Mechanism of Antiviral Activity <Emphasis Type="Italic">in vivo</Emphasis> of Polycarboxylates which induce Interferon Production

SYNTHETIC polycarboxylates have been reported to impart resistance to viral infection to experimental animals^1–8. Injection of these polyanions induces interferon^1–3,5–9, to which it therefore seemed logical to attribute the antiviral effect. The high degree and long duration of protection, however, are not in accord with the low and transitory levels of interferon induced, suggesting that mechanisms other than interferon are involved. Certain polyanions have been found directly to inactivate virus or to inhibit its adsorption to cells¹⁰in vitro. This may delay the development of viral infection in vivo. Stimulation of reticuloendothelial cell activity, as demonstrated by increased phagocytosis induced by pyran copolymer¹¹, may deviate virus from its target cells.     

The Endocommensal Ciliates of Venezuelan Sea Urchins

SYNOPSIS. Two hundred and fifty-nine specimens of the sea urchins Echinometra lucunter (201), Diadema antillarum (52), Tripneustes ventricosus (5) and Eucidaris tribuloides (1), collected on the littoral of the Federal District of Venezuela, were examined for intestinal ciliates.
Iron hematoxylin and silver-impregnation staining technics permitted determination of eight of the nine ciliates found: Anophrys aglycus, A. elongata, Cohnilembus caeci, Biggaria bermudensis, B. echinometris, Cyclidium rhabdotectum, Metopus circumlabens and M. rotundus . An unidentified species of Euplotes was also found.     

Cochlodinium heterolobatum n.sp.: Structure and Some Cytophysiological Aspects*

SYNOPSIS. Structure and morphogenesis, and cytochemical data on Cochlodinium heterolobatum, a new species of unarmored dinoflagellate, were derived from living and fixed material from culture. C. heterolobatum is characterized by the torsion of the girdle which descends in a left-hand spiral 1.8 turns; the sulcus having a torsion of 0.8 turn; a sulcus loop in the epicone; a tongue-shaped lobe in the right hypocone; nucleus in the epicone; and a stigma in the left epicone. Trichocysts and behavior of the nucleus during typical and atypical divisions are described in cells from cultures of different ages. A small form with the specific characters was found. Intracellular bacteria were seen and their growth followed in individuals from cultures of different ages. A possible relationship between those bacteria and the accumulation of metabolites inside old cells is discussed.     

RECIPROCAL BEHAVIOR OF THE RACHIS AND PEDUNCLE IN COLONIES OF Veretillum cynomorium PALL.

Some integrated patterns of behavior have been studied in coloniesof Veretillum cynomorium, whose various parts often act as ifthey were those of an individual consisting of the whole colony.The entire colony is involved in slow rhythmical movements,in which phases of contraction alternate with expansion. Thisbehavior corresponds to a permanent reciprocity (or duality)between the zooid-bearing rachis and the peduncle; overall behavioris determined by the number of "functionally active units" whicheither contains at any given time. This number is influencedby the excitatory or restraining effects of external factorssuch as light intensity or the entry of water. In this way,when contraction proceeds, activity of the rachis predominates,whereas during swelling of the colony, activity of the peduncleprevails. Observations on intact colonies and on specimens without peduncles,experiments using light and electrical stimuli, and the studyof peristalsis, all suggest that the mutually reciprocal natureof activity in the rachis and peduncle may be attributed tothe differential influence of external factors on the functionalstate of centers of spontaneous activity or of conduction pathwaysin the colony. Zooids present on the rachis are responsibleboth for the reciprocal activity of the colony and for its morphologicalpolarity.     

The Respiratory Metabolism of Strelitzia juncea Ait. Seeds. The Effect of Dormancy Release by Oxygen on certain Glycolytic Enzyme Activities and Metabolite Concentrations

The activity of the glycolytic enzymes PFK, PFP, PK and aldolaseas well as the content of glucose, fructose, glucose-6-phosphateand fructose-6-phosphate were compared in the embryos of airand oxygen-incubated seeds of Strelitzia juncea. Determinationswere made during the first 4 d of incubation, prior to radicleemergence, which commences on day five for oxygen-treated seeds. No difference in PFK activity was found for the two treatments,and for both treatments PFK tended to increase with the incubationperiod. The fr2, 6P₂-stimulated PFP activity was slightly higherfor oxygen-incubated seeds, and showed a significant increasein activity over the 4 d incubation period for both treatments.No significant change in the general trend of PK and aldolaseactivity resulted from incubating the seeds in oxygen. The almost equimolar glucose and fructose contents of the embryoswere lower after 1 d of oxygen incubation of the seeds, andthe content decreased sharply during the incubation period.It is concluded that a moderate increase in the glycolytic capacityof embryos resulted from oxygen treatment of S. juncea seeds. Key words: Dormancy, glycolysis, Strelitzia juncea     

Spikelet Sterility and Flowering Response of Rice to Water Stress at Anthesis

Water deficits at the anthesis stage of rice (Oryza sativa L.)induce a high percentage of spikelet sterility and reduce grainyield. This study attempted to elucidate the direct effectsof water stress on panicle exsertion, spikelet opening, andspikelet desiccation leading to spikelet sterility. A well-wateredtreatment and two water stress levels were imposed in pot-grownplants of IRAT 13 (upland cultivar) and IR20 (lowland cultivar)at the time of flowering under greenhouse conditions A cultivar difference was observed in the flowering responseto water stress with a high sensitivity in IR20. The time courseof panicle exsertion showed an inhibitory effect due to thelow panicle water status. Low panicle water potentials significantlyreduced the number of opened spikelets. Spikelet opening wascompletely inhibited at panicle water potentials below –1·8MPa and –2·3 MPa in IR20 and IRAT 13, respectively.However, the peak spikelet opening time in a day was not influencedby the stress treatment. Spikelets in stressed panicles wereobserved to remain open for a longer period than in the well-wateredpanicles. The role of turgor in spikelet opening is also discussedin the study. At low panicle water potentials, severe desiccationof spikelets and anthers was noted. The deleterious effectsof water deficits on spikelet opening and spikelet water losscontributed to reduced spikelet fertility Oryza sativa L., rice, spikelet sterility, flowering, water stress, panicle water potentials, turgor potentials, desiccation     

Infrasectional systematics of the genus Sideritis L. section Sideritis (Lamiaceae)

RIVERA NUÑEZ, D., OBON DE CASTRO, C., TOMAS-LORENTE, F., FERRERES, F. & TOMAS-BARBERAN, F. A., 1990. Infrasectional systematics of the genus Sideritis L. section Sideritis (Lamiaceae). A new taxonomic division of the section Sideritis is proposed on the basis of morphological, cytological and chemical characters. The following subsections art-recognized: Grandiflora, Ovata, Camarae, Linearifolia, Gymnocarpae, Stachydioides, Lacaitae, Hirsuta, Chamaedryfolia, Arborescens, Flavovirens, Leucantha, Angustifolia, Serrata and Scordioides . Possible evolutionary pathways are discussed.     

Production of ethylene by gravistimulation: a potential problem with the interpretation of data from some experimental techniques

Abstract. Gravistimulation was investigated as a potential and unwanted component in the interpretation of physiological investigations on plants. Using both seedlings and mature sunflower plants, two situations are described where gravistimulation contributes significantly to the outcome of an experiment not initially designed to include this parameter. The number of adventitious roots formed in derooted seedings decreased when the tops of the plants were allowed to bend over under their own weight, and the effect correlated positively with the rate of ethylene production by non-vertical stems. In droughted mature plants, and increase in leaf and stem ethylene caused by water stress was supplemented by additional ethylene produced in the lower halves of stems. Drought had caused these stem tissues to wilt, become gravistimulated, and thus produce more ethylene. Other situations in which gravistimulated ethylene production and its physiological consequences are likely to be complicating factors in experiments are discussed. It is concluded that procedures that unnecessarily place experimental material in non-vertical orientations should be avoided.     

Effect of Gossypol on Trypomastigotes and Amastigotes of Trypanosoma cruzi

Bloodstream Trypanosoma cruzi trypomastigotes isolated from infected mice undergo reduction of motility and structural damages after 5 to 45 min exposure to gossypol at concentrations ranging from 5 to 50 μM. When 1% serum albumin is added to the incubation medium, no alterations of parasites are observed, even with 100 μM gossypol. Intracellular T. cruzi amastigotes in infected Vero cell cultures exposed to 5 μM gossypol for 2 h do not show changes. Incubation with 5 μM gossypol for 48 h produces complete disruption of host cells; however, the amastigotes they contain show only mineor alterations. The observations indicate that, in protein-rich media, gossypol is complexed into associations which have no activity on the different forms of the T. cruzi biological cycle.     

Ionic Requirements for Catecholamine Aggregating Actions on the Teleost Poecilia reticulata Melanophores

Norepinephrine (NE) and phenylephrine (Phe) were employed to study the ionic requirements for alpha adrenoceptor activation in the teleost Poecilia reticulata melanophores. As expected the beta adrenoceptor blocker, propranolol, increased the sensitivity of the preparation to NE (5.8 times), and was therefore employed in all the experimental procedures. Neither cocaine (a neuronal uptake blocker) nor dexamethasone (an extraneuronal uptake blocker) enhanced the sensitivity of the preparation to NE, suggesting that these inactivating mechanisms would not play a role in P. reticulata pigmentary system. However, in the absence of calcium, the dose-response curve (DRC) to NE was displaced to the left about 3.5 times, whereas the DRC to Phe was not affected. These results indicate that a neuronal uptake is active, but was not demonstrated by the classical pharmacological tools, probably due to an assymmetric display of the nervous endings. The DRC to NE was rightward displaced (14.1 times) in the presence of the calcium channel blocker Verapamil, whereas the DRC to Phe was not affected. These data suggest that P. reticulata melanophores possess a mixed population of alpha₁ and alpha₂ adrenoceptors, the activation of the latter eliciting an extracellular calcium influx. In sodium-free saline, the DRC to NE was rightward shifted (6.6 times) and the response to Phe was impaired in such a way that the maximal response was not achieved. The DRC to both NE and Phe were rightward displaced (7.9 and 2.7 times respectively) in the presence of the sodium channel blocker tetrodotoxin (TTX) 10^?7M. In potassium-free saline, the melanophore sensitivity to Phe was increased, whereas the responses to NE were not affected, suggesting a differential sensitivity of the two alpha adrenoceptor subtypes to the resulting membrane hyperpolarization. Based on the literature and on our data we propose that P. reticulata melanophores possess a mixed population of alpha₁ and alpha₂ receptors. The activation of both subtypes of alpha adrenoceptors elicits a Na⁺ ion influx through TTX-sensitive sodium channels. The stimulation of alpha₂ adrenoceptors also requires an extracellular calcium influx, through the opening of slow calcium channels.