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Biomedical subjects

C Marco

Publications and source records attributed to C Marco.

67 records · Page 4Linked to original sources
PubMed1985

Evolution of 3-hydroxy-3-methylglutaryl-CoA reductase and microsomal membrane fluidity throughout chick embryo development.

The pattern of chick liver and brain 3-hydroxy-3-methylglutaryl-CoA reductase and its relationship with changes in microsomal membrane fluidity was studied during embryonic and postnatal development. A peak of brain activity was found at 19 days of embryonic development, while liver activity only increased after hatching. A significant increase in cholesterol content of brain microsomes occurred at about 14 days of incubation, decreasing afterwards. No significant variations were observed in liver microsomes during the same period. A similar profile was found in the phospholipid content of both brain and liver microsomes. The cholesterol/lipidic phosphorus molar ratio of brain and liver microsomes did not exhibit significant changes throughout embryonic and postnatal development. These results demonstrate that membrane-mediated control does not regulate the evolution of reductase activity during this developmental period.

Aging↗
PubMed1985

Ethanol sensitivity and fatty acid composition of chick liver mitochondrial and microsomal membranes.

Fatty acid composition of hepatic mitochondrial and microsomal membranes was studied in 2-day-old chicks exposed to ethanol for 60 h (short treatment) or 18 days (chronic treatment). Short ethanol treatment induced in mitochondria an increase in the 18:1/18:0 ratio as a consequence of both an increase in the percentage of oleic and a decrease in that of stearic acid. Likewise, a clear decrease in the polyunsaturated fatty acids and in the 20:4/18:2 ratio was found in mitochondria after short ethanol administration. Microsomal membranes were practically unaffected by this treatment. However, chronic ethanol exposure produced a significant increase in the percentages of polyunsaturated fatty acids in both mitochondria and microsomes as well as a decrease in the 18:1/18:0 ratio. These results suggest that delta 9 desaturase modifies its activity in response to ethanol treatment with a different pattern to those showed by delta 6 and delta 5 desaturase activities.

Animals↗
PubMed1984

Changes in chick liver and brain mevalonate kinase, mevalonate-5-phosphate kinase and mevalonate-5-pyrophosphate decarboxylase during development.

Phosphorylation and decarboxylation of mevalonate in chick liver and brain was investigated during early post hatching stages of development. In chick liver, both mevalonate kinase and mevalonate-5-phosphate kinase increased their activity from day 5 of age while pyrophosphate decarboxylase activity remained low during the first days after hatching, increased sharply up to day 9 of age, and remained practically unchanged thereafter. The developmental pattern obtained in brain shows a slight decrease in the phosphorylation and decarboxylation of mevalonate after the first week of postnatal development. Further studies were performed using the specific substrate of mevalonate-5-pyrophosphate decarboxylase, corroborating the results obtained using mevalonate as substrate. Changes in hepatic decarboxylase were more pronounced than those observed in mevalonate-phosphorylating enzymes, thus suggesting an important role for decarboxylase in the control of cholesterogenesis during postnatal development.

Aging↗
PubMed1984

Lipid composition of brain myelin from normal and hyperphenylalaninemic chick embryos.

The influence of hyperphenylalaninemia on the lipid composition of brain myelin has been investigated in 19-day-old chick embryos. CNP-ase activity was used as myelin marker enzyme for myelin isolation. CNP-ase activity was significantly lower in hyperphenylalaninemic myelin when compared with control. No significant differences were observed after experimental treatment in the total lipid content of myelin as well as in the proportion of cholesterol:phospholipid:galactolipid. Nevertheless, a clear increase in the percentage of esterified cholesterol was found. No appreciable alterations were observed in the phospholipid composition of brain myelin from both control and hyperphenylalaninemic chick embryos. However, the ratio of unsaturated to saturated fatty acids in serine plasmalogen and sphingomyelin was considerably increased by this treatment. This ratio in choline and ethanolamine phosphatides from treated embryos did not differ from that of controls.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed1984

Postnatal development of the sterol and nonsterol mevalonate metabolism in chick liver and kidneys. Effect of cholesterol feeding.

The effect of 2% cholesterol feeding on changes throughout postnatal development of total, free, and esterified cholesterol in neonatal chick liver and kidneys was studied. The increase observed in the hepatic cholesterol content after supplementation of the diet with 2% cholesterol was mainly due to the accumulation of esterified cholesterol. Small but significant differences were also found in the esterified cholesterol content in kidneys between control and cholesterol-fed animals. In normally fed chicks, the hepatic percentage of squalene synthesized from mevalonate decreased during the first days of independent life while cholesterol percentage increased. On the contrary, the percentage of squalene recovered in kidneys immediately after hatching was minimal, increasing during postnatal development. Addition of 2% cholesterol to the diet produced a clear inhibition in the mevalonate incorporation into nonsaponifiable lipids by liver slices, especially from 4 days onwards. This inhibition was particularly clear in the percentage of cholesterol synthesized. Mevalonate incorporation by kidney slices was higher than in liver, although cholesterol supplementation had little influence on the percentage of each nonsaponifiable lipid formed. In normally fed chicks, kidneys metabolized mevalonate by the shunt pathway not leading to sterols at a rate more than 50 times that of liver. Cholesterol feeding produced a clear enhancement of the hepatic shunt pathway while in kidneys it had practically no effect.

Aging↗
PubMed1983

Relationship between changes in free cholesterol and pyrophosphomevalonate decarboxylase activity during myelination.

The patterns of cholesterol content in chick brain and liver were studied during embryonic development and compared with the variations in the specific activities of mevalonate-activating enzymes during the same period. Total cholesterol content in both embryonic chick brain and liver increased during incubation. The relative percentage of free cholesterol was always maintained over 85% in brain, while in liver this percentage decreased to less than 10% during the later days of incubation. A straight parallelism was observed between free cholesterol and pyrophosphomevalonate decarboxylase activity in the embryonic brain. On the other hand, the hepatic decarboxylase exhibited a lower specific activity than in brain and did not show significant variations throughout the same period of incubation. Changes in brain pyrophosphomevalonate decarboxylase activity were more pronounced than those observed in both mevalonate kinase and phosphomevalonate kinase activities, in spite of that the specific activity of decarboxylase was the lowest of the three mevalonate-activating enzymes, suggesting that this reaction is one rate-limiting step for cholesterogenesis during myelination.

Animals↗
PubMed1981

Properties of mevalonate-activating enzymes in developing chick brain.

Phosphorylation of mevalonic acid has been studied in 1-3 day chicks. Addition of Mg2+ or Mn2+ strongly increased the formation of phosphorylated derivatives. Mevalonate phosphorylation showed an absolute nucleotide requirement, being ATP and ITP the most effective phosphate donors. Unlike other vertebrate mevalonate kinases, the enzyme from chick brain did not require thiol group protectors as activators. However, the enzyme was found to be sensitive to thiol binding reagents.

Animals↗
PubMedDate not supplied

[Increased bile lithogenicity after simultaneous total parenteral nutrition and octrotide. A model of calcium palmitate Gallstones].

Gallbladder stasis and gallstone formation are well-known complications of both fasting-associated total parenteral nutrition (TPN) and long-term treatment with octreotide. Additive noxious effects to hepatobiliary function may develop when both therapies are given together as treatment of enteric fistulae. The aim of this study was to assess the risk of gallstone formation during treatment with TPN and octreotide separately and in combination. We studied four groups of New Zealand rabbits (n = 32) during a 2-week intervention period: 14 chow-fed controls; 6 fasted and TPN-fed; 6 chow-fed and administered octreotide, and 6 fasted and treated with both TPN and octreotide. After treatment, the bile duct was cannulated and the gallbladder and liver tissue were obtained for histological analysis. Hepatic and gallbladder bile were retrieved for microscopic examination and measurement of biliary lipids, bilirubin, calcium, total protein, and cholesterol nucleation time. The chemical composition of gallstones was also analyzed. The results of the study suggest that simultaneous administration of these two therapies in rabbits has additive effects on gallbladder stasis and bile lithogenicity. The administration of both treatments can play an important role in the formation of calcium palmitate gallstones in these animals.

Animals↗
PubMedDate not supplied

Cytomorphology of a mediastinal parathyroid cyst. Report of a case mimicking malignancy.

The clinical and cytologic features of a mediastinal parathyroid cyst are presented. Cytologic examination of the cyst fluid revealed the presence of small clusters of epithelial cells, with periodic-acid-Schiff-positive cytoplasmic granules. Special attention is required when atypical proliferating fibroblasts, which may be mistaken for malignant cells, are present.

Adult↗