Chicken egg yolk antibodies for cytokinin analysis

The production, isolation, and purification of specific chicken immunoglobulins (Igs) against three main groups of naturally occurring cytokinins are reported. The specific Igs directed against, respectively, zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine are extracted from the egg yolk and used in radioimmunoassays that allow the quantification in parallel of pmol of the cytokinins in plant extracts. As little as 50 fmol of zeatin riboside, 20 fmol of isopentenyladenosine, and 40 fmol of dihydrozeatin riboside can be detected. The levels of cytokinins measured in the radio-immunoassay correlate well with physicochemical analysis methods such as high performance liquid chromatography (HPLC) with UV spectrum detection and HPLC-coupled mass spectrometric detection. Cross-reactivity studies indicate that the assay is not affected by most of the structurally related compounds. The respective antibody preparations recognized zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine and the corresponding free bases. The results obtained when analyzing crude plant extracts are expressed as zeatin riboside equivalents, dihydrozeatin riboside equivalents, and isopentenyladenosine equivalents.Abbreviations B binding activity - B ₀ maximal binding - B ₁ unspecific binding - GC gas chromatography - HPLC high performance liquid chromatography - LC-MS HPLC-coupled mass spectrometry - MOPS 4-morpholinepropanesulfonic acid - RIA radioimmunoassay - TBS Tris-buffered saline - (diH)Z dihydrozeatin - (diH) [9R]Z dihydrozeatin riboside - iP isopentenyladenine - [9R]iP isopentenyladenosine - Z zeatin - [9R]Z zeatin riboside - [9G]iP isopentenyladenine-9-glucoside - [9R-5P]iP isopentenyladenosine-5-monophosphate     

Floral development and expression of floral homeotic genes are influenced by cytokinins

Tobacco plants that are somatic mosaics for the expression of a cytokinin-synthesizing gene have viviparous leaves. Epiphyllous buds can be either vegetative or floral. Floral adventitious buds can be either normal or abnormal. Abnormalities of floral development correlate with: (i) a local activation of the cytokinin-synthesizing gene, (ii) a drastic increase in floral cytokinin content, and (iii) a decrease in the steady-state levels of mRNA homologues of the homeotic genes DEFA , GLO and PLENA of Antirrhinum majus . Thus, these data show in planta that cytokinins, a class of phytohormones, are able to alter the development of floral organs and to decrease the expression of three homeotic floral genes.     

Stimulation of indole-3-acetic acid production in Rhizobium by flavonoids

Flavonoids activate nod gene expression in Rhizobium resulting in the synthesis of Nod signals which trigger organogenesis in the host plant. This paper shows that nod-inducers also stimulate the production of the phytohormone IAA (indole-3-acetic acid).     

Alteration of surfactant protein A expression in renal cell carcinoma

Surfactant protein-A (SP-A) belongs to a family of collagen-containing C-type lectins called collectins. SP-A is expressed by renal tubule epithelial cells. We investigated the distribution of SP-A in renal cell carcinomas (RCC) using immunohistochemical techniques and western blotting. We used 35 formalin fixed, paraffin embedded (FFPE) RCC tissue samples. We compared results with clinico-pathological parameters of RCC including age, sex, Fuhrman grade, tumor volume, tumor node metastasis (TNM) and clinical stage. SP-A was localized in the glomerulus and renal tubule epithelium in nontumor tissue and strong SP-A immunoreactivity was observed in tumor tissue. SP-A was expressed in the RCC tumor cells (64%) and nontumor cells (34%) in males and RCC tumor cells (90%) and nontumor cells (30%) in females. There was a significant correlation between SP-A immunoreactivity in tumor cells and gender, age, tumor diameter, Fuhrman grade and tumor diameter. Western blot analysis supported the immunohistochemical findings. We present evidence for involvement of SP-A in RCC and suggest that increased SP-A expression in RCC is associated with favorable prognosis.     

Palatability and feeding preferences of Uresiphita maorialis (Lepidoptera: Crambidae) for three Sophora species

In a three-hour bioassay, we tested the palatability and feeding preferences of Uresiphita maorialis (kōwhai moth) for Sophora tetraptera, Sophora microphylla and Sophora prostrata. Palatability tests showed no differences among the Sophora species. Feeding preferences, on the other hand, showed that S. tetraptera and S. microphylla leaves are preferred over S. prostrata leaves. Our results support our field observations in Wellington city parks and gardens showing that S. tetraptera and S. microphylla plants frequently have higher densities of larvae than S. prostrata.     

Optimal fed batch experiment design for estimation of monod kinetics of Azospirillum brasilense: from theory to practice

In this paper the problem of reliable and accurate parameter estimation for unstructured models is considered. It is illustrated how a theoretically optimal design can be successfully translated into a practically feasible, robust, and informative experiment. The well-known parameter estimation problem of Monod kinetic parameters is used as a vehicle to illustrate our approach. As known for a long time, noisy batch measurements do not allow for unique and accurate estimation of the kinetic parameters of the Monod model. Techniques of optimal experiment design are, therefore, exploited to design informative experiments and to improve the parameter estimation accuracy. During the design process, practical feasibility has to be kept in mind. The designed experiments are easy to implement in practice and do not require additional monitoring equipment. Both design and experimental validation of informative fed batch experiments are illustrated with a case study, namely, the growth of the nitrogen-fixing bacteria Azospirillum brasilense.     

Endogenous cholesterol synthesis is associated with VLDL-2 apoB-100 production in healthy humans

Subjects with high plasma cholesterol levels exhibit a high production of VLDL apolipoprotein B-100 (apoB-100), suggesting that cholesterol is a mediator for VLDL production. The objective of the study was to examine whether endogenous cholesterol synthesis, reflected by the lathosterol-cholesterol ratio (L-C ratio), affects the secretory rates of different VLDL subfractions. Ten healthy subjects were studied after overnight fasting. During a 10 h primed, constant infusion of 13C-valine (15 micromol/kg/h), enrichment was determined in apoB-100 from ultracentrifugally isolated VLDL-1 and VLDL-2 by gas chromatography mass spectrometry. The synthesis rates of VLDL-1 apoB-100 and VLDL-2 apoB-100, catabolism, and transfer were estimated by compartmental analysis. Mean VLDL-1 apoB-100 pool size was 90 +/- 15 mg, and mean VLDL-2 apoB-100 pool size was 111 +/- 14 mg. Absolute synthesis rate of VLDL-1 apoB-100 was 649 +/- 127 mg/day and 353 +/- 59 mg/day for VLDL-2 apoB-100. There was a strong association between the absolute synthesis rate of VLDL-2 apoB-100 and L-C ratio (r 2 = 0.61, P < 0.01). In contrast, no correlation was observed between L-C ratio and absolute synthesis rate of VLDL-1 apoB-100 (r 2 = 0.302, P = 0.09). In conclusion, these data provide additional support for an independent regulation of VLDL-1 apoB-100 and VLDL-2 apoB-100 production.Endogenous cholesterol synthesis is correlated only with the VLDL-2 apoB-100 production.     

The Role of auxin,pH, and stress in the activation of embryogenic cell division in leaf protoplast-derived cells of alfalfa

Culturing leaf protoplast-derived cells of the embryogenic alfalfa (Medicago sativa subsp. varia A2) genotype in the presence of low (1 microM) or high (10 microM) 2, 4-dichlorophenoxyacetic acid (2,4-D) concentrations results in different cell types. Cells exposed to high 2,4-D concentration remain small with dense cytoplasm and can develop into proembryogenic cell clusters, whereas protoplasts cultured at low auxin concentration elongate and subsequently die or form undifferentiated cell colonies. Fe stress applied at nonlethal concentrations (1 mM) in the presence of 1 microM 2,4-D also resulted in the development of the embryogenic cell type. Although cytoplasmic alkalinization was detected during cell activation of both types, embryogenic cells could be characterized by earlier cell division, a more alkalic vacuolar pH, and nonfunctional chloroplasts as compared with the elongated, nonembryogenic cells. Buffering of the 10 microM 2,4-D-containing culture medium by 10 mM 2-(N-morpholino)ethanesulfonic acid delayed cell division and resulted in nonembryogenic cell-type formation. The level of endogenous indoleacetic acid (IAA) increased transiently in all protoplast cultures during the first 4 to 5 d, but an earlier peak of IAA accumulation correlated with the earlier activation of the division cycle in embryogenic-type cells. However, this IAA peak could also be delayed by buffering of the medium pH by 2-(N-morpholino)ethanesulfonic acid. Based on the above data, we propose the involvement of stress responses, endogenous auxin synthesis, and the establishment of cellular pH gradients in the formation of the embryogenic cell type.     

Effect of unilateral and bilateral resistance exercise on maximal voluntary strength,total volume of load lifted,and perceptual and metabolic responses

The present study investigated the effect of unilateral and bilateral resistance exercise (RE) on maximal voluntary strength, total volume of load lifted (TVLL), rating of perceived exertion (RPE) and blood lactate concentration of resistance-trained males. Twelve healthy men were assessed for the leg extension one-repetition maximum (1RM) strength using bilateral and unilateral contractions. Following this assessment, an RE session (3 sets of repetitions to failure) was conducted with bilateral and unilateral (both limbs) contractions using a load of 50% 1RM. The TVLL was calculated by the product of the number of repetitions and the load lifted per repetition. RPE and blood lactate were measured before, during and after each set. Session RPE was measured 30 minutes after RE sessions. There was a significant difference in the bilateral (120.0±11.9) and unilateral (135.0±20.2 kg) 1RM strength (p < 0.05). The TVLL was similar between both RE sessions. Although the repetitions decreased with each successive set, the total number of repetitions completed in the bilateral protocol (48) was superior to the unilateral (40) protocol (p < 0.05). In both bouts, RPE increased with each subsequent set whilst blood lactate increased after set 1 and thereafter remained stable (p < 0.05). The RPE and lactate responses were not significantly different between both sessions. In conclusion, a bilateral deficit in leg extension strength was confirmed, but the TVLL was similar between both RE sessions when exercising to voluntary fatigue. This outcome could be attributed to the number of repetitions completed in the unilateral RE bout. The equal TVLL would also explain the similar perceptual and metabolic responses across each RE session.