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Biomedical subjects

I R Hart

Publications and source records attributed to I R Hart.

174 records · Page 10Linked to original sources
PubMed1978

An in vitro quantitative assay for tumor cell invasion.

An in vitro quantitative assay of tumor cell invasion is described. The assay measures the rate at which [125I]iododeoxyuridine-labeled tumor cells migrate through the chorioallantoic membrane of developing chicken embryos. Invasion chambers were prepared from amber latex cylinders, chorioallantoic membrane, and thread ligatures. The chambers were placed in glass vials to rest on discs of photographic sponge immersed in tissue culture medium. Labeled tumor cells were added to the chamber, and the vial was incubated at 37 degrees. At various time points individual chambers were monitored to determine the number of viable, labeled cells that had passed through the membrane and were present in the medium, on the glass vial, or in the sponge. The application of the assay may be of use in delineating the mechanisms of tumor cell invasion.

Allantois↗
PubMed1977

Thyrotoxicosis detected in a mass-screening program for neonatal hypothyroidism: demonstration of placental transfer of an immunoglobulin with marked lipolytic activity.

A female infant born to a mother with active Graves disease and a strongly positive LATS developed neonatal thyrotoxicosis. The diagnosis was confirmed rapidly by the markedly elevated filter paper spot T4 (5.45 ng/40 microliter) taken on the fifth day of life as part of the Quebec Screening Program for Neonatal Hypothyroidism. Although the infant's serum was negative for LATS, it reacted strongly (as did the maternal serum) in the lipolytic assay for LATS. This case illustrates the ability of screening programs for neonatal hypothyroidism to detect cases of neonatal thyrotoxicosis and supports the hypothesis that this condition is secondary to the placental transfer of a thyroid-stimulating immunoglobulin.

Female↗
PubMed1977

The presence and distribution of beta-galactosidases in the small intestinal mucosa of the neonatal dog.

The beta-galactosidase activity of the small intestinal mucosa of the neonatal dog has been studied over the pH range 3-0 - 5-8 using different substrates and in the presence and absence of p-chloromercuribenzoate. Partial separation of two beta-galactosidases has been achieved by gel filtration. The results suggest that three beta-galactosidases, comparable with those in other mammals, exist in canine small intestinal mucosa.

Animals↗
PubMedDate not supplied

Enhanced experimental metastatic capacity of a murine melanoma following pre-treatment with anticancer drugs.

The effect of in vitro pretreatment of B16 murine melanoma cells with various cancer chemotherapeutic agents on their subsequent experimental metastatic capacity has been examined. Methotrexate, cytosine arabinoside, 5-azacytidine and aphidicolin all produced significant increases in the number of lung nodules formed following the i.v. injection of tumour cells. This effect was not seen with melphalan or 5-fluorouracil. Since the doses of melphalan and 5-fluorouracil used produced similar levels of cell kill to cytosine arabinoside and aphidicolin it appears that a cytotoxic effect was not sufficient to produce increased lung nodule formation. Analysis of the perturbations in the cell cycle induced by the drugs did not reveal any consistent differences between those drugs which enhanced experimental metastasis and those which did not. The precise mechanisms underlying this phenomenon remain to be elucidated but the results are consistent with the possibility that anticancer agents may play a role in assisting tumour progression.

Animals↗
PubMedDate not supplied

Changes in protein expression during melanoma differentiation determined by computer analysis of 2-D gels.

Cytodifferentiation in many melanocytic cells is regulated through the adenylate cyclase-cAMP pathway. To analyse the molecular changes associated with this process we have compared the proteins produced by two closely related cell lines which, though derived from a single cell line, respond very differently to modulation of this signalling pathway. The human melanoma cell line DX3 shows little change in in vitro characteristics following treatment with cAMP elevating agents; in contrast the more malignant DX3 LT5.1 variant, derived from the DX3 parental line, shows pronounced dendrification, decreased proliferation and a reduction in metastatic capacity after similar treatment. The two cell lines were treated with phosphodiesterase inhibitors for 5 days and then processed for two-dimensional gel characterization using an immobilized pH gradient for the IEF dimension. Proteins were detected by silver staining the gels and protein intensities were digitized using a laser densitometer. Two-dimensional gel patterns were edited, matched and a melanoma protein database of 637 spots constructed using PDQUEST software on an Orion 1/05 computer. Eleven proteins were lost and four new proteins were detected in both cell lines following treatment. Twenty-two proteins were present in DX3 LT5.1 after treatment but not in untreated lines or treated DX3. These differentially expressed proteins may be associated with the observed changes in differentiation patterns and metastasis. Our results illustrate the resolving power of this technique and suggest potential applications to the study of cellular differentiation.

Animals↗
PubMedDate not supplied

Different growth responses to agents which elevate cAMP in human melanoma cell lines of high and low experimental metastatic capacity.

Human melanoma variants of low and high experimental metastatic activity, which had been derived from the same parental line, showed markedly different growth responses to agents which elevated intracellular cAMP. The high metastatic line had a significant decrease in in vitro proliferation following treatment with cholera toxin (10(-9) M) and forskolin (100 microM), with both agents causing virtual cessation of cell growth after 3-5 days incubation. Pre-treatment with 10(-9) M cholera toxin reduced colony forming ability to 11-15 per cent of control values, saturation densities were decreased to 10-25 per cent of controls and these cytostatic responses were accompanied by changes in cellular morphology. Lung colonising capacity of this cell line after i.v. injection into athymic mice was reduced significantly by prior exposure to cholera toxin (a median of 2 lung nodules versus 26 lung nodules for untreated, control cells). In contrast, low metastatic cell lines showed no significant growth inhibition in the presence of these agents. Cholera toxin (10(-9) M) reduced colony forming ability of these cells to only 74 per cent of control values and there were no significant decreases in growth rate nor any morphological changes in response to either cholera toxin or forskolin. The variable response obtained in the cell lines appeared neither to be a consequence of variation in induced levels of intracellular cAMP nor in differences between the cell lines in response to the same agent; forskolin (100 microM) induced a maximal 25-fold elevation and cholera toxin (10(-9) M) a 2.5-fold elevation increase in cAMP. These data show that highly metastatic variants of a human melanoma cell line differ from their less metastatic counterparts in the way they respond to agents which elevate the second messenger molecule cAMP.

Animals↗
PubMedDate not supplied

Effects of biologically active tumour-promoting and non-promoting phorbol esters on in vitro growth of melanocytic cells.

Sapintoxin A (SAP A), a naturally occurring biologically active but non-promoting phorbol ester, acts as an effective in vitro mitogen for freshly derived human melanocytes. Seven days after addition of 50 nM SAP A there was a four to fivefold increase in melanocyte number over that observed in untreated control cultures comparable to that achieved with a 50 nM concentration of 12-0-tetradecanoylphorbol 13-acetate (TPA). The fluorescent stage 2 promoter sapintoxin D (SAP D) also supported the growth of these cells, with a 50 nM dose producing an increase in cell number comparable to that observed with 200 nM TPA. Similar results were obtained with an established, but non-tumorigenic, line of murine melanocytes. The same compounds exerted a potent anti-proliferative effect against transformed melanocyte lines of murine and human origin associated with morphological alterations and an increase in melanin production consistent with induced cytodifferentiation.

Cell Division↗