1H-NMR spectroscopy of the cell membranes of thymus lymphocytes in AKR mice

360 MHz 1H NMR was used to monitor the changes of AKR mice thymus lymphocytes in cases of spontaneous and transplantable leukemia and vincristine administration. A comparison of relative signal intensities of methyl and methylene fatty acid chains protons and phosphatidylcholine headgroups protons enables to monitor leukemia development and vincristine effect. Spin-lattice relaxation curves of the same protons of leukemic thymi lymphocytes are well fitted by biexponential functions, bringing evidence for two regions with different lipid mobility.     

Detection of herpes simplex virus-specific DNA sequences in latently infected mice and in humans.

Herpes simplex virus-specific DNA sequences have been detected by Southern hybridization analysis in both central and peripheral nervous system tissues of latently infected mice. We have detected virus-specific sequences corresponding to the junction fragment but not the genomic termini, an observation first made by Rock and Fraser (Nature [London] 302:523-525, 1983). This "endless" herpes simplex virus DNA is both qualitatively and quantitatively stable in mouse neural tissue analyzed over a 4-month period. In addition, examination of DNA extracted from human trigeminal ganglia has shown herpes simplex virus DNA to be present in an "endless" form similar to that found in the mouse model system. Further restriction enzyme analysis of latently infected mouse brainstem and human trigeminal DNA has shown that this "endless" herpes simplex virus DNA is present in all four isomeric configurations.     

Conformational changes in DNA during development of spontaneous leukosis in AKR mice

The dynamics of conformational changes in thymus and spleen DNA of 3-9-month old mice line AKR during the development of spontaneous lymphoid leukosis was studied by the retention on nitrocellulose filters. It was shown that the degree of DNA condensation for healthy and deceased animals differs, which is probably due to different intensity of endogenous oxidation. Seasonal conformational changes in spleen DNA from healthy mice of line F1 were revealed.     

Promotion of tumor growth by transfecting antisense DNA to suppress endogenous H-2Kk MHC gene expression in AKR mouse thymoma

Many AKR spontaneous thymomas are reported to express different amounts of the major histocompatibility complex class I H-2Kk molecules. Moreover, H-2Kk-deficient AKR tumor cells are found to be more malignant when compared to tumor cells that express abundant levels of the H-2Kk molecules. To corroborate further the role of H-2Kk in tumorigenesis of AKR leukemia, we have, in this study, expressed antisense H-2Kk RNA in a high-H-2Kk-expressing and poorly tumorigenic AKR thymoma cell line 369. The down-regulation of H-2Kk molecules in the transfected 369 clones rendered them more tumorigenic in syngeneic AKR/J mice. The increase in oncogenicity correlates well with a concomitant reduction in their susceptibility to tumor-specific cytotoxic T lymphocytes in vitro. These results suggest the relevance of H-2Kk molecules in the immune surveillance of AKR tumors.     

Immunosupressive effect of hypokinetic stress and sensitization of thymus to glucocorticoids

24-hour hypokinetic stress expressed in decrease of sensitivity of cellular and humoral immu nity to subsequent immunization with sheep erythrocytes was studied. The development of this phenomenon is associated with sensitization of lymphoid tissue to hypoplasia effect of glycocorticoid hormones. In introduction of glycocorticoid stress, the animals revealed a more pronounced depression of proliferative activity of thymocytes compared with non stressed animals.     

Detection of long eukaryote-specific pyrimidine runs in repetitive DNA sequences and their relation to single-stranded regions in DNA isolated from sea urchin embryos.

Precursor molecules for Escherichia coli tRNAs that accumulated in a temperature-sensitive mutant defective in tRNA synthesis (TS709) were investigated. More than 20 precursors were purified by two-dimensional polyacrylamide gel electrophoresis. The purified molecules were analyzed by RNA fingerprint analysis and/or in vitro processing after treatment with E. coli cell-free extracts. The molecular sizes of most of the precursors identified were in the range of 4 to 5 S RNAs, although several larger ones were also detected. Fingerprint analysis revealed that the precursors generally differ from the corresponding mature tRNAs in the 5′ termini, having extra nucleotides. Thus, the genetic block in TS709 was shown to affect the trimming of the 5′ side of tRNA by impairing the function of RNAase P. Although this mutant had been isolated as a conditional mutant defective in the synthesis of su⁺ 3 tRNA₁^Tyr, the synthesis of many tRNA species was affected at high temperature. On the basis of their mode of maturation in vivo, the precursor molecules were discussed as intermediates in tRNA biosynthesis in E. coli. Accumulation of these intermediates was accounted for as a common feature of E. coli mutants defective in RNAase P function.     

Detection of polyadenylation signals in human DNA sequences

We present polyadq, a program for detection of human polyadenylation signals. To avoid training on possibly flawed data, the development of polyadq began with a de novo characterization of human mRNA 3' processing signals. This information was used in training two quadratic discriminant functions that polyadq uses to evaluate potential polyA signals. In our tests, polyadq predicts polyA signals with a correlation coefficient of 0.413 on whole genes and 0.512 in the last two exons of genes, substantially outperforming other published programs on the same data set. polyadq is also the only program that is able to consistently detect the ATTAAA variant of the polyA signal.     

Detection of 5-methylcytosine in DNA sequences.

Col E1 DNA has methylated cytosine in the sequence 5'-CC*(A/T)GG-3' and methylated adenine in the sequence 5'-GA*TC-3' at the positions indicated by asterisks(*). When the Maxam-Gilbert DNA sequencing method is applied to this DNA, the methylated cytosine (5-methylcytosine) is found to be less reactive to hydrazine than are cytosine and thymine, so that a band corresponding to that base does not appear in the pyrimidine cleavage patterns. The existence of the methylated cytosine can be confirmed by analyzing the complementary strand or unmethylated DNA. In contrast, the methylated adenine (probably N6-methyladenine) cannot be distinguished from adenine with standard conditions for cleavage at adenine.     

Leukemia in AKR mice: III. Size distribution of suppressor T-cells in AKR leukemia and neonatal mice

Suppression of in vitro antibody forming potential of normal cells by leukemic cells of AKR and normal neonatal mice have many similarities. In both cases the suppression is by cell contact rather than by the elaboration of soluble suppressive factors and the suppression is sensitive to both x-irradiation and mitomycin C treatment. When the size distribution of suppressing cells in thymus and spleen were compared by velocity sedimentation, both leukemic and neonatal suppressing cells had similar size distribution in each organ. Both large and small cells in the thymus suppress but only large cells (sedimentation velocity >3.5 mm/hr) in the spleen are able to suppress. Leukemic cells in lymph node have a splenic size distribution, viz., only large cells suppress. Both large and small cells of a subcutaneously growing long passage AKR lymphoma are able to suppress. While large cells contain the bulk of cells actively incorporating tritiated thymidine and thus probably in cycle, small but significant amounts of incorporation in small suppressing cells is also seen.     

The study of DNA sequences by their sequences of twist angles

To study the properties of DNA sequences we have transformed the sequences of bases into the sequences of twist angles along the chain of DNA double helix by using the Dickerson sum function. The Fourier transform and the auto-correlation function of the twist angles sequences have been used to study the periodicity and randomness of the original DNA sequences. Basing on the correlation coefficient, a "distance" between two DNA fragments has been defined and used to compare some realistic DNA sequences. It is hoped that the techniques developed here could be used to analyze more realistic DNA sequences.