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Biomedical subjects

A Freitas

Publications and source records attributed to A Freitas.

53 records · Page 3Linked to original sources
PubMed1991

[Spectrum analysis of the variability of heart rate in athletes].

OBJECTIVES: Characterize power spectrum pattern of the heart rate variability and assessment of the relative contributions of sympathetic and parasympathetic cardiac nervous system control in athletes. STUDY DESIGN: Prospective study of athletes and sedentary healthy control group sex and age matched. SUBJECT AND METHODS: 8 athletes, 3 female and 5 male, swimming (4), canoeing (2) and cycling (2), aged 17.4 +/- 3.6 years, and 8 sedentary healthy controls. ECG signals were recorded after a period of 15 minutes in supine rest with controlled breathing at 15 cycles/min. Signal acquisition was done at 300 samples/sec. From 512 consecutive heart beats, we calculated the average, the standard deviation, the maximum and the minimum values and the rate between the longest and the shortest R-R interval (E/I). We also calculated, after computing the fast Fourier transform, the total spectrum power, the low frequency component (LF, from 0.01 to 0.15 Hz) and the high frequency component (HF, greater than 0.15 Hz) and its ratio (LF/HF). RESULTS: The average R-R interval was 921 +/- 154.2 msecs and 673.2 +/- 98 msecs, the standard deviation was 72.5 and 29.4 msecs and the ratio E/I 1.63 +/- 0.14 and 1.28 +/- 0.08, respectively for athletes and control group. Differences between groups were significant (p less than 0.01) for all parameters, with higher variability in the athletes. Both spectral bands (LF and HF) and higher power in athletes (LF = 0.54 +/- 0.23 and HF = 0.76 +/- 0.14) than in the control group (LF = 0.14 +/- 0.10 and HF = 0.18 +/- 0.15) (p less than 0.001). There were no significant differences for LF/HF ratio, or normalized LF (LF%) or normalized HF (HF%) between groups. CONCLUSIONS: The present results indicates higher power of both spectral bands (LF and HF) and higher amplitude of the respective peaks in athletes when compared with healthy sedentary, with a clear predominance of the HF band in the total spectral power density, which suggest that the higher heart rate variability observed in athletes reveals the predominance of parasympathetic activity, without reduction of the sympathetic tone.

Adolescent↗
PubMed1991

[Assessment of the first myocardial infarctions with lead ECG --implications in the study of hospital mortality and its reduction using thrombolytic drugs].

STUDY OBJECTIVE: Correlation between mortality reduction of first Myocardial Infarction (MI) by thrombolytic therapy and MI size evaluated with the classical Electrocardiogram (ECG). DESIGN: A retrospective sequential study. SETTING: Coronary Unit patients. PATIENTS: Sequential sample of 132 patients with first MI obeying all the following criteria: 1) no previous MI; 2) age less than or equal to 70 years; 3) clinical evolution less than 12 hours; 4) no Left Bundle Branch Block in the CCU first ECG; 5) ischemic ST elevation in greater than or equal to 1 initial ECG leads. Patients were divided into Group A, with less than or equal to 3 initial ECG leads with ischemic ST elevation (n = 80), and Group B, with greater than or equal to 4 initial ECG leads with ischemic ST elevation (n = 52). Only 34 patients (25.7%) did thrombolytic therapy with IV Streptokinase (SK); 15 from Group A and 19 from Group B. MEASUREMENTS AND MAIN RESULTS: 17 patients died in MI acute phase (12.8%); 4 in Group A (5%) and 13 in Group B (24.9%). Inhospital mortality was statistically worst in Group B than in Group A (24.9% vs 5% with p less than 0.01). Creatin kinase (CK) maximal values (A = 911.5 UI; B = 1444.6 UI with p less than 0.01) and initial Heart Rate (A = 75.7; B = 86.7 with p less than 0.001) were also statistically greatest in Group B. Inhospital mortality was smaller in patients treated with SK (8.8% vs 14.3%), as in Group B (10.5% vs. 33.3%), both without statistical significance. CONCLUSIONS: Inhospital mortality and thrombolytic therapy benefit were so bigger as MI size evaluated by the number of initial ECG leads with ischemic ST elevation, by initial HR and maximal values of CK. Classical ECG can be useful by identifying patients with first MI that can more benefit with thrombolytic therapy (greater than or equal to 4 leads with ischemic ST elevation).

Aged↗
PubMed1990

Divergency in the specificity of the induction and maintenance of neonatal suppression.

Neonatal treatment of BALB/c mice with anti-VHT15 antibodies suppresses serum expression of VHT15 immunoglobulins in adult animals (2 months) which remains for over 8 months in half of the cases. Suppressed mice, however, contain control numbers of B cells expressing genes of the S107VH family and producing VHT15 after mitogenic stimulation. Furthermore, immunization with phosphorylcholine (PC) breaks suppression and stimulates the production of VHT15 anti-PC antibodies. These animals, however, contain no detectable B lymphocytes expressing the T15 idiotype and produce no T15 idiotype-positive antibodies in response to PC. These results are discussed in the context of lymphocyte repertoire selection.

Animals↗
PubMed1990

[The importance of heart disease in the various types of cerebral vascular disease. A prospective study].

UNLABELLED: A prospective study was performed in 106 patients with acute stroke. The main purpose was the cardiac evaluation in the different types of cerebrovascular disease: Intracerebral hemorrhage (H), Cortical ischaemic events (C) and Subcortical ischaemic events (SC) and also to evaluate the interest of echocardiography in detecting occult cardiac sources of emboli. The study population included 54 men and 52 women with a mean age of 66.8 +/- 10.3 years. A thorough neurologic and cardiologic study with a computed tomography of the brain (TAC) and an echocardiogram (ECO) were performed in all patients. It was found 24 (23%) of H, 40 (38%) of C and 32 (30%) of SC. In the past history, heart diseases were more prevalent in C (p less than 0.04); previous stroke and systemic hypertension (HTA) were less prevalent in H (p less than 0.008) and in C (p less than 0.004), respectively. Atrial fibrillation (FA) was more frequent in ischaemic stroke (p less than 0.02) and within these in C (p less than 0.005). No more clinical and functional cardiac features or echocardiographic aspects had any difference in their prevalence in different types of stroke. Without clinical heart disease there were 19 (18%) cases but only in 10 were found in their echocardiograms a potentially embolic heart disease (PEHD) but 8 of them had questionable pathologic significance. IN CONCLUSION: C had more heart disease in their past history; FA is more frequent in C; it is difficult to diagnose a cerebral embolism with only a coexistent C and CPE, but if there is FA or a past history of heart disease in a C, the diagnosis of cerebral embolism is more probable; finally, echocardiography is of limited value to diagnose a PEHD in the elderly, however it makes possible to better evaluate most cardiac situations.

Acute Disease↗
PubMed1989

Interleukin 2 receptor expression and interleukin 2 production in exponentially growing T cells: major differences between in vivo and in vitro proliferating T lymphocytes.

In the present study we have assessed the growth requirements for in vivo proliferating mature T cells. For that purpose we have selected experimental approaches which allow the study of exponential growth in vivo of a major fraction of T cells, and make it possible to obtain large numbers of T cells in cycle. Two types of growing T cell populations were used: peripheral T lymphocytes, proliferating exponentially after transfer into syngeneic athymic nude mice, and activated T cells in lymph nodes of normal mice draining the site of oxazolone administration. The results obtained show that mature T cell growth in vivo is not accompanied by expression of high-affinity interleukin 2 (IL2) receptor in the majority of activated cells, is not abrogated by in vivo administration of anti-IL2 receptor antibodies or enhanced by the in vivo injection of recombinant IL2, and that in vivo growing T cells do not produce detectable amounts of IL2, as evaluated functionally by limiting dilution assays or the presence of IL2 mRNA, detected by Northern blots or in situ hybridization. The presented data thus indicate that the rules known to apply to T cell activation and proliferation in vitro differ from those used by in vivo growing T lymphocytes, at least in the two systems studied.

Animals↗
PubMed1988

Comparative study of VH gene family usage by newborn xid and non-xid mice, newborn NZB and adult NZB mice, and by splenic and peritoneal cavity B cell compartments.

RNA from 170 different Ig-secreting hybridomas was hybridized with VH gene probes 7183, QUPC52, S107, J558, J606, 36-60, V31, X-24 and V-GAM 3.8, with the aim of comparing xid to non-xid mice, neonatal NZB to adult NZB, and the peritoneal cavity with the splenic compartments for VH gene family expression. Our results indicate that (a) defective F1 male xid mice express with high frequency 36-60 and J606 5' proximal VH families, when compared to non-xid F1 females of the same matings. (b) Neonatal NZB mice express 3' proximal 7183 and QUPC52 families with high frequency, when compared to adult mice and to the expected values derived from VH complexity. (c) Natural antibodies against cytoskeleton proteins, DNA, rabbit IgG and 2,4,6-trinitrophenyl did not appear to prefer a particular VH family. The only difference found is related to age; neonatal clones preferentially employ 7183 and QUPC52 while J558 predominates among adult clones. (d) All the 15 antibodies directed against bromelin-treated mouse red blood cells failed to hybridize with any of the nine VH probes employed. These results confirm previous findings indicating the highly homogeneous pattern of these latter antibodies, and suggest that they are encoded by a new VH family (VH11).

Animals↗
PubMed1987

The majority of "natural" immunoglobulin-secreting cells are short-lived and the progeny of cycling lymphocytes.

Treatment of mice with hydroxyurea to selectively kill all cycling cells has been used to study population dynamics and life expectancy of "natural" immunoglobulin-secreting cells in the bone marrow and spleen of nonimmunized animals. The results show that 50 to 90% of those cells are eliminated 2 to 3 days after one cycle of hydroxyurea administration, demonstrating their recent origin from cycling precursors. Using a protocol of long-term hydroxyurea treatment which abrogates cell production from the cycling precursors compartments, it was shown that "natural" immunoglobulin-secreting cells have a very short half renewal time, in the range of 15-60 h.

Aging↗
PubMed1986

Immunocompetent autoreactive B lymphocytes are activated cycling cells in normal mice.

Frequencies of B cell clonal precursors producing antibodies that react with mouse thyroglobulin, mouse erythrocytes, beef hemoglobin, KLH, and sheep erythrocytes were determined by limiting dilution analyses among small, resting lymphocytes, and among large activated cells from normal adult mice. While frequencies of clones reacting with external antigens were equally distributed in large and small B cells, most, if not all, autoreactive B lymphocytes were found in the large cell fraction. Analysis of antithyroglobulin hybridomas isolated from normal mice revealed dissociation constants ranging from 10(-6) to 5-6 X 10(-7). Treatment of normal donors with antimitotic drugs dramatically decreases the frequencies of autoreactive B cells, but not those of B lymphocytes reacting with external antigenic molecules. Taken together, these experiments show that immunocompetent, autoreactive B lymphocytes are activated and cycling cells in the peripheral lymphoid tissues of normal individuals.

Animals↗
PubMed1979

Characterization of rat spleen-cell populations. I. Cell interactions in the regulation of in vitro response to concanavalin A.

Spleen cells from BN rats were separated in a discontinuous density gradient. Cells from different fractions were shown to be functionally diverse, light cells enhancing DNA synthesis and cell division of the dense cell fractions, while dense cells suppressed DNA synthesis and cell division of light cells. Both these effects were also present in the absence of cell stimulation, were proportional to the number of modulating cells added to the cultures, and totally independent of the magnitude of response of controls. In Con A-stimulated cultures, mitogen dose also influenced the intensity of help and suppression. Both these effects are blocked by cell treatment with cycloheximide and can be mediated by cell supernatants. A T cell seems to be responsible for both helper and suppressor effects.

Animals↗
PubMedDate not supplied

Expression of VH11-gene family in hybridoma collections from peritoneum and spleen: differential correlation with BrMRBC reactivity.

Hybridoma collections from spleen or peritoneal cells of newborn or adult individuals were screened by RNA hybridization for expression of the VH11-gene family using a V-region probe VCP12, which encodes anti-BrMRBC antibodies. No VH11 expression was observed in hybridomas derived from newborn spleen cells in either BALB/c, NZB or (CBA/N x BALB/c) F1 mice (0/93). Adult NZB and BALB/c spleen cell collections contained only one hybridoma expressing VH11 (1/242). Interestingly, however, the VH11-positive hybridoma showed no anti-BrMRBC reactivity, while one anti-BrMRBC clone in the same collection expressed a Q52 VH gene. In contrast, hybridomas derived from peritoneal cells showed an absolute correlation between expression of VH11 genes and anti-BrMRBC reactivity (15/32). The high expression in the peritoneal cavity of such cells is likely the result of local positive selection.

Animals↗
PubMedDate not supplied

[The patient with acute cerebrovascular disorders: assessment of associated diseases].

We performed a prospective study in 106 patients with acute stroke. The main purpose was to evaluate the associated diseases and to determine their prevalence and incidence in two different types of cerebrovascular disease: the intracerebral hemorrhage (HI) and ischaemic events (AI). The studied population included 54 men and 52 women with a mean age of 66.8 +/- 10.3 years. A clinical examination was performed in all patients by different specialists and all were submitted to diverse complementary tests, including a computed tomography scan of the brain (TAC) and an echocardiogram (ECO). We found 24 (23%) HI and 82 (77%) AI. In the past history, previous stroke were more prevalent in AI (p less than 0.01). Heart disease was present in 87 (82%) patients but, among them, only atrial fibrillation which was found in 19 (18%) patients, was significantly more frequent in AI (p less than 0.02). Hypertension (HTA) existed in 79 (75%) patients, respiratory complications and periferic vascular disease in 9 (8%), diabetes in 44 (42%) and dyslipidemia in 31 (29%) patients. No significant difference was found between the two groups of stroke regarding these diseases; however, there was a tendency for HTA and diabetes to be more prevalent in HI and for periferic vascular disease in AI. In the blood tests, high haematocrit was found in 35 (33%) patients, anemia in 21 (20%), hypercholesterolemia in 17 (16%), hypertrigliceridemia in 18 (17%) and uremia or creatinemia or ionic alteration in 32 (30%) patients, without any difference in their prevalence and incidence in the two groups of stroke. In conclusion, in this prospective study of patients with an acute stroke, there was 23% of HI and 77% of AI, a high prevalence of previous stroke, heart disease and HTA, but only the previous stroke and, within heart disease, the atrial fibrillation were significantly more frequent in the AI group. Also, periferic vascular disease had a tendency to be more frequent in AI, as well as diabetes and HTA had in HI.

Acute Disease↗
PubMedDate not supplied

Effects of hydroxyurea in vivo treatment on the antibody response in mice.

In the present work, we investigate the effects of hydroxyurea (HU) treatment given before antigen priming on the antibody response in the mouse. We have studied the response to both thymus-independent and thymus-dependent antigens. With both types of antigens, we have found a two- to ten-fold increase in the number of antigen-specific IgM PFC in the spleens of HU-treated primed mice. In the case of the T-dependent antigens, a simultaneous decrease in the IgG PFC response was also observed in HU-treated mice. These results suggest that major changes in the dynamic equilibrium of the cells of the immune system, induced by HU treatment, may result in different homeostatic regulation, as revealed by the modified pattern of response to exogenous antigens.

Animals↗