Biomedical subjects

A R Aldred

Publications and source records attributed to A R Aldred.

26 records · Page 2Linked to original sources

PubMed1987

Distribution of transferrin synthesis in brain and other tissues in the rat.

Levels of transferrin mRNA were measured by hybridization to transferrin cDNA in extracts from various areas of rat brain and other tissues. The highest concentrations of transferrin mRNA were found in the liver and the choroid plexus of the lateral and third ventricles. Lower concentrations were observed in the medulla and thalamus, choroid plexus of the fourth ventricle, cortex, hypothalamus, cerebellum, pituitary, testis, placenta, stomach, spleen, kidney, muscle, and heart. Yolk sac, small intestine, and adrenal glands did not contain detectable transferrin mRNA levels. The size of transferrin mRNA was the same in liver, brain, and testis. Upon incubation of choroid plexus pieces with [14C]leucine in vitro, about 4% of the radioactive protein secreted into the medium was found to be transferrin. Together with previous data (Dickson, P.W., Howlett, G.J., and Schreiber, G. (1985) J. Biol. Chem. 260, 8214-8219; Dickson, P.W., Aldred, A.R., Marley, P.D., Bannister, D., and Schreiber (1986) J. Biol. Chem. 261, 3475-3478) the obtained data suggest that the choroid plexus plays a role in maintenance of homeostasis in the microenvironment of the central nervous system by synthesizing and secreting plasma proteins.

Animals↗

PubMed1987

Rat ceruloplasmin. Molecular cloning and gene expression in liver, choroid plexus, yolk sac, placenta, and testis.

A rat ceruloplasmin cDNA clone was isolated from a rat liver cDNA library and identified by partial nucleotide sequence analysis. Rat liver ceruloplasmin mRNA levels were measured during the acute phase response to inflammation by cytoplasmic dot hybridization to ceruloplasmin cDNA. Regulation of ceruloplasmin synthesis appeared to be at the mRNA level, with the concentration of ceruloplasmin mRNA increasing significantly 12 h after induction of inflammation, reaching a maximum of 350% of normal at 36 h and returning to normal levels within 60 h. Using Northern blot analysis, extrahepatic ceruloplasmin gene expression was observed in choroid plexus, yolk sac, placenta, and testis. All these tissues are at the interface between, and possibly involved in maintaining homeostasis in, adjacent extracellular compartments. No ceruloplasmin mRNA was detected in RNA from stomach and small intestine.

Amino Acid Sequence↗

PubMed1986

Rat choroid plexus specializes in the synthesis and the secretion of transthyretin (prealbumin). Regulation of transthyretin synthesis in choroid plexus is independent from that in liver.

Synthesis of total protein and of transthyretin in rat choroid plexus was studied by measuring the incorporation of radioactive leucine into proteins in choroid plexus tissue incubated in vitro. About 20% of the protein newly synthesized in choroid plexus and about 50% of the newly synthesized protein secreted into the medium was transthyretin. Evidently, the choroid plexus is very active in the biosynthesis of this carrier protein for thyroid hormones and could be an important link in the chemical communication between the body and the central nervous system. Acute inflammation, which leads to a profound rearrangement of the pattern of plasma protein synthesis rates in the liver, produced distinct changes in the levels for plasma protein mRNAs in the liver. The levels of the mRNAs for alpha 1-acid glycoprotein and major acute phase alpha 1-protein increased more than 30-fold, those for transthyretin and albumin decreased to 27 and 57% of normal, respectively. The pattern of the observed changes in the levels of mRNAs for plasma proteins in the liver was independent of whether the acute inflammation was produced by subcutaneous injection of turpentine or intraperitoneal injection of a suspension of talcum. However, levels of transthyretin mRNA in choroid plexus were affected only very slightly, or not at all. Apparently, transthyretin synthesis in liver and choroid plexus is regulated independently during the acute phase response. No mRNA was detected in choroid plexus for albumin, alpha 1-acid glycoprotein, and major acute phase alpha 1-protein under any conditions.

Animals↗

PubMed1986

Levels of messenger ribonucleic acids for plasma proteins in rat liver during acute experimental inflammation.

The levels of mRNA for plasma proteins and for metallothionein in rat liver during the acute-phase response were studied by hybridization to specific cDNA probes. The mRNA for alpha 2-macroglobulin, the beta-chain of fibrinogen, alpha 1-acid glycoprotein (so-called acute-phase reactants) reached a maximum level between 18 and 36 h after inducing an acute inflammation. The level of mRNA for metallothionein-I peaked earlier, after 12 h. The mRNA for transferrin showed a delayed increase with a broad maximum for its relative level after 36-60 h. The mRNA levels for albumin and alpha 2u-globulin (so-called negative acute-phase reactants) decreased, reaching a minimum of 25% of the normal level after 36 h (albumin) and after 72 h (alpha 2u-globulin). The ratios of the rates of incorporation of leucine into the proteins over the levels of their mRNA in liver changed only a little, indicating that the rates of synthesis of plasma proteins in the liver are regulated at the mRNA level during the acute-phase response to inflammation.

Animals↗

PubMed1986

Synthesis of transthyretin (pre-albumin) mRNA in choroid plexus epithelial cells, localized by in situ hybridization in rat brain.

The sites of synthesis of transthyretin in the brain were investigated using in situ hybridization with [35S]-labeled recombinant cDNA probes specific for transthyretin mRNA. Autoradiography of hybridized coronal sections of rat brain revealed specific cellular localization of transthyretin mRNA in choroid plexus epithelial cells of the lateral, third, and fourth ventricles. Transferrin mRNA was also investigated and, in contrast to transthyretin mRNA, was localized mainly in the lateral ventricles. Our results indicate that substantial synthesis of transthyretin and transferrin mRNA may occur in the choroid plexus.

Animals↗

PubMed1985

High prealbumin and transferrin mRNA levels in the choroid plexus of rat brain.

Expression of plasma protein genes in various parts of the rat brain was studied by hybridizing radioactive cDNA to RNA in cytoplasmic extracts. No mRNA could be detected in brain for the beta subunit of fibrinogen, major acute phase alpha 1-protein, alpha 1-acid glycoprotein and albumin. However, per g tissue, the choroid plexus contained at least 100 times larger amounts of prealbumin mRNA than the liver and about the same amount of transferrin mRNA as liver. No prealbumin mRNA was found in other areas of the brain. The results obtained suggest very active synthesis of prealbumin in choroid plexus, which would be an important link in the transport of thyroid hormones from the blood to the brain via the cerebrospinal fluid.

Animals↗

PubMed1984

Synthesis of rat transferrin in Escherichia coli containing a recombinant bacteriophage.

Using mRNA from rat liver a cDNA library was constructed in lambda gt11Amp3. Immunochemical screening identified 15 clones producing transferrin. The identity of two clones was confirmed by nucleotide sequencing, which also indicated a presegment rich in hydrophobic amino acids but lack of a prosegment in precursor transferrin. A 920 base pair insert in one clone corresponded to 84% of the N-terminal domain of transferrin, which was synthesized as a hybrid protein with bacterial beta-galactosidase. A 1540 base pair insert in another clone corresponded to the N-terminal plus 50% of the carboxy terminal domain of transferrin. The product of this clone possessed only antigenic properties of transferrin.

Amino Acid Sequence↗

PubMed1984

Synthesis of rat apolipoprotein E by Escherichia coli infected with recombinant bacteriophage.

A cDNA library was constructed from rat liver polyadenylated RNA using the expression vector lambda gt11-Amp3. Several clones expressing antigenic determinants for rat apolipoprotein E were identified. The cDNA insert in one clone was further characterized and found to have a sufficient length (1120 base pairs) to code for full length apolipoprotein E. Restriction mapping and nucleotide sequencing showed the clone to contain the coding region for apolipoprotein E flanked by about 120 nucleotides at the 3'-side and by about 64 nucleotides on the 5'-side. One of the proteins produced by the clone was found to be a prokaryotic/eukaryotic hybrid protein reacting with antibodies to both bacterial beta-galactosidase and rat apolipoprotein E.

Animals↗