Fetal calf serum-mediated inhibition of neurite growth from ciliary ganglion neurons in vitro

Embryonic chick ciliary ganglion (CG) neurons cultured in fetal calf serum-containing medium have been previously reported to extend neurites on polyornithine (PORN) substrata precoated with a neurite-promoting factor (PNPF) from rat schwannoma-conditioned medium. On PORN substrata alone, however, no neuritic growth occurred. This was interpreted as evidence that PORN was an incompetent substratum for ciliary neuritic growth. In this study, we now find that an untreated PORN substratum allows neuritic growth in serum-free defined medium. When PNPF was added to PORN, a more rapid and extensive neuritic response occurred. After 5 hr of culture, a 60% neuritic response occurred on PNPF/PORN, whereas no neurons initiated neurites until 10-12 hr on PORN. The inhibitory effect of fetal calf serum noted above on PORN could be obtained in part by pretreating the substratum with serum for 1 hr. Maximal inhibitory effects in the PORN pretreatment were achieved after 30 min and were not further improved by treatments up to 4 hr. Bovine serum albumin was also found to inhibit neurite growth on PORN to about 60% of the inhibition obtained by an equivalent amount of serum protein. Fetal calf serum was shown to cause a 15% reduction in the percentage of neurons bearing neurites after its addition to 18-hr serum-free PORN cultures and to cause statistically significant reductions in neurite lengths measured 2 hr later.

Inhibitory activity of cartilage growth in serum of young rats

Humoral factors play an important role in growth regulation. The growth regulatory activity in serum is a complex system with both growth-promoting and growth-inhibiting factors. In this study, using in vitro cartilage from rat nasal septum as target organ, evidence is presented that inhibiting activity does exist in normal rat serum. This activity seems to play a role in modulating cartilage growth rate in young, normal animals. Furthermore, a significant interaction between age in cartilage and age in serum as regards influence on cartilage growth was found.

Serum containing tumor necrosis factor is cytotoxic for the human malaria parasite Plasmodium falciparum

Sera (BCG-lipopolysaccharide [LPS] serum) were obtained from mice infected with Mycobacterium bovis BCG 2 h after intravenous administration of bacterial endotoxin (LPS). Varying concentrations of sera were added to cultures of Plasmodium falciparum-infected human erythrocytes; parasite viability was assessed by hypoxanthine incorporation after 4 days in culture. At concentrations of 1 to 3%, cultures treated with BCG-LPS serum showed a two- to threefold increase in hypoxanthine incorporation; at higher concentrations (4 to 8%), hypoxanthine incorporation fell to 2 to 5% of that in control cultures. Concurrent assays with control sera (from untreated mice or mice treated with BCG or LPS alone) caused some stimulation but no inhibition at up to 8% concentration. Examination of cultures treated with BCG-LPS serum showed morphological, deterioration of parasites within erythrocytes. The presence of tumor necrosis factor in the BCG-LPS serum was confirmed by using a standard L-cell cytotoxicity assay. In addition, rabbit antiserum against partially purified tumor necrosis factor protected intraerythrocytic forms of P. falciparum from the toxic effects of BCG-LPS serum. These data suggest that the factor in BCG-LPS serum that is toxic to P. falciparum in human erythrocytes is antigenically similar or identical to tumor necrosis factor. This nonantibody mediator of killing may play a role in human malaria.

Characterization of macrophage function in Mycobacterium lepraemurium-infected mice: sensitivity of mice to endotoxin and release of mediators and lysosomal enzymes after endotoxin treatment

Mycobacterium lepraemurium (MLM) infection increases the sensitivity of mice to lipopolysaccharide (LPS) as do infections with other intracellular parasites. Tumour necrosis factor (TNF), lymphocyte activating factor (LAF) and increased levels of various lysosomal and cytoplasmic enzymes were found in serum samples taken 2 h after intravenous injection of a small dose of LPS suggesting that damage to a variety of cell types, including macrophages, had occurred. Sera from moribund MLM-infected mice not injected with LPS also demonstrated significant levels of TNF compared with controls. Intravenous injections of silica into leprous mice also led to increased levels of serum lysosomal and cytoplasmic enzymes but did not give rise to a significant amount of TNF or LAF. Moreover, in contrast to LPS treatment, the injection of silica did not lead to the death of leprous mice. These findings suggest that the phagocytic cells of the infected animals did not contribute to the production of these mediators after LPS challenge. Rather, the non-phagocytic granuloma macrophages or other unidentified cell types seemed to provide the main source of the monokines TNF and LAF in vivo in the present model. These mediators may have important implications for the immunopathology of MLM infection.

Activity of a kidney epithelial cell growth inhibitor on lung and mammary cells

A kidney epithelial cell growth inhibitor, isolated from BSC-1 cell-conditioned medium, has been found to be active on certain lung and mammary gland cell lines in culture. The most responsive cell observed thus far is the CCL64 mink lung cell line. With CCL64 cells, 60% inhibition of [3H]thymidine incorporation is observed at a 0.1 nanogram/ml concentration of the growth inhibitor, and approximately 95% inhibition at 1 nanogram/ml. A human mammary tumor cell line, Hs578T, shows 75% inhibition of [3H]thymidine incorporation, in cell culture. Preliminary studies indicate that injection of the kidney epithelial cell growth inhibitor in vivo into human mammary carcinomas growing in nude mice inhibits [3H]thymidine incorporation in the tumors.

Inhibitory effects of fetal calf serum on proliferation of chick neuroblasts in culture

In this study, the proliferative activity of cultured chick neuroblasts exposed to high or low concentrations of fetal calf serum (FCS) was investigated. Different experimental evidences showed that the first 2-3 days of culture correspond to a period of neuronal proliferation in our culture conditions, whereas contamination by glial cells is very low. Cell counts and measurements of [3H]-thymidine incorporation have been used as an indicator of cell proliferation. With increasing concentrations of whole, dialyzed or desalted FCS the incorporation of radioactive thymidine and the number of cells were reduced. The inhibitory effect on [3H]-thymidine incorporation of whole serum was probably due to cumulative effects of the presence of free thymidine and of inhibitory components in that serum. An inhibitory factor from FCS has been partially purified by ammonium sulfate precipitation and column chromatographies on Ultrogel AcA 34, DEAE-cellulose and hydroxylapatite; its apparent molecular weight is about 90,000. The purified fraction was active at 2 micrograms/ml of culture medium.

Mitogen-stimulated lymphocyte growth and chronic uraemia

Lymphocytes were isolated from venous blood by the Böyum method from 36 patients with chronic renal failure: the preparations were more frequently and more heavily contaminated with non-lymphoid cells than the equivalent preparations from normal controls. Volume spectroscopy measurements showed that, in the samples without gross contamination, lymphocytes from uraemic subjects react to mitogen stimulation with normal pre-S-phase cell-cycle kinetics. In other experiments, plasma from uraemic patients was shown to be more potent than serum in inhibiting the growth of mitogen-stimulated lymphocytes from normal subjects, both in the first G1-phase and in replicative growth. Thus humoral suppression appears to be more important than a cellular defect in explaining the depressed responses of uraemic blood to mitogen stimulation.

Growth inhibitors in plasma derived human serum

It was reported previously that plasma derived human serum (PDS) inhibited the growth of cells established from malignant human breast tissues and the MCF-7 cell line but did not inhibit the growth of cells from nonmalignant mammary tissues, including the HBL-100 cell line. Plasma derived human serum was fractionated in the current study by molecular sieve chromatography on Sephadex G-100 in an effort to characterize the factor(s) responsible for inhibition. Plasma derived human serum contained several growth inhibitory fractions, which were designated G-1, G-2, G-3, and G-4. THe G-1 was associated with the lipoproteins and immunoglobulins of serum. The lipid portion of G-1 inhibited the growth of both MCF-7 and HBL-100 cells, whereas the protein fraction contained a low activity factor directed against MCF-7 cells only. The G-2 also inhibited MCF-7 cell growth at a low specific activity and was separated in the serum albumin fraction. The MCF-7 inhibitory activity in the G-3 fractions from individual donors fluctuated with the level of activity in the starting sera. The cell specific G-3 components were purified further by Sephadex G-100 superfine chromatography and gel electrophoresis. A tentative molecular weight of 50,000 was assigned to the G-3 inhibitor. The G-4 fraction consisted of small molecular weight materials migrating in advance of the column volume, which inhibited the growth of both cell lines.

Stem cell (CFUs) proliferation inhibitor in blood of mice injected with hydroxyurea

Analysis of the mouse haemopoietic stem cell (CFUs) kinetics after hydroxyurea administration has provided an in vivo assay suitable for detection of factors which inhibit recruitment of non-proliferating G0-CFUs into cell cycle, or transit of CFU's through the G1 phase. Using this assay, it has been demonstrated that plasma obtained from mice which had received hydroxyurea approximately 12-14 hr previously, possesses a factor which inhibited the triggering of CFUs into the cell cycle. The appearance of this CFUs proliferation inhibitor occurred at a time when 60-70% of the CFUs were synchronized in the S phase of the cell cycle, as a consequence of hydroxyurea action. Some basic properties of the inhibitor were investigated.

Nutrition and somatomedin. IX. Blunting of insulin-like activity by inhibitor in diabetic rat serum

Poor growth in uncontrolled experimental diabetes appears due in part to increased circulating inhibitor, a factor (or factors) that blocks stimulation of growing cartilage by somatomedins. To determine if the inhibitor has other antianabolic properties, we examined effects on insulin and insulin-like action on muscle and adipose tissue. Rat epididymal fat pads were exposed to normal rat serum, somatomedins (fraction from normal rat serum) or insulin, with or without added streptozotocin-diabetic rat serum or inhibitor (fraction from diabetic serum); insulin-like activity was assessed by glucose conversion to CO2. Diabetic rat serum alone lowered glucose utilization significantly below buffer levels (P less than .010), but inhibitor alone had no effect. However, stimulation by insulin, normal rat serum, or somatomedins was decreased significantly by both diabetic rat serum or inhibitor (P less than 0.01); Lineweaver-Burk analysis suggested that such inhibition was noncompetitive. In incubations with rat diaphragm, neither diabetic rat serum nor inhibitor alone lowered glucose incorporation into glycogen, but both inhibited muscle stimulation by insulin (P less than 0.01). In in vivo studies, rats given insulin with added diabetic rat serum exhibited decreased stimulation of glucose incorporation into muscle glycogen (P less than 0.01) and into adipose tissue total lipids. These observations indicate that an inhibitor in the serum of diabetic rats can brake anabolic processes is muscle (glycogen formation) and adipose tissue (glucose utilization, lipid formation). Such an inhibitor may therefore contribute to poor growth in diabetes by decreasing calorie storage due to insulin and insulin-like actions as well as skeletal elongation due to somatomedin action.

The effect of dietary restriction, adrenaline, hydrocortisone and surgery on the rates of death of 125IUdR-labelled, intravenously injected tumour cells in the lungs of mice

Dietary restriction, adrenaline hydrocortisone or surgery reduced the rate at which pulmonarily arrested 125IUdR-labelled murine tumour cells were lost within 7 h of intravenous (i.v.) injection. Mice that had been adrenalectomised 10 days previously showed a normal intrapulmonary tumour cell loss rate with further surgery reducing this rate to approximately half that observed in normal mice that had been subjected to surgery. Thus, although it is likely that adrenal hormones play an important role in decreasing the rate of early intrapulmonary tumour cell loss, additional factors must be implicated. Mice subject to dietary restriction, adrenaline, hydrocortisone or surgery had reduced levels of in vitro growth inhibitor(s) in their sera. Despite this, individual surgically treated animals showed no correlation between serum in vitro-growth inhibitor levels and rate of loss of i.v. injected tumour cells from the lungs. Furthermore, the 24 h pre-incubation of tumour cells in inhibitor-rich serum did not influence the subsequent loss rate of such cells following i.v. injection into mice. Electron microscopic studies indicated that dietary restriction, adrenaline and surgery reduced the rate of intravascular tumour cell death. The decreased tumour cell death rate in mice receiving these treatments could not be related, however, to any consistent morphological change in the pulmonary vasculature. The decreased rate of intravascular tumour cell death in treated mice was followed by an increased number of lung tumours with only one of the tumour lines studied, indicating that the intravascular death rate need not be a major determinant of pulmonary tumour incidence.

Rat serum factors inhibiting the G1-S transition in hepatocytes. I. Production of a low molecular weight inhibitor by proteases or liver fractions

An attempt was made to detect the serum factors inhibiting the G1-S transition in synchronized, baby rat hepatocytes. In untreated adult rat serum, this inhibitory activity was always linked to high molecular weight (HMW) compounds. Incubation of serum with trypsin or chymotrypsin resulted in the formation of a low molecular weight (LMW) G1-S inhibitory factor. The same result was obtained with fractions from adult rat liver but not with kidney or spleen fractions. Separation of the LMW factor by ultrafiltration increased its specific activity by about 10(3). The active period in the cell cycle of both the LMW and HMW factors was the same: the late G1 phase. However, the activity of the LMW factor was not blocked by the Kunitz factor. An enzymatic transformation of the HMW factor might be induced by liver cell membrane-bound proteases and constitute a mechanism regulating hepatocyte proliferation.

Inhibitory effect on tumour colony formation of mouse serum associated with tumour resistance in vivo in semi syngeneic mice

Differences in tumour susceptibility between strains of mice (C57Bl/6 and C57Bl/6 X DBA/2 = B6D2F1) could be demonstrated for several tumours of C57Bl origin, both solid tumours (B16 melanoma and Lewis lung carcinoma) and lymphomas (RBL-5, 136-3 and ALC). Serum from mice with high tumour resistance in vivo (B6D2F1) showed an inhibitory effect on tumour colony formation in a soft agar colony assay. Serum from mice with lower tumour resistance (C57Bl/6) had no effect. When other F1 hybrids of C57Bl/6 parental origin were tested, the same correlation between in vitro inhibition of tumour colony formation and in vivo susceptibility was found. The serum factor was species non-specific, since the activity was expressed against in vitro grown cell lines of human origin. The tumour colony inhibitory activity was heat sensitive (56 degrees C for 30 minutes), precipitable by (NH4)2SO4, and not removed by adsorption on tumour cells. These results demonstrate the existance of a naturally-occurring humoral tumerostatic factor(s) which correlates to in vivo susceptibility to tumour cells. Its relationship to NK cell activity is discussed.

[Metabolism of erythrocyte chalone in vitro]

It has been shown that erythrocytic chalone was bound to the surface of mouse myelokaryocytes after one minute, penetrated them after 30 minutes, disintegrated and excreted in the form of low-molecular mass compounds after 4 hours of incubation. The cells treated with erythrocytic chalone or trypsin are not capable to respond to the repeated action of chalone over 2 hours, which seems likely to be related to the lack of receptor resynthesis during the period under consideration.

Inhibition of growth of human breast cancer cell line MCF-7 by serum derived from calcium chloride-clotted plasma

The growth of MCF-7 cells, established from a metastatic mammary carcinoma, and of HBL-100 cells, derived from a primary culture of human milk, was examined in medium supplemented with whole blood serum (WBS), defibrinogenated plasma, and plasma-derived serum (PDS). PDS obtained from platelet-poor plasma collected with the anticoagulant citrate phosphate dextrose and clotted by the addition of calcium chloride did not promote the growth of MCF-7 cells as well as did WBS or platelet-poor defibrinogenated plasma alone. Growth-inhibitory activity was observed when final cell densities in the presence of PDS combined with fetal bovine serum (FBS) were compared with those in control cultures maintained in FBS alone. The level of this activity in PDS varied among donors. Inhibition was not observed with HBL-100 cells. Calcium chloride did not induce inhibitory activity when added to WBS or defibrinogenated plasma, and platelet components did not alter the level of inhibition in PDS. However, platelet extracts did affect the expression of inhibition when added to plasma before clotting. Activity was diminished following dialysis of PDS, which suggested that inhibition stemmed from a small-molecular-weight factor for which expression depended on the mechanism of plasma coagulation.

A selective inhibitor of cell proliferation from normal serum

A factor in normal serum that selectively and reversibly inhibits proliferation of cells in culture has been enriched 160-fold from calf serum by sequential ammonium sulfate precipitation, gel filtration, and lectin-affinity chromatography. DNA synthesis of normal (but not transformed) rat hepatocytes, human lymphoblast lines, and mitogen-stimulated murine spleen cells is inhibited by greater than 90%, and Vero, murine myeloma, MELC, and a human colon carcinoma cell line to a lesser extent. Growth of other cell lines tested was not affected. Responsive cells are arrested apparently in G1 by this inhibitor, the effect of which is maximal by 24 hr and is spontaneously reversible thereafter unless it is renewed. The active fraction is a protein that migrates with the alpha 2-globulins; it is not a lipoprotein, and it is of high apparent molecular weight.

[Superficial origin of erythrocytic chalone in polycythemia in vitro]

It was shown in the culture of rat bone marrow cells in experimental polycythemia that the chalone activity of erythrocytic chalone considerably drops in the presence of phytohemagglutinin (PHA). The chalone inhibits the agglutinating activity of PHA with respect to bone marrow cells. Absorption of the chalone on the immobilized PHA leads to disappearance from it and of PAS-positive bands recorded electrophoretically and to a strong decrease in PAS-negative band intensity. Experiments with preliminary incubation of rat red cells before preparation of the chalone suggest that in the course of its preparation two polypeptides one of which is PAS-positive are released into the medium. It is suggested that the chalone includes superficial membrane proteins of red cells, possibly, in the form of a combination of PAS-positive and PAS-negative bands. Potential mechanisms of chalone release from the surface of cells and features of their action on the cells are discussed.

Bone marrow culture in aplastic anemia

Blood and bone marrow granulocyte colony forming units (CFUc) were assayed in 46 patients with aplastic anemia, and the serum was examined for its inhibitory action on normal CFUc growth. All patients showed a gross reduction in colonies and clusters in incidence and absolute number in the bone marrow and blood. Two proliferative abnormalities of CFUc in aplastic anaemia were identified: a significantly higher than normal cluster to colony ratio (P less than 0.05) and a higher than normal ratio of granulocytes to total aggregates in the bone marrow. Eleven out of 34 patients tested had serum inhibitory to normal CFUc. These patients were indistinguishable from the rest on haematological and CFUc culture characteristics, and no correlation between the results of CFUc assay and haematological severity was found. The results suggest that the CFUc is abnormal in aplastic anaemia, the reduction in pool size being related to a failure of self-renewal, but an immunological role in the pathogenesis of aplastic anaemia remains unproven. The close relationship of CFUc incidence to the percentage of granulocyte precursors in the marrow, together with the failure of the CFUc assay to predict clinical severity, limits the practical use of the assay to the confirmation of diagnosis in aplastic anaemia.

Granulocytic chalone inhibits rapidly proliferating committed murine progenitor cells (CFU-C)

Bovine leucocyte extract containing the granulocytic chalone inhibited proliferation of rapidly, but not slowly, prliferating murine CFU-C. The precursors of CFU-C, i.e. multipotent colon-forming stem cells (CFU-S), were apparently not affected. Inhibition of proliferation was detected as a decreased killing of DNA synthesizing cells in diffusion chamber cultures by hydroxyurea, after pre-treatment with the extract.

An inhibitor of DNA synthesis in erythrocyte-conditioned medium and its separation from haemoglobin

Erythrocyte-conditioned medium and erythrocyte lysate have been prepared from rat red blood cells. Molecular fractions of the conditioned medium and the lysate are used to test for the presence of erythrocyte chalone in short-term tissue cultures of mouse foetal liver cells. An inhibitor of erythroblast DNA synthesis has been found in the erythrocyte conditioned medium. The inhibitor is not haemoglobin, and it is not found in erythrocyte lysate soluble components.