Biomedical subjects

J S Pereira

Publications and source records attributed to J S Pereira.

At least 19 recordsLinked to original sources

PubMed2006

Metabolic responses to water deficit in two Eucalyptus globulus clones with contrasting drought sensitivity.

We compared the metabolic responses of leaves and roots of two Eucalyptus globulus Labill. clones differing in drought sensitivity to a slowly imposed water deficit. Responses measured included changes in concentrations of soluble and insoluble sugars, proline, total protein and several antioxidant enzymes. In addition to the general decrease in growth caused by water deficit, we observed a decrease in osmotic potential when drought stress became severe. In both clones, the decrease was greater in roots than in leaves, consistent with the observed increases in concentrations of soluble sugars and proline in these organs. In roots of both clones, glutathione reductase activity increased significantly in response to water deficit, suggesting that this enzyme plays a protective role in roots during drought stress by catalyzing the catabolism of reactive oxygen species. Clone CN5 has stress avoidance mechanisms that account for its lower sensitivity to drought compared with Clone ST51.

Adaptation, Physiological↗

PubMed2004

Prognostic value of P53 codon 72 polymorphism in invasive cervical cancer in Brazil.

OBJECTIVE: The prognostic value of p53 codon72 polymorphism was analyzed in Brazilian women with cervical cancer. METHODS: The present study consists of 148 women diagnosed and treated for invasive cervical carcinoma (FIGO stages Ib-IIIb) between 1992 and 2002. Demonstration of p53 polymorphism was performed in DNA extracted from paraffin-embedded sections using the polymerase chain reaction (PCR). RESULTS: Among the 148 women, arg/arg was found in 99 (67%) and, arg/pro in 49 (33%). The overall survival (OS) curves (univariate) were different between arg/arg and arg/pro patients (P = 0.01). There was slightly increased risk of death for arg/arg patients (crude HR 2.2 CI 95% 1.2-4.0), which was not confounded by FIGO stages (adjusted HR 2.4 CI 95% 1.3-4.3). For disease-free survival (DFS), two situations were considered: (1) 124 women who received any treatment, and (2) 118 who received FIGO-recommended treatment. In the first group, 59% of arg/arg patients presented recurrence as compared to 32% in the arg/pro group (P = 0.02), whereas in the second group, 61% of the arg/arg and 34% arg/pro showed recurrence (P = 0.04). The risk of recurrence adjusted by FIGO stage for the 124 patients was 2.4 (CI 95% 1.0-3.7) and for the 118 it was 1.9 (CI 95% 1.0-3.4). These adjusted models showed no confounding and no interaction. CONCLUSIONS: Despite the prognostic significance of p53 polymorphism in univariate survival analysis, there was no or only marginal evidence on the independent prognostic value of p53arg/arg in multivariate analysis. The more ominous prognosis of the homozygous (arg/arg) patients was explained by the primary treatment, independent on the FIGO stage.

Arginine↗

PubMed2004

Effects of partial defoliation on carbon and nitrogen partitioning and photosynthetic carbon uptake by two-year-old cork oak (Quercus suber) saplings.

At the end of the growing season in late July, 20-month-old cork oak (Quercus suber L.) saplings were partially defoliated (63% of leaf area) to evaluate their ability to recover leaf area after defoliation. At 18 and 127 days after defoliation, changes in starch and nitrogen pools were determined in leaves and perennial organs, and variations in photosynthetic carbon uptake were investigated. To determine the role of stored nitrogen in regrowth after defoliation, plant nitrogen was labeled in the previous winter by enriching the nutrient solution with 15N. Plants recovered the lost leaf area in 127 days. Although there was remobilization of starch and nitrogen from leaves and perennial organs, the availability of resources for growth in the following spring was not decreased by defoliation. On the contrary, starch concentration in coarse roots was higher in defoliated saplings than in control saplings, presumably as a result of the higher net CO2 exchange rate in newly developed leaves compared with pre-existing leaves.

Carbohydrate Metabolism↗

PubMed2004

Responses to water stress in two Eucalyptus globulus clones differing in drought tolerance.

We evaluated drought resistance mechanisms in a drought-tolerant clone (CN5) and a drought-sensitive clone (ST51) of Eucalyptus globulus Labill. based on the responses to drought of some physiological, biophysical and morphological characteristics of container-grown plants, with particular emphasis on root growth and hydraulic properties. Water loss in excess of that supplied to the containers led to a general decrease in growth and significant reductions in leaf area ratio, specific leaf area and leaf-to-root area ratio. Root hydraulic conductance and leaf-specific hydraulic conductance decreased as water stress became more severe. During the experiment, the drought-resistant CN5 clone maintained higher leaf water status (higher predawn and midday leaf water potentials), sustained a higher growth rate (new leaf area expansion and root growth) and displayed greater carbon allocation to the root system and lower leaf-to-root area ratio than the drought-sensitive ST51 clone. Clone CN5 possessed higher stomatal conductances at moderate stress as well as higher hydraulic conductances than Clone ST51. Differences in the response to drought in root biomass, coupled with changes in hydraulic properties, accounted for the clonal differences in drought tolerance, allowing Clone CN5 to balance transpiration and water absorption during drought treatment and thereby prolong the period of active carbon assimilation.

Dehydration↗

PubMed2002

How plants cope with water stress in the field. Photosynthesis and growth.

Plants are often subjected to periods of soil and atmospheric water deficit during their life cycle. The frequency of such phenomena is likely to increase in the future even outside today's arid/semi-arid regions. Plant responses to water scarcity are complex, involving deleterious and/or adaptive changes, and under field conditions these responses can be synergistically or antagonistically modified by the superimposition of other stresses. This complexity is illustrated using examples of woody and herbaceous species mostly from Mediterranean-type ecosystems, with strategies ranging from drought-avoidance, as in winter/spring annuals or in deep-rooted perennials, to the stress resistance of sclerophylls. Differences among species that can be traced to different capacities for water acquisition, rather than to differences in metabolism at a given water status, are described. Changes in the root : shoot ratio or the temporary accumulation of reserves in the stem are accompanied by alterations in nitrogen and carbon metabolism, the fine regulation of which is still largely unknown. At the leaf level, the dissipation of excitation energy through processes other than photosynthetic C-metabolism is an important defence mechanism under conditions of water stress and is accompanied by down-regulation of photochemistry and, in the longer term, of carbon metabolism.

Acclimatization↗

PubMed2001

Cervical coinfection with human papillomavirus (HPV) types as a predictor of acquisition and persistence of HPV infection.

Interest in coinfection with multiple types of human papillomavirus (HPV) has increased in response to the possibility of vaccination and the discovery that the host immune response appears to be mainly type specific. This study attempts to document the occurrence of coinfection with multiple HPV types and to determine whether these coinfections predicted acquisition or persistence of other HPV types in a prospective cohort of women in Brazil. Multiple HPV types were detected at the same visit in one-fifth of all women who tested positive for HPV at any time. Acquisition of an HPV infection was more likely among women with any HPV type detected on study entry. Persistence of HPV infection, the true precursor of cervical abnormalities, was independent of coinfection with other HPV types. Given the increasing prominence of HPV vaccination as a potential preventive approach, it is imperative that additional insights on cross-type protection be obtained from longer-term longitudinal investigations.

Adolescent↗

PubMed2000

Kinetic differences in cardiac myosins with identical loop 1 sequences.

The kinetics of nucleotide turnover vary considerably among isoforms of vertebrate type II myosin, possibly due to differences in the rate of ADP release from the nucleotide binding pocket. Current ideas about likely mechanisms by which ADP release is regulated have focused on the hyperflexible surface loops of myosin, i.e. loop 1 (ATPase loop) and loop 2 (actin binding loop). In the present study, we investigated the kinetic properties of rat and pig beta-myosin heavy chains (beta-MHC) in which we have found the sequences of loop 1 (residues 204-216) to be virtually identical, i.e. DQSKKDSQTPKG, with a single conservative substitution (rat E210D pig). Pig myocardium normally expresses 100% beta-MHC, whereas rat myocardium was induced to express 100% beta-MHC by surgical thyroidectomy and subsequent treatment with propylthiouracil. Slack test measurements at 15 degrees C yielded unloaded shortening velocities of 1.1 +/- 0.8 muscle lengths/s in rat skinned ventricular myocytes and 0.35 +/- 0.05 muscle lengths/s in pig skinned myocytes. Similarly, solution measurements at the same temperature showed that actin-activated ATPase activity was 2.9-fold greater for rat beta-myosin than for pig beta-myosin. Stopped-flow methods were then used to assess the rates of acto-myosin dissociation by MgATP both in the presence and absence of MgADP. Although the rates of MgATP-induced dissociation of acto-heavy meromyosin (acto-HMM) were virtually identical for the two myosins, the rate of ADP dissociation was approximately 3.8-fold faster for rat beta-myosin (135 s(-)(1)) than for pig beta-myosin (35 s(-)(1)). ATP cleavage rates were nearly 30% faster for rat beta-myosin. Thus, whereas loop 1 appears from other studies to be involved in nucleotide turnover in the pocket, our results show that loop 1 does not account for large differences in turnover kinetics in these two myosin isoforms. Instead, the differences appear to be due to sequence differences in other parts of the MHC backbone.

Amino Acid Sequence↗

PubMed1999

Plant diversity and productivity experiments in european grasslands

At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.

Journal Article↗

PubMed1997

[Tremor: adaptation of a clinical scale].

The Fahn, Tolosa e Marín's clinical rating scale for tremor was adapted to our country for evaluation of tremor. This scale was applied to 123 patients with this movement disorder, selected from the Ambulatory of General Medicine at Hospital Universitário Pedro Ernesto da Universidade do Estado do Rio de Janeiro. These patients had been chosen no matter the etiology of their condition or their age. Although some variants may had influenced the scores of this particular scale, they did not seem to change its standardization and applicability.

Adolescent↗

PubMed1997

Primary progressive freezing gait. Case report.

The clinical features of the primary progressive freezing gait, a rare and distinct neurological entity, have been described in some articles. This paper describes this gait disorder affecting one patient, whose condition's long course provoked no postural instability. As stated in the literature, the pathophysiology of the primary progressive freezing gait still remains unclear, although the lack of response to levodopa therapy suggests a possible involvement of nondopaminergic pathways. Alteration in the visual perception may be a potential cause for the condition.

Aged↗

PubMed1995

Role of nitrogen remobilization from old leaves for new leaf growth of Eucalyptus globulus seedlings.

Six-month-old Eucalyptus globulus Labill. seedlings were grown in sand culture irrigated with a nutrient solution containing 6.0 mol N m(-3) for 3 months (November-January). Before rapid growth began in February, seedlings were repotted and irrigated with either 6.0 mol N m(-3) (High-N treatment) or 1.0 mol N m(-3) (Low-N treatment). Seedlings were analyzed during the subsequent flush of growth to determine the role of old leaves, and in particular the leaf protein Rubsico, as a source of N for new leaf growth. During spring growth, the N content of old leaves of High-N seedlings decreased with decreasing leaf dry weight, although there was no change in leaf number. In High-N seedlings, the net loss of N from old leaves provided less than 10% of the N used for new leaf growth, and the new leaves quickly became the dominant sink for N. In contrast, in Low-N seedlings, the net loss of N from old leaves provided 44% of the N used for new leaf growth. During the period of spring growth, the amount of soluble proteins recovered from old leaves of Low-N seedlings dropped, but there was no change in the content of either Rubisco or chlorophyll. The photosynthetic capacity of old leaves remained constant throughout the study period, and there was no evidence that N was remobilized from Rubisco.

Journal Article↗

PubMed1995

[Cognitive disorders in Parkinson disease. Electroencephalographic correlations].

Sixty-two patients with idiopathic Parkinson disease and 30 patients of a control group were clinically evaluated in the light of cognitive and/or psychic impairments according to DSM III-R, mini-mental state examination and Hamilton rating scale for depression. These patients were also submitted to electroencephalogram registration (EEG) with photic stimulation. From the parkinsonian group, 45.2% did not have mental manifestations as classified in the DSM III-R. Other 24.2% had depression, 14.5% had anxiety, 12.9% had dysthymic disorder and 3.2% had dementia. Considering the EEG, 58.1% of the parkinsonian patients had theta waves bilaterally, with predominance in frontal temporal or temporal areas, though more frequent on the left hemisphere than on the right one. Only 16.7% of the patients from the control group had these same findings in the EEG but neither of the two groups had their EEG modified by photic stimulation. The EEG findings were statistically significant when both groups were compared. However, these findings were not significant comparing parkinsonian patients with psychic impairment with the ones who did not have such impairments.

Adult↗

PubMed1995

[Pregnancy in women with neural tube fusion defects. Report of 3 cases with different clinical course].

The advances in surgical technique for closure of myelomeningocele and its complications, mainly neurogenic bladder, have resulted not only in a increased lifespan and a better quality of life for these patients, but also a progressively higher number of women are reaching childbearing age and becoming pregnant. The reports of pregnancy in these women are still sporadic. In spite of that, obstetricians must be aware of this situation in order to manage it accordingly. In the course of these pregnancies major complications seldom occur. However there are problems (high-risk of neural tube defects in the offsprings, urinary tract complications, muscular-skeletal disorders and psychosociological problems) that should not be ignored and that may influence the prognosis of these pregnancies. The authors present three case reports with different outcomes.

Adult↗

PubMed1994

[Writing tremor: report of a case].

Primary writing tremor is induced by a specific motor activity, generally the handwriting. The case is analyzed under clinic and therapeutic points of view. The patient had a tremor elicited by handwriting without any other concurrent neurologic alteration. He neither presented familiar antecedents nor metabolic, endocrine, iatrogenic, toxic and traumatic ones. As to the therapeutic approach, the tremor did not respond satisfactorily neither to propranolol nor to primidone. But with anticholinergics improvement of the tremor was verified.

Aged↗

PubMed1993

[Essential tremor. Clinical observations].

The authors have studied 53 patients with essential tremor, focusing its clinical and epidemiological aspects. There were familial history in 37.70% of all cases, prevailing in females (56.60%) and white people (69.80%); nevertheless this difference can not be assured from the statistical point of view due to lack of population data. We agreed that the main incidence of this syndrome occurred beyond the 5th decade, specially during the 6th and 7th decades. Topographically, we could observe that the hand tremor predominanted, with an incidence of 96.20% of the total number of cases, followed by head tremor (28.30%), voice tremor (16.99%), leg tremor (11.30%), tongue tremor (3.78%) and trunk tremor (1.88%). These focal tremors were seldom observed alone and we noted frequent association with hand tremor.

Adult↗

PubMed1992

Photosynthetic capacity of leaves of Eucalyptus globulus (Labill.) growing in the field with different nutrient and water supplies.

The effects of water and nutrient availability on photosynthetic capacity of juvenile and adult leaves of Eucalyptus globulus Labill. seedlings were evaluated by measuring oxygen evolution at light and CO(2) saturation. Seedlings supplied with near optimal amounts of water and nutrients had higher growth rates than non-irrigated, unfertilized control seedlings, but photosynthetic capacity was similar in both treatments. Differences in foliar nitrogen concentrations between the two treatments were minor, which largely explains why the growth response to near optimal nutrition was not associated with an increase in photosynthetic capacity per unit leaf area. Nevertheless, the photosynthetic capacity of juvenile leaves decreased from distal to proximal positions in the mid-crown and was positively correlated with leaf nitrogen concentration expressed on a leaf surface area basis. During the dry season, non-irrigated, unfertilized seedlings fixed carbon at lower rates than irrigated seedlings supplied with near optimal nutrition because of stomatal closure even though photosynthetic capacity was unaffected by water deficits. In both treatments, there were differences between the photosynthetic capacity of adult and juvenile leaves that were largely explained by the low specific leaf area of adult leaves.

Journal Article↗

PubMed1992

A study on the action of two calcium channel blockers (verapamil and flunarizine) upon an experimental model of tardive dyskinesia in rats.

Tardive dyskinesia (TD), a serious complications of neuroleptic chronic use, has no effective therapy yet. We performed an experiment to study the action on TD, of the calcium channel blockers (CCB) drugs, verapamil and flunarizine. We obtained the TD model in rats, administering haloperidol for a 21-day period. After this, the stereotyped movement induced by apomorphine was rated. The CCB drugs were administered in acute (in the 28th day) and chronic (for 8 days, after the 25th day) experiments. Acutely, verapamil increased the stereotyped behaviour, and promoted a reduction of it in the chronic experiment. The results suggest that CCB drugs should be tested in clinical trials of TD.

Animals↗

PubMed1991

Control of growth of juvenile leaves of Eucalyptus globulus: effects of leaf age.

Biophysical variables influencing the expansion of plant cells (yield threshold, cell wall extensibility and turgor) were measured in individual Eucalyptus globulus leaves from the time of emergence until cessation of growth. Leaf water relations variables and growth rates were determined as relative humidity was changed on an hourly basis. Yield threshold and cell wall extensibility were estimated from plots of leaf growth rate versus turgor. Cell wall extensibility was also measured by the Instron technique, and yield threshold was determined experimentally both by stress relaxation in a psychrometer chamber and by incubation in a range of polyethylene glycol solutions. Once emerging leaves reached approximately 5 cm(2) in size, increases in leaf area were rapid throughout the expansive phase and varied little between light and dark periods. Both leaf growth rate and turgor were sensitive to changes in humidity, and in the longer term, both yield threshold and cell wall extensibility changed as the leaf aged. Rapidly expanding leaves had a very low yield threshold and high cell wall extensibility, whereas mature leaves had low cell wall extensibility. Yield threshold increased with leaf age.

Journal Article↗