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O Ramírez

Publications and source records attributed to O Ramírez.

29 records · Page 2Linked to original sources
PubMed1981

Special capabilities of the sexes: differences in the molecular repertoire of mammal brain, heart and skeletal muscle.

World records for men's and women's (anaerobic) 200 meter dash are 19.67 and 21.9 seconds respectively. Here the transphosphorylation mechanisms are operative and not the glycolytic anaerobic and aerobic ones. The purpose of this paper is to try to find molecular differences during the neuro-muscular sexual differentiation in the Wistar rat. Creatine kinase (CPK: EC 2.7.3.2) as model transphosphorylase and the protein synthesis pattern, determined from the post 125,000 x g cytosol fraction of the brain, heart and masseter muscle, were chosen as molecular monitors. The CPK specific activity profiles showed differences among tissues and sexes. In rats with similar weights between 200 and 320 g, the epigenetic control of protein synthesis in the studied tissues, reflected genome differential activation depending on sex and age. The electrophoretograms differed in regard to the number and position of the protein bands of homologous tissues of different sexes. As an original finding, against the generally accepted criterion (the brain fundamentally synthesizes BB-CPK isoenzyme), MB-CPK and MM-CPK isoenzymes appeared in the brain of both sexes. The molecular sexual differences in the studied tissues determine functional and anatomical differences.

Animals↗
PubMed1970

Creatine regulation in the embryo and growing chick.

1. The absence of creatine was demonstrated enzymically in the hen's-egg yolk and in the albumin contrary to former reports. 2. A comparison of the results obtained by enzymic and colorimetric methods to measure creatine is presented. 3. Creatine phosphate was not detected in the yolk extracts. 4. The content of free arginine enzymically assayed was 15.7mumol in the yolk and 3.38mumol in the albumin. Arginine amounts to practically all of the guanidine compounds in the yolk and one-half of those in the albumin. 5. No glycine amidinotransferase activity was found in the egg-yolk homogenates. 6. The heart of the chick embryo does not receive creatine from the egg and the creatine kinase activity present in this organ starting from the 27th hour of incubation suggests that the enzyme is a constitutive one working probably as an adenosine triphosphatase in a way similar to the kinase isolated from rabbit skeletal muscle. 7. Liver glycine amidinotransferase activity appeared clearly after day 5 of incubation. The specific activity reached a maximum at day 12 and then declined; however, the activity per total mass of liver increased steadily during all the prenatal period. Concomitantly with this steady increase a rise in the creatine content of the whole embryo was observed. An analogous increasing relationship between total liver amidinotransferase activity and liver creatine content was also detected during the postnatal period. 8. Repression of amidinotransferase by creatine cannot be accepted as occurring under physiological conditions since an inverse relationship between the two parameters was not observed. 9. Repression of liver amidinotransferase is observed only when pharmacological concentrations of the exogenous creatine are present in the chick liver.

Albumins↗
PubMedDate not supplied

[Role of calcium in the regulation of syncytial formation and the formation of creatine kinase during the development of muscle in the absence of creatine].

1. It is demonstrated for the first time that typically elongated chick myotubes, with more than 20 nuclei per fiber and creatine kinase, appear in cultures fed all time with partially defined auto-conditioned medium. 2. It was found that the skeletal muscle enzyme of the chick embryo is independent of the presence of creatine and consequently is another constitutive enzyme like the creatine kinase of the early embryonic chick heart. 3. Calcium elicited the activity of the enzyme and promoted fusion of myoblasts in a creatine-free partially defined medium, in the absence of embryo extract. 4. It is suggested that creatine kinase is a dual molecule, working as an ATPasa in the absence of creatine with H2O as the nucleophilic reagent. 5. Alternatively, it is possible that creatine kinase can be synthesized and localized in advance to the advent of creatine in myocardial and skeletal muscle cells.

Animals↗