Biomedical subjects

J Cornejo

Publications and source records attributed to J Cornejo.

33 records · Page 2Linked to original sources

PubMed1991

Biosynthesis of phycobilins. 15,16-Dihydrobiliverdin IX alpha is a partially reduced intermediate in the formation of phycobilins from biliverdin IX alpha.

A partially purified protein fraction from the phycocyanin-containing unicellular rhodophyte, Cyanidium caldarium, reductively transforms biliverdin IX alpha to a violet colored bilin in the presence of NADPH, ferredoxin, and ferredoxin-NADP+ reductase. This bilin has a violin-like absorption spectrum with maxima at 335 and 560 nm in methanolic HCl and at 337, 567, and 603-604 nm in CHCl3. The bilin has been determined to be 15,16-dihydrobiliverdin IX alpha by comparative spectrophotometry and 1H NMR spectroscopy. This product of biliverdin IX alpha reduction is converted enzymatically to phycobilins by further reduction. A general biosynthetic pathway is proposed which accounts for the formation of the phycobilins from biliverdin IX alpha by a two-step reduction process followed by isomerization.

Biliverdine↗

PubMed1991

Differential prolactin response to oral metoclopramide in nulliparous versus parous women throughout the menstrual cycle.

OBJECTIVE: To analyze if serum prolactin (PRL) changed throughout the menstrual cycle and if parous women have lower PRL than nulliparous women. DESIGN: A prospective study of PRL was performed in basal conditions and during oral metoclopramide stimulation on days 7, 14, and 21 of menstrual cycle. SETTING: Instituto Nacional de Perinatología, third level medical institution. PATIENTS: Four parous (group A) and seven nulliparous (group B) healthy volunteer women entered and finished the study. INTERVENTIONS: Women were studied each day before and every 30 minutes during 2 hours after oral metoclopramide (10 mg). MAIN OUTCOME MEASURE: Duplicate PRL determinations were performed by radioimmunoanalysis. Hypothesis was formulated before data collection. RESULTS: Group A and B had similar basal PRL levels and no within group differences existed in response to metoclopramide, regardless of the day studied. Group A had lower PRL increments than group B from 60 to 120 minutes on days 14 and 21 (P less than 0.05); the peak increments also were lower on days 7, 14, and 21 (P less than 0.05). CONCLUSIONS: Parous women had a diminished PRL response. Although the dopaminergic tone was similar throughout the menstrual cycle within each group, two distinct levels of dopaminergic tone existed in parous and nulliparous women.

Adult↗

PubMed1988

Algal heme oxygenase from Cyanidium caldarium. Partial purification and fractionation into three required protein components.

Enzymatic heme oxygenase activity has been partially purified from extracts of the unicellular red alga Cyanidium caldarium, and the macromolecular components have been separated into three protein fractions, referred to as Fractions I, II, and III, by serial column chromatography through DEAE-cellulose and Reactive Blue 2-Sepharose. Fraction I is retained by DEAE-cellulose at low salt concentration and eluted by 1 M NaCl. Fraction II is retained by Blue Sepharose at low salt concentration and eluted by 1 M NaCl. Fraction III is retained on 2',5'-ADP-agarose and eluted by 1 mM NADPH, while Fraction II is not retained on ADP-agarose. Fractions I-III, have Mr values of 22,000, 38,000, and 37,000, respectively (all +/- 2,000), as determined by Sephadex gel filtration chromatography. In vitro heme oxygenase activity requires the presence of all three fractions, plus substrate, O2, reduced pyridine nucleotide, and another reductant. Ascorbate, isoascorbate, and phenylenediamine serve equally well as the second reductant, but hydroquinone can also be used, with lower activity resulting. Fractions I-III are heat sensitive and inactive by Pronase digestion. Fraction I has a visible absorption spectrum similar to that of ferredoxin and is bleached by dithionite reduction or incubation with p-hydroxymercuribenzoate. Fraction I can be replaced by commercially available ferredoxin derived from the red alga Porphyra umbilicalis, and to a smaller extent, by spinach ferredoxin. Fraction III contains ferredoxin-linked cytochrome c reductase activity and can be partially replaced by spinach ferredoxin-NADP+ oxidoreductase. Reconstituted heme oxygenase and ferredoxin-linked cytochrome c reductase activities are both abolished if Fraction I or III is preincubated with 0.1 mM p-hydroxymercuribenzoate, but heme oxygenase activity is only slightly affected if Fraction II is preincubated with p-hydroxymercuribenzoate. Preincubation of Fraction II with 0.5 mM diethylpyrocarbonate inactivates heme oxygenase in the reconstituted system, and 10 microM mesohemin partially protects this Fraction against diethylpyrocarbonate inactivation. Algal heme oxygenase is inhibited 80% by 2 microM Sn-protoporphyrin even in the presence of 20 microM mesohemin. Fraction II is rate limiting in unfractionated and reconstituted incubation mixtures. None of the three cell fractions could be replaced by bovine spleen microsomal heme oxygenase or NADPH-cytochrome P450 reductase.

Catalase↗

PubMed1988

Conservative treatment of early breast cancer.

At our Institution, the treatment policy for early carcinoma of the breast (T1-2, NO, AJC) is lumpectomy followed by radiotherapy to the breast and peripheral lymphatics. From October 1976 until December 1982, 171 patients have been admitted and treated. Radiotherapy was administered with 60 Co, 5.000 cGy in 5 weeks to the breast and lymphatics plus a boost to the scar giving q.s.p. 6.400 cGy at maximum tumor depth. With a minimum follow-up of 3 years and a median follow-up of 61.7 months the locoregional control was 94.2% and survival at 8 years with no evidence of disease (NED) was 77.2% with an overall survival rate of 90%. No difference in NED survival rate was found between Stage I and II. There was a tendency to better survival rate in those patients older than 50 years and also for post menopausal patients, however the difference did not reach statistical significance (66.7% NED survival at 8 years for premenopausal and 81.8% NED survival for post menopausal, also at 8 years, p = 0.056 Gehan). The time elapsed between surgery and radiation therapy (between 1 and 2 months) was found to be nonsignificant. Only 1 out of 171 patients had axillary dissection. The importance or lack of it, is discussed.

Breast Neoplasms↗

PubMed1985

Dysfunction of dopaminergic regulation of prolactin in patients with functioning and nonfunctioning pituitary adenomas and craniopharyngiomas.

The response to domperidone (a dopamine blocking agent) of serum prolactin (PRL) levels was compared in 3 patients with amenorrhea-galactorrhea without evidence of a pituitary tumor, 23 patients with prolactinomas (10 cases with histologic confirmation), 7 patients with histologically verified large nonfunctioning pituitary adenomas with normal or moderately elevated basal PRL levels, and 6 patients with histologically verified craniopharyngiomas (3 with normal basal PRL levels and 3 with elevated PRL levels). The response was compared with that of 10 patients with postpartum hyperprolactinemia and 14 normal women. Ten milligrams of intravenous domperidone induced a rapid rise in PRL that was maximal at 30 to 45 minutes in normal, postpartum, and amenorrhea-galactorrhea patients who had no sign of tumor. In contrast, domperidone failed to induce significant changes in PRL in cases of prolactinoma, nonfunctioning pituitary adenomas, and craniopharyngioma with or without elevated basal PRL levels. The results suggest that dopaminergic control on PRL secretion was impaired in all tumor cases. The mechanisms of this abnormal dopaminergic control, however, may be different. Whereas dopamine control in cases of prolactinoma is altered at the level of pituitary dopamine receptors, alternative explanations must be found for those tumors with normal basal PRL levels and lack of response to domperidone.

Adenoma↗

PubMed1984

Enzymatic heme oxygenase activity in soluble extracts of the unicellular red alga, Cyanidium caldarium.

Extracts of the phycocyanin-containing unicellular red alga, Cyanidium caldarium, catalyzed enzymatic cleavage of the heme macrocycle to form the linear tetrapyrrole bilin structure. This is the key first step in the branch of the tetrapyrrole biosynthetic pathway leading to phycobilin photosynthetic accessory pigments. A mixed-function oxidase mechanism, similar to the biliverdin-forming reaction catalyzed by animal cell-derived microsomal heme oxygenase, was indicated by requirements for O2 and a reduced pyridine nucleotide. To avoid enzymatic conversion of the bilin product to phycocyanobilins and subsequent degradation during incubation, mesoheme IX was substituted for the normal physiological substrate, protoheme IX. Mesobiliverdin IX alpha was identified as the primary incubation product by comparative reverse-phase high-pressure liquid chromatography and absorption spectrophotometry. The enzymatic nature of the reaction was indicated by the requirement for cell extract, absence of activity in boiled cell extract, high specificity for NADPH as cosubstrate, formation of the physiologically relevant IX alpha bilin isomer, and over 75% inhibition by 1 microM Sn-protoporphyrin, which has been reported to be a competitive inhibitor of animal microsomal heme oxygenase. On the other hand, coupled oxidation of mesoheme, catalyzed by ascorbate plus pyridine or myoglobin, yielded a mixture of ring-opening mesobiliverdin IX isomers, was not inhibited by Sn-protoporphyrin, and could not use NADPH as the reductant. Unlike the animal microsomal heme oxygenase, the algal reaction appeared to be catalyzed by a soluble enzyme that was not sedimentable by centrifugation for 1 h at 200,000g. Although NADPH was the preferred reductant, small amounts of activity were obtained with NADH or ascorbate. A portion of the activity was retained after gel filtration of the cell extract to remove low-molecular-weight components. Considerable stimulation of activity, particularly in preparations that had been subjected to gel filtration, was obtained by addition of ascorbate to the incubation mixture containing NADPH. The results indicate that C. caldarium possesses a true heme oxygenase system, with properties somewhat different from that catalyzing heme degradation in animals. Taken together with previous results indicating that biliverdin is a precursor to phycocyanobilin, the results suggest that algal heme oxygenase is a component of the phycobilin biosynthetic pathway.

Biliverdine↗

PubMed1984

Enzymic Transformation of Biliverdin to Phycocyanobilin by Extracts of the Unicellular Red Alga Cyanidium caldarium.

Cell-free extracts of the unicellular red alga Cyanidium caldarium catalyze the transformation of biliverdin to a product indistinguishable from phycocyanobilin, the free bilin derived from phycocyanin by methanolysis. Crude cell-free extract requires biliverdin as the only substrate, but after removal of low molecular weight components by gel filtration, the reaction shows an additional requirement for a reduced pyridine nucleotide. Boiled extract is enzymically inactive, activity is not sedimented by high-speed centrifugation, and mesobiliverdin cannot serve as a substrate.Incubation of cell extracts with biliverdin yields two products with very similar spectrophotometric properties in acidic methanol, but which are separable by reverse-phase high pressure liquid chromatography. The same two products are formed by methanolysis of protein-bound phycocyanin chromophore, with the late-eluting one predominating. The two products derived from either phycocyanin methanolysis or cell extract incubation with biliverdin are partially interconvertible and they form the same ethylidine-free isomeric derivative, mesobiliverdin. Their absorption spectra correspond to those of the Z- and E-ethylidine isomers of phycocyanobilin. Based on previous work showing that the major methanolysis product has the E-ethylidine configuration, the other product of methanolysis and enzymic biliverdin transformation is therefore the Z-ethylidine isomer. The time course for formation of the two products during incubation suggests that the early-eluting product is the precursor of the late-eluting one. These results suggest that Z-ethylidine phycocyanobilin is the precursor of the E-ethylidine isomer, and that the latter may be a normal cellular precursor to protein-bound phycocyanin chromophore.

Journal Article↗

PubMed1983

Biosynthesis of phycocyanobilin from exogenous labeled biliverdin in Cyanidium caldarium.

Phycocyanin is a major light-harvesting pigment in bluegreen, red, and cryptomonad algae. This pigment is composed of phycocyanobilin chromophores covalently attached to protein. Phycocyanobilin is an open-chain tetrapyrrole structurally close to biliverdin. Biliverdin is formed in animals by oxidative ring-opening of protoheme. Recent evidence indicates that protoheme is a precursor of phycocyanobilin in the unicellular rhodophyte, Cyanidium caldarium. To find out if biliverdin is an intermediate in the conversion of protoheme to phycocyanobilin, [14C]biliverdin was administered along with N-methylmesoporphyrin IX (which blocks endogenous protoheme formation) to growing cells of C. caldarium. To avoid phototoxic effects due to the porphyrin, a mutant strain was used that forms large amounts of both chlorophyll and phycocyanin in the dark. After 12 or 24 h in the dark, cells were harvested and exhaustively extracted to remove free pigments. Next, protoheme was extracted. Phycocyanobilin was then cleaved from the apoprotein by methanolysis. Protoheme and phycocyanobilin were purified by solvent partition, DEAE-Sepharose chromatography, and preparative reverse-phase high-pressure liquid chromatography. Absorption was monitored continuously and fractions were collected for radioactivity determination. Negligible amounts of label appeared in the protoheme-containing fractions. A major portion of label in the eluates of the phycocyanobilin-containing samples coincided with the absorption peak at 22 min due to phycocyanobilin. In a control experiment, [14C]biliverdin was added to the cells after incubation and just before the phycocyanobilin-apoprotein cleavage step. The major peak of label then eluted with the absorption peak at 12 min due to biliverdin, indicating that during the isolation biliverdin is not converted to compounds coeluting with phycocyanobilin. It thus appears that exogenous biliverdin can serve as a precursor to phycocyanobilin in C. caldarium, and that the route of incorporation is direct rather than by degradation and reincorporation of 14C through protoheme.

Bilirubin↗

PubMed1981

Sepiolite, a potential excipient for drugs subject to oxidative degradation.

Sepiolite, a member of the fibrous mineral group of clays, is relatively free of surface ferric iron and does not accelerate significantly the oxidative degradation of hydrocortisone. The compatibility of sepiolite with drugs that can undergo oxidative degradation is in sharp contrast to the catalytic effect of attapulgite, another fibrous mineral, which contains a significant amount of surface ferric iron and which therefore accelerates oxidative degradation. Sepiolite adsorbs hydrocortisone by a weak adsorption mechanism, which was shown by IR spectroscopy to be chiefly due to hydrogen bonding. However, accelerated oxidative degradation of the adsorbed hydrocortisone does not occur. Maximum adsorption occurs at pH 7-8.5. Desorption occurs readily by washing with water. Sepiolite has similar rheological properties to attapulgite. The results of this study suggest that sepiolite may be useful as a pharmaceutical excipient for drugs that undergo oxidative degradation.

Adsorption↗

PubMed1980

Oxidative degradation of hydrocortisone in presence of attapulgite.

Degradation of hydrocortisone in attapulgite suspensions was monitored by high-pressure liquid chromatography and UV spectrophotometry. The rate of oxidative degration of hydrocortisone was accelerated significantly in the presence of attapulgite. In addition, degradation appeared to be composed of two apparent first-order reactions rather than the single apparent first-order degradation reaction observed for hydrocortisone solutions. However, the same degradation products were obtained in both hydrocortisone solutions and attapulgite suspensions, indicating that interaction with attapulgite did not alter the degradation pathway. Kinetic and adsorption studies suggested that hydrocortisone is adsorbed weakly by attapulgite and undergoes oxidative degradation, which is catalyzed by adsorbed iron oxides or hydroxides as well as by structural ferric iron at the clay surface. Since clay minerals generally contain surface ferric iron, the potentiala for accelerating the oxidative degradation of drugs should be considered whenever clays and drugs are combined.

Bentonite↗

PubMed1971