Regulation of acid hydrolysis of sucrose in acid lime juice sac cells

The sucrose content of acid lime [ Citrus aurantifolia (Christm.) Swing.] juice tissue was measured at time 0 and at various times following incubation at 15.5, 26.6 and 37.7°C. The decline in sucrose content in fruit stored at 15.5°C paralleled the expected values for a sucrose solution at pH 2.1. At higher temperatures, the in vivo sucrose content decreased at significantly lower rates than the expected values. In fruit stored at 26.6 and 37.7°C, the vacuolar pH increased 0.11 and 0.23 units, respectively. When sucrose hydrolysis was recalculated at the increased vacuolar pH of juice cells stored at 26.6 and 37.7°C, the calculated values were similar to the measured values obtained in vivo. It is concluded that within the limits of the experimental conditions, the rates of sucrose acid hydrolysis are regulated by changes in the vacuolar H⁺ concentration.     

PRODUCTION AND CHARACTERIZATION OF MULTIPLE-LAYERED POPULATIONS OF ANIMAL CELLS

Dense populations containing 129 x 10⁶ Jensen sarcoma, 134 x 10⁶ DON Chinese hamster, 28.9 x 10⁶ WI-38 human diploid, 61.8 x 10⁶ HEp-2 human carcinoma, and 67.4 x 10⁶ WISH human amnion cells were produced from dilute inocula, 0.85 to 5.33 x 10⁶, in 7 to 8 days in a perfusion system using replicate T-60 flasks. Perfusion rates as high as 560 ml medium/day/T-60 were required to maintain pH (to ca ±0.1 unit) and adequate nutrient supplies. The cell densities encountered are described by the term "monolayer equivalents" (M.E.), defined as number of cells per culture divided by number of cells in a monolayer. The M.E.'s for T-60 cultures containing unusually dense populations of 40 x 10⁶ WI-38 and 250 x 10⁶ DON cells (9-day perfusion) were 5 and 17, respectively, and numbers of cells in illustrations of stained cross-sections of membranes from these cultures were in excellent agreement. Threshold M.E.'s exist below which proliferation is the chief cellular activity and above which one or more cell functions may predominate even though proliferation persists. Cellular nutrition and metabolism may change with changes in M.E., as illustrated in different patterns of glutamic acid, proline, and glycine utilization or production in dense vs. dilute WI-38 cell populations. The results indicated that the role of contact inhibition phenomena in arresting cellular proliferation was diminished in perfusion system environments.     

Immune-complex-trapping cells in the spleen of the oriental fire-bellied toad,Bombina orientalis

Summary The spleen of the oriental fire-bellied toad, Bombina orientalis, consists of well-developed white pulp, separated from the lymphocytic marginal zone by the connective tissue boundary layer. Injection of peroxidase-conjugated rabbit anti-peroxidase revealed that these immune complexes were localized on the surface of acid-phosphatase-positive and non-specific-esterasepositive cells in the white pulp. The majority of immunecomplex-trapping cells were present around the blood vessels. Cell processes of some of these cells penetrated into the wall of blood vessels. The significance of the present findings is discussed with respect to the evolution of immune-complex-trapping cells in the spleen.     

Sustained effects of biofeedback-assisted relaxation therapy in essential hypertension

The usefulness of biofeedback-assisted relaxation as an adjunct or substitute for pharmacotherapy in essential hypertension can be enhanced if the effects are shown to persist after formal treatment has ended. Patients with essential hypertension successfully treated with biofeedback-assisted relaxation were recalled for follow-up yearly after the termination of treatment. Twenty-six of 40 patients met the BP criterion for success. At one-, two-, and three-year follow-up, 31%, 38%, and 27% of the successful completers continued to meet the criterion for success. The pretreatment-posttreatment decreases in BP were accompanied by decreases in forehead muscle tension and urinary cortisol. Forehead muscle tension, urinary cortisol, and anxiety levels were significantly lower than pretreatment one year after the end of treatment. Self-report data were used to assess continued relaxation practice. No relationship was found between practice and any other dependent measure. It appears that some patients trained in biofeedback-assisted relaxation can maintain lowered blood pressure, muscle tension, anxiety, and cortisol levels over the long term; however, the role of relaxation practice in maintaining these lowered levels remains unclear.     

Isolation and characterization of nuclear genes coding for subunits of the yeast ubiquinol-cytochrome c reductase complex

Nuclear genes coding for the M_r 17000, 14000 and 11000 subunits of the ubiquinol-cytochrome c reductase complex (complex III) in yeast have been isolated from a clone bank of yeast nuclear DNA by use of a mRNA hybridization-competition assay. This is based on our observations that levels of mRNAs for these subunits are much reduced during glucose repression and in cytoplasmic petite mutants and the procedure should be of general application for the isolation of other inducible or repressible genes coding for mRNAs present at low levels in the cell. A first characterization of the clones is presented. The genes are not closely linked in the genome and those coding for M_r 14000 and 11000 subunits are present in unique genomic environments, which suggests that there are only single copies of each in the nuclear genome.     

Fermentation pattern of sucrose to ethanol conversions by Zymomonas mobilis

General patterns of sucrose fermentation by two strains of Zymomonas mobilis, designated Z7 and Z10, were established using sucrose concentrations from 50 to 200 g/liter. Strain Z7 showed a higher invertase activity than Z10. Strain Z10 showed a reduced specific growth rate at high sucrose concentration while Z7 was unaffected. High sucrose hydrolyzing activity in strain Z7 lead to glucose accumulation in the medium at high sucrose concentrations. Ethanol production and fermentation time depend on the rate of catabolism of the products of sucrose hydrolysis, glucose and fructose. The metabolic quotients for sucrose utilization, q_s, and ethanol production, q_p (g/g·hr), are unsuitable for describing sucrose utilization by Zymomonas mobilis, as the logarithmic phase of growth precedes the phase of highest substrate utilization (g/liter·hr) and ethanol production (g/liter·hr) in batch culture.     

Leucine‐rich repeat receptor‐like kinase II phylogenetics reveals five main clades throughout the plant kingdom

Receptor‐like kinases (RLKs) represent the largest group of cell surface receptors in plants. The monophyletic leucine‐rich repeat (LRR)‐RLK subfamily II is considered to contain the somatic embryogenesis receptor kinases (SERKs) and NSP‐interacting kinases known to be involved in developmental processes and cellular immunity in plants. There are only a few published studies on the phylogenetics of LRR‐RLKII; unfortunately these suffer from poor taxon/gene sampling. Hence, it is not clear how many and what main clades this family contains, let alone what structure–function relationships exist. We used 1342 protein sequences annotated as ‘SERK’ and ‘SERK‐like’ plus related sequences in order to estimate phylogeny within the LRR‐RLKII clade, using the nematode protein kinase Pelle as an outgroup. We reconstruct five main clades (LRR‐RLKII 1–5), in each of which the main pattern of land plant relationships re‐occurs, confirming previous hypotheses that duplication events happened in this gene subfamily prior to divergence among land plant lineages. We show that domain structures and intron–exon boundaries within the five clades are well conserved in evolution. Furthermore, phylogenetic patterns based on the separate LRR and kinase parts of LRR‐RLKs are incongruent: whereas the LRR part supports a LRR‐RLKII 2/3 sister group relationship, the kinase part supports clades 1/2. We infer that the kinase part includes few ‘radical’ amino acid changes compared with the LRR part. Finally, our results confirm that amino acids involved in each LRR‐RLKII–receptor complex interaction are located at N‐capping residues, and that the short amino acid motifs of this interaction domain are highly conserved throughout evolution within the five LRR‐RLKII clades.