Endogenous hormone levels during direct somatic embryogenesis in Medicago falcata

Endogenous indole-3-acetic acid, abscisic acid and cytokinins (zeatin, zeatin riboside, N-isopentenyladenine and N-isopentenyladenosine) were evaluated in initial explants (leaves) of in vitro propagated plants of alfalfa ( Medicago falcata L.) lines varying in embryogenic capacity and during the somatic embryogenesis process. Fast embryo-genic induction was correlated with high IAA and low ABA levels in the initial explants. No significant differences were observed in the cytokinin contents. Our results suggest that a certain hormone balance is necessary to allow the expression of the embryogenic potential. The consistent stages of the direct somatic embryogenesis are also characterized by changes in hormonal levels.     

Life-history studies of heterophyid trematodes in the Neotropical Region: Ascocotyle (Phagicola) diminuta (Stunkard & Haviland, 1924) and A. (P.) angrense Travassos, 1916

The life-cycle of Ascocotyle (Phagicola) diminuta (Stunkard & Haviland, 1924) was reproduced experimentally, starting from cercariae from naturally infected Littoridina castellanosae and L. parchappei (Hydrobiidae) collected from artificial ponds in the Zoological Garden in Buenos Aires and from Los Ranchos stream, Buenos Aires Province, respectively. Metacercariae were found encysted in the gills of experimentally exposed Cnesterodon decemmaculatus (Poecilidae) and of other naturally infected freshwater fishes. Adults were obtained experimentally in chicks and mice and from a naturally infected egret, Egretta thula. A. (P.) angrense Travassos, 1916 was found parasitising the egret Ixobrychus involucris; it is considered a valid species and the morphological differences between it and A. (P.) diminuta were established. The “Phagicola-form” of the cercaria in the present life-cycle is also known in the genus Pygidiopsis.     

EMG biofeedback of the abductor pollicis brevis in piano performance

The aim of the present study was to apply EMG biofeedback as an auxiliary to piano teaching techniques. We studied the changes in integrated electromyographic activity, using the abductor pollicis brevis functioning as an agonist during the teaching of identical selective movements of piano playing in two groups, one with EMG biofeedback and the other following traditional method of instruction. The analysis of variance revealed an increase in the peak amplitude and the relaxation rate values for the biofeedback group. These results have implications for the application of piano playing techniques and reveal EMG biofeedback as an aid in the teaching of thumb attack with the abductor pollicis brevis as agonist.We are grateful for the valuable assistance of Dr. Jaime Vila (Professor of Therapy and Behavioral Modification, Faculty of Psychology, Granada), the cooperation of students at the Juventudes Musicales Music School, Santa Fe and at the Victoria Eugenia Conservatoire, (Granada), the Statistical Analysis Centre of University of Filosofia y Letras de Granada; Professor Enrique Garcia Fernandez-Abasal (Complutense University) for the design of the interface and software.     

Regular proteinaceous layers ofThermococcus stetteri cell envelope

Proteinaceous layers of theThermococcus stetteri cell envelope were investigated and found to consist of regularly arrayed subunits 18 nm in diameter. According to the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, two major proteins were present. They were glycosylated and had molecular weights of 80,000 and 210,000. In addition to two external regular proteinaceous layers, cells ofT. stetteri were found to have internal regular layers tightly attached to the cytoplasmic membrane. In the region of flagella attachment to the cell, polar membrane-like structures were found in the cytoplasm.     

Effect of gibberellins and the growth retardant CCC on the nodulation of soya

Summary The effect of exogenous applications of gibberellins (GAs) or the growth retardant -chloroethyltrimethylammonium chloride (CCC) on root nodule formation and activity (C₂H₂-reduction) in soya was studied. Daily foliar application of GA₃ (2.89×10^–6 M) delayed the formation of nodule initials and reduced the numbers mass nodule^–1 and specific activity of nodules by 43%, 31% and 47% respectively, without affecting plant growth. Similar effects on nodulation were produced by foliar application of GA₄ (3.01×10^–5 M) or GA₇ (3.03×10^–5 M), or by the addition of GA₃ (2.89×10^–6 M) to the rooting medium. GA effectiveness in reducing nodule numbers was decreased by delaying its application until after the initial infection process had occurred, but the nodules formed were smaller and less active than those of the untreated control plants. The GA effect on nodulation and nodule activity was not associated with alterations in root exudate or due to a direct inhibitory effect of the hormone on the nitrogenase system. When the endogenous root content of GA-like substances was reduced (86% decrease) by foliar application of CCC (6.30×10^–5 M), nodule numbers were increased by 56%, but nodule size and total nodule activity were similar to those of control plants. The GA and CCC treatments had no effect on rhizobial growth in liquid culture nor on root colonisation by rhizobia.The results suggest that the endogenous content of root GA may have a regulatory role in both the infection process and in subsequent nodule morphogenesis, thus controlling both the number and effectiveness of the root nodules formed.     

Electrophoretic transport of Tl+ in mitochondria

Summary The distribution of Tl⁺ between rat liver mitochondria and the medium was studied; millimolar or smaller concentrations of Tl⁺ were labeled with²⁰⁴Tl. The Tl⁺ distribution responded to transient diffusion potentials in a way that indicated electrophoretic movements of Tl⁺. The diffusion potentials were induced by efflux of K⁺ in response to addition of valinomycin to nonrespiring mitochondria suspended in a medium with low concentrations of K⁺ or by efflux of H⁺ induced by making the medium more alkaline in the presence of a protonophorous (proton-conducting) uncoupling agent. Changes in membrane potential induced by valinomycin were followed with the aid of safranine. Tl⁺ brought about collapse of the diffusion potential. It is concluded that Tl⁺ is able to penetrate the mitochondrial membrane electrophoretically.     

Waterborne transmission ofCampylobacter enteritis

Campylobacter jejuni is an important cause of human diarrheal disease throughout the world and likeSalmonella enteritidis, has a large animal reservoir which includes most of man's domestic animals. Until recently, it has been difficult to trace the chain of transmission from animals to man because of inadequate environmental sampling techniques and means to distinguish strains. Recent improvements in these techniques have made environmental studies more feasible in 2 water-related out-breaks.In 1 study,C. jejuni was found to be an important cause of sporadic, summertime diarrheal disease among hikers in national wilderness areas of Wyoming. In this setting, illness was significantly associated with drinking untreated surface water. SubsequentlyC. jejuni was isolated from surface water, including mountian streams, and from animals in the area. Some of the environmental isolates were serotypically identical to strains isolated from humans.A second study occurred as a result of an outbreak of Campylobacter enteritis in a community in northern Illinois which was epidemiologically associated with the community water system.Campylobacter jejuni was isolated from several surface water sources and from the implicated water system. These studies demonstrate that environmental isolation ofC. jejuni is now possible and may add to our understanding of disease transmission.     

Magnesium supplementation and iron status among female students: The intervention study

BackgroundLiterature data indicate the benefit of magnesium (Mg) supplementation. The aim of this study was to examine the effect of short-term Mg supplementation on iron status in healthy female participants.MethodsOne hundred healthy female students of the University of Belgrade - Faculty of Pharmacy participated the study during eleven intervention days. Students ingested Mg preparations with the same dose of the active substance. The analysis included the measurement of serum iron, unsaturated iron binding capacity (UIBC), total iron binding capacity (TIBC), total Mg (tMg), ionized Mg (iMg), complete blood count, met-, carboxyand oxy-haemoglobin (metHgb, COHgb, O2Hgb). Transferrin concentrations and percentage of transferrin saturation (SAT) were calculated manually. The association among the analyzed biochemical parameters was examined using polynomial regression. A principal component analysis (PCA) was used for the evaluation of interdependence between the analyzed parameters.ResultsA statistically significant trend for change in O2Hgb (%) by tertiles of iMg concentrations was found (P = 0.029). Serum tMg reached significant positive correlation with the SAT at concentration levels greater than 0.9 mmol/L, after 11 days of intervention (R2=0.116). Ionized Mg in a concentration higher than 0.6 mmol/L is positively correlated with SAT and serum Fe (R2=0.214; 0.199, respectively). PCA revealed variability of 64.7% for two axes after 11 days.ConclusionsMg supplementation leads to an improvement in the certain iron status parameters even in individuals with optimal levels of these indices. However, caution should be exercised when supplementing Mg, and laboratory monitoring of the interaction is required.