Search

We have routinely used a [3H]-uridine microplate assay for assessing chemosensitivity. A colorimetric assay with the advantages of safety, cost and simplicity has previously been described and relies on the ability of living cells to reduce a soluble tetrazolium salt, 3-4,5-dimethylthiazol-2,5-diphenyl-tetrazolium bromide (MMT), into an insoluble formazan precipitate. We compared the chemosensitivity of 14 human tumour cell lines of colonic, lung and cervical carcinoma origin to doxorubicin, vindesine or vindesine immunoconjugates in both the [3H]-uridine assay and a modified MTT assay to evaluate whether we could change to the non-radiolabelled method. Correlation between the concentration of drug causing 50% inhibition of cell growth (IC50) for these agents between the two assays was very poor. However, taking account of recent reports in the literature, we modified the MTT assay by removing serum-containing medium and using dimethyl sulphoxide to solubilise the formazan precipitate. This considerably improved the correlation between the assays for doxorubicin (r = 0.871; P = 0.001) and vindesine (r = 0.981; P less than 0.001). Our data indicates that the MTT assay can be used to replace the [3H]-uridine assay for chemosensitivity screening, but further modifications are necessary to improve the sensitivity and decrease the problem of cell loss after washing, which was noted with some adherent cell lines.

We have studied the interactions of liposomes with human skin fibroblasts and mouse P815Y mastocytoma cells in culture, and the perfused rat liver, with the following findings. 1. In all the systems studied serum was found to cause an increase in the uptake of a [14C]cholesterol label into cells from anionic and neutral liposomes and a decrease in the uptake of the label from cationic liposomes. 2. Evidence suggests that albumin enhances the exchange/transfer of [14C]-cholesterol between liposomes and cultured cells. 3. With [14C]cholesterol in the liposome bilayer and [3H]methotrexate entrapped in the aqueous spaces of the liposome, the alpha- and beta-globulin fractions of serum decreased the transfer of both labels from cationic liposomes into cultured cells and the perfused rat liver. The beta-globulin fraction caused increased leakage of methotrexate from fluid liposomes of all charges. 4. The alpha- and beta-globulin fractions of serum appear to enhance the uptake of anionic liposomes into the perfused rat liver.

The relationships between chronological age, year of measurement, cohort membership, education, and perception of horizontal peerships versus vertical different status associations are explored through a sample of 1,428 respondents randomly selected from two larger representative national samples of American men and women utilized in a 1957 study and in a replication of that study in 1976. Data are based upon a thematic apperception procedure in which stories projected by respondents are coded for perceptions of peerships and of status differences. Significant age changes in interpersonal preference are observed for both sexes; there is no evidence of cohort changes or interactive effects with year. Contributions are made to research involving adult peer relations as well as to theories concerned with role discontinuity and ego changes in adulthood.

The possible in vivo distribution of liposomes after they have been directly labeled with Tc-99m has been studied in rats bearing the Walker 256 carcinoma. The importance of lipid composition, charge, and size of liposome were studied with respect to possible tumor-localizing properties. Tumor uptake was best with small, fluid-membrane, negatively charged liposomes, as indicated by the distribution of the Tc-99m label. The uptake was visualized on scintigrams.

Liposomes are bilayered phospholipid vesicles that have been proposed as vehicles for the selective delivery of cytotoxic drugs into malignant cells. In vitro and in vivo experiments have indicated that the activity of a range of drugs or their active metabolites may be enhanced by encapsulation in liposomes, particularly when used against drug-resistant tumours. Moreover, liposomal entrapment certainly has a marked effect on the tissue distribution and rates of clearance of cytotoxic drugs, and also appears to reduce their toxicity in most cases. However, in both animal and patient studies, the major sites of uptake following IV administration consistently appear as the liver and spleen. Preferential tumour uptake has therefore not yet been achieved, althrough a degree of localization of liposomal labels can be demonstrated in the vicinity of experimental animal tumours in certain circumstances. Liposomes may have a future role in cancer chemotherapy, but much laboratory work remains to be done before clinical application can be considered.

Patients complaining of reduced acuity in the absence of a clearcut diagnosis present a challenge to the eye care practitioner. It is important to differentiate retinal disease from optic nerve disease as the etiology of the decrease in vision. This differentiation can have significant ramifications and must be determined for patient welfare and management. Several procedures may be used in making the differential diagnosis of macular or retinal from optic nerve disease. Some of these procedures are easy to perform and include Amsler grid, color vision testing, pupillary reflexes, light-brightness comparison, and macular dazzle. Other procedures require a greater degree of sophistication and include fluorescein angiography, the Visual Evoked Potential (VEP) and simultaneous VEPs and ERGs (Electroretinograms). The clinician should be aware of all of these procedures and how each may be useful in this differential diagnosis.

A TLX-5 mouse lymphoma which was resistant to 1-β-D-arabinofuranosyl cytosine (AraC) was used in vivo to study the possibility of using liposomes as drug-delivery vehicles in order to overcome drug resistance.The effects of free drugs (AraC, AraCTP and methotrexate) and the liposomally associated drugs on the survival time of tumour-bearing mice were determined.As a more sensitive measure of cell survival, (125)IUdR was incorporated into the DNA of the ascites TLX-5 cells before i.p. injection. Cell survival and the cytotoxic effects of the drugs on the tumour cells were determined by using a double-headed gamma counter to measure the retention of the (125)I label.Both AraC and AraCTP, either as the free drugs or liposomally associated, had no effects on the tumour. Due to the lack of response of tumour cells to these drugs, further studies were initiated with free and liposomally associated methotrexate (MTX), a drug to which the cells were known to be sensitive. It was found that the liposomally associated MTX, at a 5-10-fold lower dose than the free drug, was (a) more effective in prolonging the survival of tumour-bearing mice and (b) as effective as the free drug in killing tumour cells (as measured by the (125)I retention).In vivo MTX was more effective in the liposomally associated form, whereas liposomally entrapped AraC and AraCTP were ineffective. It is proposed that in vivo liposomally associated drugs may be acting not by actively localizing in the tumour cells, but by the liposomes providing a slow-release drug depot, improving the pharmacokinetic properties of MTX.

48 hours after oesophagoscopy and injection sclerotherapy of oesophageal varices under general anaesthesia, 11 studies of 6 children with cystic fibrosis and portal hypertension showed a significant deterioration in 4 tests of lung function. The largest falls were seen in Forced Expiration Volume in one second (p less than 0.01) and Forced Expiratory Flow between 25% and 75% of Vital Capacity (p less than 0.02). In 14 studies of 10 children with portal hypertension from other causes a significant fall occurred only in Peak Expiratory Flow Rate (p less than 0.01). The slight falls in Forced Expiratory Volume in one second and Forced Expiratory Flow between 25% and 75% of vital capacity were significantly smaller than those observed in the patients with cystic fibrosis (p less than 0.05; p less than 0.01).

The cytogenetic effects of methyl acetimidate (MAI), a lysine-specific protein crosslinking reagent, were investigated using human peripheral lymphocytes in culture. Lymphocytes were treated with the chemical either prior to PHA exposure or 2-3 days following mitogenic stimulation and assessed for perturbations in cellular proliferation and induction of SCEs. Severe reductions in the mitotic index (MI) and pronounced decreases in the proportion of metaphases proceeding beyond M(1) were observed following G0 exposure to MAI concentrations of as low as 2 mM; with complete suppression of mitotic activity in all cultures exposed to levels of 3 mM MAI or greater. Concentrations resulting in severe depression in MI caused only moderate increases in SCEs. Cells exposed to less than 10 mM MAI during the late S-G2 stages of the cell cycle and harvested at the first metaphase following treatment exhibited profound mitotic delay, impaired prophase to metaphase transitions and abnormal mitotic configurations. These findings demonstrate that protein-specific crosslinking agents may induce a wide spectrum of adverse cytogenetic outcomes in both cycling and noncycling lymphocytes.

This study has shown that while some liposomes are highly toxic to the central nervous system, others, of different composition, are tolerated well in the dosage used (0.02-0.05 ml = 4-12 mg of lipid/inoculum). Those composed of lecithin-cholesterol-dicetyl phosphate or lecithin-cholesterol-stearylamine produced generalised epileptic seizures and some deaths due to respiratory failure immediately after injection,and a subsequent widespread tissue necrosis. However liposomes composed of lecithin-cholesterol-phosphatidic acid, or dipalmitoyl lecithin only, produced minimal morphological changes and by the sixth day post-injection the pathology was limited to the mechanical trauma caused by the injection. It is concluded that liposomes of appropriate composition may be sufficiently benign to use as carriers of therapeutic agents into the CNS.