On the "activation" of cytokinins.

A number of cytokinin analogs containing modifications in the heterocyclic moiety were prepared. These compounds were tested for activity as cytokinins and anticytokinins in the tabacco bioassay and the results were used to determine whether any position(s) of the heterocyclic nucleus of cytokinins may require derivatization as part of an over-all "activation" process. 3-substituted 4-alkylaminopyrazolo [3,4-d]pyrimidines and 4-alkylaminopyrrolo[2,3-d]pyrimidines, for example, have (substituted) carbon rather than nitrogen atoms at positions 3 and 5, respectively (analogous to position 7 in purines) and would be predicted to be metabolically stable at these positions. The finding that these compounds had cytokinin activity suggested that modification at the metabolically stable positions. The finding that these compounds had cytokinin activity suggested that modification at the metabolically stable position, and by extension at position 7 in cytokinin analogues which are purines, is not a prerequisite for the expression of cytokinin activity. Similar consideration of other heterocyclic analogs which have cytokinin activity suggests that the active form of a cytokinin can be the exogenous compound itself. Certain structural analogs of cytokinins were found to inhibit the growth of tobacco callus promoted by 6-(3-methyl-2-butenylamino)purine. These compounds were studied as potential cytokinin antagonists, i.e. having activity analogous to the 7-alkylamino-3-methylpyrazolo[4,3-d]pyrimidines (Hecht, S. M., 2068-2610; Skoog, F., Schmitz, R.Y., Hecht, S.M., and Bock, R. M. (1973) Phytochemistry 12, 25-37). The activity of these compounds is discussed and criteria are proposed to distinguish between those species which are specific anticytokinins and those which otherwise inhibit growth.     

"Silent" alleles at the HLA-C locus.

Defined specificities of the HLA-C locus possess a significantly lower immunogenicity as compared with the HLA-A and HLA-B specificities. HLA-C "blanks" are not immunogenic at all. Among the possible explanations, the most likely one appears to be a low phenotypic expression of these alleles. C locus antigens as a whole are thus likely to be of minor relevance in donor/recipient matching for transplantation.     

Visualizing "greengold" clusters in the STEM.

"Greengold" is a large metallic cluster thought to contain 75 gold atoms in a compact 1.4-nm-diameter core surrounded by an organic shell. Scanning transmission electron microscope imaging shows uniform mass and size distributions with an apparent mass of 24 kDa, unaffected by radiation damage. The signal-to-noise ratio is adequate for visualization at low dose and in the presence of a relatively thick biological matrix. Under some conditions these clusters have a slight tendency to form linear chains and 2-D hexagonal arrays with a spacing of 2.6 nm. The parameters presented permit estimation of the feasibility of proposed labeling experiments.     

The "valve" of the ductus arteriosus--an enigma.

The urine/plasma creatinine ratio (U/P Cr), the urine sodium concentration (UNa), and the diuretic response to mannitol infusion in 23 patients were reviewed in an attempt to differentiate functional renal failure (FRF) from acute tubular necrosis (ATN). FRF was diagnosed if the plasma urea nitrogen (PUN) or serum creatinine stabilized within 72 hours. When renal failure persisted longer, patients had ATN. Subjects dying within 72 hours were excluded. Ten patients had ATN and five survived. The minimum duration of renal failure among survivors was 10 days. None responded to mannitol. Of 13 patients with FRF, 11 survived. Seven of 12 who received mannitol responded with a diuresis. The mean UNa in the patients with ATN was 51.4 mEq./1. ± 9.48 (SE). The mean U/P Cr was 11.2 ± 1.12. In patients with FRF, the mean UNa was 14.0 mEq./1. ± 4.2 and the mean U/P Cr was 42.5 ± 11.5. A significant overlap was present between the two groups. When UNa was factored by the U/P Cr, the resultant ratio was significantly different for the two groups of patients (P < 0.01), and this proved to be a useful clinical index with which to distinguish FRF from established ATN.     

"Antibodies--Europe. Engineering the next generation of antibodies"

Meeting report: “Antibodies-Europe. Engineering the Next Generation of Antibodies” News from academia: FEBS/EMBO Women in Science Award 2008 Teaching biotech: The stem cell game