Biomedical subjects

M C Kleid

Publications and source records attributed to M C Kleid.

3 recordsLinked to original sources

PubMed1994

Synenkephalin processing in embryonic rat brain.

Synenkephalin (proenkephalin 1-70) is produced and secreted as an intact molecule or as a part of precursors in the adult brain and adrenal medulla, respectively. However, it is cleaved to low molecular weight peptides in proliferating immune cells. Considering that the pre-proenkephalin gene is expressed in the embryonic rat brain during the cell proliferation stage, we studied the processing of synenkephalin in embryonic rat brains (E18) and compared it with the processing in adult rat brains. IR-synenkephalin was measured by RIA using a C-terminally directed antiserum. Adult rat brains contained higher concentrations of immunoreactive (IR)-synenkephalin (2,612 + 264) than embryonic rat brain (1,361 + 100) (results in fmol/mg proteins, n = 5). Gel filtration chromatography (Sephadex G-50) showed that in the extracts of adult rat brain, 50% of the IR-synenkephalin eluted in the position of the authentic peptide (8 kDa) and the rest of the immunoreactivity corresponded to partially processed peptides of 4.0 and 2.5 kDa. In embryonic rat brains synenkephalin was processed to intermediate peptides of 2.5, 1.7 and mainly to a low molecular weight peptide of 1.0 kDa. The concentration of this last peptide, which was further characterized by affinity column and HPLC, represented 45% of the total immunoreactivity. IR-met-enkephalin in embryonic rat brains (analyzed before and after enzymatic digestion with trypsin and carboxypeptidase B) corresponded principally to non-processed or partially processed products. However, these were cleaved to free met-enkephalin in adult rat brains.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1993

Differential posttranslational processing of proenkephalin in rat bone marrow and spleen mononuclear cells: evidence for synenkephalin cleavage.

Proenkephalin (PENK) messenger RNA was reported to be present in bone marrow mononuclear cells (BMMC) and spleen mononuclear cells (SMC). Nevertheless, the pattern of PENK products in normal cells of the rat immune system, which is important for defining the physiological role of PENK gene expression, has not been well established. In this work we have characterized the processing of the opioid portion (met-enkephalin-containing peptides) and nonopioid portion (synenkephalin-derived peptides) of PENK in rat BMMC and SMC. Met-enkephalin-containing peptides were detected in mononuclear cells of both hematopoietic tissues. In BMMC, free immunoreactive (IR)-met-enkephalin corresponded only to the 15% of total met-enkephalin-IR, whereas in SMC it represented the 66.5%. Gel filtration chromatography showed that BMMC contained partially processed PENK-derived peptides of high and intermediate molecular weight, whereas SMC displayed fully processed products containing met-enkephalin and/or the carboxyterminal portion of synenkephalin. HPLC purification of low molecular weight products showed that free IR-met-enkephalin in SMC mainly corresponded to met-enkephalin and oxidized met-enkephalin. In addition we have characterized in SMC three peptides lower than 3.0 kilodalton containing the C-terminal sequence of synenkephalin. These peptides were purified by gel filtration, affinity chromatography, ion exchange chromatography, and HPLC. These results show that PENK was processed in mononuclear cells of the primary (bone marrow) and secondary (spleen) organs of the rat hematopoietic system, as occurs in neural and endocrine tissues. Nevertheless, the precursor was cleaved only in the latter tissue to low molecular weight peptides. Furthermore we demonstrated that synenkephalin (proenkephalin 1-70) in SMC was processed to low molecular weight peptides containing the C-terminus free. This last result suggests that a dibasic Lys-Lys and monobasic (Lys) sites were cleaved.

Animals↗

PubMed1992

Early complete maturation of proenkephalin processing induced by dexamethasone in the adrenal gland of neonatal rats.

We have previously found that proenkephalin processing is incomplete in the neonatal rat adrenal medulla and have postulated that immaturity of either the nervous input to the gland or the endocrine hypothalamus-pituitary-adrenal axis might be involved in the failure of the gland to yield free met-enkephalin. Therefore, we investigated whether cholinergic and glucocorticoid agonists may act in vivo on neonatal proenkephalin processing; reserpine, a strong activator of precursor cleavage, was also tested. Acute administration of nicotine, pilocarpine and reserpine to 24-hour-old rats increased the content of enkephalin-containing peptides (ECP) after 72 h (4-day-old rats) and activated the posttranslational processing of proenkephalin to high, intermediate and low molecular weight peptides respectively, although free met-enkephalin was not produced. Chronic treatment with nicotine and pilocarpine neither modified the concentration of ECP nor were able to induce free metenkephalin production. Chronic administration of dexamethasone increased ECP levels in the adrenal of 4-day-old rats and caused proenkephalin processing to intermediate- and low-molecular-weight products including the production of free met-enkephalin. These results indicate that only dexamethasone was able to induce the production of met-enkephalin in the adrenal of neonatal rats, suggesting an involvement of the hypothalamus-pituitary-adrenal axis in the proteolytic maturation of proenkephalin during the ontogeny of rat adrenal medulla.

Adrenal Glands↗