Requirement of protein and RNA synthesis for lambda repressor inactivation by tif-1: effects of chloramphenicol, neomycin and rifampicin.

Summary The inactivation of repressor was followed by the specific DNA binding assay during the course of lysogenic induction provoked by incubation at 42°C of an E. coli tif-1 lysogenic strain. The presence of up to 400 g/ml chloramphenicol during the inducing treatment did not impair the loss of repressor binding activity, whilst concentrations of 200 g/ml neomycin and 100 g/ml rifampicin effectively inhibited the inactivation of repressor.Residual protein synthesis in the presence of chloramphenicol, neomycin and rifampicin was 5%, 5% and 27% respectively of that observed in the drug-free control. This residual synthesis did not appear to involve amplification of the X-protein. These results suggest that tif-mediated inactivation of the repressor requires the activation of some specific gene(s), the translation of which appears to be resistant to chloramphenicol.     

Saccharomyces cerevisiae 2-mum DNA. An analysis of the monomer and its multimers by electron microscopy.

Summary The non-tandem inverted duplication in the 2-m DNA of Saccharomyces cerevisiae has a length of 0.19 m and is located asymmetrically along the molecule. The majority of the dumb-bell structures that are formed upon denaturation and selfannealing of the 2-m monomer consists of the renatured inverted duplication sequences as double stranded stem and two single stranded loops of 0.67 m±0.06 m (S-loop) and 0.86 m±0.05 m (L-loop) length. Two additional size classes which comprised 5–10% of the measured molecules had contour lengths of around 1.7 m and 2.1 m. The smaller dumb-bells contained two S-loops and the larger dumb-bells contained two L-loops as was shown by heteroduplex mapping with an HindIII fragment from the L-loop. Two models which assume illegitimate or site specific recombination, are presented to explain the generation of double S-loop and double L-loop molecules. At least part of the 4-m and 6- circular molecules present in the yeast supercoiled DNA fraction are shown to be dimers and trimers of 2-m monomers, but often with inverted loop segments most probably due to intramolecular recombination between sequences of the inverted duplication.2-m DNA is used to indicate the supercoiled DNA fraction although in our measurements the average monomeric length is 1.9 mPart of this work has been presented at the Conference: The Genetics and Biogenesis of Chloroplasts and Mitochondria, Munich, August, 1976     

Lemdana latifi n. sp. (Filarioidea: Onchocercidae) from the red jungle fowl (Gallus gallus spadiceus)

Lemdana latifi n. sp. was found in connective tissues around the trachea and crop and in the body-cavity of seven of 14 Malayan red jungle fowl Gallus gallus spadiceus. The new species is described and illustrated. Morphologically it is most closely related to Lemdana pavonica and Lemdana francolini. Lemdana latifi is distinguished from the eight valid species of Lemdana by the mean spicular ratio of 1.7:1; the right spicule with a right margin 18–29% (15–31 m; mean 24 m) longer than the left margin; the distal half of the left spicule twisted and S-shaped; and the absence of unpaired papillae at tip of male tail. The new species has smaller adults, a shorter left spicule and a shorter glandular oesophagus than those of L. pavonica and a wider male, shorter spicules and a longer muscular oesophagus than those of L. francolini. The male of L. latifi is 7–9 (8.1)mm long, the left spicule 164–215 (184)m long and the right spicule 98–117 (108)m long. The female is 17–23 (21)mm in length. Sheathed microfilariae from blood smears are 78–100 m long and those from the uterus are 89–103 m long. This is the sixth valid species of Lemdana in the Phasianidae.     

Glycogen in Methanothrix

An intracellular glycogen was purified and characterized from the acetoclastic bacteria Methanothrix str. FE, its average chain length was about 13 glucose residues. Acetyl-CoA was shown to be synthesized by the action of acetate thiokinase; in addition pyruvate synthase, phosphoenolpyruvate synthetase and enzymes of gluconeogenesis were detected in cell extracts. For glycogen synthase activity, both adenosine diphosphate glucose and uridine diphosphate glucose were used as glycosyl donors, apparent K _m were, respectively, 8 M for ADPGlc and 625 M for UDPGLe, at the opposite the V _m were the same for both precursors. This was in accordance with competition experiments and strongly suggested that only one glucosyl transferase was involved and that ADPGlc was the physiological glycosyl donor in Methanothrix str. FE. In addition branching enzyme activity (1-4-glucan-6-glucosyl transferase) was detected in cell extracts.Abbreviations ADPGlc adenosine diphosphate glucose - UDPGlc uridine diphosphate glucose     

Developmental aspects of long-term callus culture ofVicia faba L.

Summary Vicia faba callus line (VFS 1), isolated from expiants of immature embryo, grew satisfactorily onMurashige andSkoog complete medium with 1.38 M 2,4-D, or with 0.92 M 2,4-D to which 1.0 M kinetin was added. It also grew well on the B 5 modified medium containing 2.3 M 2,4-D and 25.0 M kinetin. On the last of these media the cultures grew more uniformly and without necrosis. They also showed diminishing variation in polyploidy in favour of diploids and corresponding aneuploids (hypodiploids).After being cultured for nearly three years on MS containing 1.38 M 2,4-D, 8–33% of cultures of VFS 1 were able to regenerate roots when transferred to either MS half strength with 5.37 M NAA, or to a medium without 2,4-D, or else to media with the addition of kinetin only (in various concentrations).     

The filtration apparatus of Cladocera: Filter mesh-sizes and their implications on food selectivity

Summary The filtering apparatus of eleven Cladoceran species was studied. The distances between the setulae, which act as filters, were measured. Among adult individuals, they vary from 0.2 m in Diaphanosoma brachyurum to 4.7 m in Sida crystallina. Species can be grouped according to the mesh-sizes, as fine mesh filter-feeders: Diaphanosoma brachyurum, Ceriodaphnia quadrangula, Chydorus sphaericus, Daphnia cucullata and Daphnia magna; medium mesh filter-feeders: Daphnia galeata, D. hyalina. D. pulicaria, Bosmina coregoni, and coarse mesh filter-feeders: Holopedium gibberum and Sida crystallina. In Daphnia hyalina, the distances between setulae increase from 0.3–0.4 m in small juveniles, to 0.8–2.0 m in adults. In Daphnia magna, the mesh-size of the filter does not increase significantly with growth. There is good evidence that the relative abundance of the filter-feeding types varies with the trophic state of the lake. In oligotrophic lakes the coarse mesh filter-feeders usually dominate throughout the year. The seasonal succession of zooplankton species in eutrophic lakes can be interpreted as a succession of feeding types; during winter coarse mesh filter-feeders dominate, while fine mesh filter-feeders are most abundant during summer phytoplankton blooms. Our results support the hypothesis that the species composition of filter-feeding zooplankton is strongly influenced by the amount of suspended bacteria which are available as food only for filter-feeding species with fine meshes.     

Ceratomyxa seriolae n. sp. and C. buri n. sp. (Myxozoa: Myxosporea) from the gall-bladder of cultured yellowtail Seriola quinqueradiata

Ceratomyxa seriolae n. sp. and C. buri n. sp. (Myxozoa: Myxosporea) were found in the gall-bladder of cultured yellowtail Seriola quinqueradiata Temminck & Schlegel (Carangidae) in Japan. Mature spores of C. seriolae n. sp. were elongate and 6.5 (6.0-7.5) m long and 33.7 (28.0-41.5) m thick. Disporous plasmodia of C. seriolae n. sp., 40-100 m in size, were amoeboid to spherical. C. buri n. sp. were elliptical with a flattened posterior end, 6.5 (5.5-7.5) m long and 14.3 (11.0-16.5) m thick. Spherical plasmodia of C. buri n. sp., 15-20 m in diameter, were disporous. In periodical sampling of yellowtail bile from August, 1999 to February, 2000, the two new species of Ceratomyxa, as well as Myxobolus spirosulcatus Maeno, Sorimachi, Ogawa & Kearn 1995, first appeared in October, and the prevalences were very variable (20-100%) during the study period.     

Myxobolus spirosulcatus n. sp. (Myxosporea,Bivalvulida) infecting the bile duct of the yellowtail Seriola quinqueradiata from Japan

Myxobolus spirosulcatus n. sp. (Myxosporea: Bivalvulida), infecting the cultured yellowtail Seriola quinqueradiata, is described. M. spirosulcatus n. sp. was found in the bile duct of yellowtails collected in the southern part of Japan during June 1990. The plasmodium of the new species has various shapes and contains a vegetative form plus maturing and mature spores. Mature spores, on average, measure 8.9 m in length, 7.8 m in width and 6.7 m in thickness. The unique morphological characteristics of the new species are spiral furrows in the peripheral part of the spore valves.     

Intestinal microflora in the deep-sea isopodBathynomus giganteus

Observations with the scanning electron microscope showed that the deep-sea isopodBathynomus giganteus harbors a dense microflora within the digestive tract. The gut microflora is composed of a diversity of microorganisms, including an unusually large bacterial morphotype that predominates almost exclusively in the anterior end of the hindgut. The majority of these large bacteria measured 1.9 m×8.5 m and many reached a size of 2.0 m×10.0 m.     

Different effects of inorganic and triethyl lead on growth and ultrastructure of lily pollen tubes

Summary Pollen tubes ofLilium longiflorum growingin vitro were treated for 1 h with inorganic lead (Pb) and with triethyl lead (TriEL) and studied by light and electron microscopy. Pb was considerably more toxic in relation to inhibition of pollen tube growth (EC₅₀=6 M Pb) than was TriEL (EC₅₀=60 M TriEL). On the other hand, at almost the entire concentration range tested (25-500 M) TriEL caused aberrant tubes and tube swellings. Pb did not cause tube swellings, even at highly growth-impairing concentrations. Pb (60 M) predominantly affected the ultrastructure of the growing cell walls without impairing the distribution of the cell organelles in the tube tips. In contrast, 50 and 100 M TriEL did not visibly influence cell wall ultrastructure but it severely damaged dictyosomes; 100 M TriEL also disturbed the original order of cell organelles in the tube tips. Cortical microtubules were selectively and completely destructed by TriEL at concentrations (50 M) where no effect on polar organization of the tube tips occurred but they remained unimpaired by 60 M Pb, indicating selective and effective interaction of TriEL with these cell organelles.Abbreviations EC⁵⁰ effective lead concentration causing 50% inhibition of pollen tube growth - MTs microtubules - Pb inorganic lead - TriAL trialkyl lead - TriEL triethyl lead     

Multiple shoot-bud formation and plantlet regeneration on Castanea sativa Mill. seeds in culture

Primordial initiation and development of shoot-buds has been accomplished by using shoots derived from chestnut (Castanea sativa Mill) seedlings cultured with added 6-benzylaminopurine (BAP). Germination of chestnut seeds in the presence of BAP (4 – 40 M) stimulated varying numbers of shoot-buds in those areas of the main axis that were favorably altered. When excised single shoots from these treated seeds were subcultured on a fresh medium containing BAP (4 – 40 M) continual shoot production was observed. Bud growth and shoot elongation were stimulated by transferring cultures to a reduced concentration of BAP (2 M) plus indole-3-butyric acid (IBA 0.4 M). Plant regeneration occurred in the presence of IBA (0.8 M) after a preconditioning treatment in which naphthaleneacetic acid (NAA 50 M) and kinetin (k 2 M) were applied to the tissue culture shoots for 7 days in light.     

Ultrastructural analysis of the sperm cells of mature pollen of maize,Zea mays

Summary Ultrastructural analysis of the mature viable unhydrated pollen of maize,Zea mays from dehiscent anthers shows that the sperm cells are physically distant, each bounded by an envelope comprising their own plasma membrane and the inner plasma membrane of the vegetative cell. The chondriome is unusual in containing one or more filamentous complexes, up to 12m in length appressed to the side of the sperm nucleus. The extensions at each end of the elongate sperm cells contain longitudinally-oriented arrays of endoplasmic lamellae. In a three-dimensional reconstruction of serial thin sections, there is a long J-shaped sperm, c. 35 × 5m and up to 1m in thickness, sited within pointed evaginations of the vegetative nucleus and a second shorter sperm c. 20 × 5m and up to 3.5m in thickness.Abbreviations PA-TCH-SP periodic acid-thiocarbohydrazide-silver proteinate - DAPI 4,6-diamino-2-phenylindole - SC sperm cell - Sn sperm nucleus - Ua-Pb Uranyl acetate-lead citrate staining - ER endoplasmic reticulum     

Distribution of magnesium in wheat (Triticum aestivum L.) in relation to supply

The aims of this study were to describe the distribution of magnesium (Mg) and its retranslocation within wheat, in order to develop diagnostic procedures for Mg deficiency. Plants were grown in solution culture with both constant supply (0, 5, 10, 20, 40, 80, 160 MMg) and discontinued supply (40 M and 160 M decreased to nil).Magnesium was depleted from old leaves when Mg supply to the roots was halted. However, initial deficiency symptoms occurred on young leaves under constant but inadequate supply, contrasting with previous reports. Magnesium concentrations were also lower in young leaves compared to old leaves. Symptoms of yellowing and necrosis occurred if the leaf tissue contained <1194 gg^–1, irrespective of leaf age. The minimum Mg concentration in whole shoots associated with maximum shoot weight was 932 gg^–1; for the youngest emerged blade (YEB) it was 861 gg^–1. Symptoms were apparent on the young leaf before a reduction in shoot weight was measurable. The concentration of Mg in the YEB and whole shoot were better related to solution Mg concentration than was the Mg concentration in the old leaf.     

Lead‐related effects on rat fibroblasts

Lead (Pb) is an environmental toxicant that can induce structural and functional abnormalities of multiple organ systems, including the central nervous and the immune systems. The aim of this study was to evaluate the effects of extracellular Pb supplementation on the cellular content of the metal and on the proliferation and the survival of normal rat fibroblasts.We found that the concentration of Pb in the culture medium was 0.060 M and the normal Pb concentration in rat fibroblasts was 3.1 ± 0.1 ng/10⁷ cells. Then we exposed the cells to increasing concentration of Pb (as Pb acetate) from 0.078–320 M. We observed a dosedependent inhibition of cell proliferation after 48 h, which was already apparent at a concentration of 0.312 M (p = 0.122) and became statistically significant for concentration higher than 0.625 M (p = 0.0003 at 5 M). Cell proliferation was completely compromised at 320 M Pb total inhibition of cell proliferation.To investigate the mechanisms of Pbmediated inhibition of cell proliferation, we evaluated the occurrence of apoptosis in the same cells and found that cytosolic DNA fragments, hallmark of apoptotic cell death, increased significantly at Pb concentrations from 2.5–10.0 M. The occurrence of apoptosis was also confirmed by FACS analysis which showed the appearance of a subdiploid peak at Pb concentrations from 5–20 M. The distribution of cells in the cell cycle showed a dosedependent accumulation of cells in the G₀/G₁ phase mainly compensated by a decrease in the percentage of cells in the S phase. In conclusion, our results demonstrate that induction of apoptosis contributes to the Pbinduced inhibition of cell proliferation in rat fibroblasts.     

Dry to wet weight biomass conversion constant for Tetrahymena elliotti (Ciliophora,Protozoa)

Summary The wet and dry weights of both axenic and monoxenic cultures of the ciliate Tetrahymena were determined directly. These estimates are dependent upon the method of volume determination. Assuming a prolate spheroidal shape for the ciliate, we calculate a mean wet weight of 0.4157±0.0713 pg m^-3 and a mean dry weight of 0.2793±0.0652 pg m^-3. Using electronic cell sizing, our estimates are 0.7869±0.1659 pg m^-3 and 0.5239±0.1101 pg m^-3, respectively. Independent of the method of volume determination, we estimate a mean biomass conversion ratio (dry weight/wet weight) of 0.59±0.08.     

The endogenous development of four new species of Isospora Schneider, 1881 (Apicomplexa: Eimeriidae) from Australian geckos

Four new species of Isospora are described from Australian geckoes. Isospora gehyrae n. sp. from Gehyra cf. variegata in South Australia have 18.5-22.5×17.5–20.0 m oöcysts with 10.0-12.5×7.5-9.0 m sporocysts; endogenous stages develop in the host cell cytoplasm. Of the two species found in Heteronotia binoei from northern Queensland, Isospora cytoheteronotis n. sp., with oöcysts of 20.0-26.0×17.5-25.0 m and sporocysts of 10.0-13.5×7.5-11.5 m, undergoes endogenous development in its host cell cytoplasm, whereas I. nucleoheteronotis n. sp., with oöcysts of 17.5-22.5×17.5-21.5 m and sporocysts of 9.0-12.5×6.5-10.0 m, develops in the host cell nucleus. I. oedurae n. sp. from Oedura rhombifer in northern Queensland has oöcysts of 22.5-25.0×22.5-24.0 m and sporocysts of 12.5-14.0×7.5-11.5 m, and undergoes endogenous development in its host cell nuclei.     

Characterization of regucalcin effect on proteolytic activity in rat liver cytosol: relation to cysteinyl-proteases

The increasing effect of regucalcin, isolated from rat liver cytosol, on neutral proteolytic activity in the hepatic cytosol was characterized. The proteolytic activity was markedly elevated by the addition of regucalcin (0.1–0.5 M) in the absence of Ca²⁺. This increase was not significantly altered by the presence of diisopropylfluorophsophate (DPF;2.5 mM)—although DFP caused a significant decrease in the proteolytic activity. Regucalcin (0.25 M) additively enhanced the dithiothreitol (DTT; 1.0 mM)—increased proteolytic activity, while the regucalcin or DTT effect was completely abolished by NEM (5 mM), indicating that regucalcin may act on the SH group in proteases. Also, regucalcin (0.25 M) enhanced the effect of Ca²⁺ (10 M) increasing liver proteolytic activity, suggesting that regucalcin does not influence on the active sites for Ca²⁺ in proteases. Moreover, the proteolytic activity of regucalcin (0.25 M) was significantly decreased by the presence of calpastatin (24 g/ml), an inhibitor of Ca²⁺-activated neutral protease (calpain). Now, regucalcin (0.25 M) increased about 7-fold the activity ofm-calpain isolated from rabbit skeletal muscle. These observations demonstrate that regucalcin directly activates cysteinyl-proteases. Regucalcin may have a role as a potent proteolytic activator in the cytoplasm of liver cells.     

In vitro culture of Aloe Barbadensis Mill.: Micropropagation from vegetative meristems

A method for rapid and highly effective plant micropropagation from vegetative meristems was established for Aloe barbadensis Mill. Plant micropropagation was achieved culturing apices on medium containing 1.1 M 2,4-dichlorophenoxyacetic acid and 2.3 M kinetin for 15–30 days. High morphogenetic ability was maintained by transferring explants (after 60 days) on media containing 0.11 M 2,4-dichlorophenoxyacetic acid and 2.2 M 6-benzylaminopurine.     

Direct Organogenesis from Mature Leaf and Petiole Explants of Eryngium Foetidum L.

Eryngium foetidum L. plants were regenerated from mature leaf and petiole explants through direct organogenesis without intervening callus phase. From leaf explants, adventitious multiple shoots raised on Murashige and Skoog (MS) medium supplemented with 4.43 M benzylaminopurine (BAP) and 0.57 M indole-3-acetic acid (IAA), whereas in petiole explants shoot regeneration occurred at 8.86 M BAP and 0.57 M IAAA. 80% of the leaf explants and 44% of petiole explants produced shoots after four weeks of culture. The regenerated plants were rooted on MS medium supplemented with 2.46 M indole-3-butyric acid and 2.88 M gibberellic acid. The plants were successfully established in the soil and showed 70.9% survival in the field.     

The complex life-cycle of a polymorphic prokaryote epibiont of the photosynthetic bacterium Chromatium weissei

In natural populations of the anaerobic phototrophic bacterium Chromatium weissei, many cells support a prokaryotic epibiont. This epibiont appears in several forms, all from the life cycle of a single species. A typical epibiont consists of one to five flattened coccoid cells stacked one above the other, perpendicular to the C. weissei surface. The cells at the proximal and distal ends of the stack are 0.6 m in diameter and 0.8 m in length; mid-stack cells are slightly shorter. A typical three or four cell stack is 2 m in length. Small mesosome-like inclusions in the distal cell are involved in the development of droplet shaped cells which are released from the end of each stack. These specialised droplet cells probably transfer to new hosts when C. weissei cells collide, thereafter developing into new epibiont stacks. It is likely that the epibiont grows heterotrophically using the substantial production of dissolved organic carbon within the dense plates of photosynthesising C. weissei which develop naturally. Thus the epibiont uses its unusual method of growth and dispersion to maintain position in the microbial plate upon which it depends.