A murine teratocarcinoma stem cell line carries suppressed oncogenic virus genomes

Murine teratocarcinoma stem cells are nonpermissive for productive infection by a variety of DNA (polyoma and SV40 virus) and RNA (murine leukemia and sarcoma virus) tumor viruses whereas differentiated murine cells derived from the stem cells are permissive for productive (or abortive in the case of SV40) infection by these same viruses. The block to productive infection by these oncogenic viruses is at a postpenetration step in the replication cycle of these viruses but the precise level of the block has not been established for any of these viruses. In this report we describe teratocarcinoma-derived stem and differentiated cell lines which should be especially useful in determining the level of the block to replication of ecotropic murine leukemia virus in murine teratocarcinoma stem cells. The stem cell line, OTT6050AF1 BrdU, which is completely nonpermissive to productive infection by Moloney murine leukemia virus and consists of 97% pluripotent stem cells, contains DNA copies of an RNA tumor virus which is indistinguishable from the N-tropic murine leukemia virus of AKR mice. The stem cells are negative for expression of viral reverse transcriptase, p30 and gp69/71 and no virus is found by XC plaque assay or other biological tests. Differentiated cells established from the same teratocarcinoma tumor are 100% positive for viral gp69/71, p30, and produce large amounts of reverse transcriptase activity and N-tropic virus as detected by biological assay. The virus isolated from the differentiated cells is closely related, if not identical to AKR N-tropic virus by nucleic acid hybridization studies and is thus not an endogenous virus of the 129 strain of mice. The teratocarcinoma tumor from which the cell lines were established had been carried in 129 mice and perhaps at some time in the mouse passage history the tumors were infected (nonproductively) with the N-tropic virus. Regardless of the origin of this viral DNA, the OTT6050A derived stem and differentiated cell lines should be extremely useful in defining in stem cells the step at which ecotropic murine leukemia virus replication is blocked.

Follow-up families who experience a perinatal death

We conducted a retrospective study by telephone interview (10 to 22 months later) of 26 families who had experienced a perinatal death. Six of 26 mothers had a prolonged grief reaction (12 to 20 months). Those mothers with a surviving twin or subsequent pregnancy less than five months following the death were at higher risk for a prolonged grieving period than were those without subsequent pregnancy or one more than six months later. Half of the families obtained information about the cause of death and risk of recurrence only during hospitalization; subsequent contact, weeks to months later, provided additional information for the other half. Twenty-two of 26 mothers met predetermined criteria for having an adequate understanding of cause of death and risk of recurrence; four of 26 knew neither. Sixty percent of the mothers who had adequate understanding and who had no prolonged grief response felt totally dissatisfied or only partially satisfied with the information they received and the way they received it. Follow-up contact by phone or in person increased understanding significantly; mothers who had had in-person follow-up were more likely to be satisfied with the information they received.

Transmembrane migration ('flip-flop') of cholesterol in erythrocyte membranes

After exchange with [14C]cholesterol-labelled plasma lipoproteins for 0.5-4h, erythrocytes were extracted with bile-salt solutions. The extracted cholesterol (mainly from the outside of the erythrocyte membrane) had the same specific radioactivity as the residual sterol. Thus cholesterol equilibrates rapidly (half-time less than 1 h) between the two sides of the membrane.

The dispersion of cholesterol with phospholipids and glycolipids

Of the polar lipids studied (phospholipids and glycolipids), only phosphatidylcholine and sphingomyelin can disperse in water with up to 2 mol cholesterol/mol polar lipid. However, mixtures of phosphatidylethanolamine with small amounts of phosphatidylcholine and mixed lipids from mitochondria and myelin will also form sterol-rich dispersions. Steroids in which the 3beta-OH group is replaced by an oxo function do not form such steroid-rich dispersions. Electron microscopy and optical rotatory dispersion (ORD) show that sterols disperse with cerebrosides and gangliosides to form cylindrical structures with the regions around C atoms 3 and 7 of the sterol in less polar environments than those they occupy in phospholipid liposomes. It is proposed that choline-containing phospholipids facilitate entry of sterol molecules into the outer leaflet of cell surface membranes but that the phospholipid composition itself will not give rise to an asymmetric distribution of sterol in membranes with a high cholesterol content.

Cellular response to treatment with 4-(3-(2-chloroethyl)-3-nitrosoureido)-cis-cyclohexanecarboxylic acid, a water-soluble nitrosourea derivative

The lethal effects of 4-(3-(2-chloroethyl)-3-nitrosoureido)-cis-cyclohexanecarboxylic acid (cis-acid), a water-soluble nitrosourea derivative, were investigated on a human lymphoma cell line. The survival of asynchronous cells exposed to increasing concentrations of the drug was characterized by a threshold exponential curve (Do = 20 microgram/ml; Dq = 20 microgram/ml, 1 hour) similar to that of other nitrosourea derivatives. cis-Acid exerted its main killing effect on cells in early S and in late G2 phase. Cells in mid S and early G1 phase were tenfold more resistant. Changes in survival response as a function of cell cycle stage were reflected primarily by changes in the extent of the shoulder region of the survival curve. In contrast to other nitrosoureas, the lethal effectiveness of cis-acid in solution was stable and the drug could sterilize large numbers of cells in short periods of time. Another important major difference observed for cis-acid with respect to classic nitrosourea derivatives was the capacity of treated cells to recover from sublethal and potentially lethal damage. Our studies have shown that cis-acid is as effective in killing cultured human lymphoma cells as other nitrosoureas, but possibly with a mechanism different from that of these compounds. The major shortcoming noted for cis-acid, namely the capacity of treated cells to recover from drug-induced damage, is offset by the relatively long stability of its killing effect. This, and the fact that cis-acid can be administered in an aqueous solution, make this agent an appealing compound for clinical trials.

Antigen-binding lymphocytes in guinea pigs. I.B cell expansion to the monovalent antigen L-tyrosine-p-azophenyl trimethylammonium (tyr(TMA)) in the absence of antibody production

The monofunctional antigen L-tyrosine-p-azophenyltrimethylammonium chloride, tyr(TMA), and the polyfunctional antigen, TMA-human gamma-globulin (TMA-HGG), were used to investigate the antigen structural requirements necessary for clonal proliferation of B cells. This clonal expansion was characterized with respect to receptor immunoglobulin class and affinity maturation. Antigen-binding analysis revealed that inoculation of tyr(TMA), although only of m.w. 344, triggers clonal expansion of B lymphocytes 9-fold in the absence of any apparent antibody production. There does not appear to be any maturation with respect to antibody class since greater than 90% of the tyr(TMA)-specific B cells bear the micron receptor in the nonimmune and immune state. However, the average avidity of the B cells for this antigen increases with time after immunization. In contrast, immunization with TMA-HGG results in an 18-fold increase in B lymphocytes with significant amounts of anti-TMA antibody production. With time after immunization, both maturation of average avidity and class of Ig receptor (micron leads to gamma shift) occur. These findings indicate that the functionally T cell-specific antigen tyr(TMA) can trigger clonal B cell expansion and affinity maturation at the receptor level in the absence of detectable antibody production.

Combination chemotherapy in vitro with cis-dichlorodiammineplatinum(II)

Cis-dichlorodiammineplatinum(II) (DDP) was paired with 11 other chemotherapeutic drugs in a search for possible synergistic pairs. Cell lethality was investigated by the colony-formation technique utilizing a long-term culture of human lymphoma cells. Synergistic effects were noted for pair combinations with all alkylating agents, bleomycin, adriamycin, camptothecin, and cytosine arabinoside. Additive effects were recorded for combinations with prednisolone and VP-16-213, while DDP reduced the capacity of cells to absorb sublethal damage induced by alkylating agents.

Sialic acid uptake by fibroblasts

The existence of surface sialytransferases that use cytidine monophosphate (CMP)-sialic acid as substrate has been postulated in previous studies. This is based on the assumption that if whole, viable cells can catalyze the transfer of sialic acid from CMP-sialic acid to endogenous acceptors, then the transferases carrying out the reaction must be on the cell surface, provided that (1) CMP-sialic acid does not enter the cells, and (2) CMP-sialic acid does not break down outside the cells, yielding free sialic acid which then may enter the cells, in amounts large enough to explain the incorporation. We now report evidence showing that after incubation of intact NIL, BHK, and 3T3 fibroblasts with CMP-sialic acid, at least 78% of the sialic acid incorporated by these cells is the result of free sialic acid uptake. When cells growing in a monolayer were incubated with a mixture of CMP-[14C]sialic acid and [3H]CMP-sialic acid with a ratio of 3H/14C=0.60, this ratio was found to be markedly increased in whole cells. Chemical analyses of the radioactive species in the incubation medium showed that a considerable portion of the radiolabeled sugar nucleotide had broken down to cytidine, phosphoric acid, and sialic acid. Upon incubation of cells with doubly labeled sugar nucleotide in the presence of a large excess of both nonradiolabeled cytidine and sialic acid, the cells incorporated less than 6% of both isotopes. Incubation of cells with a mixture of CMP-[14C]sialic acid and [3H]sialic acid resulted in only 20-40% of the radioactivity within the cells being membrane bound, and 70-90% of this incorporation could be inhibited by the addition of 10 mM azide to the incubation medium. The possibility that a small fraction of the total incorporation of sialic acid by these cells is due to surface sialytransferases cannot be completely ruled out. The uptake of free sialic acid by these fibroblasts is concentration dependent and a portion of it is incorporated into glycoproteins and glycolipids. Considerable loss of cell integrity was observed when fibroblasts grown on plates were removed by (ethylenedinitrilo)-tetraacetic acid or trypsin and subsequently incubated in buffer, indicating that these preparations are not suitable for intact cell studies.

Isolation and preliminary characterization of two varieties of low molecular weight immunoglobulin in the bullfrog, Rana catesbeiana

Two varieties of low m.w. immunoglobulins have been isolated from the serum of Rana catesbeiana frogs. They are highly cross-reactive, although each also contains unique antigenic determinants. Since both low m.w. immunoglobulins were identified in the serum of 22 individual frogs, it was concluded that they are isotypic variants. The light chains of R. catesbeiana and mammalian high and low m.w. immunoglobulins are similar in electrophoretic mobility on polyacrylamide gels containing sodium dodecyl sulfate. The heavy chains of fropg high m.w. immunoglobulins have the mobility of mammalian mu-chains; the heavy chains of both variants of frog low m.w. immunoglobulins migrate between mammalian mu- and gamma-chains in approximately the position of mammalian alpha-chains. An unusual structural feature of the R. catesbeiana high ald low m.w. immunoglobulins is that the unreduced proteins are partially dissociated in sodium dodecyl sulfate.

Low molecular weight immunoglobulins in Rana catesbeiana tadpoles

Rana catesbeiana tadpoles formed high and low m.w. antibodies in response to immunization with a bacteriophage. Although the neutralizing activity associated with the low m.w. immunoglobulins was relatively weak, the existence of antibodies in this class was clearly demonstrated by radioimmunoelectrophoresis. Moreover, two antigenically distinct variants of the low m.w. antibodies were detected. These were serologically indistinguishable from the two types of low m.w. immunoglobulin previously isolated from the serum of adult frogs of this species.

Immunoglobulins in ranid frogs and tadpoles

Three distinct immunoglobulins (Igs) have been isolated from serum of Rana catesbeiana frogs. One of these is high in molecular weight and probably corresponds to the IgM-like Igs that have been isolated from a variety of vertebrate species. The other 2 Igs are lower in molecular weight (approximately 7S) and very similar in subunit structure. They were highly cross-reactive, although each contained unique antigenic determinants. Their relationship to other vertebrate Ig classes remains to be established. The mode of subunit linkage in all 3 Igs is unusual since the unreduced proteins were partially dissociated in detergent. Serum from R. catesbeiana tadpoles contained Igs that were antigenically identical to each of the Igs in adults of this species. Sera from R. pipiens and R. clamitans frogs and tadpoles contained Igs that cross-reacted with the R. catesbeiana high and low molecular weight Igs.

Fluorescence studies of protein-sterol relationships in human plasma lipoproteins

Cholesta-5,7,9(11)-trien-3beta-ol and its oleate ester were incorporated into human low-density lipoprotein and reconstituted high-density lipoprotein. The unesterified sterol was more efficient than its ester in quenching tryptophan fluorescence, especially in low-density lipoprotein. The results, which indicate that in such lipoproteins unesterified sterols are more closely associated with peptide than are esterified sterols, are used to assess possible structures for the lipoproteins.

Optical-rotatory-dispersion studies of compounds related to cholesterol in liposomes and the membranes of erythrocyte 'ghosts'

1. Steroid molecules containing the alpha,beta-unsaturated oxo group in various positions were incorporated with egg phosphatidylcholine into liposomes and into human erythrocyte membranes. 2. The liposomes formed contained 0.3-0.94mol of steroid/mol of phospholipid and the steroids replaced 19-76% of the erythrocyte membrane sterol. 3. The optical rotatory dispersion (o.r.d.) spectra of the steroids in these structures were compared with those obtained in solvents of different polarity. 4. The o.r.d. spectra of cholesta-4,6-dien-3-one and 3-hydroxycholest-3-en-2-one in liposomes resembled those obtained with polar solvents such as ethanol or triethyl phosphate-water (1:1, v/v). 5. The o.r.d. spectra of 3-hydroxycholest-7-en-6-one and 3-hydroxycholest-5-en-7-one in liposomes resembled those obtained with moderately polar solvents such as dioxan. 6. The o.r.d. spectrum of 3-hydroxycholest-8(14)-en-15-one in liposomes resembled those obtained with non-polar solvents such as cyclohexane. 7. 3-Hydroxycholest-3-en-2-one did not exchange with erythrocyte membrane cholesterol, but the other steroids did do so and the o.r.d. spectra of the membranes containing them closely resembled those obtained with liposomes. 8. From the results, the position of sterol molecules with respect to the phospholipid molecules in liposomes and membranes of human erythrocyte ;ghosts' can be deduced.

Delinquency, personality tests and relationships to measures of guilt and adjustment

The validity of personality tests designed by Quay (1966) to differentiate within a heterogeneous delinquent population were evaluated with 115 delinquent adolescents. The personality tests were: the Personal Opinion Inventory based on a self-rated questionnaire; the Case History Scale, based on social history information; and the Behavior Rating Scale, based on ratings of institutional behavior. The results indicate that the Psychopathic and Neurotic factors of the Case History and Behavior Rating Scales have some modest multitrait-multimethod validity. These tests, generally, have more predictive validity than the Personal Opinion Inventory. The Neurotic factors of the three tests were reinterpreted as measuring maladjustment and as being independent of guilt. The Psychopathic factor seems to be related to poor institutional adjustment and aggressive behavior. The Socialized and Immature factors appear to have poor validities.

The role of the plasma membrane in fatty acid uptake by rat liver parenchymal cells

1. Suspensions of isolated rat liver parenchymal cells incorporate [(14)C]palmitic acid into glycerides at about 40% of the rate obtained with liver slices. 2. At short time-intervals most of the incorporation is into phosphatidylcholine and this is recovered mainly in the plasma-membrane fraction. 3. At later times (5min to 2h) the [(14)C]palmitic acid is mainly found in triglyceride, but this is not recovered in the plasma-membrane fraction. 4. Addition of lysophosphatidylcholine increases incorporation of palmitic acid into both phosphatidylcholine and triglyceride, with maximum effect at about 0.1mm. 5. In vivo, 1min after injection of [(14)C]palmitic acid, radioactive phosphatidylcholine is concentrated in the plasma-membrane fraction, but the proportion present in this fraction declines rapidly. 6. The phosphatidylcholine of the plasma-membrane fraction has, at 1min after injection, a specific radioactivity 30-fold greater than that of the whole tissue. 7. This phosphatidylcholine reaches its maximum specific radioactivity before the tissue phosphatidic acid or diglyceride. 8. The phosphatidylcholine of the plasma-membrane fraction has a very rapid turnover. 9. It is proposed that the rapid formation of phospholipids in the plasma membrane is by acylation of their lyso-derivatives and the role of this process in fatty acid uptake is discussed.

The exchange of unesterified cholesterol between human low-density lipoproteins and rat erythrocyte 'ghosts'

1. The exchange of unesterified cholesterol molecules between rat erythrocyte ;ghosts' and human low-density lipoproteins has been studied under a number of different experimental conditions. 2. The process is pH-dependent, the rate being minimal at about pH5. 3. Cholesterol exchange does not vary greatly with temperature, the rate at 50 degrees being less than twice that at 2 degrees . 4. Large variations in the ionic strength or Ca(2+) concentration of the medium have little effect, but the exchange rate is greatly increased in the presence of a wide range of chemical compounds, e.g. urea, alcohols, acetone, dimethyl sulphoxide and tetra-alkyl-ammonium salts. 5. Acetone and dimethyl sulphoxide have a much greater effect at 37 degrees than at 8-10 degrees . 6. It is proposed that hydrophobic bonding is of great importance in maintaining the structure of ;ghosts' and lipoproteins. 7. The results are discussed in relation to current theories of membrane and lipoprotein structure.

The uptake of lipids by rat liver cells

1. Unesterified cholesterol, cholesterol esters and triglycerides of chylomicrons were taken up at the same rate by isolated hepatic parenchymal cells. 2. On incubation of hepatic cells, isolated 2min. after the injection of chylomicrons in vivo, the chylomicron triglyceride associated with the cells underwent hydrolysis. 3. In cells isolated 5min. after the injection of chylomicrons, the chylomicron triglyceride bound to the hepatic cells was accessible to added clearing factor lipase. 4. ;Ghost' hepatic cells had the same binding capacity and lipolytic activity per cell as intact cells. 5. Of all subcellular fractions studied, the ;plasma membrane' fraction showed the greatest capacity per unit weight for non-esterified fatty acid and chylomicron triglyceride binding and for triglyceride hydrolysis. 6. Once non-esterified fatty acids entered the hepatic cell, they were apparently metabolized in the same manner, whether taken up from the circulation as such or derived from chylomicron triglyceride.

Plasma membranes: phospholipid and sterol content

The molar ratios of sterol to phospholipid in plasma membranes of five different types of rat cells range from 0.24 to 1.32. The composition of the plasma membrane of a cell has no fixed relation to that of the mitochondria. Thus the structure of cellular membranes shows both tissue and functional specificity.