Low-molecular-weight organic acids in rhizosphere soils of durum wheat and their effect on cadmium bioaccumulation

Cadmium (Cd) accumulation has been found to vary between cultivars of durum wheat (Triticum turgidum var. durum), and it is hypothesized that low-molecular-weight organic acids (LMWOAs) produced at the soil-root interface (rhizosphere) may play an important role in the availability and uptake of Cd by these plants. The objective of this study, therefore, was to (1) investigate the nature and quantity of LMWOAs present in the rhizosphere of durum wheat cultivars Arcola (low Cd accumulator) and Kyle (high Cd accumulator) grown in three different soils: Yorkton, Sutherland and Waitville, and (2) determine the relationship between Cd accumulation in these plants and LMWOAs present in the rhizosphere. Plants were grown for two weeks in pot-cultures under growth chamber conditions. Oxalic, fumaric, succinic, L-malic, tartaric, citric, acetic, propionic and butyric acids were found and quantified in the water extracts of rhizosphere soil, with acetic and succinic acids being predominant. No water extractable LMWOAs were identified in the bulk soil. Total amount of LMWOAs in the rhizosphere soil of the high Cd accumulator (Kyle) was significantly higher than that for the low Cd accumulator (Arcola) in all three soils. Furthermore, large differences in amounts of LMWOAs were found in the rhizosphere soil for the same cultivars grown in different soils and followed the pattern: Sutherland > Waitville > Yorkton. Extractable soil Cd (M NH4Cl) and Cd accumulation in the plants also followed the same soil sequence as LMWOA production. Cadmium accumulation by the high and low Cd accumulating cultivars was proportional to the levels of LMWOAs found in the rhizosphere soil of each cultivar. These results suggest that the differing levels of LMWOAs present in the rhizosphere soil played an important role in the solubilization of particulate-bound Cd into soil solution and its subsequent phytoaccumulation by the high and low Cd accumulating cultivars.     

The isolation and in vitro culture of bovine preantral and early antral follicles of different size classes

The ovary of cattle contains thousands of oocytes which are enclosed primarily in the preantral follicles. Methods of culturing preantral follicles are now being developed. The aim of this study was to investigate the effect of the size of bovine preantral and early antral follicles and culture media on their in vitro growth. Individual follicles isolated by microdissection of the ovarian slices were sorted into the following size classes: 75 to 124, 125 to 174, 175 to 224, 225 to 274, 275 to 324 and > or = 325 microns. The follicles were cultured individually in TCM 199 + fetal calf serum (FCS) + supplements (FSH, estradiol-17 beta, insulin, transferrin, sodium selenite, sodium pyruvate, 1-glutamine and hypoxanthine) or in Menezo B2 + FCS + supplements (Experiment 1) and in TCM 199 + steer serum (SS) with or without additional supplements (Experiment 2). The total number of isolated follicles of different size classes was similar in heifers and cows. No significant difference in the growth rate of follicles of different sizes was seen in the 2 media (TC 199 and B2). However, the culture of follicles in the TCM 199 that was supplemented only with SS and contained no other additives significantly reduced follicular survival and growth in comparison with follicles cultured in the supplemented medium. The survival time of follicles was related to their initial size at the beginning of culture. The longest period of growth was for follicles 275 to 324 microns in diameter (i.e., 10.7 +/- 5.7; 12.1 +/- 6.2 and 12.2 +/- 2.7 d, respectively, for culture in supplemented Menezo B2, TCM 199 + FCS and TCM 199 + SS). Survival and growth of some follicles was maintained for 23 d.     

Effects of Aluminum and Calcium on Acetyl-CoA Metabolism in Rat Brain Mitochondria

Abstract: Al complexes are known to accumulate in extra- and intracellular compartments of the brain in the course of different encephalopathies. In this study possible effects of Al accumulation in the cytoplasmic compartment on mitochondrial metabolism were investigated. Al, like Ca, inhibited pyruvate utilization as well as citrate and oxoglutarate accumulation by whole brain mitochondria. Potencies of Ca²⁺_total effects were 10–20 times stronger than those of Al. Al decreased mitochondrial acetyl-CoA content in a concentration-dependent manner, along with an equivalent rise of free CoA level, whereas Ca caused loss of both intermediates from mitochondria. In the absence of P_i in the medium, Ca had no effect on mitochondrial metabolism, whereas Al lost its ability to suppress pyruvate utilization and acetyl-CoA content in Ca-free conditions. Verapamil potentiated, whereas ruthenium red reversed, Ca-evoked suppression of mitochondrial metabolism. On the other hand, in Ca-supplemented medium, Al partially overcame the inhibitory influence of verapamil. Accordingly, verapamil increased mitochondrial Ca levels much more strongly than Al. However, Al partially reversed the verapamil-evoked rise of Ca²⁺_total level. These data indicate that Al accumulated in cytoplasm in the form of the Al(PO₄)OH⁻ complex may inhibit mitochondrial functions by an increase of intramitochondrial [Ca²⁺]_total resulting from the Al-evoked rise of cytoplasmic [Ca²⁺]_free, as well as from inhibitory interference with the verapamil binding site on the Na⁺/Ca²⁺ antiporter.     

Tentative determination of the molecular weight of substances stimulating the flowering of winter wheat

Murashige & Skoog nutrient was supplemented with substances of molecular weight (M_W) less than 5 kDa, which were separated from extract of winter wheat ears by means of Sephadex G-25 ultrafiltration. Isolated embryos of the same wheat cultivar (Grana) were vernalized in the nutrient for 0 and 7 days at 2 °C for 2 weeks and planted in a glass-house. After 150 days of growth (20/17 °C day/night) the development of the shoot apices was observed. It was found that substances of M_W<5 kDa strongly stimulated the generative development of the plants, enabling the earing of 30 % of non-vernalized plants (control=0%) and 100 % plants vernalized for 7 days (control=29 %). The substances present in the extract of both spring (cv. Jara) and winter (cv. Grana) varieties were fractionated by means of Sephadex chromatography into 300 fractions of M_W=1 to 5 kDa and each of them was added to the isolated embryos of cv. Grana. The embryos were vernalized at 2 °C for 7 days and then cultured as previously described. It was found that the differentiation of the shoot apices was stimulated by over 34 % by fractions of winter wheat extract and more than 50 % by fractions of the spring wheat extract. However, only a few of identical fractions of the extracts of both wheat varieties were able to induce the earing of the plants. These fractions were grouped in 4 continuous intervals of M_W equal to about 4.5–4.9, 3.2–3.3, 2.1–2.6 and 1.00–1.03 kDa. Within the three intervals was identified a small group of identical fractions, which affected the growth of the seedlings in similar mode i.e. inhibiting or stimulating. Thus it can be assumed that these intervals contained identical or similar substances capable of stimulating strongly the earing of winter wheat.     

Stunting and flower buds deficiency of Lilium sp.: a new phytoplasma associated disease

The presence of phytoplasmas in Lilium sp. showing severely stunted growth, leaf malformation and flower buds deficiency was demonstrated for the first time using polymerase chain reaction assays with primers amplifying phytoplasma 16S rDNA regions. These phytoplasmas were found in leaves as well as roots and bulb scales of symptomatic and CMV and/or LSV affected and asymptomatic virus-free lilies.     

Effect of a short-term dietary creatine supplementation on high-energy phosphates in the rat myocardium.

The aim of this study was to find out whether creatine (Cr) feeding affects total creatine (TCr), phosphocreatine (PCr), adenine nucleotide contents and beta-hydroxy-acyl-CoA-dehydrogenase (HAD) activity in myocardium as compared to red skeletal muscle. Ten adult Wistar rats received Cr (2.5% of diet weight) for 7 days. In Cr fed rats, PCr was increased (by approx. 20%) in cardiac and in soleus muscles with ATP elevated in myocardium and TCr and free Cr in soleus. In both muscles, Cr feeding enhanced HAD activity. It is concluded, that dietary Cr does increase cardiac muscle high energy phosphate reserves and its oxidative potential.     

The ovaries of Mecoptera: basic similarities and one exception to the rule

Two entirely different types of ovaries (ovarioles) have been described in mecopterans. In the representatives of Meropeidae, Bittacidae, Panorpodidae and Panorpidae the ovarioles are of the polytrophic-meroistic type. Four regions: a terminal filament, germarium, vitellarium and ovariole stalk can be distinguished in the ovarioles. The germaria house numerous germ cell clusters. Each cluster arises as a result of 2 consecutive mitoses of a cystoblast and consists of 4 sibling cells. The oocyte always differentiates from one of the central cells of the cluster, whereas the remaining 3 cells develop into large, polyploid nurse cells. The vitellaria contain 7-12 growing egg chambers (= oocyte-nurse cell complexes). In contrast, the ovaries of the snow flea, Boreus hyemalis, are devoid of nurse cells and therefore panoistic (secondary panoistic). The ovarioles are composed of terminal filaments, vitellaria and ovariole stalks only; in adult females functional germaria are absent. Histochemical tests suggest that amplification of rDNA takes place in the oocyte nuclei. Resulting dense nucleolar masses undergo fragmentation into multiple polymorphic nucleoli. The classification of extant mecopterans as well as the phylogenetic relationships between Mecoptera and Siphonaptera are discussed in the context of presented data.