Structural and functional alterations induced by two sulfonamide antibiotics on barley plants.

Synthetic veterinary medicines are introduced routinely in the environment after animal treatment to prevent and control infectious diseases and up to 80% the administered dose can be excreted unaltered. As a consequence, the soil is the environment most contaminated by such molecules. However, information about their implications on the growth of vegetal organisms is still scarce. With the aim of better elucidating the effects of veterinary antibiotics on plants, barley was grown in a nutrient solution containing 40 µM (about 11,500 µg L(-1)) of two well-known sulfonamide antibiotics, sulfadimethoxine (SDM) and sulfamethazine (SZ). After 15 d of treatment, the effects on root apparatus were particularly evident, while the photosynthetic tissues remained almost unaffected. SDM and SZ stimulated root hairs and lateral root development a few mm behind the root tips. In particular, from a structural point of view, treated plants showed root shortening and an advanced differentiation in comparison to controls, later confirmed using light microscopy. At a functional level, the two active molecules were found to induce root electrolyte release, such as K(+), possibly due to an impairment of membrane permeability. The research concludes that sulfonamides can have profound effects on morphology and functionality of roots of crop plants. As these alterations might have consequences on their productivity, further studies are necessary to assess effects on plants at laboratory and field conditions.

Gamma-glutamyl transferase in the cell wall participates in extracellular glutathione salvage from the root apoplast.

The molecular properties and subcellular location of bound gamma-glutamyl transferase (GGT) were studied, and an experimental setup devised to assess its functions in barley roots. Enzyme histochemistry was used to detect GGT activity at tissue level; immunocytochemistry to localize the protein at subcellular level; and modelling studies to investigate its surface charge properties. GGT activity in vivo was measured for the first time. Functions were explored by applying chemical treatments with inhibitors and the thiol-oxidizing drug diamide, performing time-course chromatographic and spectrophotometric analyses on low-molecular-weight thiols. Gamma-glutamyl transferase activity was found to be high in the root apical region and the protein was anchored to root cell wall components, probably by basic amino acid residues. The results show that GGT is essential to the recovery of apoplastic glutathione provided exogenously or extruded by oxidative treatment. It is demonstrated that GGT activity helps to salvage extracellular glutathione and may contribute to redox control of the extracellular environment, thus providing evidence of a functional role for gamma-glutamyl cycle in roots.

Bleaching herbicide effects on plastids of dark-grown plants: lipid composition of etioplasts in amitrole and norflurazon-treated barley leaves.

The effects of the bleaching herbicides amitrole (125 micro M) and norflurazon (100 micro M) on etioplast lipids were studied in barley plants (Hordeum vulgare L. cv. Express) grown for 7 d either at 20 degrees C or 30 degrees C in darkness. Total lipid, glycolipid and phospholipid contents of control etioplasts were increased at 30 degrees C in comparison with those at 20 degrees C. The two herbicides caused a decrease in the total lipid, glycolipid and phospholipid amounts compared to the untreated etioplasts and lowered the lipid to protein ratio. In the controls, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) accounted for about 66 mol% of the etioplast polar lipids, while the remainder was represented by sulphoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG), in approximately equal proportions. Both amitrole and norflurazon increased MGDG at both temperatures, but decreased DGDG except with norflurazon at 30 degrees C. As a consequence, the MGDG to DGDG molar ratio was higher in the herbicide-treated etioplasts compared to the controls at both the growth temperatures. The amount of the negatively charged polar lipids SQDG and PG were decreased by treatments with amitrole at 20 degrees C and norflurazon at 30 degrees C. The two herbicides determined different responses in the fatty acid unsaturation of the individual polar lipids. Changes in the lipid composition of etioplasts and the interaction between the pigment-protein complex, protochlorophyllide-NADPH-protochlorophyllide oxidoreductase, and polar lipids are discussed.

Amitrole treatment of etiolated barley seedlings leads to deregulation of tetrapyrrole synthesis and to reduced expression of Lhc and RbcS genes.

The effect of amitrole, known as an inhibitor of carotenoid biosynthesis, upon tetrapyrrole biosynthesis and its regulation has been studied. Etiolated barley (Hordeum vulgare L.) seedlings, grown in 125 microM amitrole, accumulated high levels of 5-aminolevulinate, Mg-protoporphyrin, Mg-protoporphyrin monomethyl ester, and protochlorophyllide. The amitrole-treated seedlings did not form paracrystalline prolamellar bodies, and the induction of Lhc and RbcS gene expression was reduced by non-photooxidative, low-intensity light. None of these events was observed upon treatment of the seedlings with 100 microM norflurazon, another inhibitor of carotenoid biosynthesis. The effect of amitrole cannot be explained solely by interaction with a presumed feedback inhibition of 5-aminolevulinate synthesis since incubation with amitrole and 5-aminolevulinate indicated that deregulation also occurs at later steps of tetrapyrrole biosynthesis. A possible relationship between this deregulation and ultrastructural changes is discussed. In connection with previously published data, we discuss Mg-protoporphyrin and its monomethyl ester as possible candidates for a "plastid signal" that operates as a negative factor, reducing the expression of Lhc and RbcS genes in this higher plant.

Responses to bleaching herbicides by leaf chloroplasts of maize plants grown at different temperatures.

The effects of growth temperature on chloroplast responses to norflurazon and amitrole, two herbicides inhibiting carotenogenesis, at phytoene desaturation and lycopene cyclization, respectively, were studied in leaves of maize plants grown at 20 degrees C and 30 degrees C in light. At the lower temperature both chemicals caused severe photo-oxidative damage to chloroplasts. In organelles of norflurazon-treated leaves neither carotenoids nor chlorophylls were detectable and the thylakoid system was dismantled. In organelles of amitrole-treated leaves lycopene was accumulated, but small quantities of beta-carotene and xanthophylls were also produced. Moreover, some chlorophyll and a few inner membranes still persisted, although these latter were disarranged, lacking essential protein components and devoid of photosynthetic function. The increase in plant growth temperature to 30 degrees C did not change the norflurazon effects on carotenoid synthesis and the photo-oxidative damage suffered by chloroplasts. By contrast, in organelles of amitrole-treated leaves a large increase in photoprotective carotenoid biosynthesis occurred, with a consequent recovery of chlorophyll content, ultrastructural organization and thylakoid composition and functionality. This suggests that thermo-modulated steps could exist in the carotenogenic pathway, between the points inhibited by the two herbicides. Moreover it shows that, unlike C(3) species, C(4) species, such as maize, can express a strong tolerance to herbicides like amitrole, when supplied to plants growing at their optimum temperature conditions.

A multicenter, randomized, double-blind, placebo-controlled trial of influenza immunization in multiple sclerosis.

We determined the effect of influenza vaccine in patients with relapsing/remitting MS. Considerable controversy surrounds the question of whether to administer influenza vaccines to MS patients. Prevention of a febrile viral illness is clearly desirable in MS, and previous studies suggest that immunization is safe. Despite this, many clinicians avoid vaccination because they fear precipitating an MS exacerbation. We conducted a multicenter, prospective, randomized, double-blind trial of influenza immunization in patients with relapsing/remitting MS. In the autumn of 1993, 104 patients at five MS centers received either standard influenza vaccine or placebo. Patients were followed for 6 months for evaluation of neurologic status and the occurrence of influenza. Influenza was operationally defined as fever > or = 38 degrees C in the presence of coryza, cough, or sore throat at a time when the disease was present in the community. Attacks were defined in the standard manner, requiring objective change in the examination. Patients were examined at 4 weeks and 6 months after inoculation and were contacted by telephone at 1 week and 3 months. They were also examined at times of possible attacks but not when they were sick with flu-like illness. Three vaccine patients and two placebo patients experienced attacks within 28 days of vaccine (no significant difference). Exacerbation rates in the first month for both groups were equal to or less than expected from published series. The two groups showed no difference in attack rate or disease progression over 6 months. Influenza immunization in MS patients is neither associated with an increased exacerbation rate in the postvaccination period nor a change in disease course over the subsequent 6 months.

Cognitive dysfunction and change in multiple sclerosis.

A cross-sectional study of 60 multiple sclerosis outpatients assessed neuropsychological variables in relation to age, duration of disease, and degree of disability. The test battery included subtests of the WAIS (Vocabulary, Similarities, and Digit Span);the Raven matrices; and memory tests (Wechsler Paired Associates, Benton Visual Retention). Results showed that cognitive functioning of MS patients varies considerably. There is a general mild decline that affects abstract reasoning and memory as the disease progresses. These deficits are usually not sufficient to impair occupational or social functioning. In addition, there is spotty deterioration in certain cognitive functions for some patients (17%). Only a small subsample (6.7%), however, showed global deterioration significant enough to be highlighted by an Index of Dementia that was developed for this investigation.

Employment in individuals with multiple sclerosis.

The major objectives of this research were to examine unemployment in the MS population on a national level, and to identify factors which might influence an MS individual's employment status. Data used were from the National Multiple Sclerosis Survey conducted by the National Institute of Neurological and Communicative Disorders and Stroke. Data analysis was restricted to a subset of the sample who had worked at some time in their lives. Of 949 persons 79.7% were currently unemployed. While 65.2% had worked at the time of first symptom, only 27.2% were working at the time of the interview, an average of 17 years later. Path analyses revealed the overwhelming importance of mobility for remaining employed, particularly for males. Additional differences found between male and female path models were interpreted in terms of social role theory.