Biomedical subjects
Publications and source records attributed to H Garcia.
Malignant tumours of the nasal cavity were induced in 19 of 56 (34%) female MRC-Wistar rats by 1-nitrosopiperazine administered orally for life. These tumours were of neurogenic origin, according to classical histologic criteria.
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Groups of male MRC Wistar rats were treated for 2 years either with morpholine (10 g/kg food) together with sodium nitrite (3 g/l drinking water) or with N-nitrosomorpholine (NM, 0.15g/l drinking water). In both cases, a group of rats was given sodium ascorbate (22.7 g/kg food) in addition to these treatments. When ascorbate was present, the liver tumors induced by morpholine and nitrite showed a 1.7-fold longer induction period, a slightly lower incidence, and an absence of metastases in the lungs, indicating that ascorbate had inhibited the in vivo formation of NM. Ascorbate did not affect liver tumor induction by the performed NM. The group treated with morpholine, nitrite, and ascorbate had a 54% incidence of forestomach tumors, including an 18% incidence of squamous cell carcinomas, possibly because ascorbate promoted NM action in this organ.
We tested fresh amelanotic and dry amelanotic melanoma tissue, gelatin, embryo and adult connective tissue, fresh and dry liver, fibrinogen, fibrin, pouch membrane, starch, dry hamster embryo and placental tissue, and glycogen in the transparent cheek pouch chamber of the Syrian hamster to explore the specificity of tumor angiogenesis and the mechanism that may selectively inhibit proliferation of blood vessels in the pouch membrane. Differences between the proliferations induced by tumor and normal tissues, various proteins, and polysaccharides were qualitative as well as quantitative. The glucocorticoid 6 alpha-methylprednisolone (MPS) decreased and sometimes totally inhibited the vascularization phenomenon. Dry tumor tissue induced capillary proliferation in seven of eight chambers 3 days after surgery; two of seven chambers of MPS-treated animals showed a reaction 10 days after the operation. MPS suppressed (in some cases only partially) capillary proliferation in chambers with implants of adult connective tissue, fresh liver, starch, or glycogen.
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3-Methylcholanthrene (MC) in chloroform and trifluoroacetic acid-d1 yielded 3-methylcholanthrene-d4 (MC-d4), a compound selectively deuterated at the 1-, 5-, and 6-carbon atoms. In turn, the protodedeuteration of the labeled hydrocarbon at the 6-carbon atom led to 3-methylcholanthrene-d3 (MC-d3). A comparative test for carcinogenicity between MC and MC-d3 by repeated skin painting on female Swiss mice showed a significantly lower tumorigenic activity of the latter. The result implies that the 1-carbon atom of the hydrocarbon is a critical binding-site to cellular targets in the tumor-initiating process.
A new method for studying liver regeneration has been introduced. In the isolated perfused liver partial hepatectomy has been performed and -3H-thymidine incorporation into DNA was observed. The short term incorporation observed in vitro was comparable to that observed in vivo under similar conditions. The results suggest that similar regenerative mechanisms are operating in vivo and in vitro, and that the liver is at least one source of the regenerating stimuli.
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