Augmentation of mouse natural killer cell activity by LS 2616, a new immunomodulator

The quinoline-3-carboxamide LS 2616 administered to mice in drinking water increased spontaneous cytotoxicity against YAC-1 cells in a dose-dependent manner. The enhancement of spontaneous cytotoxicity was found to be mediated by NK cells, as judged by their lack of adherence to nylon wool columns, relative resistance to treatment with antibodies to Thy-1.2 and complement, and almost total abrogation after depletion of asialo-GM1+ cells. Enhancement of NK activity was evident after 2 days of treatment, was maximal after 4 days, and remained elevated during the 14-day exposure period studied. NK activity returned to control levels 4 days after cessation of treatment. NK activity was significantly increased in spleen, peripheral blood, lymph nodes, and bone marrow of LS 2616-treated mice, while activity in peritoneal exudate cells and thymus remained low. LS 2616 was able to elevate NK activity in several mouse strains studied, including mice homozygous for the beige gene. Serum interferon levels were not increased during treatment with LS 2616. Combined injection of the interferon inducer Poly I:C and LS 2616 did not increase NK activity above that of animals injected with Poly I:C alone. However, Poly I:C, in contrast to LS 2616, increased NK activity in peritoneal exudate cells. Studies at the single cell level revealed that LS 2616 increased NK activity by increasing the number of lytically active cells via recruitment of new target-binding cells and not by increasing the lytic activity of pre-existing binders.     

Late enzymes of vindoline biosynthesis

From differentiated plants of Catharanthus roseus (L.) G. Don we have isolated a specific enzyme of the vindoline biosynthetic pathway catalysing the S-adenosylmethionine-dependent methylation of 11-O-demethyl-17-O-deacetyl-vindoline. The enzyme we named S-adenosyl-L-methionine : 11-O-demethyl-17-O-deacetylvindoline 11-O-methyltransferase. This transferase exhibits a high substrate specificity. Obviously the O-methylation at C-11 precedes the O-acetylation at the C-17 position during the biosynthesis of vindoline.A second enzyme was detected which hydrolyses the acetyl function of vindoline. The distribution of this acetylesterase in C. roseus plants demonstrates that the enzyme is not specifically associated with the vindoline distribution in the plant material. Most probably this enzyme plays no essential role in the biosynthesis of vindoline.     

Late enzymes of vindoline biosynthesis. Acetyl-CoA: 17-O-deacetylvindoline 17-O-acetyl-transferase

From differentiated plants of Catharanthus roseus (L.) G. Don, a specific enzyme was isolated and named acetyl-CoA : 17-O-deacetylvindoline 17-O-acetyltransferase, acting on the biosynthetic formation of the Aspidosperma type alkaloid vindoline.The enzyme shows a high selectivity towards different substrates. The acetyl-CoA-dependent transferase also catalyses the reverse reaction by hydrolysis of the 17-O-acetyl group of vindoline in the presence of free CoA. This enzyme is localized only in vindoline-containing plant parts, but was so far not detectable in cell suspension cultures of C. roseus. The enzyme allows the synthesis of labelled vindoline with high specific activity, applicable for instance as tracer for radioimmunoassays of vindoline.     

Impaired natural killer cell function in hemophiliacs with or without continuous substitution

In the present study, 28 hemophiliacs substituted continuously and 5 hemophiliacs who had received almost no blood products were investigated. Cells of OKT 3+, OKT 4+, and OKT 8+ subsets were counted. Percoll separated fractions of peripheral blood mononuclear cells were examined by morphological criteria and were tested for NK cell activity. We found that the NK cell activity of both groups of hemophiliacs was decreased on testing Ficoll separated cells or low density Percoll separated cells. Normal NK cell activity was found in medium density cells of hemophiliacs. Two possible explanations are discussed: first, the NK cell activity may be suppressed in hemophiliacs and secondly, there may be a block in maturation of NK cell activity. It is unlikely that chronic substitution by blood products counts for these alterations. The possible role of chronic infections is discussed.     

FV blood group and haemoglobin type versus haematological and blood chemical parameters in young Swiss bulls

A relationship between the FV blood group phenotype and 4 out of 45 haematological and blood chemical parameters--red cell number, mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), and serum iron--has been demonstrated in young bulls of three Swiss cattle breeds. There was also a relationship between haemoglobin type and 7 out of 45 haematological and blood chemical parameters (haemoglobin concentration, red cell number, MCV, MCHC and red cell concentrations of K+ and Na+ and their sum). In addition to expanding the species in which there is an effect of haemoglobin phenotype on MCV to include cattle, these data also demonstrate a significant correlation between their FV phenotype and MCV.     

Statistical treatment of VAM infection data

Summary The amount of vesicular-arbuscular mycorrhizal (VAM) infection, when expressed as length of infected roots, is commonly quite variable among replicate pots within an experimental treatment. In this paper we show that frequency distributions of VAM infection parameters are often non-normal in form and may follow the negative binomial, a distribution commonly associated with aggregated organisms in nature. The lack of normality means that statistical procedures should either be non-parametric or should include data transformations.     

SALT REGULATION AND LEAF SENESCENCE IN AGING LEAVES OF JAUMEA CARNOSA (LESS.) GRAY (ASTERACEAE), A SALT MARSH SPECIES EXPOSED TO NaCl STRESS

The effects of increasing salt stress on leaf senescence and salt regulation were investigated in the halophyte Jaumea carnosa in hydroponic culture experiments. The plants were grown in Hoagland's nutrient solution plus additional NaCl salt (0, 300, 400, 500 mm NaCl). Decreases in nucleic acids, protein, and chlorophyll were used as indicators of leaf senescence. The results indicated no definitive pattern of acceleration in leaf senescence with increasing salt stress. Salt regulation was also unaffected as leaves aged under increasing NaCl concentrations. The results are consistent with those of previous studies of the halophyte which indicated that the species was very tolerant of high NaCl concentrations.     

Homoserine kinase from Escherichia coli K-12: properties, inhibition by L-threonine, and regulation of biosynthesis

We have partially purified homoserine kinase from a genetically derepressed strain of Escherichia coli K-12. The optimum pH of the enzyme-substrate reaction was 7.8 and the K(m) values for l-homoserine and adenosine 5'-triphosphate were both 3 x 10(-4) M. K(+) (or NH(4) (+)) as well as Mg(2+) were required for its activity. The sedimentation coefficient determined by ultracentrifugation in a sucrose density gradient was 5.0 +/- 0.25S. l-Homoserine was an excellent protector against heat inactivation of homoserine kinase. l-Threonine was a competitive inhibitor of homoserine kinase, suggesting that end-product inhibition of this enzyme plays a role in vivo in the overall regulation of threonine biosynthesis. The specific activity of aspartokinase I-homoserine dehydrogenase I and of homoserine kinase showed a strong positive correlation in extracts from strains under widely varying conditions of genetic or physiological derepression; it was concluded that these two enzymes are coordinately regulated in E. coli K-12.     

Histochemical changes in the developing abscission layer in fruits of Prunus cerasus L.

Summary Abscission layer formation in the sour cherry (Prunus cerasus L.) during fruit maturation occurred in the transition zone between the fruit and the pedicel. The abscission layer, consisting of 5–8 rows of cells, was first identified by its low affinity for haematoxylin. The walls of cells in the abscission layer contained less total polysaccharides than adjacent cells. The pectins were degraded and the cellulose was partially broken down resulting in cell separation. The Ca level in the abscission zone decreased and Ca and Mg were lost from the walls of cells in the layer during abscission. After the abscission layer formed, cells associated with the layer had a lower capacity to bind ⁴⁵Ca than cells distal or proximal to the layer.Michigan Agricultural Experiment Station Journal Article No. 4607