A plant gene up-regulated at rust infection sites

Expression of the fis1 gene from flax (Linum usitatissimum) is induced by a compatible rust (Melampsora lini) infection. Infection of transgenic plants containing a beta-glucuronidase (GUS) reporter gene under the control of the fis1 promoter showed that induction is highly localized to those leaf mesophyll cells within and immediately surrounding rust infection sites. The level of induction reflects the extent of fungal growth. In a strong resistance reaction, such as the hypersensitive fleck mediated by the L6 resistance gene, there is very little fungal growth and a microscopic level of GUS expression. Partially resistant flax leaves show levels of GUS expression that were intermediate to the level observed in the fully susceptible infection. Sequence and deletion analysis using both transient Agrobacterium tumefaciens expression and stable transformation assays have shown that the rust-inducible fis1 promoter is contained within a 580-bp fragment. Homologs of fis1 were identified in expressed sequence tag databases of a range of plant species including dicots, monocots, and a gymnosperm. Homologous genes isolated from maize (Zea mays; mis1), barley (Hordeum vulgare; bis1), wheat (Triticum aestivum; wis1), and Arabidopsis encode proteins that are highly similar (76%-82%) to the FIS1 protein. The Arabidopsis homologue has been reported to encode a delta1-pyrroline-5-carboxylate dehydrogenase that is involved in the catabolism of proline to glutamate. RNA-blot analysis showed that mis1 in maize and the bis1 homolog in barley are both up-regulated by a compatible infection with the corresponding species-specific rust. The rust-induced genes homologous to fis1 are present in many plants. The promoters of these genes have potential roles for the engineering of synthetic rust resistance genes by targeting transgene expression to the sites of rust infection.     

Zn++ stimulation of the induction of alcohol dehydrogenase by anaerobiosis in roots of Zea mays L.

Summary Zn⁺⁺ at an optimum concentration of 5×10^–4 M caused a two fold stimulation in the level of alcohol dehydrogenase (ADH) induced by anaerobic conditions. Isozymes specified by different genes and alleles show disproportionate increases in activity, such that, unequal representation of gene products while not eliminated, is invariably reduced by Zn⁺⁺ treatment. Thus in the case of alleles at the Adh-1 locus, there was a greater increase in the protein subunit specified by the Adh-1S allele. From previous work (Fischer and Schwartz, 1973) this protein is known to have a reduced affinity for Zn⁺⁺. This suggests that zinc availability during ADH induction is limiting and may provide an alternative to the cis-linked regulatory gene model proposed by Schwartz (1971) to explain the unequal expression of genes and alleles.     

A comparison of the disposition of 14C-Δ9-tetrahydrocannabinol and 3H-Δ9-tetrahydrocannabinol

Preliminary experiments suggested that total levels of radioactivity disappeared from the blood of male, Fischer rats much more rapidly following intragastric administration of ¹⁴C-Δ⁹-tetrahydrocannabinol (¹⁴C-THC) than ³H-THC. Collaborative experiments at the Stanford Research Institute (SRI) and the Research Institute on Alcoholism (RIA) verified and characterized the initial observations. In rats that had food available throughout the experiments, the concentrations of total ³H and ¹⁴C in fresh plasma reached a maximum at 2 – 4 hours after treatment with ³H-THC plus ¹⁴C-THC. Thereafter, ¹⁴C levels fell while ³H levels decreased very slowly or not at all. In fasted rats, peak plasma concentrations of both isotopes were not attained until about 8 hours following drug administration. The concentrations of ¹⁴C then decreased more rapidly than ³H. The differences between the plasma disappearance curves for ¹⁴C and ³H were not dependent upon the method of blood collection or the techniques of isotope counting. However, when plasma or whole blood samples were dried before radioisotope analysis, the difference between ¹⁴C and ³H concentrations was virtually abolished in fed and fasted rats. Experiments suggest that tritiated water, produced during the metabolism of ³H-THC, may be responsible for the prolonged maintenance of high ³H levels in the blood.     

Evaluation of the forced expiration technique as an adjunct to postural drainage in treatment of cystic fibrosis.

Sixteen patients with cystic fibrosis were treated with conventional physiotherapy aided by an assistant. The results were compared with those produced by physiotherapy using the forced expiration technique cleared more sputum in less time than conventional physiotherapy. A sputum in less time than conventional physiotherapy. A second study showed that an assistant did not further improve the results obtained by the patient performing the forced expiration technique himself. These findings mean that patients with cystic fibrosis who have had to rely on the help of others for their home treatment may now perform more effective treatment without help. The forced expiration technique might also be helpful for patients with chronic bronchitis, asthma, or bronchiectasis.     

Interspecific hybridisation in poplar

Summary Interspecific compatibility and incompatibility have been examined through the genus Populus. General methods of manipulation have been developed to break the incompatibility barriers. These methods are described and a hypothesis is put forward to account for the results. This proposes that at least two factors are involved, one attached to the pollen (P) and one to the stigma (S), and that the interaction of these (PS) is critically involved in the total process. Implications for future plant breeding are discussed.

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Zusammenfassung Interspezifische Verträglichkeit und Unverträglichkeit sind im Genus Populus untersucht worden. Wo Unverträglichkeit vorliegt, wurden Methoden entwickelt, um sie zu überwinden. Diese Methoden werden beschrieben. Die Ergebnisse führen zu einer Hypothese, in der angenommen wird, daß mindestens 2 Faktoren eine Rolle spielen. Einer ist mit dem Pollenkorn (P) verbunden, der andere mit dem Stigma (S). Ihr Zusammenspiel im Verträglichkeitsprozess ist von entscheidender Bedeutung. Schlußfolgerungen für zukünftige Züchtungsarbeiten werden erörtert.

     

How far does ozone penetrate into the pulmonary air/tissue boundary before it reacts?

A simple method is suggested for calculating the time it takes ozone to traverse a biological region, such as a bilayer or a cell, and comparing this time to the halflife of ozone within that region. For a bilayer the calculations suggest that most of the ozone reacts within a bilayer, but a fraction may exit unreacted. For the lung lining fluid layer (LLFL), the calculations show that ozone cannot cross this layer without reacting where the LLFL is thicker than about 0.1 microns. However, since the LLFL varies from 20 to 0.1 microns in thickness with patchy areas in the lower airways that are virtually uncovered, some ozone could reach underlying cells, particularly in the lower airways. For cells (such as alveolar type I epithelial cells), the calculations show that ozone reacts within the cell too rapidly to pass through and exit unreacted from the other side. These calculations have implications for ozone toxicity. In vivo, the toxicity of ozone is suggested to result from the effects of a cascade of products that are produced in the reactions of ozone with primary target molecules that lie close to the air/tissue boundary. These products, which have a lower reactivity and longer lifetime than ozone itself, can transmit the effects of ozone beyond the air/tissue interface. The variation in thickness of the LLFL may modulate the species causing damage to the cells below it. In the lower airways, where the LLFL is thin and patchy, more cellular damage may be caused by ozone itself; in the upper airways where the LLFL is thicker, secondary products (such as aldehydes and hydrogen peroxide) may cause most of the damage. In vitro studies must be designed in an attempt to model the lung physiology. For example, if cells in culture are studied, and if the cells are exposed to ozone while under a supporting medium solution that contains ozone-reactive substances, then the cells may be damaged by products that are formed in the reactions of ozone with the cell medium rather than by ozone itself.     

Free radical generation in the brain precedes hyperbaric oxygen-induced convulsions.

We tested the hypothesis that hyperbaric oxygenation (HBO) generates free radicals in the brain before the onset of neurological manifestations of central nervous system (CNS) oxygen poisoning. Chronically cannulated, conscious rats were individually placed in a transparent pressure chamber and exposed to (1) 5 atmospheres absolute (ATA) oxygen for 15 min (n = 4); (2) 5 ATA oxygen for 30 min (n = 5), during which no visible convulsions occurred; (3) 5 ATA oxygen for 30 min with recurrent convulsions (n = 6); (4) 5 ATA oxygen until the appearance of the first visible convulsions (n = 5); (5) 4 ATA oxygen for 60 min during which no convulsions occurred (n = 5); and (6) 5 ATA air for 30 min (n = 5, controls). Immediately before compression, 1 mL of 0.1 M of alpha-phenyl-N-tert-butyl nitrone (PBN) was administered intravenously (iv) for spin trapping. At the termination of each experiment, rats were euthanized by pentobarbital iv and decompressed within 1 min. Brains were rapidly removed for preparation of lipid extracts (Folch). The presence of PBN spin adducts in the lipid extracts was examined by electron spin resonance (ESR) spectroscopy. ESR spectra from unconvulsed rats exposed to 5 ATA oxygen for 30 min revealed both oxygen-centered and carbon-centered PBN spin adducts in three of the five brains. One of the five rats in this group showed an ascorbyl signal in the ESR spectrum.(ABSTRACT TRUNCATED AT 250 WORDS)     

A rapid method to identify exo-protease inhibitors.

A new approach to the evaluation of exo-protease inhibitor candidates is presented. The application of new water-soluble substrates that release organic-soluble fluorescent groups upon proteolytic cleavage allows amplification of the assay signal via concentration of the cleavage product. A combinatorial library of disubstituted xanthenes designed to resemble a known inhibitor was screened and a new HLE inhibitor (Ki = 79 microM) was identified.     

Effects of the nematode Gyrinicola batrachiensis on development, gut morphology, and fermentation in bullfrog tadpoles (Rana catesbeiana): a novel mutualism

We describe a novel mutualism between bullfrog tadpoles (Rana catesbeiana) and a tadpole-specific gastrointestinal nematode (Gyrinicola batrachiensis). Groups of tadpoles were inoculated with viable or nonviable nematode eggs, and development, morphology, and gut fermentation activity were compared between nematode-infected and uninfected tadpoles. Nematode infection accelerated tadpole development; the mean time to metamorphosis was 16 d shorter and the range of times to metamorphosis was narrower in nematode-infected tadpoles than in uninfected tadpoles. At metamorphosis, infected and uninfected bullfrogs did not differ in body size or condition. Colon width, wet mass of colon contents, and concentrations of most fermentation byproducts (short-chain fatty acids: SCFAs) in the hindgut were greater in infected tadpoles. Furthermore, in vitro fermentation yields for all SCFAs combined were over twice as high in infected tadpoles than in uninfected tadpoles. One explanation for accelerated development in infected tadpoles is the altered hindgut fermentation associated with the nematodes. Energetic contributions of fermentation were estimated to be 20% and 9% of the total daily energy requirement for infected and uninfected tadpoles, respectively. Infection by G. batrachiensis nematodes potentially confers major ecological and evolutionary advantages to R. catesbeiana tadpoles. The mutualism between these species broadens our understanding of the taxonomic diversity and physiological contributions of fermentative gut symbionts and suggests that nematodes inhabiting the gut regions of other ectothermic herbivores might have beneficial effects in those hosts.