: Absolute counts of CD4+ T-lymphocytes are used in the management of patients with human immunodeficiency virus infection. Low absolute counts of CD3+CD4+ cells have also been observed in healthy people--a phenomenon called idiopathic CD4 lymphocytopenia. It is common practice for normal ranges for lymphocyte subsets to be derived from samples taken from blood donors. STUDY DESIGN AND METHODS: A sample of EDTA blood was taken through the donation line tubing, after donation from 565 blood donors in Sydney, Australia, who were selected from a range of age groups. An additional 12 donors provided a predonation sample as well as a postdonation sample. Hematologic assays were performed on two analyzers. Samples were stained for CD3, CD4, CD8, CD19, and CD56 and analyzed on a flow cytometer. RESULTS: Three donors were found to have absolute CD3+CD4+ counts < 300 cells per microL. The percentage of CD3+CD4+ cells was found to increase with age. Both the percentage and the absolute count of CD3+CD8+ cells decreased with age, which resulted in an increased CD4:CD8 ratio with age. Men had consistently higher absolute counts of CD3-CD56+ cells than women. The 12 additional donors all had greater percentages of CD3+CD4+ cells and lower absolute counts for CD3+, CD3+CD4+, CD3+CD8+, CD19+ and CD3-CD56+ cells after donation than they had before donation (p < 0.001). CONCLUSION: It is not satisfactory to base normal ranges for lymphocyte subsets on donor blood, from which the blood sample has been obtained after donation.

Adolescent↗
PubMed1995

A nodule-specific gene encoding a subtilisin-like protease is expressed in early stages of actinorhizal nodule development.

To identify genes specifically expressed during early stages of actinorhizal nodule development, a cDNA library made from poly(A) RNA from root nodules of Alnus glutinosa was screened differentially with nodule and root cDNA, respectively. Seven nodule-enhanced and four nodule-specific cDNA clones were isolated. By using in situ hybridization, two of the nodule-specific cDNAs were shown to be expressed at the highest levels in infected cells before the onset of nitrogen fixation; one of them, ag12 (A. glutinosa), was examined in detail. Sequencing showed that ag12 codes for a serine protease of the subtilisin (EC 3.4.21.14) family. Subtilisins previously appeared to be limited to microorganisms. However, subtilisin-like serine proteases have recently been found in archaebacteria, fungi, and yeasts as well as in mammals; a plant subtilisin has also been sequenced. In yeast and mammals, subtilases are responsible for processing peptide hormones. A homolog of ag12, ara12, was identified in Arabidopsis; it was expressed in all organs, and its expression levels were highest during silique development. Hence, our study shows that subtilases are also involved in both symbiotic and nonsymbiotic processes in plant development.

Amino Acid Sequence↗
PubMed1994

An in vivo assay for members of the cAMP response element-binding protein family of transcription factors.

The CREB/ATF family of dimeric basic/leucine zipper (bZIP) transcription factors have been implicated in signal transduction by several agents including intracellular cAMP. The ubiquity of the cAMP-signaling pathway in mammalian cells has made it difficult to assay individual family members in their native form and dissect their roles in signal transduction. In light of observations that ATF1 exhibits several cell-specific characteristics and is allosterically regulated, the above problem has represented a particular limitation for studying ATF1. To address this we have exploited the modular nature of the bZIP domain to design fusion proteins that closely resemble native ATF1 but have altered DNA binding and dimerization specificity. The activity of these novel proteins can be monitored following their introduction into a cAMP-responsive cell type. Thus we describe an assay for members of the CREB family that should be generally applicable in a range of cell types and to other bZIP protein families.

Amino Acid Sequence↗
PubMed1994

Immunostimulatory effect of thalidomide in normal C57BL/6 mice is compatible with stimulation of a highly connected central immune system.

Although thalidomide has been used with success in the treatment of increasing numbers of autoimmune diseases, the therapeutic effects have not been satisfactorily explained so far. We describe here some findings that may contribute to a better understanding of the immunomodulatory effects of this drug. Several immunological changes were observed after treating C57BL/6 mice with 3 mg of thalidomide. The numbers of natural IgM PFC against sheep red blood cells were increased in the spleen, and occasionally a dramatic oscillatory increase in the numbers of non-specific splenic IgM and IgG PFC was observed in these mice. However, these oscillatory increases were progressively lower, after two and three treatments with thalidomide at 20-day intervals. Furthermore, the absolute numbers of splenic CD5+ B and CD5- B lymphocytes were increased whereas depletion of CD4+ CD8+ cells in the thymus and of lymphoid cells in the bone marrow was seen after a single treatment with 3 mg of thalidomide. Taken together, these results suggest that thalidomide stimulates both peripheral and central immune systems and consequently enhances the connectivity of the central immune system.

Animals↗