Chloramphenicol is an inhibitor of photosynthesis.

Chloramphenicol inhibited significantly but incompletely photosynthesis in leaf segments of rice. Fluorescence and polarographic experiments indicated that chloramphenicol competes with the CO2 reducing cycle for electrons from photosystem I because it serves as an electron acceptor of photosystem I and its reduction intermediate transfers its electron to molecular oxygen.     

The introduction ofMimorista pulchellalis [Lepidoptera: Pyraustidae] into South Africa for the biological control of jointed cactus,Opuntia aurantiaca. 2. Field evaluation

The mothMimorista pulchellalis was monitored over 2 years after liberation in a jointed cactus (Opuntia aurantiaca) infestation in South Africa. Moth and cactus densities were estimated using a system of randomly-assigned quadrats and the impact of the moth on the cactus population quantified. Moths appeared adapted to survive on the etiolated form of jointed cactus plants, killing approximately 1% of the increment in small plants annually. Large plants were also attacked but damage was negligible. The moths occurred in low numbers throughout the study period and generally went through 3 generations in a year.

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Résumé La pyraleMimorista pulchellalis a été surveillée durant les deux années qui suivirent sa libération dans une infestation de figuier de Barbarie en Afrique du Sud. Les densités de pyrale et de cactus ont été estimées en utilisant un système de quadrats distribués au hasard et l'impact de la pyrale sur la population de cactus a été quantifiée. Les pyrales semblaient adaptées à survivre sur la forme étiolée des plants de cactus tuant approximativement 1% de l'accroissement annuel des petits plants. Les gros plants étaient aussi attaqués, mais les dégats étaient négligeables. La pyrale existait en faibles nombres durant toute la période d'étude et elle présentait généralement 3 générations par an.

     

Isolation of nitrogen deregulated mutants of erythromycin biosynthesis

Summary Ammonium represses erythromycin synthesis bySaccharopolyspora erythraea and insensitive mutants to this effect were isolated. Six mutants were selected and one of them produces 50% more antibiotic than the wild type in 100 mM NH₄Cl as nitrogen source. Glutamine synthetase and alanine dehydrogenase levels in the mutants were determined and no differences with wild type strain were observed.     

Dynamics of functional reciprocal connections between cerebral motor cortex neurons under stimulation in cats

Activity was recorded from neurons belonging to the representation of the forelimb in the motor cortex (sulcus cruciatus, L 7–9 mm) using multiple multi-channel/barrel electrodes during acute experiments on cats. Cross-correlation analysis of impulse trains was adopted to investigate dynamics of interneuronal connections during passive flexion and electrical stimulation of the limb contralateral to the recording site. It was found that neither passive bending nor electrical stimulation of the limb leads to a significant increase in the total number of direct relationships between cortical neurons. At the same time, passive flexion does produce a considerable decrease in the number of instances of both inputs operating in neighboring neurons (50–100 µm apart) and an increase in cells located further (between 100 and 400 µm) apart. Some increase in the number of direct inhibitory interactions between neighboring neurons was observed during electrical stimulation.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Nentskii Institute of Experimental Biology, Warsaw, Poland. Center of Experimental and Clinical Medicine, Warsaw, Poland. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 73–80, January–February, 1991.