Nucleotide sequence and characterization of a maize cytoplasmic ribosomal protein S11 cDNA

We isolated a Zea mays cDNA encoding the 40S subunit cytoplasmic ribosomal protein S11. The nucleotide sequence was determined and the derived amino acid sequence compared to the corresponding Arabidopsis thaliana protein showing an homology of 90%. This ribosomal protein is encoded by a small multigene family of at least two members. The mRNA steady-state level is about one order of magnitude higher in rapidly growing parts of the plant such as the roots and shoots of seedlings compared to fully expanded leaf tissue.     

Central injections of arginine vasopressin prolong extinction of active avoidance

Behavioral and physiological effects of arginine vasopressin (AVP) were examined following intracerebroventricular (ICV) injection in the rat. ICV injections prolonged extinction of active avoidance at doses of 1.0 and 10.0 ng/rat and this effect was blocked by peripheral injection of the vasopressor antagonist of vasopressin [dPtyr(Me)AVP] at a dose of 30 micrograms/kg (SC). However, 1.0 ng of AVP ICV failed to alter systemic blood pressure and also failed to produce taste aversions in a one or two bottle test. Results suggest that central AVP has a central action independent of systemic changes in blood pressure, but that the receptor mediating this action is functionally similar to the AVP V1 (vasopressor) receptor.     

Plasmids in Listeria monocytogenes in relation to cadmium resistance.

One hundred and seventy-three unrelated Listeria monocytogenes strains isolated from humans, animals, the environment, and food were analyzed for the presence of plasmids. Extrachromosomal DNA was found in 28% of the strains. Plasmid DNA was extracted more frequently from L. monocytogenes serogroup 1 strains (35%) than from serogroup 4 strains (15%). Among strains from food and the environment, 40% and 29%, respectively, harbored plasmids, whereas only 13% of the strains from humans and animals with listeriosis bore plasmids. We also investigated the susceptibility of 90 strains to seven antibiotics and four heavy-metal salts. No antibiotic resistance could be detected, but 95.3% of the plasmid-positive strains and only 12.7% of the plasmid-negative strains were resistant to cadmium. The plasmid-determined genetic basis of cadmium resistance was proven by conjugation between strains of L. monocytogenes and by cure of the plasmid. This is the first time that plasmids of L. monocytogenes have been shown to be associated with cadmium resistance.     

Effects of glucose on 45Ca2+ outflow, cytosolic Ca2+ concentration and insulin release from freshly isolated and cultured adult rat islets

The present study aimed at comparing the effects of glucose on ionic and secretory events in freshly isolated and 5-7 day cultured rat pancreatic islets. The capacity of glucose to provoke insulin release was severely reduced in islets maintained in culture. Whether in freshly isolated or cultured islets, glucose provoked a marked and sustained decrease in 45Ca2+ outflow from islets deprived of extracellular Ca2+. In the presence of extracellular Ca2+ throughout, the magnitude of the glucose-induced secondary rise in 45Ca2+ outflow was reduced in cultured islets. Glucose provoked a weaker increase in [Ca2+]i in islet cells obtained from cultured islets than in islet cells dissociated from freshly isolated pancreatic islets. On the other hand, the stimulatory effect of carbamylcholine on 45Ca2+ outflow was unaffected by tissue culture. Lastly, in islet cells obtained from cultured islets, the increase in [Ca2+]i evoked by K+ depolarization averaged half of that observed in control experiments. These results indicate that the reduced secretory potential of glucose in cultured pancreatic islets can be ascribed to the inability of the nutrient secretagogue to provoke a suitable increase in Ca2+ influx.     

Modelling extreme stretching of DNA.

Molecular modelling with Jumna is used to study extreme stretching of the DNA double helix. The results, which correlate well with recent nanomanipulation experiments, show how the double helix can be extended to twice its normal length before its base pairs break. Depending on the way the duplex is stretched two types of conformation can occur, either an unwound flat ribbon or a narrow fibre with negatively inclined base pairs. The energetics of both types of deformation are similar and existing structures show that at least the flat ribbon form can exist locally under biological conditions.     

The soil fauna: the other last biotic frontier

Different approaches to biodiversity yield global totals as small as 3 million or as large as 80 million species. Erwin's calculation and estimation leads to an estimate of ca 30 million species and relies on four assumptions of which one concerns the ratio between the number of canopy insects and those found elsewhere, especially in the soil. A short survey of the microarthropods living in coastal sand dunes and collected with a new flotation method yielded amazing results. In spite of the severity of the habitat (low organic matter content and extreme dryness), the density of microarthropods varied between 175 000 and 1 400 000 individuals per square metre, i.e., densities 3 to 10 times higher than densities usually observed in any other type of soil. A total of 31 species was recorded, most undescribed and smaller than 200 m. The consequences of these findings on the estimation of the number of species are discussed. It is suggested that the soil, including the deepest horizons and the rhizosphere, might constitute a huge reservoir for biodiversity.     

Use of VIRAZOLE® to eradicate odontoglossum ringspot virus from in vitro cultures of Cymbidium Sw.

Odontoglossum Ringspot Virus has been eradicated from Cymbidium Sw. through chemotherapy based on incorporation of ribavirin (VIRAZOLE^®) into the in vitro culture medium of protocorms. Applications of the virustatic agent for several consecutive subcultures freed protocorms of the virus. Acclimated plantlets regenerated from those protocorms are healthy as determinated by enzyme-linked immunosorbent assay (ELISA). No resurgence of virus occurred over a period of 5 years. Besides, trueness to type was total at flowering level and the batch grown was perfectly homogeneous.To secure fast and effective eradication of the virus during the consecutive subcultures of protocorms with ribavirin, three factors proved to be of prime importance: accurate isolation of new growths from initial tissues, VIRAZOLE^® concentration and frequency of transplanting in new media.     

Electron microscopic study of the mandibular glands of Kalotermes flavicollis Fabr. (Isoptera; Calotermitidae)

Summary The mandibular glands of Kalotermes were examined in different castes. They showed sexual dimorphism in the soldiers and primary reproductives. Moreover, in female soldiers and queens, mandibular gland cells contained numerous crystalline structures of mitochondrial origin. The role of these glands (secretion of saliva or pheromone) is discussed.

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Résumé Les glandes mandibulaires de Calotermes sont étudiées dans les différentes castes. Elles présentent un dimorphisme sexuel chez les soldats et les sexués. Après la mue imaginale, les cellules glandulaires ont toujours une activité sécrétrice. De plus, chez les soldats femelles et les reines, elles contiennent de nombreuses formations cristallines d'origine mitochondriale. Le rôle de ces glandes (sécrétion de salive ou de phéromone) est discuté.

     

A microfluorometric method for alkaline phosphatase: Application to the various segments of the nephron

A microtechnique has been developed for the measurement of alkaline phosphatase in minute amounts of renal tissue. This microtechnique utilizes the known fluorescent property of 4-methylumbelliferyl phosphate following enzymatic hydrolysis. The reaction is sensitive and reproducible and is inhibited by l-bromotetramisole, a specific alkaline phosphatase inhibitor. The microdetermination of alkaline phosphatase activity in the various segments of the mouse nephron allowed the localization of the enzyme in the glomeruli, and in the proximal convoluted tubule where the activity progressively decreases from the capsule of Bowman to the more distal segments. The enzyme was absent from the pars recta or S3 and from the rest of the nephron. This technique is applicable to very small amounts (0.1 μg of protein) of any tissue containing alkaline phosphatase.     

Regulation of calcium fluxes in rat pancreatic islets: Quinine mimics the dual effect of glucose on calcium movements

The effects of quinine and 9-aminoacridine, two blockers of potassium conductance in islet cells, on ⁴⁵Ca efflux and insulin release from perifused islets were investigated in order to elucidate the mechanisms by which glucose initially reduces ⁴⁵Ca efflux and later stimulates calcium inflow in islet cells. In the absence of glucose, 100 μM quinine stimulated ⁴⁵Ca net uptake, ⁴⁵Ca outflow rate and insulin release. Quinine also dramatically enhanced the cationic and the secretory response to intermediate concentrations of glucose, but had little effect on ⁴⁵Ca net uptake, ⁴⁵Ca fractional outflow rate and insulin release at a high glucose concentration (16.7 mM). The ability of quinine to stimulate ⁴⁵Ca efflux depended on the presence of extracellular calcium, suggesting that it reflects a stimulation of calcium entry in the islet cells. In the absence of extracellular calcium, quinine provoked a sustained decrease in ⁴⁵Ca efflux. Such an inhibitory effect was not additive to that of glucose, and was reduced at low extracellular Na⁺ concentration. At a low concentration (5 μM), quinine, although reducing ⁸⁶Rb efflux from the islets to the same extent as a non-insulinotropic glucose concentration (4.4 mM), failed to inhibit ⁴⁵Ca efflux. In the presence of extracellular calcium, 9-aminoacridine produced an important but transient increase in ⁴⁵Ca outflow rate and insulin release from islets perifused in the absence of glucose. In the absence of extracellular calcium, 9-aminoacridine, however, failed to reduced ⁴⁵Ca efflux from perifused islets. It is concluded that quinine, by reducing K⁺ conductance, reproduces the effect of glucose to activate voltage-sensitive calcium channels and to stimulate the entry of calcium into the B-cell. However, the glucose-induced inhibition of calcium outflow rate, which may also participate in the intracellular accumulation of calcium, does not appear to be mediated by changes in K⁺ conductance.