Structural correlates of cellular tumorigenicity and anchorage independence in transformed fibroblasts

The ability on nonhematopoietic cells to proliferate in vitro without attachment to a solid surface (anchorage independence) is known to be highly correlated with their ability to form tumors in nude mice. Transformed cells in vitro frequently also show less organization of the intracellular actin-containing microfilament bundles and less cell-surface fibronectin compared to normal cells. We have examined whether the loss of the anchorage requirement for growth is related to either of these structural changes in the cellular cytoskeleton. Our approach was to select a series of subclones from a nontransformed Syrian hamster fibroblast line, NIL8, for the acquisition of either anchorage independence in vitro or tumorigenicity in nude mice. These subclones were then examined for concomitant changes in the cytoskeletal structures. We found that anchorage independence, decreased actin cable organization, and tumorigenicity in nude mice were coordinately induced in both the in vitro- and in vivo-selected subclones, whereas the loss of fibronectin was not consistently coinduced with these three markers. These results suggest that the transformation-associated decrease in actin cable organization in this type of cell enhances the ability to grow without anchorage in vitro and to form tumors in vivo.

Tumor formation by SV40-transformed human cells in nude mice: the role of SV40 T antigens

Human cells transformed in vitro by SV40 rarely form tumors in nude mice. We examined whether these cells as a group are inherently nontumorigenic or whether they are potentially tumorigenic but rejected by the athymic host, possibly by nonspecific immune mechanisms. SV80 and NG8 are SV40-transformed human cell lines that express all of the transformed properties, including anchorage-independent growth, but do not form tumors in adult nude mice after injection of as many as 10(8) cells. Both the SV80 and NG8 cell lines have SV40-specific transplantation antigens which crossreact with those present on SV40-transformed (but tumorigenic) rodent cells. We found that SV80 cells, though not NG8 cells, induced progressively growing lethal tumors if the cells are injected repeatedly into neonatal nude mice. Somatic cell hybrids between SV80 or NG8 cells and a highly tumorigenic cell line derived from a human tumor continue to express the virus-induced antigens and fail to form tumors in adult nude mice. These results strongly suggest that at least for some SV40-transformed human cells, the failure to form tumors in nude mice may be due to their expression of virus-induced transplantation antigens rather than the absence of tumorigenic potential.

Evidence from opiate binding studies that heroin acts through its metabolites

The relative affinity to opiate receptors of heroin, 6-acetylmorphine and morphine was estimated by determining their ability to displace specifically bound 3H-naltrexone from rat brain opiate binding sites. In vitro hydrolysis of heroin to 6-acetylmorphine was monitored in the binding assay filtrate by use of a quantitative HPLC procedure. The rate of heroin hydrolysis was significantly slower at 0 degrees C than at 37 degrees C. The displacement of 1 nM 3H-naltrexone by unlabeled ligand at concentrations ranging from 7 to 500 nM was measured at 0 degrees C for 120 minutes, yielding IC50 values of heroin = 483 nM, 6-acetylmorphine = 73 nM and morphine = 53 nM. When the binding data for heroin were recalculated to include the displacement that could be attributed to the 6-acetylmorphine derived from heroin degradation during the incubation, all of the apparent heroin binding was accounted for by the 6-acetylmorphine. These results are consistent with previous reports of the low binding affinity of morphine congeners (e.g., codeine) that lack a free phenolic 3-hydroxyl group and support the view that heroin is a prodrug which serves to determine the distribution of its intrinsically active metabolites, 6-acetylmorphine and morphine.

Diabetes susceptibility of BALB/cBOM mice treated with streptozotocin. Inhibition by lethal irradiation and restoration by splenic lymphocytes

In genetically susceptible strains of mice, repeated injections of a subdiabetogenic dose of streptozotocin induces the development of progressive insulin-dependent hyperglycemia. We showed previously that host T-cell functions play an obligatory etiologic role in this experimental disease by demonstrating that the athymic nude mouse is resistant to diabetes induction unless its T-cell functions are reconstituted by thymus graft (Paik et al., Proc. Natl. Acad. Sci. USA 77:6129-33, 1980). Here we show that lethal irradiation of euthymic (+/nu) mice of BALB/cBOM background causes selective resistance of the mice to the diabetogenic effects of the multiple low doses of streptozotocin without affecting their sensitivity to a high pharmacologic dose of the toxin. We also show that reconstitution of the irradiated mice with splenic lymphocytes causes the restoration of diabetes susceptibility. Lethally irradiated mice thus represent a useful experimental model for analyzing the host functions involved in the development of this disease. These results provide an additional support for the hypothesis that the induction of diabetes in this model system is mediated by an autoimmune amplification mechanism.

X-ray diffraction gratings for synchrotron radiation spectroscopy: a new fabrication method

Silicon dioxide lamellar gratings fabricated by a new technique combining holographic exposure and reactive ion-beam etching are found experimentally to be appropriate to and useful for synchrotron radiation spectroscopy. Methods to improve edge roughness and to control the land-to-groove width ratio are also investigated. The fabrication technique developed here is relatively simple in comparison with the ruling technique which needs delicate control. Therefore, it is a promising way to employ these bakable original gratings for synchrotron radiation spectroscopy.

Induction of insulin-dependent diabetes by streptozotocin. Inhibition by estrogens and potentiation by androgens

Susceptibility of mice to experimental insulin-dependent diabetes as induced by multiple subdiabetogenic doses of streptozotocin has been shown to be strongly gender-dependent, males being much more susceptible than females. We examined this gender difference further in two strains of genetically susceptible mice to determine whether exogenous steroid sex hormones can both suppress the high susceptibility of males and potentiate the low susceptibility of females. Our results show that, in both BALB/cBOM and C57BL/6 mice, exogenous estrogens can suppress the high susceptibility of males. Conversely, the normally streptozotocin-resistant females become as highly susceptible as males after the administration of androgens. The inhibitory effect of estrogens and the potentiating effect of androgens can be demonstrated after the hormones are given to the mice either chronically (in slow-release capsules implanted at a subcutaneous site), or immediately prior to streptozotocin injection. These observations are consistent with the view that the critical factor that determines the susceptibility of mice to the hyperglycemic effects of streptozotocin is not the absolute concentration of androgens per se, but rather the relative overall level of androgens over estrogens in the recipient animal. Several alternative mechanisms for the effect of sex hormones on diabetogenic sensitivity are discussed.

Tumorigenicity of partial transformation mutants of Rous sarcoma virus

Chicken embryo cells infected with partial transformation mutants of Rous sarcoma virus were tested for tumor-forming ability in chickens and in nude mice. Cells transformed by each of these partial transformation mutants display different combinations of transformation parameters. They therefore present a potentially favorable system for analyzing which properties of transformed cells are necessary for tumor formation. We found that the relative tumorigenicity of the virus mutants was generally similar in chickens and in nude mice, except that certain temperature-conditional mutants appeared to be sensitive to the differences in body temperature of the two experimental animals. (The body temperature of nude mice is 4 to 5 degrees C lower than that of chickens). Thus, the nude mouse appears to be a suitable system for testing the tumorigenicity of transformed chicken cells. Because mice are nonpermissive for Rous sarcoma virus infection and replication, it was possible to recover the transformed chicken cells from the tumors in this host and to determine what phenotypic changes they had undergone during tumor development. We also examined the relationship between various cellular properties of the virus-infected chicken cells in vitro and their tumorigenicity in nude mice. The combined results of these two studies indicated that anchorage independence and plasminogen activator production were highly correlated with the tumor-forming ability of these cells, whereas loss of fibronectin did not correlate with tumorigenicity. Furthermore, the inability of the least tumorigenic virus mutant to stimulate the phosphorylation of a 36,000-Mr target of pp60src raises the possibility that the 36,000-Mr protein plays a role in tumor formation.

Preovulatory changes in luteinizing hormone releasing hormone concentrations in peripheral plasma in constant estrous rats at induced ovulation

Cervical stimulation was used to induce synchronous ovulation in rats that were induced into constant estrus by exposure to continuous lighting. Anti-LHRH or anti-LH serum completely blocked the induced ovulation when administered iv within 5 or 40 min after cervical stimulation. Peripheral concentrations of LH and LHRH hypothalamic content of LHRH were quantified before and at various intervals (0.5-70 min) after cervical stimulation. The radioimmunoassay for LHRH employed a specific antiserum, OAL-513, with high affinity and specificity and highly purified 125I-LHRH. Measurement of LHRH in extracts of 3-5 ml of plasma gave values that were readable in the middle portion of the standard curve. A two-fold increase in the LHRH concentration in peripheral plasma was observed 30 sec after the start of cervical stimulation. The elevated LHRH level was sustained for 15 min, though associated with large fluctuations. Serum LH levels started to rise 4 to 10 min and returned to the basal level 70 min after cervical stimulation. The hypothalamic LHRH content continued to increase throughout the entire experimental period and attained 140% of the initial level. No significant deflection due to LHRH release was observed in the hypothalamic LHRH content. Changes in the peripheral hormone level after cervical stimulation were component for chronologically reasoning the effectiveness of the antihormone treatment for blockage of the induced ovulation. From these results it is concluded that LHRH release before the preovulatory LH surge in light-estrous rats was brief in duration and erratic in mode.

Glucagon radioimmunoassay with use of antiserum to glucagon C-terminal fragment

In this pancreatic-glucagon-specific radioimmunoassay we used C-terminal-region-specific antiserum. OAL-123, produced against a 19-29 C-terminal fragment of porcine glucagon. On measurement of pooled plasma the ranges for intra- and inter-assay coefficients of variation were 4.8-8.1% and 7.5-10.7%, respectively. The concentration of immunoreactive glucagon in plasma of healthy subjects, as measured with the OAL-123 assay system, was 87.9 (SD 23.8) ng/L. Measurement of the same plasma samples with the 30K assay system (30K being an antiserum highly specific for pancreatic glucagon) showed a comparable value, 86.2 (SD 26.3) ng/L. We followed changes in human and dog plasma immunoreactive glucagon concentrations on arginine infusion and after glucose load, using the OAL-123 and the 30K assay systems, with identical results. Combining other results of comparative immunochemical characterization of the OAL-123 and 30K assay systems, we confirmed that the antisera raised against the C-terminal fragment of glucagon can be used in radioimmunoassay of pancreatic glucagon.

Glucagon radioimmunoassay with use of antiserum to glucagon C-terminal fragment

In this pancreatic-glucagon-specific radioimmunoassay we used C-terminal-region-specific antiserum. OAL-123, produced against a 19-29 C-terminal fragment of porcine glucagon. On measurement of pooled plasma the ranges for intra- and inter-assay coefficients of variation were 4.8-8.1% and 7.5-10.7%, respectively. The concentration of immunoreactive glucagon in plasma of healthy subjects, as measured with the OAL-123 assay system, was 87.9 (SD 23.8) ng/L. Measurement of the same plasma samples with the 30K assay system (30K being an antiserum highly specific for pancreatic glucagon) showed a comparable value, 86.2 (SD 26.3) ng/L. We followed changes in human and dog plasma immunoreactive glucagon concentrations on arginine infusion and after glucose load, using the OAL-123 and the 30K assay systems, with identical results. Combining other results of comparative immunochemical characterization of the OAL-123 and 30K assay systems, we confirmed that the antisera raised against the C-terminal fragment of glucagon can be used in radioimmunoassay of pancreatic glucagon.

Production of antisera to des Asn28 Thr29 Homoser27-glucagon; the development of radioimmunoassay for total glucagon-like immunoreactivity in human plasma

Antisera having a strong and strictly constant cross-reactivity for gut-GLI were raised in seven rabbits immunized with immunogen, a conjugate of BSA and des-Asn28, Thr29, Homoser27 -glucagon (CNBr-glucagon). All of the anti-CNBr-glucagon sera exhibited titer and affinity for glucagon sufficiently high enough to develop a sensitive radioimmunoassay. The relative crossreactivity of the antisera to gut-GLI was comparable to that of antiserum K-4023 which strongly crossreacted with gut-GLI. One of the anti-CNBr-glucagon sera, OAL-196, did not react with the glucagon 19-29 fragment at all. The intra- and inter-assay coefficients of variation were 3.8-5.0 and 6.0-7.3%, respectively, in the radioimmunoassay system for total GLI in human plasma using OAL-196. The fasting plasma total GLI was 374 +/- 18 pg/ml. The plasma total GLI during 50 g oral glucose load in normal subjects increased significantly, whereas the plasma IRG level measured with the anti-glucagon 19-29 serum, OAL-123, assay system was lowered. In the gastrectomized subjects, plasma total GLI measured with the present assay system elicited a marked increase following an oral glucose load. These results suggest that the radioimmunoassay using anti-CNBr-glucagon sera will be useful in measuring plasma total GLI.

Immunochemical identification of the chick HPRT gene transferred from chick erythrocytes to mammalian somatic cells

Immunochemical methods were used to identify the genetic origin of hypoxanthine phosphoribosyltransferase (HPRT) expressed in heteroploid, HPRT-deficient mouse (A9) cells and Chinese hamster ovary (K627) cells, after these cells were fused with chick embryo erythrocytes and selected for resistance to hypoxanthine-aminopterin-thymidine (HAT) medium. All of the HAT-selected clones produced HPRT activity which was immunoprecipitable by an antiserum specific for chick HPRT, but not by an antiserum specific for mouse and hamster HPRT. Furthermore, the HPRT activity in these clones was electrophoretically indistinguishable from chick liver HPRT and clearly different from mouse liver HPRT. These data provide evidence that the HPRT activity expressed in cell hybrids produced by the fusion of HPRT-negative mammalian cells and chick erythrocytes containing genetically inactive nuclei is indeed coded by the chick HPRT gene and that an avian gene can be stably incorporated and correctly expressed in a mammalian cells.

Specific resistance to 8-azaguanine in cells with normal hypoxanthine phosphoribosyltransferase (HPRT) activity: the role of guanine deaminase

The role of guanine deaminase in selective cellular resistance to 8-azaguanine was examined, using eight mammalian cell lines and their subclonal derivatives isolated on the basis of increasing resistance to this drug. 8-Azaguanine and 6-thioguanine are synthetic analogs of guanine and are lethal to cells with normal hypoxanthine phosphoribosyltransferase (HPRT) activity. In principle, however, HPRT-positive cells could become selectively resistant to 8-azaguanine if, by any mechanism, the cells expressed higher levels of guanine deaminase. This is because 8-azaguanine, but not 6-thioguanine, is converted by this enzyme to a noncytotoxic metabolite, 8-azaxanthine. Our study shows that HPRT-positive cells inherently resistant to relatively high levels of 8-azaguanine contain high levels of guanine deaminase. In general, guanine deaminase activity was higher in 8-azaguanine-resistant cells, regardless of their HPRT activity. Our results support the view that elevated guanine deaminase activity constitutes a potential mechanism of selective 8-azaguanine resistance in cells with normal HPRT activity. Guanine deaminase levels were significantly elevated in HPRT-positive cells briefly exposed to sublethal concentrations of 8-azaguanine, but this elevation was transient. Long-term exposure of cells to increasingly higher levels of the drug did not lead to high stable levels of guanine deaminase, indicating that 8-azaguanine is not an inducer of guanine deaminase in the cells examined.

Heterogeneity of immunoreactive motilin

Motilin-like immunoreactivities were examined in extracts of duodena of pig, human, dog, rat, cat, rabbit and guinea pig with a combination of radioimmunoassays using three different antisera possessing distinct region-specificities. Antisera GP-1103 and R-1104 were rather C-terminal specific, but the immunological feature of GP-1103 was different from that of R-1104. In the case of antiserum GP-1103, the Glu residue in position 15 in the motilin molecule participated in antigen-antibody interaction, but not in the case of R-1104. Antiserum MBR-02 was N-terminal specific, with of the three assay systems, only a single major peak was detected in the elution profile from BioGel P-10 column of motilin-like immunoreactivity in the porcine duodenal extract, of which the elution volume corresponded to that for synthetic porcine motilin. On the other hand, the gel filtration profiles of the human and canine duodenal extracts consisted of two or three peaks of the immunoreactivity. The major peak emerged in the elution volume identical with that for synthetic porcine motilin and the other two peaks were eluted earlier. The peak which was eluted in the volume corresponding to that for BSA marker was detectable only by the assay system with N-terminal specific antiserum MBR-02. The immunoreactivity of the major peak component in the human, canine or rat extract was found to be lower than that in the porcine extract. The present data may indicate the existence of heterogeneity of motilin-like immunoreactivity and species variation of the structure of the immunoreactive motilin.

pJT2: unusual H1 plasmid in a highly virulent lactose-positive and chloramphenicol-resistant Salmonella typhimurium strain from calves

A lactose-positive and chloramphenicol-resistant strain of Salmonella typhimurium of high virulence was isolated from an outbreak of enteric and septicemic salmonellosis in veal calves. the lactose-positive marker was located on an H1 plasmid, pJT2, together with resistance to chloramphenicol, streptomycin, sulfonamides, and tetracycline, pJT2 was unusually large and had a molecular weight of about 150 X 10(6). A similar plasmid was also present in a third of the Escherichia coli strains isolated from the intestines of septicemic calves during the outbreak. Spontaneously derived Lac- derivatives of pJT2 had an approximate molecular weight of 140 X 10(6).

Heterogeneity of plasma motilin in patients with chronic renal failure

Plasma immunoreactive motilin (IRM) concentrations were strikingly higher in patients with chronic renal failure (CRF) than in normal subjects. IRM in azotemic plasma was heterogeneous in gel-filtration profile. The first peak eluted in the void volume of the column and the second and the third one, comprising a major portion of IRM content, came out coincidentally with insulin and authentic motilin, respectively. By contrast, no discernible amount of IRM was found in the region corresponding with the second peak in gel-filtration of the plasma from normals and very little in a patient with ileus whole plasma IRM level was elevated. The hypermotilinemia and the accumulation of this high molecular weight motilin in patients with CRF suggest that the kidney plays some role in the elimination of motilin, and further, that the clearance of the high molecular motilin is more dependent on renal function than that of authentic motilin. The present paper emphasizes the necessity for clarifying the significance of the heterogeneity of IRM in CRF.

Isolation of somatic cell mutants with specified alterations in hypoxanthine phosphoribosyltransferase

Cellular resistance to 6-thioguanine is almost always associated with a complete loss of hypoxanthine phosphoribosyltransferase (HPRT) activity, while resistance to 8-azaguanine has frequently been shown to occur independently of any changes in the HPRT activity. As a result, mutant cells selected for resistance to 6-thioguanine are also resistant to 8-azaguanine, but cells selected for 8-azaguanine resistance are not necessarily cross-resistant to 6-thioguanine. Our previous studies demonstrated that this difference is due to differential utilization of the two purine analogs by HPRT in the cells. In this paper we describe a novel selective procedure for the systematic isolation of cellular mutants that contain wild-type levels of HPRT, are sensitive to 6-thioguanine, and yet are able to survive in medium containing both HAT and a high level of 8-azaguanine. We also present evidence which shows that such mutants arise through a mutation that specifically alters the HPRT molecule so that the enzyme no longer recognizes 8-azaguanine as a substrate, while remaining catalytically functional with hypoxanthine and 6-thioguanine. Mutants of this type may be useful as a marker in gene-transfer experiments.

A sudden decline in ampicillin resistance in Salmonella typhimurium

Starting in 1975, an abrupt decline in ampicillin resistance of Salmonella typhimurium (the most common and antibiotic-resistant serotype) occurred in New York City. The present lower rate of 5% to 7.9% at our hospitals represents a return to the 1965 level. At the same time, the ampicillin resistance in S typhimurium from calves and other farm animals from upper New York State, which has been rising since 1972, has reached 75%. Substantial differences between levels of resistance in Escherichia coli from animals and humans were also noted. The divergence of the trends in S typhimurium from these two sources in New York State suggests a substantial degree of separation of the respective reservoirs of Salmonella and of antibiotic resistance.

Production of anti-glucagon sera with a C-terminal fragment of pancreatic glucagon

The C-terminal region-sepcific anti-glucagon sera were raised in rabbits using as immunogen, and conjugate of BSA and a C-terminal fragment of pancreatic glucagon. The hapten was prepared by trypsin digestion of the glucagon, which was proved to be a 1:3 mixture of glucagon (18--29) and (19--29). Six rabbits were immunized by subcutaneous injection of an emulsion of the conjugate with complete Freund's adjuvant and five of the rabbits produced antibodies to the glucagon (GC-1, GC-2, GC-3, GC-5 and GC-6). For comparison, rabbit antisera were also produced against glucagon polymer (GA-10) and syrupy glucagon fibrils (PGA-2). All these antisera as well as the pancreatic glucagon-specific antiserum 30 K were characterized with dog gut-extract (gut-GLI) and glucagon-related peptide fragments in the radioimmunoassay systems. The assay systems utilized 125 I-monosubstituted pancreatic glucagon as tracer and human mono-component glucagon as standard. All sera of the GC-series crossreacted with the dog gut-extract very weakly and antisera GC-5 and GC-6 exhibited the lowest crossreactivities with the extract, which were shown to be as low as that of 30k. Characterization of the antiserum GC-5 with purified glucagon related fragments indicated that the major antigenic determinant located exactly in the C-terminal region of glucagon. The present results clearly showed high efficiency of the use of the glucagon C-terminal fragment as hepatenic immunogen in obtaining the C-terminal region-specific, i.e., pancreatic glucagon-specific antisera.

Tumorigenicity of revertant from an SV40-transformed line

A syndrome of in vitro properties correlates with the tumorigenicity of SV40-transformed rodent cells. These properties are: plasminogen activator production, loss of large actin cables, and anchorage-independent growth. An established rat fibroblast line, its SV40 transformant, several T-antigen negative revertants, and a spontaneous retransformant isolated from one of the revertants were analyzed in vivo for their tumorigenicity and in vitro for the syndrome. The two transformed lines were highly tumorigenic, and had clearly abnormal in vitro properties. The parental rat line was weakly tumorigenic in nude mice and demonstrated a slightly transformed response in the in vitro assays. The revertants were completely nontumorigenic. Expression of the in vitro syndrome was not uniform for all revertants; however, most cell lines maintained the correlation of the syndrome and tumorigenicity.

Cellular tumorigenicity in nude mice. Role of susceptibility to natural killer cells

The athymic nude mouse is a useful animal model for assaying the neoplastic growth potential in vivo of animal cells transformed in vitro. Despite the demonstrated absence of thymus-dependent immunological functions, however, the nude mouse has now been shown to reject transplants of certain highly malignant heterologous tumors. In addition, a few transformed mammalian cell lines that exhibit all or most of the cellular phenotypes usually associated with malignancy fail to grow as tumors when injected into nude mice. In a continuing study to identify the in vitro phenotypes associated with tumor-forming ability in vivo, we investigated the role of cellular susceptibility to the naturally occurring, thymus-independent lymphocytes (natural killer or NK cells) in determining tumor induction by animal cells in nude mice. A representative collection of animal cells (ranging from normal human diploid cell strains to highly tumorigenic clonal cell lines, either transformed in vitro or derived from experimental tumors) was tested to see if the ability of cells to form tumors is consistently correlated with their susceptibility to NK cell-mediated lysis measured in vitro with splenic leukocytes from nude mice. If the physiological role of the NK cells in vivo were to recognize, and possibly to destroy, incipient tumor cells in situ, a direct association between cellular tumorigenicity and susceptibility to NK activity, might be expected. If, on the other hand, the formation of growing tumors by animal cells in nude mice depended on their ability to escape the cytolytic activity of NK cells, cellular tumorigenicity would be associated with cellular resistance to NK cells. Results obtained in this study failed to confirm either of these associations. Thus, cellular suscepbibility to NK cells, at least as determined by direct cytotoxicity assay in vitro, is not a useful predictive indicator of cellular tumorigenicity in nude mice.

An approach to defining the etiology of animal abortions

Attempts to define the etiology of abortions on a regular continuing basis have been few, and largely unsuccessful. Problems of such a project include cost, difficulty of securing satisfactory samples, a laboratory organization of sufficient breadth, capacity and dedication to perform and interpret the necessary examinations, knowledgeable cooperation of the practitioner, and past reliance on isolated findings substituting for sound criteria for diagnosis. A program was created which was intended to overcome the difficulties. The plan was so constructed as to permit addition or removal of procedures as indicated.