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R Contreras

Publications and source records attributed to R Contreras.

28 records · Page 2Linked to original sources

Promoter-dependent transcription of tRNAITyr genes using DNA fragments produced by restriction enzymes.

Two DNA fragments prepared from the transducing bacteriophage strains ø80psuIII+ and ø80hpsuIII+,- by digestion with restriction enzymes contain one tyrosine tRNA gene (suIII+) and two tyrosine tRNA genes (suIII+, su-) in tandem, respectively, a single promoter in both cases, and some additional DNA regions at the two ends of both. Using these fragments, we have studied characteristics of the promoter-dependent transcription of the tyrosine tRNA genes. The promoter-dependent transcripts were shown to correspond to the expected tRNA precursors. Exposure of the transcript from the single gene fragment to an S100 extract from Escherichia coli gave, via intermediates, 4S material which was active in enzymatically accepting tyrosine and contained some modified bases.

Adenosine Triphosphate

Aortic bacterial endarteritis.

Micotic aneurisms are very rare. They are produced as a consequence of a bacterial infection of the endartery. They are divided into "primary", or those of an unknown septic focus, and "secondary" to bacterial endocarditis, to intravascular in infection or to infection located in a neighboring region. Two cases of the National Institute of Cardiology of Mexico are presented, with "primary" micotic aneurysm, which is the least frequent. One of them was because of bacterial endarteritis located in the thoracic aorta, an extremely rate entity. Due to the frequent rupture of these aneurysm with a very high mortality, emphasis is placed on the convenience of rapid surgical treatment of patients diagnosed.

Adolescent

[Presence of antibodies against Toxoplasma gondii in adolescents from the African continent].

It was determined the presence of antibodies anti-T. gondii in young, 13-16 year old, belonging to Republic Arab Saharaui; Popular Republic of Angola; Ethiopia and Republic of Ghana. From a total of 707 sera analyzed, the 71.43% of them showed the presence of specific antibodies. The prevalence of antibodies did not differ significantly (P > 0.05) between males and females in Angola and Republic Arab Saharaui. It was found a significant difference (P < 0.0001) among countries.

Adolescent

[Further cases of Ehlers-Danlos syndrome of the renovascular dysplasic variety].

One hundred and twenty patients with arterial hypertension and 3 cases of fibromuscular displasia of the renal arteries (FDRA) (group D) were studied; besides the usual arterial hypertension work up, a search of Ehlers-Danlos syndrome stigmata was carried out in all patients. The population of 120 hypertensive patients were classified in 3 groups: group A, fromed by 104 subjects without EDS stigmata; group B, constitued by 7 cases with hypermobility of one to three metar-carpophalangic joints and group C in which 9 subjects with hipermobility of more than 3 metacarpophalangic joints were included. Neither case of groups A and B showed arteriographic signs of FDRA. In 4 cases of group C there were arteriographic evidence of FDRA (3.3% of the whole population) and stigmata of SED (2 cases with skin biopsy positive for this entity). Two cases of group D showed stigmata of SED and a positive skin biopsy; the other case had a normal histology of skin and no clinical signs of SED. The presence of SED stigmata in a patient with arterial hypertension should alert the clinician in the diagnosis of FRDA; in such a case it is recommended that a renal arteriography be performed. In this paper similarities of SED of the arterial type and some cases of FDRA are remarked and it is proposed the both entities share the same or a very closed molecular collagen defect.

Adult

[Primary fibrosarcoma of the right ventricle].

Mexican literature has information of two fibrosarcomas in the atria. In the present work the first fibrosarcoma of the present work the first fibrosarcoma of the right ventricle found in Mexico is presented. This case behaved clinically, electrocardiographically, and phonomechanocardiographically like an Ebstein's disease, with the exception that in the phono a giant "a" wave was found. A review is mad of the clinical history, EKG, radiologic, and phono findings, as well as the laboratory analysis and data found in the autopsy.

Autopsy