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Results for “Liver Extracts”

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At least 109 records · Page 6Linked to original sources
PubMed1976

Naturally occurring immunosuppressive agents. II. The ability of cell-free liver extracts to modify the rejection of allogeneic skin grafts in the rabbit.

It has been demonstrated that cell-free extracts of pig, rabbit and human liver, but not of other parenchymal organs, contain a factor or factors capable of suppressing the proliferative responses of allogeneic and xenogeneic lymphoid cells stimulated with PHA, PWM, Con-A and allogeneic lymphocytes. Intravenous injection of the liver extract is capable of modifying significantly the skin allograft rejection reaction in normal adult outbred rabbits. Work is now in progress to isolate this factor and to determine its composition.

Animals↗
PubMed1995

Enzymatic release of 5-formyluracil by mammalian liver extracts from DNA irradiated with ionizing radiation.

To identify a repair enzyme for 5-formyluracil (5-FU) caused by ionizing radiation in DNA, we used a radiolabelled product-release assay for this thymine-damaged substrate. Double-stranded poly(dA-dT)-poly(dA-dT) was radiolabelled by nick translation with [2-14C]-thymidine triphosphate. The DNA was irradiated with X-rays and incubated with cell extract from mouse liver. Radiolabelled products released from the irradiated DNA into an ethanol-soluble fraction were analysed by reversed-phase hplc. Released 5-FU was detected as a free base during reaction with the cell extract. 5-Formyl-2'-deoxyuridine was not detected in the ethanol supernatant. Boiling the extract at 97 degrees C for 15 min completely abolished its ability to release 5-FU. Similar enzymatic activity was observed with rat liver extract. These results demonstrated that mammalian cells have enzymatic activity to release 5-FU from DNA.

Animals↗
PubMed1995

Analysis of tilmicosin in swine liver extracts by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

Tilmicosin is a semisynthetic macrolide antibiotic used in the treatment of respiratory disease in cattle and swine. The technique of liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) was employed in an on-line capacity for the analysis of tilmicosin in extracts from spiked swine liver. Increasing the potential in the cone/skimmer region of the ion source resulted in an increased abundance of unique structurally indicating fragment ions of tilmicosin. Three ions, [M+H]+ and two diagnostic fragment ions were chosen for confirmation of the presence of tilmicosin in swine liver tissue extracts using the mass spectrometer in selected-ion monitoring mode. The ion abundance ratios arising from any given combination of ions in data acquired from extracts of swine liver tissue spiked with tilmicosin at 5 and 10 ppm were within +/- 10% of the corresponding mean standard abundance ratio, and duplicate sample analyses exhibited < 10% relative standard deviation. These results suggest the potential for the application of LC/APCI-MS as a confirmatory technique for tilmicosin in swine liver.

Animals↗
PubMed1978

[Cytological and cytochemical effects of a liver extract from an adult rat on chick embryo hepatocytes and fibroblasts cultivated in vitro].

The effects of an extract from adult liver on chick embryo hepatocytes and fibroblasts cultivated in vitro are studied with cytological and quantitative cytochemical methods. This substance inhibits the multiplication of hepatocytes adn prevents these cells from entering into the S phase of the cycle. No effect is observed on the chick embryo fibroblasts. Not any morphological alterations are observed in the two cell types.

Animals↗
PubMed1978

Hepatic activity in the generation of somatomedins: effects of administration of a liver extract.

The problem of the generation of growth factors (somatomedins) (SM) is at present a matter of investigation. The liver has been proposed as the primary site of production of SM. In order to verify this hypothesis, SM activity has been assayed in patients with impairment of liver function. The subjects have been divided into three groups according to the severity of the hepatic damage, assessed with conventional diagnostic tests. In every group, somatomedin A (ASM) has been assayed by means of a biological procedure, in basal conditions and after treatment with a liver extract. The results show that the ASM activity is reduced in proportion to the degree of hepatic damage. The administration of liver extract restores the production of the ASM in the first two groups of patients, i.e. in those with mild and moderate hepatic involvement.

Humans↗
PubMed1975

Does phospholipase C stimulate thymide kinase activity of rat liver extracts prepared after partial hepatectomy.

Our purpose was to determine whether phospholipase C stimulated thymidine kinase activity of regenerating rat liver. We determined effects of phospholipase C upon TMP formation by rat liver extracts prepared at 0, 12, 24, 36 and 48 hr following partial hepatectomy. Data were obtained which supported these conclusions: (a) Commercial preparations of phospholipase C contained nucleoside phosphotransferase activity; (b) phospholipase C exerted no appreciable stimulatory influence upon thymidine kinase activity of regenerating rat liver; and (c), apparent stimulation of thymidine kinase was associated with linked activities of two enzymes, viz., liver extract-ATPase activity and nucleoside phosphotransferase activity.

Adenosine Monophosphate↗
PubMed1981

Stimulation of transfer of methyl groups from O6-methylguanine in DNA to protein by rat liver extracts in response to hepatotoxins.

An enzymatic activity present in rat liver extracts catalyzes the transfer of methyl groups from O6-methylguanine in DNA to protein. This activity was stimulated by treatment of rats with thioacetamide, carbon tetrachloride, 1,2-dimethylhydrazine, diethylnitrosamine, dimethylnitrosamine and by partial hepatectomy but not by treatment with N-methyl-N-nitrosourea or streptozotocin. These results suggest that an enhancement of this activity accompanies the increase in cell division brought about by these agents and is not necessarily a specific response to the presence of alkylated bases in DNA.

Animals↗
PubMed1982

Spontaneous activation of phenylalanine hydroxylase in rat liver extracts.

A wide variety of modifications of rat liver phenylalanine hydroxylase, such as limited proteolysis and phosphorylation, leads to a selective increase in the tetrahydrobiopterin-dependent hydroxylase activity without affecting the 6-methyltetrahydropterin or the 6,7-dimethyltetrahydropterin-dependent activity. The ratio of hydroxylase activity in the presence of tetrahydrobiopterin and one of these synthetic pterins, therefore, can serve as an indicator of the state of activation of the enzyme. Comparisons of this ratio for the crude and the pure liver enzyme, indicated that the purified enzyme has undergone activation. We have studied this activation under controlled conditions and have found that it is a Mn2+-sensitive process that occurs in liver extracts that have been freed of small molecules. The activation appears to be different from any of those that have been described previously.

Animals↗