A new protein factor functional in the ferredoxin-independent light activation of chloroplast fructose 1,6-bisphosphatase

A protein purified from chloroplasts (the “new protein factor”) activated Fru-P₂ase in a photochemical reaction that depended only on chloroplast membranes. The results suggest that chloroplasts utilize the newly found mechanism for the photoregulation of Fru-P₂ase in addition to the recently described ferredoxin/thioredoxin system.     

Ferralterin: An iron-sulfur protein functional in enzyme regulation in photosynthesis

The chloroplast new protein factor that was recently shown to link light to the activation of fructose 1,6-bisphosphatase was identified as a previously unrecognized iron-sulfur protein. This protein, given the name “ferralterin,” was purified to homogeneity from spinach leaves and from the blue-green alga (cyanobacterium) Nostoc muscorum. Ferralterin from both sources showed a visible absorption peak at 410nm, a molecular weight of about 30,000 and (provisionally) 4 g-atoms per mole each of nonheme iron and acid labile sulfide. The homogeneous ferralterin preparations catalyzed a light-dependent activation of chloroplast fructose 1,6-bisphosphatase that was dependent only on chlorophyll-containing membranes.     

Release of norepinephrine from the rat ovary: local modulation of gonadotropins.

Experiments were undertaken to define the role of gonadotropins in the release of norepinephrine and the relationship with beta-receptors of the ovary. Rat ovaries were removed at different stages of the estrous cycle and incubated in [3H]norepinephrine. Subsequently, ovaries were electrically stimulated and the release of [3H]norepinephrine was recorded. There were no changes in the norepinephrine content during the estrous cycle. The ovary exhibited cyclical variation in norepinephrine-induced release during the estrous cycle. The lowest release of norepinephrine was found during diestrus; there was an increase during proestrus and estrus followed by a decline during metestrus. The release of norepinephrine changed in the opposite way to the beta-receptor number, suggesting a process involving down-regulation between norepinephrine release and beta-receptors of the ovary. Norepinephrine released from the ovary was locally regulated by gonadotropins. The presence of FSH in the superfusion medium stimulated the norepinephrine-induced release from the ovaries of rats in diestrus (by 20%) and estrus (by 40%), but no effect was found during proestrus. In addition, the presence of hCG stimulated (by 40%) norepinephrine-induced release during proestrus, but no changes were apparent during the other stages of the estrous cycle. These results suggest that the local action of gonadotropins on nerve terminals of the ovary might be one of the factors governing the changes in norepinephrine release through the estrous cycle. The changes in the norepinephrine released to the synaptic cleft might exert down-regulation on the beta-adrenergic receptor content of the ovary and in this way control the ovarian steroid secretory activity.     

A neural model of the interaction of tectal columns in prey-catching behavior

Building on a simple model of a tectal column as the unit of processing in the amphibian tectum, we conduct a computer analysis of the interaction of a linear array of such columns. The model suggests that the inhibitory and excitatory activity in the tectum may have three functions: 1) spatiotemporal facilitation of column activity to a moving stimulus; 2) preference for the head of the stimulus, probably to avoid possible defensive reactions of the prey; and 3) modulating the state of excitation of the column once it has produced a response. The model also shows that the spatio-temporal effects of excitation and inhibition increases the acuity of the animal to the direction of the prey, through processes similar to lateral inhibition.The search reported in this paper was supported in part by NIH grant NS14971-02. Our thanks to Peter Ewert and David Ingle for valuable discussions of the experimental data; and to Andrew Cromarty and Donald House for their help with the computer implementation     

A micro-method for the assay of polyadenylate-containing ribonucleic acid by gel electrophoresis.

A micro-method for the determination of the electrophoretic profile of the various poly(A)-containing RNA species in a RNA sample was developed. The method is simple to carry out and allows for great reproducibility. It combines the resolving power of electrophoresis in agarose with the specificity of binding of poly(A) to poly(U)-containing glass-fibre filters. It consists of the following steps. (1) The molecules in an RNA sample are first separated according to their molecular weight by electrophoresis in agarose, at low ionic strength. 2. The molecules thus seperated are then submitted to a second electrophoresis in 'binding buffer' in a direction perpendicular to the first one. In the course of this electrophoresis the poly(A)-containing RNA species are seperated from other RNA species as they bind to a poly(U)-containing glass-fibre filter which is placed across the electrophoresis path. The method was used to determine the electrophoretic profile of Rhynchosciara salivary-gland messenger RNA. It was found that the population of messenger RNA in the gland is dominated by forms moving as 18 and 158 S peaks, but there is also polydisperse RNA with slower mobility.     

Neurotrophic Effects of Extracellular Guanosine

Central nervous system (CNS) astrocytes release guanosine extracellularly, that exerts trophic effects. In CNS, extracellular guanosine (GUO) stimulates mitosis, synthesis of trophic factors, and cell differentiation, including neuritogenesis, is neuroprotective, and reduces apoptosis due to several stimuli. Specific receptor-like binding sites for eGUO in the nervous system may mediate its effects through both MAP kinase and PI3-kinase signalling pathways. Extracellular guanine (eGUA) also exerts several effects; the trophic effects of eGUO are likely regulated by conversion of eGUO to eGUA by a membrane located purine nucleoside phosphorylase (ecto-PNP) and by conversion of eGUA to xanthine by guanine deaminase.     

Resistance of the AF-28 sorghum variety to Contarinia sorghicola

The variety AF-28 of Sorghum bicolor Pers and the hybrid R-1090 were compared in relation to the sorghum midge, Contarinia sorghicola (Coquillet), (Diptera: Cecidomyidae) in two counties of the State of São Paulo. They were compared in seven successive monthly trials beginning in September 1972. Averages of 252 and 137 adult flies emerged per head of the hybrid R-1090 in Campinas and Jaboticabal respectively, while 2.9 and 0.8 emerged from AF-28. The damage was graded with a visual scale from 0 to 4. Average damage grades of 3.5 and 3.3 were attributed to the hybrid R-1090 in Campinas and Jaboticabal respectively, while the variety AF-28 had averages of 0.5 and 0.3, respectively.

---

Résumé La variété AF-28 et l'hybride R-1090 de Sorghum bicolor Pers. ont été comparés à différentes époques de l'année et en deux localités différentes de l'Etat de Sâo Paulo, Brésil.On n'a pas constaté d'interaction variété x époque ou variété x lieu.AF-28 a prouvé sa résistance à toutes les époques, aussi bien dans un lieu que dans l'autre; l'hybride par contre s'est montré grandement susceptible.Des moyennes de 252,2 et 136,7 mouches par panicule ont été observées pour l'hybride R-1090 à Campinas et à Jaboticabal contre 2,9 et 0,8 seulement par panicule de AF-28. Le préjudice a été estimé visuellement selon une échelle de 0 à 4. Des préjudices d'une valeur moyenne de 3,5 et 3,3 ont été attribués à l'hybride R-1090 à Campinas et à Jaboticabal respectivement, alors que simultanément la variété AF-28 ne subissait que des préjudices évalués à 0,5 et 0,3 respectivement.Quatre espèces de microhyménoptères parasites de Contarinia sorghicola ont été récoltées au cours de ce travail: Eupelmus popa et trois espèces différentes du genre Tetrastichus.

---

---

Part of a thesis presented to the School of Sciences of Bauru for fulfilment of the requirement for the degree of Doctor of Science. This research was financed by the Project 72/1471 of the agreement UNIÃO-ESTADO-FAPESP and by CNPq Project 12910/73.