Tissue culture plastic adhesivity was precisely varied by applying different concentrations of poly(2-hydroxyethyl methacrylate). The extent of cell spreading was thus accurately controlled so that cells cultured on these substrata could be held at any one of a graded series of quantitated cell shapes. Cell shape was found to be tightly coupled to DNA synthesis and growth in nontransformed cells. These findings suggest a mechanism that is important in growth control of mammalian cells, and provide a more fundamental interpretation of such phenomena as density dependent inhibition of cell growth and anchorage dependence.

Role of cell shape in growth control

Glutamate is ubiquitously distributed in brain tissue, where it is present in a higher concentration than any other amino acid. During the last 50 years glutamate in brain has been the subject of numerous studies, and several different functions have been ascribed to it. Early studies by Krebs (1935) suggested that glutamate played a central metabolic role in brain. The complex compartmentation of glutamate metabolism in brain was first noted by Waelsch and coworkers (Berl et al., 1961). These studies were precipitated by the claim that glutamate improved mental behaviour and was beneficial in several neurological disorders including epilepsy and mental retardation. Other scientists pointed out its function in the detoxification of ammonia in brain (Weil-Malherbe, 1950). Glutamate is also an important building block in the synthesis of proteins and peptides, including glutathione (Meister, 1979). The toxic effect of administered glutamate and its analogues kainic acid, ibotenic acid, and N-methyl aspartic acid on CNS neurones has become a large and independent line of research (Lucas and Newhouse, 1957; Olney et al., 1974; Lund-Karlsen and Fonnum, 1976; Coyle, 1983). Attention has also been focused on the role of glutamate as a precursor for the inhibitory neurotransmitter y-aminobutyric acid (GABA) (Roberts and Frankel, 1950). Electrophysiological studies (Curtis and Watkins, 1961) focused early on the powerful and excitatory action of glutamate on spinal cord neurones. Since the action was widespread and effected by both the Dand Lforms, it was at first difficult to believe that glutamate could be a neurotransmitter. During the last 15 years, however, several studies have provided support for the concept that glutamate is a transmitter in brain (for review see Curtis and Johnston, 1974; Fonnum, 1978; 1981; Roberts et al., 1981; DiChiara and Gessa, 1981). Glutamate satisfies today to a large extent the four main criteria for classification as a neurotransmitter: (1) it is presynaptically localized in specific neurones; (2) it is specifically released by physiological stimuli in concentrations high enough to elicit postsynaptic response; (3) it demonstrates identity of action with the naturally occurring transmitter, including response to antagonists; and (4) mechanisms exist that will terminate transmitter action rapidly. The evidence for glutamate as a transmitter at the locust neuromuscular junction has recently been carefully evaluated by Usherwood (1981). In that case the identity of action of glutamate with the naturally occurring transmitter on the neuromuscular receptor, the release from nerve terminals, and its similarity to acetylcholine at the mammalian neuromuscular junction with regard to presynaptic pharmacology and denervation supersensitivity are compelling evidence for glutamate as a neurotransmitter. The main methods used to identify glutamergic pathways in brain will be critically reviewed and discussed. The effect of lesions on high-affinity uptake and release are particularly important, but immunohistochemical methods to study enzymes and glutamate itself are becoming more interesting. The release of glutamate has been demonstrated by several different procedures using both in vivo and in vitro preparations. The synthesis of large groups of specific agonists and antagonists has been important both for identification and characterization of the glutamate receptor by electrophysiological techniques and for the isolation of glutamate receptors. High and perhaps low-affinity uptake into nerve terminals and glial cells is important for the termination of transmitter action. Particular attention is given in this review to the complex compartmentation of glutamate synthesis and the possibility of identifying the transmitter pool of glutamate.

Glutamate: a neurotransmitter in mammalian brain.

Fluidity Parameters of Lipid Regions Determined by Fluorescence Polarization

Calcium regulation of growth and differentiation of mouse epidermal cells in culture

Metastases do not result from random survival of cells released from the primary tumour but from the selective growth of specialised subpopulations of highly metastatic cells endowed with specific properties that befit them to complete each step of the metastatic process.

/pdf/the-pathogenesis-of-cancer-metastasis-50jty52rxh.pdf

The pathogenesis of cancer metastasis

Transmembrane control of the receptors on normal and tumor cells: I. Cytoplasmic influence over cell surface components☆

Trans-membrane control of the receptors on normal and tumor cells. II. Surface changes associated with transformation and malignancy.

Two metastatic cell lines, mouse B16-Fl melanoma and human Hs939 melanoma, were examined for their abilities to adhere to confluent vascular endothelial cell monolayers and to the underlying endothelial extracellular matrix. Tumor cells attached slowly to the endothelial cell monolayers while they adhered rapidly to isolated extracellular matrix. When analyzed by poly-acrylamide gel electrophoresis in sodium dodecylsulfate solutions, the extracellular matrix was shown to be primarily composed of a protein of identical migration and molecular weight to fibronectin. Tumor-cell adhesion to fibronectin-coated polyvinyl surfaces mimicked the rapid rate of attachment of tumor cells to extracellular matrix, and tumor cells adherent to either extracellular matrix or fibronectin-coated polyvinyl dishes adopted an unusual, highly spread and flattened morphology with numerous small projections. These results suggest that fibronectin associated with the endothelial basement membrane may be, in part, responsible for establishing an adhesive gradient that could be important in malignant cell extravasation.

Metastatic tumor cells adhere preferentially to the extracellular matrix underlying vascular endothelial cells

ONE of the most clinically troublesome aspects of cancer is metastasis the spread of tumour cells from primary to distant multiple secondary sites1–3. Metastasis initially occurs through tissue invasion followed by transportation of tumour cells through the circulatory system lymphatics or coelomic cavities1,2. In blood-borne metastasis free tumour cells or cell aggregates are carried into various organs and tissues where they stop in the first capillary bed encountered; however most of these arrested tumour cells break loose recirculate and stop in other organs4,5. In many tumour systems the location and extent of established secondary tumour colonies are non-random suggesting that unique cell properties are important in tumour arrest and metastasis3,6. In support of this hypothesis Fidler7 was able to select from a murine B16 melanoma line variants that showed enhanced metastatic behaviour by repeated cycling of tumour cells from lung colonies to tissue culture administering the tumour cells intravenously on each cycle. We report here the organ adhesive specificity of four B16 variant cell lines selected for enhanced lung metastasis.

Organ specificity of blood-borne tumour metastasis determined by cell adhesion.

Animal tumor models for blood-borne metastasis have been developed by in vitro cloning or in vivo selection of malignant tumor cell populations to obtain organ-preferring variant tumor cell lines with altered arrest, survival, invasion, and growth properties. Selection and some tumor cell characteristics of lung-, brain-, and ovary-colonizing metastatic B16 melanoma, liver-colonizing RAW114 lymphosarcoma, and lung-colonizing MSV3T3 vasoformative sarcoma variant lines will be discussed along with additional data, suggesting that tumor cells of varying malignant potential preeexist in the unselected tumor population.

https://cancerres.aacrjournals.org/content/canres/38/11_Part_2/4105.full.pdf

Garth L. Nicolson

Papers

Transmembrane control of the receptors on normal and tumor cells: I. Cytoplasmic influence over cell surface components☆

Trans-membrane control of the receptors on normal and tumor cells. II. Surface changes associated with transformation and malignancy.

Metastatic tumor cells adhere preferentially to the extracellular matrix underlying vascular endothelial cells

Organ specificity of blood-borne tumour metastasis determined by cell adhesion.

Specificity of Arrest, Survival, and Growth of Selected Metastatic Variant Cell Lines