16S-23S and 23S-5S intergenic spacer regions of Streptococcus thermophilus and Streptococcus salivarius,primary and secondary structure

The 16S-23S intergenic spacer region (spacer region 1) of Streptococcus salivarius, S. thermophilus, and Lactococcus lactis subsp. cremoris and the 23S-5S intergenic spacer region (spacer region 2) of S. salivarius and L. lactis subsp. cremoriswere sequenced and compared with the spacer regions 1 and 2 of other streptococci. A high degree of intraspecific conservation was observed for S. thermophilus and L. lactis, and very similar sequences were found for S. salivarius and S. thermophilus. Whereas spacer region 1 is highly conserved in the genus Streptococcus sensu-stricto,only the tRNA gene and the rRNA processing stems are highly conserved in the three genera: Streptococcussensu-stricto, Lactococcus, and Enterococcus. The presence of a unique tRNA^Ala gene without the 3 terminal CCA sequence seems to be a general feature of the streptococci spacer region 1. A secondary structure model was built to show the interaction between the spacer regions 1 and 2 of S. thermophilus and S. salivarius. The rapid evolution of spacer region 1 in streptococci is in part due to insertions and deletions of small RNA stem/loop structures.     

The effect of lysolecithin on prostanoid and platelet-activating factor formation by human gall-bladder mucosal cells

It has been demonstrated that lysolecithin (lysophosphatidyl choline, LPC) produces experimental cholecystitis in cats mediated by arachidonic acid metabolites. LPC is a cytolytic agent that has been postulated as a contributing factor in the development of cholecystitis in humans. The purpose of this research was to evaluate the effect of LPC on human gall-bladder mucosal cell phospholipase A(2) and cyclooxygenase activity. Gall-bladder mucosal cells were isolated from the gall-bladders of patients undergoing routine cholecystectomy. Fresh, isolated cells were maintained in tissue culture and stimulated with varying doses of LPC. Platelet-activating factor concentration was quantitated as an index of phospholipase A(2) activity and prostanoids were measured as an index of cyclooxygenase activity. Also, the effect of LPC on cyclooxygenase 1 and 2 expression in microsomal protein was evaluated. LPC caused dose related increases in 6-keto-PGF(1alpha) and PAF produced by human gall-bladder mucosal cells. Exposure of human gall-bladder mucosal cells to LPC failed to elicit expression of constitutive cyclooxygenase-1, while the expression of inducible cyclooxygenase-2 was increased. The results of this study indicate that LPC induces the formation of prostanoids and PAF by human gall-bladder mucosal cells, suggesting that this substance may promote the development of gall-bladder inflammation.     

Phosphate Nutrition of Rhizobium spp

This study was conducted to determine the behavior of 40 strains from six species of Rhizobium in liquid defined media containing orthophosphate at levels likely to be encountered naturally, ranging from the high concentrations expected in nodules and artificial media to the low concentrations of soil solutions. Storage capacity in strains with high levels (2 mM) of P and ability to utilize this stored P for growth after transfer to low levels (0.06 μM) of P varied with each strain. Storage varied from about 1 to 2% P (dry weight) for all strains, with the number of generations supported dependent on the quantity of P stored and on the utilization efficiency. The ability to store P at high levels is probably less important than the uptake and utilization efficiency of P supplied at low levels. Strains varied greatly in tolerance to low levels of P maintained in solution by an iron oxide buffering system. Differences in growth rate at low levels of P were large enough to be agronomically important.     

Development of Nitrogen Assimilation Enzymes during Photoautotrophic Growth of Chenopodium rubrum Suspension Cultures

We have shown previously that ethylene, which accumulates in the air spaces of submerged stem sections of rice (Oryza sativa L. cv “Habiganj Aman II”), is involved in regulating the growth response caused by submergence. The role of gibberellins in the submergence response was studied using tetcyclacis (TCY), a new plant growth retardant, which inhibits gibberellin biosynthesis. Stem sections excised from plants that had been watered with a solution of 1 micromolar TCY for 7 to 10 days did not elongate when submerged in the same solution or when exposed to 1 microliter per liter ethylene in air. Gibberellic acid (GA₃) at 0.3 micromolar overcame the effect of TCY and restored the rapid internodal elongation in submerged and ethylene-treated sections to the levels observed in control sections that had not been treated with TCY. The effect of 0.01 to 0.2 micromolar GA₃ on internodal elongation was enhanced two- to eight-fold when 1 microliter per liter ethylene was added to the air passing through the chamber in which the sections were incubated. GA₃ and ethylene caused a similar increase in cell division and cell elongation in rice internodes. Thus, ethylene may cause internodal elongation in rice by increasing the activity of endogenous GAs. In internodes from which the leaf sheath had been peeled off, growth in response to submergence, ethylene and GA₃ was severely inhibited by light.     

Coevolution: Mathematical analysis of host-parasite interactions

An SIS epidemic transmitted by two similar strains of parasite acting on a host population of three genotypes which differ in their reaction to the disease is modelled and analyzed. Singular perturbation techniques are used to reduce the original system of nine differential equations to a coupled system of two equations describing the slowtime coevolution of gene frequency and parasite strain frequency.Karen Christine Beck died June 25, 1983 at home.Born February 8, 1952 in Madison, Wisconsin, She received a B.A. degree in 1974 from Luther College, Decorah, Iowa and a Ph.D. in mathematics in 1980 from the University of Iowa. Since that time she has been an instructor in the Mathematics Department at the University of Utah. She was to become an Assistant Professor at the University of Texas, Arlington, beginning Autumn, 1983. Dr. Beck's areas of specialization in mathematics were Mathematical Analysis and Mathematical Biology. She published numerous research articles that resolved various problems in these areas.     

Nucleotide sequence and genome organization of foot-and-mouth disease virus.

A continuous 7802 nucleotide sequence spanning the 94% of foot and mouth disease virus RNA between the 5'-proximal poly(C) tract and the 3'-terminal poly(A) was obtained from cloned cDNA, and the total size of the RNA genome was corrected to 8450 nucleotides. A long open reading frame was identified within this sequence starting about 1300 bases from the 5' end of the RNA genome and extending to a termination codon 92 bases from its polyadenylated 3' end. The protein sequence of 2332 amino acids deduced from this coding sequence was correlated with the 260 K FMDV polyprotein. Its processing sites and twelve mature viral proteins were inferred from protein data, available for some proteins, a predicted cleavage specificity of an FMDV encoded protease for Glu/Gly(Thr, Ser) linkages, and homologies to related proteins from poliovirus. In addition, a short unlinked reading frame of 92 codons has been identified by sequence homology to the polyprotein initiation signal and by in vitro translation studies.