Systematic gene silencing identified Cryptosporidium nucleoside diphosphate kinase and other molecules as targets for suppression of parasite proliferation in human intestinal cells.

Cryptosporidiosis is a major cause of diarrheal disease. The only drug approved for cryptosporidiosis has limited efficacy in high-risk populations. Therefore novel drugs are urgently needed. We have identified several enzymes as potential targets for drug development and we have optimized a rapid method to silence genes in Cryptosporidium. In this study, we knocked down expression of the four selected genes: Actin (Act), Apicomplexan DNA-binding protein (Ap2), Rhomboid protein 1 (Rom 1), and nucleoside diphosphate kinase (NDK). After gene silencing, we evaluated the role of each target on parasite development using in vitro models of excystation, invasion, proliferation, and egress. We showed that silencing of Act, Ap2, NDK, and Rom1 reduced invasion, proliferation, and egress of Cryptosporidium. However, silencing of NDK markedly inhibited Cryptosporidium proliferation (~70%). We used an infection model to evaluate the anticryptosporidial activity of ellagic acid (EA), an NDK inhibitor. We showed that EA (EC50 = 15-30 µM) reduced parasite burden without showing human cell toxicity. Here, we demonstrated the usefulness of a rapid silencing method to identify novel targets for drug development. Because EA is a dietary supplement already approved for human use, this compound should be studied as a potential treatment for cryptosporidiosis.

Brain activation profiles in dyslexic children during non-word reading: a magnetic source imaging study.

The purpose of the study was to identify spatiotemporal brain activation profiles associated with phonological decoding in dyslexic children using magnetic source imaging. For this purpose maps of regional cerebral activation were obtained from eleven children diagnosed with dyslexia and ten children without reading problems during engagement in a pseudoword rhyme-matching task. All dyslexic children showed aberrant activation maps consisting of reduced activity in temporoparietal areas in the left hemisphere (including the posterior part of the superior temporal, angular and supramarginal gyri) and increased activity in the right homotopic region. In contrast, the two groups of children did not differ in the degree of activity in basal temporal areas that typically precedes temporoparietal activation. This is the first study to demonstrate the existence of distinct activation profiles associated with phonological decoding in individual dyslexic children.

Carbon exchange rates of shoots required to utilize available acetylene reduction capacity in soybean and alfalfa root nodules.

The CO(2)-exchange rate required to make full use of available N(2)-fixation capacity, measured as acetylene reduction, was determined in soybean and alfalfa. Carbohydrates of root systems were depleted during a 40-hour dark treatment; then plants were exposed to a 24-hour light period during which different CO(2)-exchange rates were maintained with various CO(2) concentrations. In three- and four-week-old soybeans and four-week-old alfalfa plants, acetylene-reduction capacity was used fully with CO(2)-exchange rates as low as 10 milligrams CO(2) per plant per hour. In six-week-old alfalfa plants, however, acetylene reduction rates increased linearly, and apparent N(2)-fixation capacity was not used fully when CO(2)-exchange rates were higher than 40 milligrams CO(2) per plant per hour. Under the conditions established, the energy cost of N(2) fixation, measured as Delta(respiration of roots + nodules)/Deltaacetylene reduction over dark-treatment values, was 0.453 milligrams CO(2) per micromole C(2)H(4) for all rates of acetylene reduction and for both ages of soybean and alfalfa plants. Thus, root-plus-nodule respiration was not promoted by higher rates of apparent photosynthesis after C(2)H(2)-reduction capacity became saturated, and all available capacity for apparent N(2) fixation had the same energy requirement.

Myasthenia gravis. Study of humoral immune mechanisms by passive transfer to mice.

To study the role of humoral factors in the pathogenesis of myasthenia gravis, we employed passive transfer of human serum fractions to mice. Immunoglobulins from 16 patients with myasthenia gravis were injected into mice daily for one to 14 days. Typical myasthenic features of reduction in amplitude of miniature end-plate potentials (mean change more than 50 per cent, P less than 0.005) or reduction in acetylcholine receptors at neuromuscular junctions (mean change more than 50 per cent, P less than 0.005) (or both) were produced by immunoglobulin from 15 of the 16 patients. Some mice showed weakness or decremental responses to repetitive nerve stimulation as well. The active fraction was identified as IgG by three different purification methods. Its effect was enhanced by the third component (C3) of the complement system, but the fifth component (C5) had no effect. These data suggest that the pathogenesis of myasthenia gravis often involves and antibody-mediated autoimmune attack on the acetylcholine receptors of the neuromuscular junction.

QUANTITATIVE CATION REQUIREMENTS OF SEVERAL GREEN AND BLUE-GREEN ALGAE(2).

In contrast with studies which have based essential element requirements of algae on nutrient solution concentrations, in this investigation the requirements of each of 6 species of green and blue-green algae for calcium, magnesium, and potossium were quantitatively evaluated in terms of critical cell concentrations of the 3 cations. A critical cell concentration was considered the minimum cell content of an element which permitted maximum or near maximum total growth of an organism. In comparison with the needs of angiosperm crop plants, the requirements of all 6 species for calcium were extremely low (critical cell contents of 0.06% or less, oven-dry basis); requirements for magnesium were equal to or only slightly less than in higher plants (0.15-0.30%) with the exception of Scenedesmus quadricauda (0.05%); and the requirements for potassium varied greatly, from critical levels less than the average values established for higher plants (0.25-0.50%) to values equal to or in excess of higher plant averages (0.80-2.40%). The nutrition of S. quadricauda was of particular interest because of extremely low requirements for all 3 cations. The results provide a more precise and meaningful expression of the essential cation requirements of algae than have previous data. The results also suggest differences in the physiology and functions of cations in the algae studied and in angiosperms which seem worthy of further investigation.