Nitric oxide decreases superoxide anion generation by microsomes from soybean embryonic axes

Experiments were carried out to evaluate the effects of exposure to nitric oxide on the ability by NADPH‐dependent microsomal electron transfer to generate oxygen radicals. Such interactions could play a role in the potential antioxidant action of nitric oxide (NO). Isolated microsomes from soybean ( Glycine max [L.] Merr. cv. Hood) embryonic axes were exposed to an exogenously added source of nitric oxide (NO) (S‐nitrosoglutathione + dithiothreitol). The O₂⁻ generation rate by microsomes exposed to NO decreased significantly as compared to the rate measured in microsomes incubated in the absence of NO. The exposure of the microsomes to the NO donor did not alter the microsomal rate of hydroxyl radical generation. Preincubation of the microsomes with the NO donor affected neither iron reduction rate nor activity of cytochrome c reductase. However, cytochrome P₄₅₀ activity was significantly inhibited after exposure to NO. This inhibition was completely prevented by hemoglobin. The data are consistent with the hypothesis that NO exhibits a potential antioxidant role in the plant cell by decreasing the rate of generation of superoxide anion. Since endogenous NO was detected in homogenates of soybean embryonic axes by EPR studies, this interaction between NO and cytochrome P₄₅₀ in soybean embryonic axes could be a factor of relevance for the control of oxidative stress in vivo.     

Ultrastructure d'une cyanophycée aérienne calcifiée cavernicole: Geitleria calcarea Friedmann

Résumé L'ultrastructure de Geitleria calcarea Friedmann, cyanophycée filamenteuse aérienne, calcifiée et cavernicole, rarement signalée, est étudiée ici pour la première fois. La cytologie de cet organisme présente des originalités. Huit enveloppes cellulaires concentriques sont dénombrées: membrane plasmique, L I, L II, L III, L IV, enveloppe pariétale, gaine fibreuse et gaine carbonatée. La dernière est décrite à l'aide du M.E.B. Les thylacoïdes très nombreux ont une forme extrêmement contournée. Ils supportent des phycobilisomes cylindriques alternant avec des polysaccharides de même allure. L'organisation des synapses est détaillée. L'élongation est apicale et le mode de ramification est soit latéral, soit dichotomique.

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The ultrastructure of the atmophytic lime-encrusted filamentous blue-green alga Geitleria calcarea Friedmann, which grows in caves, is studied here for the first time. The cytology of this organism presents original features concerning the cellular sheath, envelopes, wall, thylacoïds and pit connections. Its filament growth is apical and its type of branching is lateral and dichotomous.

     

Circadian rhythm of serum and tissue lipids in fed and fasted rats

The oscillations of the free fatty acid concentration in the serum and white (epididymal) adipose tissue, of triglycerides in the serum and liver, of total serum, liver and adrenal cholesterol and of serum phospholipids were studied at 3-hour intervals for a period of 24 hours in fed male Wistar rats and in animals fasted for 24 hours (both adapted to an illumination regimen of 12 hours' light and 12 hours' darkness. The rhythm--studied by means of the cosinor analysis--was present in most of the given parameters; it was not recorded in the liver triglycerides and serum phospholipids of fasted rats and in the adrenal cholesterol of fed animals. Apart from the circadian rhythm, many parameters distinctly displayed an ultradian rhythm, mainly an approximately 12-hour period. In general, one day's starvation did not significantly affect the course of the circadian oscillations of the given indicators of rat lipid metabolism.     

Ontogeny of the proventitious epicormic buds in Quercus petraea.

In the present work, we described the fate of proventitious epicormic buds on the trunks of 40-year-old Quercus petraea trees and in parallel the vascular trace they produced in the wood. Our results show that small and large individual epicormic buds can survive as buds for 40 years and that both are composed of a terminal meristem and scales. Meristematic areas are detected in the scale axils of small buds; in addition to these meristems the large buds also have secondary bud primordia. The small buds are connected to the pith of the main stem by a unique trace, whereas the large buds are connected by one or multiple traces. A single trace might imply that the whole bud is still alive and multiple traces might indicate that the terminal meristem has died. In the latter case, each trace is connected to a secondary bud of the large bud. The buds found in a cluster are composed of a terminal meristem and scales with axillary meristems in the scale axils. A cluster is connected to the pith of a stem either by a unique trace when it seems to be the result of partial abscission of an epicormic shoot or multiple traces when it might have originated from an epicormic bud in which the terminal meristem has died. Whatever the type of the bud, the vascular trace in the bark is composed of a cambium, secondary xylem and parenchyma cells and the trace present in the wood had parenchyma cells with vestiges of secondary xylem. Each year, the vascular trace should be produced in the bark by the cambium of the tree but not by the bud itself. On 40-year-old Q. petraea, we observed a proliferation of epicormic buds and in parallel a multiplication of the number of vascular traces in the trunk, but the knots caused by the traces of epicormic buds in the wood, either as individuals or in clusters, are minor since their colours are only slightly darker than those of woody rays and they are less than 2 mm in diameter. The knots will appear when epicormic buds develop into shoots. Received: 30 March 1999 / Accepted: 09 June 1999     

Ribosomal subunits and ribosomal proteins of Tetrahymena thermophila. Effect of the presence of iodoacetamide during ribosome extraction on the properties of the subunits

Proteolytic degradation of ribosomal proteins occurs during the preparation of subunits of the cytoplasmic ribosomes of the protozoa Tetrahymena thermophila and the isolated subunits are inactive. Addition of 5 mM iodoacetamide to cell suspensions before extraction inhibits proteolytic activity and permits isolation of active subunits. The protein complements of these subunits have been characterized in two different two-dimensional electrophoretic systems, and their molecular weights have been determined.     

Ferritin in normal human peripheral blood T-lymphocyte subpopulations

Six peripheral blood lymphoid fractions (total lymphocytes, non-T, T, Tar (autologous rosette-forming T cells/precursor), T mu (helper), and T gamma (suppressor) lymphocytes) isolated through rosetting procedures were examined for the presence of ferritin by a direct immunofluorescence technique. Although ferritin was present in all lymphoid fractions studied, a significantly higher proportion of ferritin-containing cells were detected in the T-cell fraction than in the non-T-cell fraction, (mean +/- SD = 7.9 +/- 1.6% and 5.0 +/- 1.2%, respectively). T mu- and T gamma-cell fractions showed a twofold increase in the number of ferritin-positive cells (14.1 +/- 1.4% and 15.4 +/- 2.6%, respectively), as compared with Tar (7.0 +/- 0.9%)-and total lymphocyte (6.9 +/- 1.3%)-cell fractions. These results indicate that ferritin is preferentially distributed in T mu and T gamma lymphocytes and may constitute the basis for explaining some of the roles exercised by these cells in the control of other biological systems.     

Impaired beta-cell regeneration in perinatally malnourished rats: a study with STZ.

We investigated the mechanisms implicated in beta-cell mass reduction observed during late fetal and early postnatal malnutrition in the rat. Beta-cell regeneration, including proliferation and neogenesis, was studied after neonatal beta-cell destruction by streptozotocin (STZ). STZ was injected at birth and maternal food restriction was continued until weaning. Beta-cell mass, proliferation, and islet number were quantified by morphometrical measurements on pancreatic sections in STZ-injected normal (C-STZ) and malnourished (R-STZ) rats, with noninjected C and R rats as controls. At day 4, only 20% of the beta cell-mass remained in C-STZ rats. It regenerated to 50% that of noninjected controls, mainly through active neogenesis, as shown by the entire recovery of islet number/cm(2), and also through moderately increased beta-cell proliferation. In contrast, beta-cell mass from R-STZ animals poorly regenerated, despite a dramatic increase of beta-cell proliferation, because islet number/cm(2) recovered insufficiently. In conclusion, perinatal malnutrition impairs neogenesis and the capacity of beta-cell regeneration by neogenesis but preserves beta-cell proliferation, which remains the elective choice to increase beta-cell mass. These results provide an explanation for the impaired capacity of malnourished animals to adapt their beta-cell mass during aging or pregnancy, which aggravate glucose tolerance.     

Endorphin mediated increase in pain threshold induced by long-lasting exercise in rats

Rats were trained to run spontaneously, without stress, in running wheels. The running activity increased gradually and could reach a plateau of 7 km/night after 3–4 weeks. During the first hour of running in the dark phase the squeak threshold increased significantly and remained high in the morning. The degree of increased threshold was correlated to the amount of running activity. The squeak threshold declined during the following 6 hours of inactivity. A rapid decrease in threshold occurred after naloxone (1–2 mg/kg i.p.). It is suggested that long-lasting muscle exercise (e.g. jogging), acupuncture, and low frequency electrical stimulation of afferent nerve fibres produce discharges in muscle afferents which influence central endorphin mechanics giving analgetic effects.