Peroxidation of lipids and growth inhibition induced by UV-B irradiation

Cotyledons excised from dark-grown seedlings of cucumber (Cucumis sativus L.) were cultured in vitro under UV radiation at different wavelengths, obtained by passage of light through cut-off filters with different transmittance properties. Growth and the synthesis of chlorophyll (Chl) in cotyledons were inhibited and malondialdehyde was accumulated upon irradiation at wavelengths below 320 nm. Exogenous application of scavengers of free radicals reversed the growth inhibition induced by UV-B. Measurement of the fluorescence of Chl a suggested that electron transfer in photosystems was affected by UV-B irradiation. On the basis of these results, the involvement is postulated of active species of oxygen in damages to thylakoid membranes and the growth inhibition that are induced by UV-B irradiation.Abbreviations Chl chlorophyll - F_m maximal fluorescence (dark) - F_m maximal fluorescence (light) - F_v variable fluorescence (dark) - F_v variable fluorescence (light) - MDA malondialdehyde - O₂ Superoxide radical - PS photosystem - q_N non-photochemical quenching of fluorescence - q_P photochemical quenching of fluorescence - UV-B_BE biologically effective UV-B radiation - WL(T = 0.5) wavelength at which 50% transmittance occurs     

Yezonia,a new section ofAraucaria (Araucariaceae) based on permineralized vegetative and reproductive organs ofA. vulgaris comb. nov. from the upper cretaceous of Hokkaido,Japan

A new specimen of an araucarian cone,Araucaria nihongii, was found attached to the vegetative organs ofYezonia vulgaris, and is described asAraucaria vulgaris comb. nov. Thick branches show characteristic bark structure with lenticular patches. Secondary wood is usually araucarioid. Leaves are arranged helically on shoots, which are imbricate, appressed and fused to surface of the stem. External and anatomical features of leaves closely resembleBrachyphyllum. The seed cone is spherical with winged bracts and thin ovuliferous scales. One seed is borne per cone-scale complex. The seed coat and nucellus wall show typical araucarian structure. An araucarian plant that boreBrachyphyllum-like foliage and aEutacta-like seed cone was predicted by Harris in 1979. This reconstructed plant,Araucaria vulgaris, supports this theory and proves the presence of an extinct characteristic-form of the genus. A new section of the genus was proposed forAraucaria vulgaris. Structure and Affinities of the Petrified Plants from the Cretaceous of Northern Japan and Saghalien XV, Consecutive number from previous paper (Nishidaet al. 1993).     

Electron microscopic study of endogenous peroxidase activity in human liver macrophages

We evaluated the conditions of fixation for ultrastructurally demonstrating the endogenous peroxidase (PO) activity of macrophages in biopsied human liver. The application of microwaving and immersion fixation with tannic acid and aldehydes allowed excellent visualization of PO activity in the nuclear envelope (NE), rough endoplasmic reticulum (rER), and cytoplasmic granules (CG), with good preservation of cellular ultrastructures. The macrophages with PO activity showed one of the following five patterns of PO localization: positive in both the NE and rER but negative in the CG (type 1); negative in both the NE and rER but positive in the CG (type 2); negative in the NE but positive in both the rER and CG (type 3); positive in all three (type 4); PO negative (type 5). The type 1 cells resembled typical Kupffer cells, type 2 cells monocytes, and type 3 and 4 cells the exudate-resident macrophages considered to be a transitional form between exudate and resident macrophages. Type 5 cells may also be a transitional form between the exudate and resident macrophage, or an end-stage macrophage derived from exudate macrophages which have lost their PO activity. Tannic-acid-aldehyde immersion fixation with microwaving may be a useful method in the study of the PO activities of macrophages in biopsied human liver specimens.     

Properties of thermolysin immobilized in polymer matrix by radiation polymerization

Thermolysin (Bacillus thermoproteolyticus neutral proteinase, EC 3.4.24.4) has been immobilized by radiation polymerization of hydrophilic and hydrophobic monomers, and its properties, such as enzyme activity, thermal stability and durability, have been studied. The activity of the immobilized enzymes increased with an increase in the hydrophilicity of the polymer matrix and with a decrease in monomer concentration. Immobilization with hydrophilic monomers increased the thermal stability of the enzymes, but the thermal stability of the enzymes immobilized with hydrophobic monomers was comparable with that of native enzymes. The durability of the immobilized enzymes was examined by continuous hydrolysis of casein; enzymes immobilized with a high concentration (90%) of hydrophilic monomers appeared to be stabilized and could be used for long times.     

Survival and Repopulation of Irradiated 'Pre-Cfu-C' In Mice

ABSTRACT Supernatants of murine bone-marrow cultures contain a colony-promoting factor (CPF) which increases the number of granulocyte and macrophage colonies in semi-solid agar cultures in the presence of colony-stimulating factor (CSF). Incubation of bone-marrow cells with CPF results in an increase in the number of granulocyte/macrophage progenitor cells (CFU-c) and the CPF-responsive cells may be younger than the CFU-c. We have investigated the radiosensitivity and the pattern of the recovery after irradiation of CPF-responsive cells. We found that the radiosensitivity of CPF-responsive cells was significantly lower than those of CFU-c. burst-forming units-erythroid (BFU-e) and pluripotent stem cells in vivo (CFU-s) and in vitro (CFU-mix). the CPF-responsive cells remained subnormal even at 28 days after irradiation of the mice, a time when the CFU-s and CFU-c had recovered completely. Therefore the CPF-responsive cells may constitute a separate compartment, namely ‘pre-CFU-c’, in the maturation sequence of granulopoiesis, and this maturation of the ‘pre-CFU-c’ to CFU-c seems to be highly stimulated after irradiation to counterbalance the influx from CFU-s.     

Internal calcium concentration and potassium permeability in Paramecium

Ca or EGTA was ionophoretically injected into Paramecium tetraurelia to change [Ca]₁. Ca decreased the resting membrane resistance and hyperpolarized the membrane. EGTA had the opposite effect. EGTA following TEA, which suppress G_K, had little effect on resistance or resting potential. The I—V relation at steady state was studied before and after EGTA injection while the cell bathed in either K- or TEA-solution. The response to inward test pulses after EGTA injection was similar to that after TEA injection. These results show that [Ca]_i controls a steady-state K permeability in Paramecium tetraurelia. A prolonged Ca-spike was recorded after EGTA injection. The plateau potentials in various Ca concentrations in a TEA-solution show the Nernst slope (29 mV for tenfold change in [Ca]₀). This result suggests that the prolonged depolarization in this condition is due to a Ca current, after suppression of K-permeability and when [Ca]_i is low. The difficulty of obtaining quantitative data an the internal Ca, and the difference between the effects of EGTA injection and TEA injection are discussed.     

Action spectra for the light inhibition of flowering and its reversal inLemna paucicostata T-101

Lemna paucicostata Hegelm. T-101, a short-day plant, flowers when plants preirradiated with red light (R) for 24 h are subjected to inductive darkness for 72 h followed by two short-day cycles (6 h R+ 18 h dark). However, flowering is inhibited by blue-or far-red-light pulses applied at the beginning of the inductive dark period. These inhibitory light effects are fully reversible by a R pulse. The action spectra for the inhibitory light effect and for its reversal show that the light pulses act exclusively through phytochrome. It is concluded that a low level of Pfr at the beginning of the inductive dark period prevents flowering.Abbreviations R red (light) - B blue (light) - FR far-red (light)     

Viomycin favours the formation of 70S ribosome couples

Summary The peptide antibiotic viomycin at a concentration of 10 M inhibits E. coli ribosomes to the extent of about 70% as measured in the poly(U) system, and to about 85% in a natural mRNA (R17) system. Ribosomes from M. smegmatis show no activity at all at this concentration of the antibiotic. Experiments on the Mg²⁺ dependent dissociation and association of the ribosomal subunits revealed that viomycin stabilizes the 70S couples and promotes association of ribosomal subunits. This response is related to the drug action as indicated by the observation that viomycin resistant strains are not affected by viomycin with respect to dissociation and 70S couple information. A model for the inhibitory action of the drug is proposed.