PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “NEOPLASMS, EXPERIMENTAL”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1978

[Thrombocytic reactions in experimentally induced neoplasms (author's transl)].

Strain XVII mice with Graffi virus induced leukemia of various hematological types showed a pronounced thrombocytopenia which was severe in erythroblastic leukemia and weaker in lymphatic ones. The thrombocytic reactions shortly following Friend and Rauscher virus applications and occurred 3 weeks after birth in AKR mice are not found in Graffi virus system. A significant preleukemic thrombocytopenia did appear only 8 weeks after Graffi virus infection. The origin of both the preleukemic and the secondary thrombocytic reactions are discussed. (XVII X AKR) F1 hybrids, neonatally treated with N-nitroso-N-methylurea (NMU), resulted also in a decline in the number of thrombocytes after manifestation of leukemia. In contrast to the expection following NMU treatment a preleukemic thrombocytopenia appeared as in viral leukemogenesis too. The possibility of a co-operation of oncogenic viruses in chemical carcinogenesis is considered.

Animals↗
PubMed1978

Islet cells as a component of pancreatic ductal neoplasms. I. Experimental study: ductular cells, including islet cell precursors, as primary progenitor cells of tumors.

The ductular complex of the Syrian hamster pancreas represents a system of conduit which encompasses intercalated (intralobular), periinsular, and intrainsular ductules. The intercalated (intralobular) ductules comprise centroacinar and intercalated cells. A meshwork of small ductules (invisible by usual histologic procedures) surrounds islets (periinsular ductules) and extends in the form of often ramified tiny channels within the islet (intrainsular ductules). Although the function of the latter ductules is obscure, their cells seem to make up one of the undifferentiated cellular units of the pancreas, and as such are also the progenitors of beta-cells of the islets (islet cell precursor = IP). Systematic histologic examination of the pancreas in this species treated with pancreatic carcinogen N-nitrosobis(2-oxopropyl)amine indicated that ductular cells, especially those of periinsular and intrainsular origin, are the most responsive to this carcinogen. The neoplastic process was initiated with hyperplasia of intercalated (intralobular) ductular and interlobular ductal cells associated with newly formed islets (nesidioblastosis). This process was followed by excess formation of mature but especially of immature islet cells and their precursors (IP) in the islet periphery, as well as with the appearance, distention, and multiplication of periinsular and particularly of intrainsular ductules. The hyperplasia, metaplasia, and malignant alteration of these periinsular and intrainsular ductules (including IP) and, to a lesser degree, of intercalated ductules indicated their histogenetic relationship and their potency for reproducing embryonic tissue on carcinogenic stimulus. The similarity of some induced lesions to diabetes has been emphasized.

Animals↗
PubMed1982

The oncostatic effect of methyl-CCNU on various experimental lymphoreticular neoplasms.

Studies on the chemotherapeutic potential of methyl-CCNU on experimental leukemias were undertaken. A number of murine transplantable in vivo lines (chemical carcinogen-induced T and B leukemias; radiation- and viral-induced T leukemias of C57BL/6, C3H/eb and SJL/J origin; radiation-induced myeloid leukemias and spontaneous reticulum cell neoplasms of SJL/J mine) were used in these studies. The optimal dose of methyl-CCNU and optimal timing of administration were extensively investigated on two sample lines of T cell leukemias of C57BL/6 mice. Leukemic cell eradication could be achieved in almost all of the different leukemias treated, irrespective of whether induction was brought about by chemical or physical means or due to a viral leukemogenic agent. Studies undertaken to elucidate the effect of methyl-CCNU on the establishment of preleukemic cells following induction of leukemia by the radiation leukemia virus (RadLV) or by total body irradiation, indicated the oncostatic effect of methyl-CCNU on early preleukemic cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Effects of intestinal bacteria on the development of colonic neoplasm: an experimental study.

Effects of intestinal microflora on the development of colonic neoplasm induced by 1,2-dimethylhydrazine (DMH) were observed using conventionalized and gnotobiotic mouse models. The incidence of colonic adenoma in germ-free mice (IQI/jic) (GF), mice conventionalized after DMH injection (Cvz-post-DMH) and conventionalized mice (Cvz, conventionalized before DMH injection) was 74%, 69% and 58%, respectively. The mean number of adenomas per mouse in the three groups was 2.6, 2.0 and 1.4, respectively. However, the adenoma in Cvz was larger than in GF. The incidence of adenoma in mice mono-associated with Mitsuokella multiacida, Clostridium butyricum, Bifidobacterium longum, Clostridium paraputrificum, Escherichia coli and Lactobacillus acidophilus was 68%, 68%, 63%, 50%, 50% and 30%, respectively. However, the adenoma in the Cl. paraputrificum group and the Cl. butyricum group was larger than in GF. Faecal pH in Cvz and the L. acidophilus group was significantly lower than in GF. The deconjugation rate of faecal bile acids in Cvz, the Cl. paraputrificum group and the Cl. butyricum group was significantly higher than in GF. These findings suggested two different effects of microflora on the development of DMH-induced adenoma: either an inhibition of the incidence of adenoma or a promotion of tumour growth. Effects of L. acidophilus may be mediated by faecal pH and effects of Cl. paraputrificum and Cl. butyricum by deconjugated bile acids.

1,2-Dimethylhydrazine↗
PubMed2000

Critical windows of exposure for children's health: cancer in human epidemiological studies and neoplasms in experimental animal models.

In humans, cancer may be caused by genetics and environmental exposures; however, in the majority of instances the identification of the critical time window of exposure is problematic. The evidence for exposures occurring during the preconceptional period that have an association with childhood or adulthood cancers is equivocal. Agents definitely related to cancer in children, and adulthood if exposure occurs in utero, include: maternal exposure to ionizing radiation during pregnancy and childhood leukemia and certain other cancers, and maternal use of diethylstilbestrol during pregnancy and clear-cell adenocarcinoma of the vagina of their daughters. The list of environmental exposures that occur during the perinatal/postnatal period with potential to increase the risk of cancer is lengthening, but evidence available to date is inconsistent and inconclusive. In animal models, preconceptional carcinogenesis has been demonstrated for a variety of types of radiation and chemicals, with demonstrated sensitivity for all stages from fetal gonocytes to postmeiotic germ cells. Transplacental and neonatal carcinogenesis show marked ontogenetic stage specificity in some cases. Mechanistic factors include the number of cells at risk, the rate of cell division, the development of differentiated characteristics including the ability to activate and detoxify carcinogens, the presence of stem cells, and possibly others. Usefulness for human risk estimation would be strengthened by the study of these factors in more than one species, and by a focus on specific human risk issues.

Adult↗
PubMedDate not supplied

Retrovirus-mediated gene therapy of experimental brain neoplasms using the herpes simplex virus-thymidine kinase/ganciclovir paradigm.

Recent results in experimental brain tumors indicate that transfer of sensitizing genes to tumor cells in vivo with subsequent drug treatment can reduce tumor masses and prolong the survival of rodents. In the present study, the 9L rat gliosarcoma model was used to evaluate the therapeutic effectiveness of the herpes simplex virus-thymidine kinase (HSV-tk) gene, delivered by a retrovirus vector, against tumor cells in the rat brain after systemic application of the nucleoside analogue ganciclovir (GCV). The HSV-tk gene was inserted into a retroviral vector (pMFG), which was produced using the amphotropic packaging cell line CRIP-MFG-S-HSV-TK. Packaging cells were implanted into established 9L tumors in the brains of syngeneic rats to effect gene delivery to tumor cells, followed by intraperitoneal GCV injections. Treated animals survived significantly longer (more than twice as long) than did the control groups. Brains from GCV-treated and nontreated animals were examined immunohistochemically at different time intervals after grafting of CRIP-MFG-S-HSV-TK cells and GCV treatment. Tumors in GCV-treated animals were significantly smaller as compared with nontreated animals at all time points. Sections stained immunohistochemically for HSV-TK confirmed gene transfer to tumor cells, which could be distinguished from packaging cells by different morphology and immunohistochemical staining for the retroviral envelope protein gp70. Approximately 45% of the cells in tumors implanted with CRIP-MFG-S-HSV-TK cells, but not treated with GCV, showed immunocytochemical staining for HSV-TK, demonstrating a high-efficiency of retrovirus-mediated gene transfer. Tumors in rats treated with packaging cells and GCV showed only 9% HSV-TK-positive cells after treatment, indicating that most cells expressing the HSV-tk gene were killed. The success of this therapeutic modality in experimental animals depends in large parts on the high efficiency of gene delivery and on the immune response against tumor cells.

Animals↗
PubMed1995

Selective uptake of viral and monocrystalline particles delivered intra-arterially to experimental brain neoplasms.

In this study we investigated the intra-arterial delivery of viral and nonviral particles to experimental brain tumors. A herpes simplex virus (HSV) vector and monocrystalline iron oxide nanoparticles (MION) were injected into the internal carotid artery of Fisher 344 rats harboring intracerebral 9L gliosarcomas, using bradykinin to disrupt the blood-tumor barrier. Brain and internal organs were stained both for virus-mediated gene expression and for iron. Quantitative comparisons of gene expression and MION uptake with and without blood-tumor barrier disruption were performed in the center and at the periphery of the tumor mass, as well as in normal brain. In addition, MION distribution was traced in vivo by MR imaging. Delivery of HSV into 9L gliosarcoma cells was greatly enhanced by intra-carotid bradykinin infusion. Virus-mediated expression of the HSV-thymidine kinase (TK) and beta-galactosidase gene products was highest at the tumor periphery as compared to the tumor center. Selective HSV infection of multiple tumor foci was achieved in both hemispheres without affecting normal brain. MION uptake was high at the tumor periphery even without blood-tumor barrier disruption. Bradykinin increased MION uptake predominantly in the center of the tumor with virtually no effect at the periphery. These findings show that selective blood-tumor barrier disruption by bradykinin can be used to enhance HSV-mediated gene delivery to tumor cells in the periphery of brain tumors. A crucial aspect in the treatment of malignant brain tumors is the eradication of tumor cells infiltrating the brain; bradykinin may facilitate access of vectors to these areas by selective disruption of their neovasculature.

Animals↗