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Biomedical subjects

R A Caro

Publications and source records attributed to R A Caro.

At least 37 records · Page 2Linked to original sources
PubMed1990

A simplified competition data analysis for radioligand specific activity determination.

Non-linear regression and two-step linear fit methods were developed to determine the actual specific activity of 125I-ovine prolactin by radioreceptor self-displacement analysis. The experimental results obtained by the different methods are superposable. The non-linear regression method is considered to be the most adequate procedure to calculate the specific activity, but if its software is not available, the other described methods are also suitable.

Animals↗
PubMed1984

Further studies on the histamine metabolism in the M-2 adenocarcinoma.

Further studies of the histamine metabolism in the M-2 adenocarcinoma have shown that the tumor and the intestinal histidine decarboxylase should have similar conformations, since both enzymes exhibit superimposable curves of activity vs. pH as well as nearly identical 50% inhibitory concentrations for the specific inhibitor NSD-1015. It has also be found that the increase of the radioactivity uptake by the tumor nuclear fraction compared to the intestinal nuclear fraction after their incubation with 3H-histamine, may be due to qualitative differences between the nuclei, since endogenous contents of DNA and associated proteins were not significantly different. The specific binding of 3H-histamine to different purified DNAs demonstrated very dissimilar proportions of bound histamine, suggesting a possible interaction of histamine with DNA, similar to some of the proposed mechanisms for the modulation of the genomic expression of DNA by some polyamines.

Adenocarcinoma↗
PubMed1981

Abnormal histamine metabolism in a transplantable syngeneic spontaneous murine mammary adenocarcinoma.

Histamine metabolism of a transplantable syngeneic spontaneous murine mammary adenocarcinoma with a high degree of undifferentiation was studied. The endogenous histamine content is significantly higher than in normal intestine and lung. This is not due to an increase of the histamine biosynthetic capacity, which is lower than in the lung. The administration of histamine, 0.1 mg per kg body, for 7 days, decreased significantly the biosynthesis of histamine in the tumor, but not its endogenous histamine content; in the intestine and in the lung no significant modification of histamine biosynthesis was observed. It has also be shown that the proportion of radioactivity in the purified nuclear fraction of the tumor is significantly higher than in the intestine, after incubating either tissue with 3H-histamine. Since the mast-cell content of the tumor has been found to be low, our results should be considered as a specific alteration of the function of histamine in these tumor cells.

Adenocarcinoma↗
PubMed1978

Biosynthesis and subcellular localization of histamine in H-110 lymphoma.

The histidine decarboxylase activity has been studied in the H-110 Lymphoma implanted in Balb-c mice. The enzymatic activity has been determined using DL-Histidine 1-14C by measuring the I--14CO2 liberated during the incubation. It has been found that the histidine decarboxylase activity in the tumor is the highest of the studied tissues. The pretreatment for 5 days with two cytostatic drugs, cyclophosphamide and 5-fluoruracile, determined a decrease of the enzymatic activity in the tumor of 33 and 54 per cent, respectively. This effect has not been observed in the lung. The pretreatment of the animals during 10 days with 0.1 mg per kg body of histamine, which in other experimental tumors induces an increase of the endogenous content of histamine, produces a decrease of the tumoral histidine decarboxylase activity. The histamine-14C uptake was not modified by this pretreatment. The subcellular localization of the radioactivity after pretreatment with histamine-14C evidenced that the nuclear fraction of the tumor contained between 2 and 10 times the radioactivity of other tissues of the same animal.

Animals↗