摘要:

SummaryThree mouse tumour cell lines grew continuously in 3 μM 5‐bromodcoxyuridine (BUdR). One line (MC‐2) produced a retrovirus and altered in morphology in the presence of BUdR or 5‐iododeoxyuridine (IUdR). These effects, which could be reversed by growth in normal medium, were similar to those reported for the B‐16 mouse melanoma line. The B‐16 line used in this study, however, as well as a variety of human cells (six melanoma lines and three fibroblast strains), were much more sensitive to BUdR, 0·03–0·1 μM being the maximum tolerated levels for continuous growth. No virus production or changes in morphology were induced in these cells by BUdR, deoxyuridine (UdR), 5‐fluorodcsoxyuridine (FUdR) or thymidine (TdR). The results of cell labelling and growth studies showed a correlation of Incorporation of BUdR into DNA with toxicity. Compared on a competitive basis with 1 μM TdR, the order of incorporation of 1 μM nucleosides by two human cell lines was TdR = BUdR = 1UdR ≥ UdR ≥ ≥ FUdR. In contrast to previous reports that FUdR is incorporated into RNA but not into DNA, half of the FUdR label was found in alkali‐stable, DNase‐sensitive material. Over 90% of the other compounds was incorporated into DNA. All of the UdR and 60% of the 1UdR label was incorporated as thymidine: this conversion could be inhibited by labelling in the presence of FUdR.

ISSN:0004-945X    

DOI:10.1038/icb.1979.58

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryCholecystokinin‐(CCK) like peptides have been measured in the brain and small intestine of ob/ob hyperglycaemic mice and lean littermates. CCK‐like peptides were measured by radioimmunoassay employing an antiserum to CCK octapeptide (CCK 8) and gastrin 17 I125label. Although this antiserum detects gastrin with equal affinity to CCK, concomitant assay of tissue extracts with a gastrin specific antibody failed to reveal any detectable gastrin. Extracts of brain and small intestine showed levels of CCK of 96 ± 12·6 pmolg−1and 45 ± 6·1 pmol g−1in the obese mice; 101 + 8·7 pmol g−1and 36 ± 2·5 pmol g−1in the lean mice. These were not significantly different. It has been suggested that CCK may be a satiety factor and it has been reported that there is less CCK in brain of obese mice compared with lean mice. This study has failed to confirm the previous finding and indicates that, in this animal model, tissue levels of CCK probably do not modulate appetite.

ISSN:0004-945X    

DOI:10.1038/icb.1979.59

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

ISSN:0004-945X    

DOI:10.1038/icb.1979.60

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryRotavirus RNA prepared from calf, pig, mouse, deer, foal and dog‐adapted human isolates was compared using polyacrylamide gel electrophoresis. Reproducible differences in the RNA migration patterns, were found between all isolates. There were 11 clearly resolved segments in the pig, mouse and foal samples. The calf rotavirus RNA and deer rotavirus RNA separated into 9 bands and 10 bands, respectively. The dogs‐adapted human virus migrated in 12 bands, and this probably mulls from the complex passage history of the original human rotavirus isolate.

ISSN:0004-945X    

DOI:10.1038/icb.1979.61

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryWhen human tonsillar lymphocytes are cultured with pokeweed mitogen they generate a large number of antibody‐secreting cells. A substantial number of the plaque‐forming cells generated have specificity for sheep erythrocytes but very few are specific for either bovine or horse erythrocytes. We have investigated the physical properties of sheep erythrocyte‐specific precursors and have found that they have characteristics of larger lymphocytes and are heterogeneous with respect to density. Our results support the concept that the percursors which can be induced by pokeweed mitogen to develop into plaque‐forming cells belong to a pie‐activated sub‐population of lymphocytes.

ISSN:0004-945X    

DOI:10.1038/icb.1979.62

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryCultures of human tonsillar lymphocytes stimulated by pokeweed mitogen in the presence of hydrocortisone succinate generate more sheep red blood cell‐specific plaque‐forming cells than when the hydrocortisone is absent. Such enhancement is even more marked when sheep red blood cells and pokeweed mitogen are present in cultures this contrasts with the inability of sheep red blood cells to enhance pokeweed mitogen‐stimulated response in cultures lacking hydrocortisone. Hydrocortisone causes greater enhancement when the concentration of cells in culture is high than when it is low. These data are consistent with hydrocortisone inhibiting the activity of suppressor cells which would otherwise mask helper effects.

ISSN:0004-945X    

DOI:10.1038/icb.1979.63

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryIn this methodological paper an immunoprecipitation technique has been optimised for the identification of antigens ofPlasmodium berghei‐infected blood which react with antibody specificities in a host‐protective antiserum. Extracted3H‐leucine biosynthetically‐labelled products of infected blood were sequentially reacted and precipitated with sera from mice which had been exposed toP. bergheibut which were either non‐protected or protected against lethal infection, protection having been shown to be transferable to naive recipients with the appropriate scrum. As analysed by polyacrylamide gel electrophoresis under reducing conditions, a small number of molecular species was detected in immunoprecipitates using host‐protective sera which were apparently not quantitatively precipitated out of the complex mixture of labelled products of infected blood using sera from non‐protected mice.

ISSN:0004-945X    

DOI:10.1038/icb.1979.64

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryTwo separate experiment were conducted to examine the effects of exogenous oestrogen on selective transfer of IgG1into mammary secretion of ewes. In one experiment, non‐pregnant ewes were induced to lactate artificially by first developing mammary glands with injections of progesterone plus low doses of oestrogen then triggering milk secretion with either glucocorticoid or high doses of oestrogen. In the other experiment, lactating ewes were injected with oestrogen each day for 6 days.The results of the experiments suggest that oestrogen affects selective transfer of IgG1into mammary secretion of the ewe. Moreover, the results show that, in the absence of high levels of oestrogen in blood, the magnitude of the selective transfer of IgG1into mammary secretion is related inversely to the synthetic activity of the glandular epithelium.

ISSN:0004-945X    

DOI:10.1038/icb.1979.65

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryCells of (CBA/H × BALB/c) F1hybrid mice express CBA/H‐derived H‐2kantigens more weakly than do CBA/H ceils, but H‐2dantigens are similarly expressed by F1and BALB/c cells. This was evident when F1hybrid macrophages were compared with CBA/H and BALB/c macrophage as targets for both alloreactive and H‐2 restricted antiviral Tc cells. Quantitative absorption of anti‐H‐2Kkserum by spleen cells of F1or CBA/H mice also suggested about 3‐fold less H‐2Kkantigen on F1cells. With the use of two anti‐H‐2Kkmonoclonal antibodies. 30R3 and 27R9, the reduced expression of H‐2Kkin this F1hybrid was further analysed in a two‐stage radio‐immunoassay employing the uptake of125I‐protein A to measure antibody binding. By a thermodynamic approach, estimates were made of the dissociation constant for antibody binding, and of the relative numbers of H‐2 molecules expressed by both F1hybrid and CBA/H spleen cells. The results indicate that there is a two‐fold reduction in the number of H‐2Kkmolecules expressed on the surface of F1cells. Similar dissociation constants for F1and CBA/H cells indicated no detectable qualitative difference in their H‐2Kkantigens with respect to sites recognized by 30R3 and 27R9.

ISSN:0004-945X    

DOI:10.1038/icb.1979.66

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY

摘要:

SummaryAdministration of a protein antigen preparation fromSalmonella enteritidis11RX at the site of challenge with Lewis lung carcinoma inhibited tumour development in mice previously immunised with live bacteria, but not control mice. The kinetics of tumour growth indicated that the inhibition of tumour development was due to a reduction of the initial tumour inoculum rather than the development of specific anti‐tumour immunity.

ISSN:0004-945X    

DOI:10.1038/icb.1979.67

出版商:Nature Publishing Group    

年代:1979

数据来源: WILEY