Biomedical subjects
Publications and source records attributed to C Peña.
The solid phase synthesis of fragments 75-120-NH2 and 73-128-GlyNH2 of the human growth hormone sequence is described. Purification was by solvent extraction, gel filtration and partition chromatography. No growth-promoting activity was detected in any of the peptides by the rat body-growth assay. An immunochemically reactive area was located in the sequence 73-128 when tested by complement fixation assays.
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Antigenic determinant areas were detected in bovine growth hormone fragments 6--124 and 125--149, the former being predominant. Reduction and carboxymethylation of disulfide bridge 53--164 destroys the immunological reactivity of the area which is little affected by reduction and carbamoylmethylation. All the activity found in fragment 6--124 seems to be concentrated in the sequence 87--124.
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125I-derivatives of Tyr1-kallidin, Tyr5-bradykinin, and Tyr8-bradykinin were prepared. A technique for purification of the monoiodinated derivative is described. Bradykinin antisera were tested for their ability to bind the mono-iodinated analogues. Each antiserum had a characteristic preference for one of the three labeled peptides. The sensitivity of each antiserum was greatest when it was used with the label bound most avidly by that antiserum. The specificity of an antiserum was not changed by varying the labeled analogue. Some common enzyme inhibitors had significant effects on the antigen-antibody reactions. Lecithin interfered with the reaction between antiserum and Tyr1-kallidin. The data suggest that antisera for bradykinin radioimmunoassay be tested with several radioactive iodobradykinins to maximize their usefulness. In addition, enzyme inhibitors used to stabilize levels of kinins in biological fluids should be tested for their effects on the assay. Biologic samples rich in lipid may give spurious radioimmunoassay results unless they are freed of those phospholipids that can bind labeled and unlabeled peptides.
A malignant meningioma was studied by light and electron microscopy. Histologically, the tumour was composed predominantly of spindle shaped cells arranged in interlacing bundles with numerous mitoses and much nuclear atypia. There were many necrotic foci as well as invasion of the cerebral cortex, dura mater and blood vessels. Ultrastructurally, the main findings included moderate plasma membrane interdigitation, many intracytoplasmic filaments, and junctional attachments of three kinds: desmosomes, hemidesmosomes, and zonulae adhaerentes. These subcellular features are suggestive of arachnoidal cell origin.
The immunological properties of a synthetic human growth hormone fragment comprising the amino acids 73 through 128 and of the homologous natural horse growth fragment formed by amino acids 73 through 123, have been comparatively studied. Antisera obtained in rabbits inoculated with the native human hormone or with the fragments, were used. By hemagglutination experiments both fragments have the same reactivity toward the anti-human growth hormone serum, but complement fixation curves detect the existence of at least two populations of antibodies presumably originated against the sequence 73-128 of human growth hormone. Of these, only one of the corresponding antigenic areas is present in the homologous region of equine growth hormone. The known cross-reactivity detected between both hormones is thus partially explained.
The interaction of angiotensin with its receptor has been studied on the basis of the tachyphylaxis shown by the rat uterus towards angiotensin II when pH and Ca2+ concentration are below physiological levels. 14C-Angiotensin binding and 45Ca2+-uptake investigations suggest tachyphylaxis to be due to increased binding at low pH and Ca2+ concentration. Studies with alkylating (affinity labeled) angiotensin derivatives containing the N-mustard chlorambucil suggest a "Charnière type" inhibition at the Ca-binding site of receptor and an irreversible inhibition at an anionic site. Angiotensin inhibitors containing chlorambucil do not alkylate tissue but are competitive inhibitors suggesting that the aromatic side chain in angiotensin may induce conformational changes in the receptor. The results obtained lead to a logical model for the angiotensin receptor allowing for normal activation by the hormone as well as for production of tachyphylaxis.
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