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Biomedical subjects

O Santana

Publications and source records attributed to O Santana.

8 recordsLinked to original sources
PubMed2001

Heart rate modulates the slow enhancement of contraction due to sudden left ventricular dilation.

In isovolumic blood-perfused dog hearts, left ventricular developed pressure (DP) was recorded while a sudden ventricular dilation was promoted at three heart rate (HR) levels: low (L: 52 +/- 1.7 beats/min), intermediate (M: 82 +/- 2.2 beats/min), and high (H: 117 +/- 3.5 beats/min). DP increased instantaneously with chamber expansion (Delta(1)DP), and another continuous increase occurred for several minutes (Delta(2)DP). HR elevation did not alter Delta(1)DP (32.8 +/- 1.6, 33.6 +/- 1.5, and 34.3 +/- 1.2 mmHg for L, M, and H, respectively), even though it intensified Delta(2)DP (17.3 +/- 0.9, 20.7 +/- 1.0, and 26.8 +/- 1.2 mmHg for L, M, and H, respectively), meaning that the treppe phenomenon enhances the length dependence of the contraction component related to changes in intracellular Ca(2+) concentration. Frequency increments reduced the half time of the slow response (82 +/- 3.6, 67 +/- 2.6, and 53 +/- 2.0 s for L, M, and H, respectively), while the number of beats included in half time increased (72 +/- 2.9, 95 +/- 2.9, and 111 +/- 3.2 beats for L, M, and H, respectively). HR modulation of the slow response suggests that L-type Ca(2+) channel currents and/or the Na(+)/Ca(2+) exchanger plays a relevant role in the stretch-triggered Ca(2+) gain when HR increases in the canine heart.

Animals↗
PubMed1996

The role of the nodI and nodJ genes in the transport of Nod metabolites in Rhizobium etli.

A kinetic analysis of secretion of lipo-chitin oligosaccharides (LCO) produced by Rhizobium etli (Re) wild-type (wt) strain and derivatives carrying disrupted nodI or nodJ genes was performed. LCO were detected in the growth media of the wt strain as early as 1 h after nod gene induction. In contrast, strains carrying nodI or nodJ mutations secreted less LCO, and accumulated LCO metabolites intracellularly after 4 h of induction. These Re mutants presented a delayed nodulation phenotype and a reduction in the maximum number of nodules formed in Phaseolus vulgaris roots.

ATP-Binding Cassette Transporters↗
PubMed1993

The NodL and NodJ proteins from Rhizobium and Bradyrhizobium strains are similar to capsular polysaccharide secretion proteins from gram-negative bacteria.

The NodL and NodJ nodulation proteins have been described in different Rhizobium and Bradyrhizobium species. The nodLJ genes belong to the nod regulon. Other genes from this regulon are involved in the biosynthesis and modification of lipo-oligosaccharide molecule(s) which are morphogenic signals when acting on legume roots. It has been proposed that the NodL and NodJ proteins belong to a bacterial inner membrane transport system of small molecules. Nucleotide sequencing of Mudll PR13 insertions in the nodulation region of the symbiotic plasmid from a Rhizobium leguminosarum bv. phaseoli strain CE3 has revealed the presence of nodL and nodJ-related sequences downstream of nodC. Computer nucleotide sequence analysis of the entire NodL and NodJ sequences from R. leguminosarum bv. viciae and Bradyrhizobium japonicum strains show that both proteins are similar to the KpsT and KpsM proteins from Escherichia coli K1 and K5 strains, to the BexB and BexA proteins from Haemophilis influenzae and to the CtrD and CtrC proteins from Neisseria meningitidis, respectively. Except for the NodL and NodJ proteins, all of them have been involved in the mechanism of secretion of polysaccharides in each of their harbouring species. On the basis of the similarity found, we propose that the NodL and the NodJ proteins could be involved in the export of a lipo-oligosaccharide.

ATP-Binding Cassette Transporters↗
PubMed1992

Doppler echocardiography.

In the past year, Doppler echocardiography has continued to transform the "echo laboratory" into a "cardiac imaging and hemodynamics laboratory." Evaluation of blood flow through the cardiac chambers and great vessels is moving from semiquantitative to quantitative. The potential for measuring mitral regurgitant flow more precisely has been demonstrated by evaluating the zone of flow acceleration that occurs on the left ventricular side of the mitral valve. Direct imaging of pulmonary venous return to the left atrium using transesophageal Doppler echocardiography has also allowed more precise quantification of mitral regurgitation. Left ventricular systolic function may be better quantified in patients with mitral regurgitation by calculating the ratio of the change in pressure to the change in time from the continuous wave spectrum of regurgitant flow. The practical application of transmitral flow.in evaluating diastolic function has been applied to cardiac amyloidosis.

Blood Flow Velocity↗
PubMed1984

Megaesophagus and seroreactivity to Trypanosoma cruzi in a rural community in northeast Brazil.

The relationship of symptoms and radiographic abnormalities suggestive of esophageal motility disorders with electrocardiographic (ECG) alterations and seroreactivity to Trypanosoma cruzi was studied in a defined population in a rural area endemic for Chagas' disease in Bahia, Brazil. Between January and June 1981, 680 individuals 5 years of age or older were examined with serologic tests, ECGs and questionnaires for esophageal motility disorder. Of these, 39.9% were seropositive for Chagas' disease. Symptoms of dysphagia occurred 2.5 times more frequently among seropositive individuals than among seronegative individuals. Radiographic esophageal abnormalities were 3.6 times more frequent among seropositive individuals than among seronegative individuals in the symptomatic group. Symptoms and radiographic abnormalities were more common in men than in women although this was not statistically significant. Among seropositive individuals the percentage with symptoms of dysphagia increased with age, with a peak prevalence rate of 23.9% in the 45- to 64-year-old age group. Also, in the seropositive group, 41.7% with X-ray abnormalities of the esophagus and 26.3% with symptoms of dysphagia presented an abnormal ECG.

Adolescent↗
PubMed1979

Computer programs to implement retinal models.

To implement retinal models of some complexity a set of computer programs, coordinated by a main program is required. A set of said programs is presented here which permits the design and the experimentation with linear and non-linear retinal layered models. A main program, called RETINA, is the basis for the building of a model, the generation of the input stimuli and the experimentation with the overall system.

Computers↗