The major pterin in Tetrahymena pyriformis is 6-(D-threo-1,2,3-trihydroxypropyl)-pterin (D-monapterin) and not 6-(L-threo-1,2-dihydroxypropyl)-pterin (ciliapterin).

The major pterin in Tetrahymena pyriformis, strain W, earlier suggested to be L-threo-biopterin and named ciliapterin [1] is now identified as D-threo-neopterin (D-monapterin). This is the first example of a natural D-monapterin. This compound was characterized by its chromatographic behavior, its fluorescence properties and by its oxidation product with alkaline permanganate. The final identification was obtained by comparison with an authentic material using an exchange ligand chromatography method with D-phenylalanine as chiral modifier and Cu (II) as metal ion. D-monapterin is also present as the major pterin in Tetrahymena pyriformis strains GL and ST, and in Tetrahymena thermophila.     

Prion replication-once again blaming the dendritic cell.

The lymphoid system is known to be involved in the propagation and spread of scrapie. However, the identity of the cell type responsible for scrapie replication remains controversial. A new study provides evidence that the follicular dendritic cells in the spleen are the targets of this infectious form of prion (pages 1308-1312).     

Biotinylated oligonucleotide probes for the detection and the characterization of TEM-type extended broad spectrum β-lactamases in enterobacteriaceae

Point mutations in the nucleotide sequence of the structural genes for the TEM-type penicillinases can broaded their substrate spectrum towards all beta-lactams except cephamycins and imipenem. The presence of such variants on self-transferable plasmids accounts for the dissemination of this new type of resistance to numerous species of Enterobacteriaceae in various countries. We have synthetized biotinylated oligonucleotide probes for the detection and the discrimination of parental and mutated nucleotide sequences of TEM enzymes. Seven clinical isolates belonging to four species and harbouring TEM-1, TEM-3 or TEM-6 were studied. The results obtained indicate that detection of TEM-derived broad spectrum beta-lactamases in clinical isolates of Entero-bacteriaceae is possible with biotinylated oligonucleotide probes.     

Ribosome specificity for the formation of guanosine polyphosphates

Ribosomes obtained from $\text{Bacillus brevis}$ (ATCC 8185) were slightly active in synthesizing guanosine polyphosphates, which activity was greatly stimulated by addition of $\text{Escherichia coli}$ stringent factor. $\text{Chlamydomonas reinhardtii}$ chloroplast ribosomes did not produce guanosine polyphosphates on incubation but responded with abundant synthesis to addition of the stringent factor from $\text{E. coli}$. In contrast, cytoplasmic ribosomes from the same organism did not respond. Interchange experiments between either subunit from chloroplasts with the $\text{E. coli}$ counterparts showed good activity. When the small subunit of cytoplasmic $\text{Chlamydomonas}$ ribosomes was combined with the large subunit of $\text{E. coli}$ or of chloroplasts, a small but definite response was obtained.     

Alkaloids of callus tissues and redifferentiated plantlets in the papaveraceae

The callus tissues from 11 representative species of the Papaveraceae and the redifferentiated plantlets from four species were successfully derived and maintained. The alkaloids in the callus tissues and redifferentiated plantlets were examined in comparison with those of the original plants. All the callus tissues are similar in their alkaloid chemistry and contain benzophenanthridine, protopine and aporphine type alkaloids. By contrast, the plantlets have a more specific alkaloid pattern, being similar in content to the original plants.     

The effect of season of growth on the chemical composition of cambial saps of Eucalyptus regnans trees

Summary Bark was stripped, at monthly intervals, from the stems of ten previously-unsampled trees of Eucalyptus regnans F. Muell. The exposed surfaces of inner phloem and outer xylem yielded phloem and cambial saps which were rapidly frozen. After freeze drying to determine the contents of water and dry-matter, the samples were extracted with 80% ethanol. The main components in this extract are low molecular weight carbohydrates and salts of inorganic acids. The carbohydrates comprise stachyose, raffinose, sucrose, galactinol, glucose, fructose, myo-inositol and galactose; sucrose is invariably the major component. The amounts of all components varied widely during the sampling period. Multiple regression analyses showed that season of growth has a significant effect on sucrose, glucose, fructose, total sugars and soluble dry-matter, maxima being recorded near the beginning of autumn and spring, and minima near the beginning of winter and summer; that oligosaccharide and myoinositol contents are significantly related to atmospheric temperature; and that rainfall has a significant effect on the hexose and total sugar contents, saps from the xylem surfaces being more affected than those from the phloem surfaces. The translocated photosynthates in E. regnans appear to be oligosaccharides of the raffinose family and sucrose. Significant negative correlations between oligosaccharides and both sucrose and myoinositol, and significant positive correlations between sucrose and both glucose and fructose, are consistent with enzymic hydrolysis and resynthesis of most di- and oligosaccharides. The biosynthetic demands of developing secondary tissues and/or the fluctuations in composition of sieve-tube assimilates appear to control the composition of the sugars in the saps. Oligosaccharides and sucrose may function as soluble reserve substances as well as translocated photosynthates. It is possible that myoinositolis a key component in the interconversion processes of the sugars; experiments with radioactive sugars tend to lend support to this contention, especially during winter conditions.     

Deficiency of transporter for antigen presentation (TAP) in tumor cells allows evasion of immune surveillance and increases tumorigenesis.

Proteins involved in class I MHC (MHC-I) Ag processing, such as the TAP, are deficient in some human tumor cells. This suggests that antitumor responses by CD8 T cells provide selection pressure to favor outgrowth of cells with defective processing of tumor Ags. Nonetheless, this evidence is only correlative, and controlled in vivo experiments have been lacking to demonstrate that TAP deficiency promotes survival of tumor cells. To explore the role of Ag processing defects in tumor progression, matched panels of TAP1-positive and TAP1-negative tumor cell lines were generated from a parental transformed murine fibroblast line. Inoculation of C57BL/6 mice with TAP1-negative cells produced large and persistent tumors. In contrast, TAP1-positive cells did not generate lasting tumors, although small tumors were detected transiently and regressed spontaneously. Both TAP1-positive and TAP1-negative cells produced tumors in athymic mice, confirming that TAP-dependent differences in tumorigenicity were due to T cell-dependent immune responses. Inoculation of C57BL/6 mice with mixtures of TAP1-positive and TAP1-negative cells produced tumors composed exclusively of TAP1-negative cells, indicating in vivo selection for cells with TAP deficiency. Thus, loss of TAP function allows some tumor cells to avoid T cell-dependent elimination, resulting in selection for tumor cells with deficient Ag processing.     

Seawater requirement for the production of lipoxazolidinones by marine actinomycete strain NPS8920

A novel marine actinomycete strain NPS8920 produces a new class of 4-oxazolidinone antibiotics lipoxazolidinone A, B and C. Lipoxazolidinone A possesses good potency (1-2 microg/mL) against drug-resistant pathogens methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE). Strain NPS8920 exhibits different morphologies in both agar and submerged cultures. The ability of strain NPS8920 to sporulate on saline-based agar media but not on deionized water-based agar medium supported that strain NPS8920 is a marine actinomycete. While strain NPS8920 does not require seawater for growth, the production of lipoxazolidinones by strain NPS8920 can only be detected in the seawater-based media. The optimal production of lipoxazolidinones was observed in the natural seawater-based medium. Strain NPS8920 produced 10-20% of lipoxazolidinones in the synthetic sea salt Instant Ocean-based medium and no production in the sodium chloride-based and deionized water-based media.