Serological identification of viral and virus-related antigens on DBA/2 mouse leukemia lymphocytes

Characterization and pathogenic potential of a soil isolate and an ocular isolate of Acanthamoeba castellanii in relation to Acanthamoeba keratitis

Acanthamoeba castellanii, one isolate from the eye and one from the soil, were compared on the basis of: (a) pathogenic potential; (b) plasminogen activator activity; (c) chemotactic activity; (d) cytopathic effects; (e) collagenolytic activity; (f) binding ability to contact lenses; and (g) and binding ability to corneal buttons. The ocular isolate of A. castellanii was found to be pathogenic based on its ability to produce corneal infections in Chinese hamsters. By contrast, the soil isolate produced only mild lesions in a single Chinese hamster. Amoebae from the ocular isolate bound to corneal epithelium in greater numbers than the soil isolate counterparts. Moreover, ocular isolate organisms displayed plasminogen activator activity that was not detected in cultures from soil isolates of A. castellanii. Although neither the soil isolate nor the ocular isolate amoebae responded chemotactically to epithelial or stromal components, the ocular isolate displayed a curious and reproducible positive chemotactic response to endothelial extracts. Both A. castellanii isolates produced cytopathic effects on pig corneal epithelium, however the cytotoxicity from the ocular isolate was significantly greater than that of the soil isolate. The results indicate that the pathogenic potential of A. castellanii is correlated with the parasite's capacity to bind to corneal epithelium, respond chemotactically to corneal endothelial extracts, elaborate plasminogen activators, and produce cytopathic effects on corneal epithelium.

A mechanism for the loss of cytochrome P-450 in primary mouse hepatocytes

This study examined various biochemical parameters such as mitochondria and mitochondrial DNA (mtDNA), total heme and cyto P450 content in fresh hepatocytes and dedifferentiated hepatocytes. These parameters were chosen in order to understand the dramatic decrease in drug metabolism in cultured hepatocytes. The data in this study shows a temporal decrease in cytochrome P450, a total heme and also a decrease in mitochondria. Also, the ratio of mtDNA content to mitochondrial density was found to increase as hepatocytes underwent dedifferentiation. Stereological analysis of cell preparations provided a measure of mitochondrial density per cell area and mtDNA content was assessed by the use of a specific radiolabelled probe. This study demonstrates that a loss of the organelle which is partially responsible for synthesis of heme correlates with a decrease in cytochrome P450.

Decreased transforming growth factor-beta response and binding in insulin-independent teratoma-derived cell lines with increased tumorigenic properties

The mouse C3H teratoma-derived cell line 1246 is an adipogenic cell line which stringently requires insulin to proliferate and differentiate in defined medium. From this cell line an insulin-independent cell line called 1246-3A was isolated. It was found that, in contrast to 1246 cells, 1246-3A cells had lost the ability to differentiate and became tumorigenic when injected at a density of 10(6) cells/mouse into syngeneic host C3H mice. In addition, they produce in their culture medium transforming growth factor alpha- and beta-like polypeptides which stimulate their proliferation. Highly tumorigenic insulin-independent cell lines able to give rise to tumor when injected at a density of 10(4) cells/mouse were isolated by using an in vitro-in vivo shuttle technique. The highly tumorigenic cell lines have lost the response to TGF-beta 1. The binding of TGF-beta 1 to the nontumorigenic parent cell line or to cells displaying increased tumorigenic properties was investigated. The data presented here indicate that the increased tumorigenicity is accompanied by a progressive decrease of specific binding of TGF-beta 1 to the cells. However, the decreased number of cell surface TGF-beta 1 binding sites in the highly tumorigenic cells did not correlate with an increase in the secretion of TGF-beta protein by the tumorigenic cells, as all of TGF-beta produced by the cells was in a latent form. Affinity cross-linking experiments indicated that the 1246 cell line displayed several TGF-beta cross-linked molecular species (MW 140, 92, and 70 kDa). Increase of tumorigenicity was accompanied by a marked decrease in the intensity of the cross-linked bands, particularly of the 92 and 70 kDa species.

Regulated expression of cytochrome P-450scc (cholesterol-side-chain cleavage enzyme) in cultured cell lines detected by antibody against bacterially expressed human protein

The first step in the synthesis of steroids is catalysed by cytochrome P-450ssc (cholesterol-side-chain cleavage enzyme). We have investigated the synthesis of this enzyme in three cultured cell lines at the protein and hormone secretion levels. Hormone levels were measured by an enzyme immunoassay using a monoclonal antibody against progesterone. The protein level was detected using polyclonal antibodies directed against a P-450scc fusion protein overproduced in Escherichia coli. Utilizing a bacteriophage T7 promoter expression system, a large amount of human P-450scc fusion protein was produced and easily purified. P-450scc was synthesized in the mouse adrenal tumour cell line Y1 and human choriocarcinoma cell line JEG-3, but not in monkey kidney cell line COS-1. The production of P-450scc in Y1 and JEG-3 cells was stimulated by 8-bromo cyclic AMP, the effect of which was not observed until 6 h after induction and was more pronounced at 24 h. Y1 and JEG-3 cells exhibited a difference in progesterone secretion after induction.

Activated T cells express a novel gene on chromosome 8 that is closely related to the murine ecotropic retroviral receptor

A novel cDNA clone (20.5) which is differentially expressed between two closely related T-lymphoma cell clones was isolated by subtraction-enriched differential screening. SL12.4 cells, from which the cDNA was isolated, have characteristics of thymocytes at an intermediate stage in development. A sister cell clone derived from the same tumor, SL12.3, does not express this mRNA, has a distinct phenotype, and expresses fewer genes required for mature T-cell function. The cDNA sequence predicts a highly hydrophobic protein (approximately 49.5 kilodaltons) which contains seven putative membrane spanning domains. The gene was expressed on concanavalin A-activated T lymphocytes and was designated Tea (T-cell early activation gene). The Tea gene mapped to chromosome 8 and appeared to be conserved among mammalian and avian species. The Tea gene is distinct from, but bears extensive amino acid and DNA sequence similarity with, the murine ecotropic retroviral receptor which is encoded by the Rec-1 gene. Neither gene product displayed significant homology with other known transmembrane-spanning proteins. Thus, the Tea and Rec-1 genes establish a new family encoding multiple membrane-spanning proteins.

Activated T cells express a novel gene on chromosome 8 that is closely related to the murine ecotropic retroviral receptor

A novel cDNA clone (20.5) which is differentially expressed between two closely related T-lymphoma cell clones was isolated by subtraction-enriched differential screening. SL12.4 cells, from which the cDNA was isolated, have characteristics of thymocytes at an intermediate stage in development. A sister cell clone derived from the same tumor, SL12.3, does not express this mRNA, has a distinct phenotype, and expresses fewer genes required for mature T-cell function. The cDNA sequence predicts a highly hydrophobic protein (approximately 49.5 kilodaltons) which contains seven putative membrane spanning domains. The gene was expressed on concanavalin A-activated T lymphocytes and was designated Tea (T-cell early activation gene). The Tea gene mapped to chromosome 8 and appeared to be conserved among mammalian and avian species. The Tea gene is distinct from, but bears extensive amino acid and DNA sequence similarity with, the murine ecotropic retroviral receptor which is encoded by the Rec-1 gene. Neither gene product displayed significant homology with other known transmembrane-spanning proteins. Thus, the Tea and Rec-1 genes establish a new family encoding multiple membrane-spanning proteins.

Gonadotropes in a novel rat pituitary tumor cell line, RC-4B/C. Establishment and partial characterization of the cell line

An epithelial cell line (RC-4B/C) was established from a pituitary adenoma obtained from a 3-yr-old (ACI/fMai X F344/fMai)F1 male rat. Before Year 5 in vitro, RC-4B/C cells could not be viably recovered from cryogenic storage. Recovery of viable cells from cryogenic storage in Year 5 was associated with a more transformed phenotype, including the appearance of endogenous C-type rat retroviral particles. The ultrastructural appearance of the cells was similar to that of differentiated anterior pituitary cells; the cultured cells contained numerous, electron dense, secretory granules, Golgi complexes, and extended arrays of rough endoplasmic reticulum. Immunocytochemical study showed that all cell types present in the rat anterior pituitary gland were present in the cell line. The percentage of luteinizing hormone beta (LH beta) cells in the cell line was higher (19.9%) and that of growth hormone cells was lower (12.2%) than in normal male rat pituitary, whereas the cell line contained a comparable percentage of follicle stimulating hormone beta (FSH beta), prolactin (PRL), ACTH, and thyrotropin beta cells. Radioimmunoassay data demonstrated the PRL content of the cells was comparable to that of normal male rat pituitary gland, whereas the content of LH and FSH was 70- and 800-fold lower, respectively. Assay of specific receptor sites for gonadotropin releasing hormone (GnRH) using Scatchard plots of the data established the RC-4B/C cells contained GnRH receptor sites of the same affinity as in the pituitary gland, but of twofold lower capacity. These data suggest the RC-4B/C cell line warrants further study as a model for the induction and maintenance of the gonadotropic function of the pituitary gland.

Quantitative determination of lymphocyte ACTH1-39

A method was developed for quantitative measurement of ACTH1-39, produced by human lymphocytes. It was shown that pH adjustment to 2 was essential for processing of the precursor molecule proopiomelanocortin (POMC). Linearity between time of incubation and ACTH production was shown. The existence of specific endopeptidases in lymphocytes for processing of the POMC molecule remains doubtful.

Frontiers in mammalian cell culture

For the past 60 years, fundamental discoveries in eukaryotic biology using mammalian cell cultures have been significant but modest relative to the enormous potential. Combined with advances in technologies of cell and molecular biology, mammalian cell culture technology is becoming a major, if not essential tool, for fundamental discovery in eukaryotic biology. Reconstruction of the milieu for cells has progressed from simple salt solutions supporting brief survival of tissues outside the body to synthesis of the complete set of structurally defined nutrients, hormones and elements of the extracellular matrix needed to reconstruct complex tissues from cells. The isolation of specific cell types in completely defined environments reveals the true complexity of the mammalian cell and its environment as a dynamic interactive physiological unit. Cell cultures provide the tool for detection and dissection of the mechanism of action of cellular regulators and the genes that determine individual aspects of cell behavior. The technology underpins advances in virology, somatic cell genetics, endocrinology, carcinogenesis, toxicology, pharmacology, hematopoiesis and immunology, and is becoming a major tool in developmental biology, complex tissue physiology and production of unique mammalian cell-derived biologicals in industry.

Antitumor effects of polysaccharides of human-type Mycobacterium tuberculosis on collagenation in human cancer xenografts

The most important activity of SSM is stimulation of collagenation from cancer-infiltrated stromal tissue which confines the cancer. In order to elucidate the proliferative responses of collagen in cancer, single and double xenografts were prepared by transplantation of human gastric cancer (HGC), human lung cancer (HLC), and NB41A3 (mouse neuroblastoma) into nude mice. The collagen responses were dependent on the type of cancer cell used, particularly the cell membranes. SSM distinctly stimulated the proliferation of collagen fibers which showed a response to these cancer cells. When examined by CD, stromal collagenation was found to be dependent upon changes in the molecular structure of the cancer cell membrane. One of the glycoproteins, fibronectin, was presumed to be the most important of the substances involved.

Glucocorticoid receptor-like antigen in lymphoma cell membranes: correlation to cell lysis

S-49 mouse lymphoma cells undergo lysis when treated with glucocorticoids; the mechanism of this effect is not understood. A protein was detected in the plasma membrane of these cells by means of direct immunofluorescent labeling with a monoclonal antibody to the soluble glucocorticoid receptor. Cellular heterogeneity in the content of this glucocorticoid receptor-like molecule was evident. By immunoadsorption to antibody-coated tissue culture plates, the cells were separated into populations positive (100%) and depleted (38%) for this membrane antigen. Gel electrophoresis, specific immunoblot, and autoradiographic (binding of [3H]dexamethasone mesylate) analysis of the membrane proteins from the membrane antigen-positive group revealed multiple protein bands ranging in size from 85 to 145 kilodaltons. Furthermore, comparison of the glucocorticoid sensitivity of these groups of cells showed complete lysis of the membrane antigen-positive cells and only partial lysis of the antigen-deficient group, which suggests that the lysis response of cells to glucocorticoids is mediated by a glucocorticoid receptor-like molecule located in the plasma membrane.

The effects of taxol, a microtubule-stabilizing drug, on steroidogenic cells

The effects of taxol on steroid production and microtubule polymerization were examined using Y-1 adrenocortical tumor cells, MLTC-1 Leydig tumor cells, and primary cultures of bovine adrenocortical cells. Taxol inhibited the following steroidogenic processes within the Y-1 and MLTC-1 cells: (1) hormonal increase of steroid production, (2) dibutyryl cyclic AMP-increased steroid production, and (3) hormone-stimulated pregnenolone production. The inhibitory action of taxol was concentration dependent and also resulted in an increase in cytoplasmic microtubules. In addition, the inhibitory action of taxol on hormone-stimulated steroid production was reversible. Taxol appeared to inhibit cholesterol movement to the mitochondrial site of cholesterol side-chain cleavage enzyme but did not affect overall protein synthesis. Interestingly, taxol did not affect hormone-stimulated steroid production in bovine adrenocortical cells. This lack of inhibition may correspond to the ultrastructural observation that microtubule bundling after taxol treatment was observed in the tumor cells but not in similarly treated bovine adrenal cells. With this conflicting information between cell types, a direct relationship between taxol treatment and inhibition of steroid production has not been established. However, these results suggest that taxol alters the rate of transport of cholesterol to the cholesterol side-chain cleavage enzyme within the steroidogenic tumor cells.

On the mechanism of action of ACTH: the role of actin

The discovery of a role for the cytoskeleton in the responses to ACTH and cyclic AMP was somewhat unexpected - at least this was the case 9 years ago (1). In fact, many endocrinologists are forced to confess that they were innocent of any understanding of the cytoskeleton and were not even aware that all mammalian cells possess microfilaments and microtubules. A new generation of endocrinologists has arrived on the scene who have been brought up with the cytoskeleton so that we can expect to see considerable progress during the coming decade in our understanding of the role of the cytoskeleton in endocrine cells.

Transplantation of ACTH-secreting pituitary tumor cells in athymic nude mice

Chronic excess of glucocorticoids results in Cushing's syndrome in humans. A common cause of excess cortisol secretion is the presence of an adrenocorticotropin secreting pituitary tumor which stimulates the adrenal cortex to produce excess glucocorticoids. ACTH-secreting AtT-20 mouse pituitary cells transplanted subcutaneously in oestrogenized athymic nude mice form tumors rapidly. Six weeks after receiving the tumor transplants, the mice weighed 45% more than normal mice due to the increase in body fat. The tumor-bearing mice exhibit the familial "buffalo hump" appeaance due to the abnormal distribution of body fat. The adrenal glands of the tumor-bearing animals are enlarged due to hypertrophy of the zona fasciculata. The foamy looking fasciculata cells in normal mice were converted to dense, eosinophilic cells in the tumor-bearing mice. Transplantation of normal pituitary glands to athymic nude mice with or without oestrogen treatment did not produce these morphological changes. The experimental model described here may be useful for future studies of Cushing's syndrome.

Human lymphocyte production of corticotropin and endorphin-like substances: association with leukocyte interferon

Human leukocyte interferon (hIFN-alpha) preparations contain immunologically and biologically recognizable endorphin and corticotropin-like (ACTH-like) activities. The ACTH bioactivity was demonstrable only after pepsin or acid treatment. Highly purified hIFN-alpha was composed of two molecular species of interferon (18,500 and 23,000 daltons). Endorphin activity was associated with both of these molecules. Pepsin treatment of the 23,000-dalton but not the 18,500-dalton hIFN-alpha generated ACTH activity. In acid, the 23,000-dalton hIFN-alpha broke down into the 18,500-dalton form and ACTH (4500 daltons). The ACTH derived from hIFN-alpha by pepsin digestion comigrated with a purified ACTH standard in NaDodSO4/polyacrylamide gel electrophoresis. hIFN-alpha-producing lymphocytes showed positive immunofluorescence after staining with highly specific antisera to ACTH alpha-(1-13) and gamma-endorphin. Essentially 100% of the human peripheral lymphocytes were capable of producing both ACTH and gamma-endorphin-related substances, presumably associated with hIFN-alpha. These results strongly suggest a circuit between the immune and neuroendocrine systems which involves neuroendocrine hormone-like substances, some of which are associated with hIFN-alpha

Origin of malignant adenocarcinoma cell line induced by retrovirus-like particles from DMBA rat mammary tumors

Intraperitoneal inoculation of neonate Sprague Dawley rats with cell-free extracts containing retrovirus-like particles from DMBA-induced rat mammary tumors resulted in a fivefold increase of benign mammary neoplasias in the survivor animals, in comparison to the spontaneous tumor incidence rate. In addition, four animals developed metastasizing abdominal adenocarcinomas. The ascitic cells of one of the abdominal tumors were established as a permanent tissue culture line (HH-1). After subsequent animal passage, cells of the permanent line HH-9 clone 14 showed increased malignancy manifested by the number of takes per animals injected, and by the number of remote metastases observed.

Development of two cloned epithelial cell lines from normal adult mouse and rat ventral prostates

Two epithelial cell lines were established, one from adult C3H mouse and one from adult Fischer rat ventral prostate. These cell lines were obtained from explant cultures, using Ham's F12 medium supplemented with HEPES, insulin, testosterone, hydrocortisone, epidermal growth factor, and 7.5% fetal bovine serum. A low concentration of trypsin and EDTA in Ca++- and Mg++-free phosphate buffer was used for passaging the cells. The rat cell line was established following implantation of prostate tissue in nude mice. These cell lines stained positively for acid phosphatase and were dependent upon epidermal growth factor for growth. Morphological studies, including electron microscopy, revealed a highly characteristic epithelial morphology of both cell lines. These cell lines have hypotetraploid chromosome number and are capable of metabolizing benzo(a)pyrene. We propose the application of these cells as models for the study of prostate carcinogenesis.

An improved basal medium for Y-1 mouse adrenal cortex tumor cells in culture. 2. Stability of steroidogenic pathway and chromosome number

Y-1 cells were passaged weekly for 6 wk in MACT IV medium without a period of adaptation to this basal medium that requires 1% dialyzed fetal bovine serum as a supplement. The steroid pathway and chromosome number, reported earlier for this cell line under culture conditions that used much higher concentrations of nondialyzed sera, remained stable despite dialysis and reduction of the fetal bovine serum to 1%.

Interferon and adrenocorticotropic hormone induction of steroidogenesis, melanogenesis and antiviral activity

Adrenocorticotropic hormone (ACTH) and mouse but not human interferon caused a steroidogenic response and induced antiviral activity in mouse adrenal tumor (Y-1) cells. ACTH and human but not mouse interferon caused induction of melanin synthesis and antiviral activity in human melanoma cells. ACTH did not induce antiviral activity in mouse L or human amnion (WISH) cells. The hormonal activities of interferon were neutralized by specific rabbit anti-interferon sera. Thus, interferon has species-specific hormonal activity and ACTH has cell-specific antiviral activity. These results are discussed in terms of the possible natural functions of interferon polypeptide hormones.

Alternate culture and animal passage of human glioma

The method of the alternate culture and animal passage was introduced in the study of human glioma. For animal passage the hereditary asplenicathymic (lasat) mice were used as a carrier. Because the lasat mice have practically no cellular and only little humoral immunity, the rate of tumor take was expected to be raised, and successful results were obtained. Ultrastructural and immunohistochemical (GFA protein) studies were also done. The overgrowth of stromal elements in reculture of tumors in lasat mice was less vigorous than in athymic nude mice. After four passages through lasat mice, an established well differentiated cell nests, and this alternate culture and animal passage suggested to enhance the differentiation and growth capacity. After three passages through lasat mice, the tumor line, KNS-42-L, produced tumors also in athymic nude mice and their histological features were essentially the same as those in lasat mice, and hence the lasat mice could be saved.

Human leukocyte interferon: structural and biological relatedness to adrenocorticotropic hormone and endorphins

Anti-alpha-corticotropin [anti-ACTH alpha (1-13)](also alpha-melanotropin) and anti-gamma-endorphin antisera neutralized human leukocyte interferon activity but not fibroblast interferon activity. Human leukocyte interferon was not neutralized by anti-human lutenizing hormone (lutropin) or follicle-stimulating hormone (follitropin) antisra. Conversely, antisera to human leukocyte interferon neutralized ACTH activity. The neturalization of human leukocyte interferon by anti-human leukocyte interferon serum was partially blocked by ACTH. These studies show strong antigenic relatedness among human leukocyte interferon, ACTH, and endorphins, implying that there are underlying structural similarities. Structural relatedness is shown by pepsin cleavage of ACTH activity from human leukocyte interferon. The implication for the natural functions of human leukocyte interferon are discussed.

Human platelet lysate contains growth factor activities for established cell lines derived from various tissues of several species

Factors have been studied from human platelets that promote the growth of a hormone-responsive rat mammary adenocarcinoma cell line MTW9/PL, the BALB/c 3T3 mouse embryo fibroblasts, and numerous other established cell lines. A wide variety of the commonly employed cell lines, including lines of human, mouse, monkey, chicken, rat, Chinese hamster, and Syrian hamster origin, were tested for their growth response to a standard concentration of 200 microgram/ml human platelet lysate, and the lysate was found to contain mitogenic activity for 24 of the 29 different lines assayed. A comparison was made between the platelet growth activity for the MTW9/PL cells and the well characterized platelet mitogen for the BALB/c 3T3 cells, platelet-derived growth factor (PDGF). When the platelet lysate was subjected to digestion by highly purified trypsin, the mitogenic activity for the MTW9/PL cells was not affected whereas that for the BALB/c 3T3 cells was essentially destroyed. Crude PDGF was prepared by heating the human platelet lysates at 100 degrees C for 2 min followed by clarification, dialysis, lyophilization, and reconstitution. This PDGF material had no apparent growth activity for MTW9/PL cells, although chromatography of this material on Biogel P-100 revealed a high molecular weight (approximately 40,000 daltons) activity for the BALB/c 3T3 cells (presumably PDGF) and two growth activities for the MTW9/PL cells, one high molecular weight activity and a second activity of molecular weight less than 10,000. These studies demonstrated a form of epithelial tumor cell growth activity separable from the 3T3 type PDGF in crude heated extracts.

Inhibition of DNA synthesis in adrenocortical cells by cytochalasin B

ACTH inhibits DNA synthesis in normal rat and mouse tumor Y-1 adrenocortical cells within the same concentration range that it stimulates steroidogenesis. These processes can be independently regulated as demonstrated by the divergent actions of cytochalasin B on these cells. In the normal cells, cytochalasin B does not increase steroidogenesis in serum-free or serum-containing media, and it decreases the stimulation produced by ACTH. In the absence of serum, the Y-1 cells respond in a similar way. However, in serum-containing media, cytochalasin B increases steroidogenesis in these cells and does not inhibit the response to ACTH. In both cell types, cytochalasin B inhibits [3H]thymidine incorporation into DNA by a mechanism different than that of ACTH. In the Y-1 cells, this inhibition is caused by a decreased uptake of [3H]thymidine into the cell, which probably reflects a decreased transport across the cell membrane. In the normal cells, cytochalasin B, like ACTH, does not affect [3H]thymidine transport, but it decreases DNA synthesis much more rapidly than does ACTH. This inhibition may be the result of the disruption of microfilaments by cytochalasinB, because our evidence indicates that it is not caused by a decrease in glucose uptake by the cells.

Selective growth of some rodent epithelial cells in a medium containing citrulline

We have defined a medium (called Sun's modified Waymouth medium) that selectively cultures some rodent epithelial cells that are capable of using citrulline in place of arginine. A growth-response study of the ability of 47 different mammalian cell cultures (of mouse, rat, Syrian hamster, Chinese hamster, guinea pig, rabbit, monkey, and human origin) to use arginine or its biosynthetic precursors, ornithine, citrulline, or argininosuccinate, showed that all epithelial cells and some fibroblasts are capable of growing in citrulline medium; however, primary embryo fibroblasts and 12 established fibroblast cell lines derived from Syrian hamsters failed to grow. The citrulline medium also allowed selective outgrowth of epithelial cells, without contaminating fibroblasts, from Syrian hamster tracheal explants. This absolute nutritional difference between Syrian hamster epithelial and fibroblast cells allows citrulline medium to be used for selective cultivation of epithelial cells, which should be valuable for study of growth, differentiation, and malignant transformation of mammalian epithelial cells.

Establishment of rat pancreatic endocrine cell lines by infection with simian virus 40

The feasibility of infection and transformation by SV40 (simian virus 40) of primary cell cultures derived from newborn-rat pancreas was investigated. As judged by the presence of intranuclear SV40 T-antigen, exposure to the virus resulted specifically in infection and transformation of epithelioid (predominantly endocrine) cells. The transformed cells were subcultured (more than 64 passages) and cloned. Culture medium and acid/ethanol extracts of the cells did not contain detectable amounts of immunoreactive insulin after the third subculture. However, inoculation of such SV40-transformed pancreatic cells into immunodeficient rats results in tumours in which insulin production was partially restored through the passage in vivo, since the tumour cells contained and synthesized small amounts of immunoreactive insulin which co-migrated with an insulin marker on gel chromatography. Interestingly, the transformed cells maintained under tissue-culture conditions produced a protein immunologically related to insulin, soluble in aqueous buffer but insoluble in acid/ethanol. This 3000-dalton protein is too large to be a translation product of the rat preproinsulin 9S mRNA. SV40-transformed pancreatic cells might prove useful in the investigation of the factors controlling and maintaining insulin biosynthesis.

Growth and transplantability of clonally related tumorigenic murine cell lines

A malignant cell line derived from the s.c. inoculation of Adenovirus 12 into a CBA mouse has been isolated in vitro, cloned, and within 10 passages the clones have been investigated for their karyotype, morphology, growth rate, saturation density and response to plant lectin in vitro, and their tumorigenicity and growth rate in vivo. The cell lines rapidly acquired a highly heterogeneous karyotype, but remained homogeneous with respect to more complex physiological parameters. Examination of the cellular characteristics has indicated that the rate of growth of the cell lines in vivo, but not their tumorigenicity, may be related to their in vitro potentials. The clones responded differently to the cytotoxic effects of concanavalin A, but there was no correlation between the effect of the lectin and the malignant potential of the cells.

The ultrastructure of functional mouse adrenal cortical tumor cells in vitro

Cells derived from a transplantable mouse adrenal cortical tumor maintain their differentiated function in vitro and secrete steroids in response to ACTH and other stimulatory agents. The cell line has been widely employed for various biochemical investigations but there have been few attempts to correlate this work with morphologic data. This communication describes the electron microscopic appearance of the tumor transplant in vivo and primary cultures derived from it at various intervals after the cells are placed in culture. Tumor cells in vivo bear considerable resemblance to normal adult mouse adrenal cortical cells. Organelles generally considered to be directly involved in steroid biosynthesis (mitochondria, smooth endoplasmic reticulum and lipid droplets) are not drastically altered. Certain modifications of the vasculature and cell membrane, seemingly related to steroidogenesis, are present in both the tumor and normal adrenal cortex. Within 2 days after the tumor cells are introduced to culture, their cytoplasm assumes a more simplified appearance. Smooth endoplasmic reticulum is less conspicuous and free ribosomes and polysomes are very abundant. Mitchondrial inner membranes are reorganized from a saccular arrangement in the cells in vivo into distinct lamellar cristae. The tumor cells now resemble undifferentiated embryonic adrenal cells, or cultured adrenal cells from various mammalian sources which have dedifferentiated in the absence of ACTH. In their morphologically unspecialized state, the normal cells are incapable of functional responses to ACTH. In contrast, the cultured, dedifferentiated tumor cells respond within minutes to this hormone and can demonstrate 5-20 fold increases in their basal steroid output. These data suggest that substantial steroidogenic activity can occur although the characteristic appearance of adrenal mitochondria is absent.

Estrogen induction of growth factors specific for hormone-responsive mammary, pituitary, and kidney tumor cells

The problem of estrogen-promoted tumor cell growth has been studied extensively in an attempt to establish the direct mitogenic role of these steroid hormones. We have developed cell lines from three estrogen-responsive tumors or cell populations: the H-301 kidney tumor cells established from a parent estrogen-dependent hamster kidney tumor, the GH3/C14 rat pituitary tumor cell line established as a subline of the original GH3 population, and the MTW9/PL mammary cell line developed from a parent estrogen- and prolactin-responsive MT-W9A carcinogen-induced rat tumor. With all three of these cell lines, we have encountered a paradox: although estrogens are obligatory for tumor formation in vivo, no direct mitogenic effect of estrogens can be shown in culture when assayed by an increase in cell number. We have thus considered the possibility that estrogens may induce growth factors in vivo that are then responsible for tumor formation by the three cell lines described. Experiments presented in this report show that extracts of rodent uterus, kidney, or liver contain growth activity for these three tumor cell lines, that estrogen treatment causes an increase in tissue content of these activities, and that the estrogen-induced activities are specific for the estrogen-responsive cells. These studies suggest that estrogen-responsive tumor growth in vivo includes the mechanism of estrogen leads to uterus, kidney, or liver leads to specific growth factors leads to estrogen-responsive tumor cells.

Cytochalasin-stimulated steroidogenesis from high density lipoproteins

The cytochalasins stimulate steroid secretion of Y-1 adrenal tumor cells two-to threefold. The order of potencies is cytochalasin E is greater than D is greater than B, but the maximum response is the the same and always less than with ACTH. Like that with ACTH, the stimulation has a rapid onset, is easily reversible, is inhibited by cucloheximide and aminoglutethimide, and occurs at a stage before pregnenolone. Although the cytochalasin, like ACTH, produce cell rounding, it is shown that this morphological change is not necessarily coupled to steridogenesis. Unlike ACTH, cytochalasin B does not measurably increase cellular levels of cAMP at concentrations that lead to maximal steroidogenesis. The cytochalasin B-induced stimulation of steroidogenesis, unlike the short-term ACTH effect, fails to occur in the absence of serum. This lack of response can be corrected by even low concentrations of human high density lipoproteins (HDL) but not by low density lipoproteins (LDL). We, therefore, propose that cytochalasin B enhances the availability of cholesterol bound to HDL for steroidogenesis by Y-1 adrenal cells.

Effects of steroid hormones on the level of corticotropin messenger RNA activity in cultured mouse-pituitary-tumor cells

Studies have been made with the mouse pituitary tumor cell line AtT-20 in culture to determine whether or not the suppression of pituitary corticotropin messenger RNA activity observed upon the administration of glucocorticoids to adrenalectomized rats is due to a direct action of these steroid hormones on the pituitary. The levels of corticotropin messenger RNA activity in AtT-20 cells treated with various steroid hormones were measured with the use of the cell-free protein-synthesizing system derived from wheat germ. The addition of dexamethasone to culture medium reduced the level of corticotropin messenger RNA activity to 30-40% of that in untreated cells. Corticosterone and cortisol exhibited a suppressive effect to a lesser extent. In contrast, nonglucocorticoids such as testosterone and 17beta-estradiol were essentially ineffective. These results indicate that at least part of the glucocorticoid action is exerted directly on the pituitary to suppress corticotropin messenger RNA activity.

Transmission and scanning electron microscopic observations of mouse adrenocortical adenoma cells (Y-1) in non-stimulated and stimulated states

ACTH sensitive murine adrenocortical adenoma cells (Y-1) were examined by transmission and scanning electron microscopes under non-stimulated and stimulated conditions. They showed the ultrastructural characteristics which were fairly different from those of the original adrenocortical cells of LAF1 mice. The smooth-surfaced endoplasmic reticulum (sER) were poorly developed, and the mitochondrial cristae showed lamellar rather than tubular or tubulo-vesicular type. Administration of ACTH induced rounding-up of the Y-1 cells with slight increase in sER, BUt no mitochondria with vesicular inner structure appeared. The effects of dbcAMP on the morphology of the Y-1 cells were similar to those of ACTH except that the rounding-up occurred more rapidly and uniformly.

Synthesis of opiate peptides by a clonal pituitary tumor cell line

Clonal mouse pituitary tumor cells, AtT-20, synthesize at least four species of peptides with opiate activity. The endorphin concentration of AtT-20 cells was estimated to be 300-600 pmol/mg of protein. The two most abundant endorphins with apparent molecular weights of 1800 and 2400 were purified 300- and 24-fold, respectively; additional minor components were found with apparent molecular weights of greater than 3000 and less than 750.