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Biomedical subjects

A Ferreira

Publications and source records attributed to A Ferreira.

At least 19 recordsLinked to original sources
PubMed1999

Brain natriuretic peptide as a marker of cardiac involvement in hypertension.

Hypertensive patients with heart abnormalities have increased risk of cardiovascular events. Brain natriuretic peptide is a natriuretic peptide mainly of ventricular origin produced in response to pressure and stretch. We hypothesise that brain natriuretic peptide could be a useful marker of cardiac remodelling in hypertensive patients. We studied 36 consecutive community mild-to-moderate hypertensive patients and 11 well-matched normotensive controls with respect to clinical characteristics, brain natriuretic peptide, creatinine and echocardiography parameters (M-mode, 2-D arid transmitral pulsed Doppler). Brain natriuretic peptide levels were significantly higher in hypertensive patients than in controls [36.54 (IQR: 38.61) vs. 10.30 (IQR: 13.20) pg ml(-1), p<0.0001] and it was correlated with left ventricular mass index. Hypertensive patients with impairment of diastolic filling had significantly higher brain natriuretic peptide concentrations than patients with no abnormalities on echocardiography [61.16 (45.38) vs. 31.27 (18.10) pg ml(-1), p=0.001]. Multivariate analysis showed that only diastolic dysfunction and left ventricular mass index were significantly and independently related with brain natriuretic peptide concentrations in this population. In conclusion, impairment of diastolic function and left ventricular mass index are related to brain natriuretic peptide levels, thus giving the insight that this peptide can be a marker of ventricular remodelling in hypertensive patients.

Aged↗
PubMed1999

Characterization of proteinases in Herpetomonas anglusteri and Herpetomonas roitmani.

We have analyzed the proteinase profile of two Herpetomonas species, H. anglusteri and H. roitmani (a symbiont-bearing trypanosomatid), by in situ detection of enzyme activities on SDS-PAGE gels containing copolymerized gelatin as substrate. Two major cell-associated proteolytic activities, a 60 kDa zinc-metalloproteinase and a 45 kDa cysteine proteinase could be detected based on the inhibition of their activities by 1, 10-phenathroline and E-64, respectively. The trypanosomatids released into the growth medium distinct proteinases. H. anglusteri expressed three digestion haloes in the gels of approximately 60, 50, and 40 kDa, whereas H. roitmani secreted only a 60 kDa enzyme. However, these activities were inhibited by 1,10-phenanthroline, suggesting that all of them are zinc-metalloproteinase.

Animals↗
PubMed1999

Characterization of rpoS alleles in Escherichia coli O157:H7 and in other E. coli serotypes.

The rpoS nucleotide and predicted amino acid sequences from three Escherichia coli O157:H7 isolates were compared with those from three other E. coli isolates, including the likely O157:H7 progenitor, E. coli O55:H7. These clinical and environmental isolates all had identical sigma S amino acid sequences, while laboratory strains K12 and DH1 had three and one amino acid alterations, respectively, in comparison with the majority sequence. To extend the analysis of sigma S sequence conservation to include other Gram-negative bacteria, the E. coli sigma S sequences were compared with those from diverse Gram-negative organisms; sigma S sequence identities ranged from 50.2 to 99.7% among the available sequences. The results further confirm the existence of rpoS alleles among different E. coli strains, although all strains were classified as acid-resistant with survival rates > 10% after 2 h exposure to pH 2.5. It was also found that all E. coli O157:H7 isolates tested had a unique nucleotide at position 543, thus differentiating these strains from other E. coli serotypes.

Alleles↗
PubMed1999

Abnormal synapse formation in agrin-depleted hippocampal neurons.

Agrin, a 200 kDa extracellular matrix protein, participates in the maturation of the postsynaptic target at the neuromuscular junction. Although agrin has also been detected in central neurons, little is known about its role in the formation of their synapses. In the present study, the pattern of expression, localization and function of agrin in developing hippocampal neurons were analyzed. The results indicate that an increase in agrin protein levels precedes synaptogenesis in cultured hippocampal neurons. This increase in agrin expression is accompanied by its extracellular deposition along the distal third of the axon. To investigate whether agrin plays a role during synapse formation, its expression in cultured hippocampal neurons was suppressed by means of antisense oligonucleotide treatment. The suppression of agrin expression results in the impairment of dendritic development and the formation of fewer synapses than in non-treated or sense-treated neurons. Moreover, this decreased synaptic density is accompanied by a selective inhibition of the clustering of GABA receptors. These results lead to the conclusion that agrin may be an important regulator of the maturation of dendrites and synaptogenesis in central neurons.

Agrin↗
PubMed1999

Noise assessment during aircraft run-up procedures.

BACKGROUND: A comprehensive noise survey was conducted at Oficinas Gerais de Material Aeronautico (OGMA), Alverca, Portugal, and at several Portuguese Air Force (PoAF) bases, as part of an ongoing occupational noise assessment program. The major objectives consisted of measuring and analyzing noise radiated by various types of military aircraft while undergoing maintenance, repair, or testing. METHODS: Amplitude, frequency, time history and statistical analysis were conducted on noise emitted by aircraft during run-up procedures. Analysis and evaluation used various noise indexes (Leq and Lmax), frequency spectra, and sound pressure time histories for the assessment of noise exposure on the employees during their working life span. RESULTS: The results show a predominance of large pressure amplitudes within the lower frequency bands. This was correlated with long-term clinical observations in these workers. This study corroborates the definition of vibroacoustic disease as a systemic, noise-induced occupational pathology caused by long-term (>10 yr) exposure to large pressure amplitude (> or = 90 dB SPL) and low frequency (< or = 500 Hz) noise.

Aerospace Medicine↗
PubMed1999

[Superficial siderosis of the central nervous system].

We report five cases of superficial siderosis of the central nervous system. All patients developed progressive deafness and cerebellar ataxia associated with pyramidal tract signs or mental deterioration. The cerebrospinal fluid examinations usually revealed an elevated protein level, without other abnormalities. Magnetic resonance imaging typically showed a hypointense rim around the cerebral and cerebellar hemispheres, the brainstem and the spinal cord on T2-weighted images. A definite source of bleeding was only found in two patients. The literature on superficial siderosis is reviewed. The etiologies and the pathogenesis are discussed.

Adult↗
PubMed1998

Evidence for the participation of the neuron-specific CDK5 activator P35 during laminin-enhanced axonal growth.

Cultures of cerebellar macroneurons were used to study the pattern of expression, subcellular localization, and function of the neuronal cdk5 activator p35 during laminin-enhanced axonal growth. The results obtained indicate that laminin, an extracellular matrix molecule capable of selectively stimulating axonal extension and promoting MAP1B phosphorylation at a proline-directed protein kinase epitope, selectively stimulates p35 expression, increases its association with the subcortical cytoskeleton, and accelerates its redistribution to the axonal growth cones. Besides, suppression of p35, but not of a highly related isoform designated as p39, by antisense oligonucleotide treatment selectively reduces cdk5 activity, laminin-enhanced axonal elongation, and MAP1b phosphorylation. Taken collectively, the present results suggest that cdk5/p35 may serve as an important regulatory linker between environmental signals (e.g., laminin) and constituents of the intracellular machinery (e.g., MAP1B) involved in axonal elongation.

Animals↗
PubMed1998

Blockade of the anxiolytic action of 8-OH-DPAT in lactating rats.

The anxiolytic action of 8-OH-DPAT (0.125, 0.5, and 0.75 mg/kg, I.P., -15 min) was evaluated in ovariectomized and 7-day lactating mother rats. This serotonergic anxiolytic produces a clear reduction in cumulative burying behavior and in freezing time (parameters denoting a reduction in anxiety levels) in ovariectomized subjects. However, in 7-day lactating mother rats, 8-OH-DPAT lacked its antianxiety effects. Additionally, as an extra parameter of the animal's emotionality the number of defecation bolus was registered. A reduction in this parameter in ovariectomized animals after 8-OH-DPAT (0.5 mg/kg) injection was found. This effect was also blocked in 7-day lactating rats. None of the doses of the compound tested altered the burying behavior latency (a parameter inversely representing the animal's reactivity). The general ambulatory behavior of ovariectomized subjects was significantly impaired at the highest dose (0.75 mg/kg) of 8-OH-DPAT. Lower doses did not alter this parameter or the number of times lines are crossed (a parameter denoting exploratory activity). Discussion is focused on the relationship between the activity of the serotonergic system and the secretion of prolactin in this period.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1998

Predictors of myocardial dysfunction in human immunodeficiency virus-infected patients.

BACKGROUND: Some of the most frequent manifestations of heart involvement in human immunodeficiency virus (HIV) infection include right and left ventricular dysfunction. The pathogenesis remains obscure. METHODS AND RESULTS: This prospective clinical and echocardiographic study involved 181 patients at all stages of HIV infection. We tested a set of clinical variables using a backward logistic regression model to assess their ability to independently predict the presence of ventricular dysfunction. The presence of pulmonary infections (all etiologies mixed) was the only variable independently associated with isolated right ventricular dysfunction (odds ratio = 4.08; P = .02). Signs suggestive of pulmonary arterial hypertension were present in 71% of the patients with right ventricular dilation. History of previous opportunistic infections (all etiologies mixed) (odds ratio = 10.9; P = .0026) and time since the diagnosis of acquired immunodeficiency syndrome more than 12 months (odds ratio = 6.6; P = .03) were the only two independent predictors of left ventricular dysfunction. CONCLUSIONS: Isolated right ventricular dysfunction may be secondary to pulmonary hypertension caused by repetitive pulmonary infections and not to primary myocardial disease. The aggressive treatment of opportunistic infections may become an important element of heart failure prophylaxis in HIV infection because they may be associated with left ventricular dysfunction.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Phenotypical and functional characterization of Herpesvirus saimiri-immortalized human major histocompatibility complex class II-deficient T lymphocytes.

CD8+ T lymphocytes from two unrelated cases of MHC class II deficiency were immortalized in vitro using Herpesvirus saimiri. In both cases, a lack of expression of surface MHC class II molecules was ascertained, whereas variable defects were shown for MHC class I, CD74 (invariant chain) and LAG-3 (an MHC class II ligand). The functional analysis of both H. saimiri-immortalized T-cell lines revealed the existence of a proliferation impairment in response to anti-CD3 but not to other surface or transmembrane stimuli. Further characterization of this functional defect indicated that it was not associated with impaired early activation events (like calcium flux) but, rather, with certain late events, like the induction of IL-2. H. saimiri-immortalized T cells may be valuable in studying the biological role of MHC class II molecules in activated human T cells.

Cell Transformation, Viral↗
PubMed1998

Sudden Wenckebach periods and their relationship to neurocardiogenic syncope.

Throughout a 9-month period during which 1,125 Holter tapes were reviewed prospectively we identified 13 nonmedicated patients with an arrhythmia, which for the purposes of this presentation was categorized, because of their mode of initiation, as sudden Wenckebach periods (WP). The episodes emerged abruptly from a normal (< or = 200 ms) PR interval with sudden prolongation of PR and PP intervals (and reversed PR-RP relationship) that took place over 1-8 cycles. The postpaced PR interval was shorter than that of the last conducted beat. The episodes were separated into two groups. Group I included 11 patients with symptoms other than syncope and Group II included 2 patients with syncope. There were 26 episodes of sudden WP in Group I. Twenty-five terminated in a single (and one in double) blocked P waves. Most episodes occurred between 10 PM and 7 AM. Symptoms did not correlate with the episodes. Mean 24-hour rates were < 90. In Group II there were 22 episodes, all occurring between 6 AM and 10 PM. The mean sinus cycle lengths before the phenomenon started to occur in Group I (861 +/- 185 ms) as well as the cycle lengths at the onset of block (1,096 +/- 215 ms) were statistically longer than those in Group II (591 +/- 40 ms and 747 +/- 63 ms, respectively, P < 0.0001). Although the mode of onset in the episodes in Group II was similar to Group I, 16 episodes terminated in 2-6 blocked P waves. Thus, the entire number of episodes could be categorized as an unusual type (because of the PR prolongation) of paroxysmal, or advanced second degree AV block. Because these patients had negative electrophysiological studies, positive tilt tests, and absent syncope after oral propranolol therapy, they were considered as having neurocardiogenic syncope. In addition, the faster than normal (> 100) mean 24-hour rates) suggested that they also had so-called inappropriate sinus tachycardia. In summary, Group I consisted of patients with a normal, benign, vagal-induced second-degree AV block, whereas the Holter findings in Group II appeared to reflect unusual (but natural, i.e., nonprovoked) electrocardiographic manifestations of certain patients with neurocardiogenic syncope.

Acute Disease↗
PubMed1998

[Uveitis].

Uveitis is a general term that refers to the inflammation of uveal tract, which is an important cause of blindness in young people. It is well known that uveitis can be the initial manifestation of a systemic disease (S.D.), and may appear years before the diagnosis of the primary disease. Uveitis should be integrated in a systemic study with proper testing. Therefore, the diagnosis is a matter for the ophthalmologist and the Specialist in internal medicine. We have made a retrospective study of 71 patients with chronic uveitis or panuveitis. We found 54.9% of primary uveitis and 45.1% of S.D. associated uveitis, most of them with Behçet's disease (16/71) and Ankylosing Spondilytis (7/71). HLA typing of the patients showed a decreased frequency of HLA A1 and HLA A3 antigens and an increased frequency of the HLA B27 antigen, when compared to a Portuguese control population. We confirmed the important role of HLA B27 as an independent susceptibility factor for anterior uveitis. The lowest HLA A3 frequency was observed in the group of S.D. associated uveitis, which could suggest that this antigen may play a role as a factor of resistance to uveitis.

Adolescent↗
PubMed1998

Distinct roles of synapsin I and synapsin II during neuronal development.

The synapsins are a family of neuron-specific proteins, associated with the cytoplasmic surface of synaptic vesicles, which have been shown to regulate neurotransmitter release in mature synapses and to accelerate development of the nervous system. Using neuronal cultures from mice lacking synapsin I, synapsin II, or both synapsins I and II, we have now found that synapsin I and synapsin II play distinct roles in neuronal development. Deletion of synapsin II, but not synapsin I, greatly retarded axon formation. Conversely, deletion of synapsin I, but not synapsin II, greatly retarded synapse formation. Remarkably, the deletion of both synapsins led to partial restoration of the wild phenotype. The results suggest that the synapsins play separate but coordinated developmental roles.

Animals↗
PubMed1997

Complement evasion by Echinococcus granulosus: sequestration of host factor H in the hydatid cyst wall.

Hydatid disease, which affects humans and various livestock species, is caused by the larval stages of the cestode parasite Echinococcus granulosus. The disease involves the growth of a fluid-filled cyst in the host's internal organs. The hydatid cyst wall is generally thought to preclude the access of host immune cells to the cyst, while allowing passage of macromolecules. Thus, evasion of humoral effector mechanisms, in particular the complement system, may be crucial to parasite survival. Evasion of complement might involve inhibition of the C3b deposition step, which can in principle be achieved through parasite-derived or host-derived and parasite-bound regulatory molecules. In this work, extracts from bovine hydatid cysts were analyzed for the presence of factor H-like function, namely the cofactor activity for the breakdown of amidated bovine C3 by bovine factor I. Both this activity and antigenically detectable bovine factor H were found in most extracts. The cofactor activity was retained by an anti-bovine factor H Ab column; as no factor H-cross-reactive parasite molecules were detected in the active extracts, the activity was indeed due to host factor H. The pattern of extraction of host factor H from the parasite tissue indicated that at least part of it was selectively bound to the cyst wall, and that a strong charge component was involved in the binding. Our results indicate that the selective concentration of host factor H from plasma/interstitial fluid may contribute to complement evasion by E. granulosus.

Animals↗