Formyl-met-tRNA inff supMet,a questionable initiator tRNA in eukaryotic systems

Met-tRNA _inff ^supMet is a much more efficient initiator in cell-free eukaryotic protein synthesis than the formylated species. Chemically and enzymatically formylated Met-tRNA _inff ^supMet exhibit the same activity. In contrast acetyl Met-tRNA _inff ^supMet is unable to initiate polypeptides in vitro.     

A model for the tertiary structure of transfer ribonucleic acids

In view of the possible changes of the structure of DNA at different relative humidities, a similar model for tRNA is proposed. In the native form, the sugar phosphate backbone folds repeatedly on itself resulting in a circular rod structure of about 50 Å in length and about 25 Å in diameter. Both the amino-acyl end and the anticodon site are surrounded by segments of base sequences common to different tRNA’s.     

Immune response in human subjects at high altitude

Levels of immunoglobulins were determined in persons exposed to high altitude. The individuals studied included high altitude natives, sea level residents at high altitude for 2 years, and recent arrivals at high altitude. Increased IgG and IgA levels were found in high altitude natives and sea level residents at high altitude for 2 years when compared with sea level residents. In recent arrivals marked increase of IgG and IgG levels and slight rise in IgM was seen. Recent arrivals who suffered from high altitude pulmonary oedema showed marked elevation of IgG, IgM, and IgA. Immunoglobulin responses to both primary and secondary TAB inoculation were of a higher magnitude and more sustained at high altitude than at sea level.     

The investigation of the effect of pollination on ribosomal RNA,transfer RNA and DNA contents in styles ofNicotiana alata.

Using the phenol extraction method and MAK column chromatography the contents of nucleic acids in styles ofNicotiana alata were estimated before and up to 48 h after compatible pollination. As a result of pollination, high-molecular-weight rRNA and DNA registered a significant increase in their content approximating 30% and 16% respectively. The change in sRNA (4-S tRNA and 5-S rRNA) level was very slight and non-significant. In pollen grains there is an unusually high amount of rRNA with respect to the content of other nucleic acids and the rRNA/tRNA ratio approximates 14 : 1. On the other hand, in non-pollinated styles the content of rRNA is only about 6 times higher than that of tRNA. The changes in nucleic acid level found in styles after pollination are at least in a major part the result of the addition of the nucleic acids present in the amount of pollen used for pollination. The high rRNA level relatively to tRNA being generally associated with rapidly growing cells, its significance in pollen may be related to the rapid growth of pollen tubes.     

NaturalMycoplasma arthritidis infection in mice

B6C3F₁ mice from a hybrid production colony frequently were serologically positive by enzyme-linked immunosorbent assay (ELISA) and consistently negative by culture forMycoplasma pulmonis. Subsequently, 162 mice were obtained and intensively studied using an expanded group of cultural procedures, ELISA, and histopathology. Lesions attributable to mycoplasma infection were not found, butMycoplasma arthritidis was isolated from 20 mice. TheM. pulmonis ELISA was positive (IgM, IgG, or both) in 113 mice. Selected sera were tested simultaneously in both theM. pulmonis ELISA and in an ELISA usingM. arthritidis antigen, and were found to be positive in both the IgM and IgG classes in both ELISAs. Thus, cross-reacting antibody was produced in mice naturally infected withM. arthritidis, confirming previous observations based on experimental infections. To our knowledge, this is the first report of naturalM. arthritidis infection in laboratory mice.     

tRNA synthesis in germinating pollen

The synthesis of tRNA was demonstrated in pollen ofNicotiana tabacum L. according to the incorporation of labeled uracil, adenosine and guanosine during 4 h of germination. tRNA was extracted from postribosomal supernatant and purified by polyacrylamide gel electrophoresis. The incorporation of guanosine was about 1.68 times higher than that of adenosine. This finding indicates that the whole tRNA chain is formed in pollen tubes.     

The role of homoeologous group 1 chromosomes in the control of rRNA genes in wheat

The presence of rRNA genes on homoeologous chromosomes 1A, 1B, and 1D of hexaploid wheat was investigated by rRNA/DNA hybridization, using DNA purified from aneuploid and substitution line derivatives of the variety Chinese Spring. Doubling the number of 1B chromosomes increased the number of rRNA genes by 31–49% but deleting the 1B chromosomes decreased the number by only 15–23%. This suggests that changes may occur in rRNA gene multiplicity at other nucleolar organizer sites to partially compensate for a deficiency of rRNA genes. There was no unequivocal evidence of rRNA genes on Chinese Spring chromosome 1A or 1D, but other varieties were shown to have rRNA genes on chromosome 1A. These results are consistent with the cytological observations that chromosomes 1A and 1B but not 1D possess nucleolar organizers.     

Biological activity of 125iodine labelled globin mRNA in an Ehrlich ascites cell-free system

Globin mRNA was isolated from avian erythroblasts and labelled with ¹²⁵iodine to a specific activity of 4.5×10⁶ dpm μg^-1 mRNA. The labelling procedure was modified as compared to common techniques in order to protect the mRNA against degradation. When this RNA is translated in an Ehrlich ascites cell-free system globin chains are synthesized as is demonstrated by the analysis of the in vitro synthesized products. The biological activity of ¹²⁵iodine labelled mRNA has proven to be 30% of that of unlabelled mRNA.