PubMed Health⌕ Search

Biomedical subjects

S Farias

Publications and source records attributed to S Farias.

8 recordsLinked to original sources
PubMed2000

Comparative analysis of two different subunits of antigen B from Echinococcus granulosus: gene sequences, expression in Escherichia coli and serological evaluation.

Two different Echinococcus granulosus antigen B subunits (AgB8/1 and AgB8/2) were characterized and the structure of the genes encoding these two proteins were compared. DNA sequences were expressed in Escherichia coli and the antigens' diagnostic value was then assessed. The genomic sequence of AgB8/1 has a 92 bp intron in the position corresponding to amino acid 16; the AgB8/2 genomic sequence presents a 68 bp intron in the position corresponding to amino acid 20. Both introns are located between the putative N-terminal hydrophobic sequence and the secreted peptide. A comparison between the AgB8/1 and AgB8/2 nucleotide sequences showed a 53.5% identity among exons and a 50% identity between introns. According to the molecular diversity analysis, the elapsed time since both genes shared a common ancestor would be around 4.2x10(7) years. When the native AgB and the two recombinant antigens (rAgB8/1 and rAgB8/2) were tested in an anti-IgG ELISA, the sensitivity of the native antigen B was 77.41% and its specificity was 81.9%, while rAgB8/1 showed 54.84% of sensitivity and 80.17% of specificity and rAg138/2 had an 83.87% sensitivity and a 98.28% specificity. Statistical analysis confirms that rAgB8/2 has a better performance than rAgB8/1 and native AgB in ELISA.

Amino Acid Sequence↗
PubMed1999

End-diastolic pressure-volume relationship in sepsis: relative contributions of compliance and equilibrium chamber volume differ.

BACKGROUND: Compliance is a complex parameter to measure both clinically and in the laboratory. Investigations in recent years have interpreted changes in the end-diastolic pressure-volume relationship (EDPVR) as changes in compliance. However, without considering the equilibrium chamber volume (LV volume when transmural pressure = 0), changes in the EDPVR may not reflect changes in left ventricular chamber compliance. In the present study, chamber compliance was differentiated from equilibrium chamber volume to determine their respective contributions to the EDPVR in a clinically relevant animal model of chronic sepsis. MATERIALS AND METHODS: Rats were made septic by intraperitoneal injection of a cecal slurry (200 mg/kg; 5 ml/kg of 5% dextrose in water). At 1, 3, and 7 days post-sepsis induction, hearts were perfused on an isolated heart apparatus. A latex balloon was placed in the left ventricle to record peak systolic and end-diastolic pressures at various volumes, and the starting volume in the balloon was recorded. Systolic performance was evaluated by calculating the developed pressure (systolic pressure minus end-diastolic pressure) and peak dP/dt at end-diastolic pressures of 5 and 10 mm Hg. RESULTS: Developed pressure and peak dP/dt were impaired 3 days after sepsis induction and continued to be so through Day 7 of sepsis. The diastolic data were fitted to an exponential equation, the results of which indicated a strong leftward shift in the EDPVR through 7 days of sepsis with a concomitant decrease in equilibrium chamber volume. The LV chamber compliance decreased at 1 day after sepsis induction, as indicated by significant changes in regression coefficients for the curves, transiently returned toward control by Day 3, but decreased again by 7 days of sepsis. CONCLUSIONS: Our data indicate that early in sepsis, compliance changes contribute to a left-shifting EDPVR, but at later times in the course of the disease, unstressed chamber volume becomes an important determinant of the left shift. The decrease in compliance (suggesting diastolic dysfunction) occurred prior to systolic impairment, which may have valuable prognostic implications for septic patients.

Animals↗
PubMed1998

Cardiac myofilament protein function is altered during sepsis.

Male Sprague-Dawley rats (350-500 g) were made septic by intraperitoneal injection of 200 mg/kg cecal material in 5% dextrose in water (D5W; 5 ml/kg). Control rats (n = 11) received D5W. Preparations were studied on days 1 (n = 7), 3 (n = 7), and 7 (n = 8) of sepsis. In isolated hearts, ventricular function was depressed on days 3 and 7 of sepsis. Densitometric analysis of myofilament proteins from septic rats separated by SDS-PAGE showed no differences in relative amounts of actin, troponin, tropomyosin and myosin light chains compared to control. Myofilament function, assessed by measuring ATPase activities, was altered during sepsis. CA(2+)-independent Mg-ATPase activity was elevated on days 1 and 3 of sepsis, returning toward control by day 7. Maximal ATPase activity was unchanged on day 1, but was increased on days 3 and 7 sepsis. Myofibrillar myosin K(EDTA)-, Ca(2+)-, and Mg(2+)-ATPase activities were not altered, nor were there any apparent changes in myosin heavy chain isoform populations. Our data are the first to demonstrate alterations in minimal and maximal ATPase activities and myofilament CA(2+)-sensitivity during chronic peritoneal sepsis. These alterations may contribute to observed changes in ventricular function.

Animals↗
PubMed1997

Sepsis alters myocardial and plasma concentrations of endothelin and nitric oxide in rats.

Cardiovascular derangements during sepsis may arise from a mismatch between endothelin (ET) and nitric oxide (NO). We hypothesized that progression of chronic peritoneal sepsis would affect cardiac performance and would modulate the concentrations of NO and ET in the heart and plasma. Male Sprague-Dawley rats (340-390 g) were catheterized and made septic with a cecal slurry (200 mg/kg: i.p.). Heart rate, mean arterial pressure, and plasma ET and nitrite/nitrate (NOX) were determined at 0, 4, 8, 12, 24, and 48 h after induction of sepsis. Septic rats were found to have tachycardia at 48 h following induction of sepsis. Mean arterial pressure and pulse pressure were not altered in septic and non-septic rats. In a separate series of experiments, the function of isolated hearts from septic and non-septic rats was assessed at preload pressures of 2, 5, and 10 mmHg. Sepsis produced a significant decrease in rates of pressure development and relaxation (+/-dP/dt) at 24 and 48 h as compared to the hearts of non-septic rats. In septic rats, plasma concentrations of ET were significantly increased at t = 4, 8, 12 h as compared to basal values, and at 12 h as compared to non-septic rats, and returned to basal levels at 24 and 48 h. In contrast, circulating NO levels did not become elevated until t = 8 h and remained elevated throughout the remaining times. In the left ventricle, the concentration of ET was found to be significantly increased both in septic and non-septic rats at 4 and 8 h as compared to t = 0 h. In the left ventricles of non-septic rats, ET levels returned to baseline values at 12 h, while in septic rats, the concentration of ET remained significantly elevated until 12 h. In septic rats, left ventricular NO levels were found to be significantly increased at t = 12 h. It appeared that induction of sepsis contributed to an imbalance in the plasma concentration of ET and NO 12 h after the induction of sepsis. However, a similar imbalance was not observed in the left ventricle. It is concluded from these observations that peritoneal sepsis in a chronic rat model produced a divergence of plasma NO and ET levels. This suggests a homeostatic imbalance between vasoactive mediators, i.e. ET and NO, could contribute to the cardiovascular derangements that occur during sepsis.

Animals↗
PubMed1993

Identification of a fifth neutralizable site on type O foot-and-mouth disease virus following characterization of single and quintuple monoclonal antibody escape mutants.

A monoclonal antibody (C3) produced against foot-and-mouth disease virus type O1Caseros was found to neutralize quadrivalent monoclonal antibody escape mutant (G67) of foot-and-mouth disease virus type O1Kaufbeuren. This mutant had been characterized at the sequence level as having distinct changes affecting four non-overlapping neutralizable sites. The C3 monoclonal antibody was used to prepare a quintuple escape mutant from the G67 and a single escape mutant from the parental O1Kaufbeuren viruses. Polyclonal post-vaccinated and infected cattle sera as well as polyclonal mouse and guinea-pig sera, which neutralized the quadrivalent mutant, no longer neutralized the quintuple mutant, indicating that a fifth site had been identified and that changing the fifth site eliminated all neutralization. The site was characterized using serological techniques and found to be conformationally dependent, trypsin-sensitive and independent of sites previously characterized by monoclonal antibodies. Amino acid sequencing comparing parental, single C3 and quintuple mutants showed that a single change from a glutamine to a histidine, at amino acid 149 in the structural protein VP1, (1D) characterized the C3 mutation. The fifth site probably represents a conformational epitope which is formed due to the interaction of the VP1 loop region with other surface amino acids.

Amino Acid Sequence↗