The eyes of mesopelagic crustaceans

Summary The compound eyes of the mesopelagic euphausiid Thysanopoda tricuspidata were investigated by light-, scanning-, and transmission electron microscopy. The eyes are spherical and have a diameter that corresponds to 1/6 of the carapace length. The hexagonal facets have strongly curved outer surfaces. Although there are four crystalline cone cells, only two participate in the formation of the cone, which is 90–120 m long and appears to have a radial gradient of refractive index. The clear zone, separating dioptric structures and retinula, is only 90–120 m wide. In it lie the very large oval nuclei of the seven retinula cells. Directly in front of the 70 m long and 15 m thick rhabdom a lens-like structure of 12 m diameter is developed. This structure, known in only a very few arthropods, seems to be present in all species of Euphausiacea studied to date. It is believed that the rhabdom lens improves near-field vision and absolute light sensitivity. Rod-shaped pigment grains and mitochondria of the tubular type are found in the plasma of retinula cells. The position of the proximal screening pigment as well as the microvillar organization in the rhadbdom are indicative of light-adapted material. The orthogonal alignment of rhabdovilli suggests polarization sensitivity. Behind each rhabdom there is a cup-shaped homogeneous structure of unknown, but possibly optical function. Finally, the structure and the function of the euphysiid eye are reviewed and the functional implications of individual components are discussed.This study was begun during the 1975 Alpha Helix South East Asia Bioluminescence Expedition to the South Moluccan Islands     

Der Feinbau des Auges der Mehlmotte,Ephestia kuehniella Zeller (Lepidoptera,Pyralididae)

Zusammenfassung Die Retinula im Ommatidium der Mehlmotte besteht aus einer wechselnden Anzahl (9–12, meist 11) langgestreckter, prismatischer Sinneszellen. Außerdem enthält jede Retinula nahe der Basalmembran im Zentrum zwischen diesen distalen Retinulazellen noch eine basale Retinulazelle. Die Längsachse der Retinula wird von der Achsenstruktur eingenommen, die aus Mikrovilli besteht. Ihr distaler Teil ist der Achsenfaden, der breitere, proximale Teil bildet das Rhabdom. Dieses erscheint im Querschnitt meist vierstrahlig gelappt, da seine Außenseite in Längsrichtung tief gekehlt ist. Der Rhabdomquerschnitt gliedert sich in mehrere Schöpfe parallel angeordneter Mikrovilli (Rhabdomsektoren); jeder Rhabdomsektor besteht aus 1 oder 2 Rhabdomeren. Die basale Retinulazelle entsendet einen kleinen Schopf von Mikrovilli in die proximale Spitze des Rhabdoms. Die distalen Retinulazellen setzen sich proximal in Neuriten fort, welche sich in Einkehlungen der basalen Retinulazelle bzw. der Tracheenendzelle einschmiegen. Jeweils eine Tracheole durchbricht zusammen mit dem Neuritenstrang einer Retinula die Basalmembran; sie verzweigt sich distal zu ca. 30 Tracheolen, die die Retinula umhüllen.Die Kristallkegelzellen grenzen distal an die Cornea; proximal laufen die Kristallkegelzellen eines Ommatidiums in einen gemeinsamen Fortsatz aus, der zwischen den Retinulazellen unmittelbar am Achsenfaden endet. — Nur das helladaptierte Auge wurde untersucht. Hierbei erscheint im distalen Teil der Retinula nur der Achsenfaden lichtdurchlässig, das Cytoplasma der Retinulazellen hingegen von Pigmentgrana durchsetzt und für Licht undurchlässig.

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Fine structure of the eye of the meal moth, Ephestia kuehniella Zeller (Lepidoptera, Pyralididae)

Summary In each ommatidium of the meal moth a retinula is formed from a varying number (9–12, mostly 11) of elongated, prismatic sense cells. In addition, a basal retinular cell is situated near the basement membrane in the center of the other (distal) retinular cells. The axis of the retinula is occupied by many microvilli forming the axial structure, the distal section of which is the slender axial thread. Proximally, the axial structure widens (to 8.5 m instead of 1 m in diameter) and is now called rhabdom. Cross sections of the rhabdom mostly look like a petaloid with four petals; this figure is due to longitudinal infoldings along the length of the rhabdom surface. The rhabdom cross section is subdivided into several brushes of microvilli (rhabdom sectors), each one being characterized by an approximately parallel arrangement of its microvilli. One rhabdom sector may be composed of one or two rhabdomeres respectively.The basal retinular cell participates in rhabdom formation through a small brush of microvilli at the proximal end of the rhabdom. Proximally, the distal retinular cells taper into slender neurites which are embedded in grooves at the surface of the basal retinular cell and the tracheal end cell respectively. One tracheole piercing the basement membrane together with the neurites of one retinula branches into about 30 tracheoles surrounding the retinula.The crystalline cone cells touch the cornea; proximally, their cytoplasm forms a point which eventually terminates amongst the distal tips of the retinular cells, immediately at the axial thread.—Our work was restricted to light adapted eyes; in this condition, light transmission in the distal part of the retinula seems to be blocked by retinular cell pigment except inside the axial thread.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Optimization of in vivo tumor targeting in SCID mice with divalent forms of 741F8 anti-c-erbB-2 single-chain Fv: effects of dose escalation and repeated i.v. administration

Single-chain Fv molecules in monovalent (sFv) and divalent [(sFv')₂] forms exhibit highly specific tumor targeting in mice as a result of their small size and rapid systemic clearance. As a consequence, there is a rapid reversal of the sFv blood/tumor gradient, resulting in diminished retention of sFv species in tumors. In this report we investigate two distinct strategies, dose escalation and repetitive intravenous (i.v.) dosing, aiming to increase the absolute selective retention of radiolabeled anti-c-erbB-2¹²⁵I-741F8 (sFv')₂ in c-erbB-2-overexpressing SK-OV-3 tumors in mice with severe combined immunodeficiency (SCID). A doseescalation strategy was applied to single i.v. injections of¹²⁵I-741F8 (sFv')₂. Doses from 50 g to 1000 g were administered without a significant decrease in tumor targeting or specificity. High doses resulted in large increases in the absolute retention of¹²⁵I-741F8 (sFv')₂. For example, raising the administered dose from 50 g to 1000 g increased the tumor retention 24 h after injection from 0.46 g/g to 9.5 g/g, and resulted in a net increase of greater than 9 /g. Over the same dose range, the liver retention rose from 0.06 g/g to 1 g/g, and resulted in a net increase of less than 1 g/g. The retention of 9.5 g/g in tumor 24 h fllowing the 1000-g dose of (sFv')₂ was comparable to that seen 24 h after a 50-g dose of¹²⁵I-741F8 IgG, indicating that the use of large doses of (sFv')₂ may partially offset their rapid clearance. When two doses were administered by i.v. injection 24 h apart, the specificity of delivery to tumor observed after the first dose was maintained following the second injection. Tumor retention of¹²⁵I-741F8 (sFv')₂ was 0.32 g/g at 24 h and 0.22 g/g at 48 h following a single injection of 20 g/g, while 0.04 g/ml and 0.03 g/ml were retained in blood at the same assay times. After a second 20-g injection at the 24-h assay time, tumor retention increased to 0.49 g/g, and blood retention was 0.06 g/ml, at the 48-h point. These results suggest that multiple high-dose administrations of radiolabeled 741F8 (sFv')₂ may lead to the selective tumor localization of therapeutic radiation doses.Supported by National Cancer Institute (NCI) National Cooperative Drug Discovery Group grant U01 CA51880, CA06927, an appropriation from the Commonwealth of Pennsylvania, and the Bernard A. and Rebecca S. Bernard Foundation     

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).     

In vitro meristem cloning of Eucalyptus tereticornis Sm.

Rapid multiplication of axillary meristems and direct shoot development occurred from nodal explants of mature Eucalyptus tereticornis Sm. with 5.3 M NAA, 1.1 M IAA and 4.4 M BA in Murashige-Skoog medium. Repeated subcultures of the second generation shoot cultures into low cytokinin-auxin containing media (0.44–0.88 M BA+0.1 M NAA) yielded axillary microshoots in large numbers. Half-strength MS liquid medium with 4.9 M IBA, 5.5 M IAA and 5.3 M NAA for four days, half-strength semi-solid hormonefree MS medium with charcoal, and MS liquid medium without charcoal and hormones, in sequence, induced rooting of shoots in the dark. This system is suitable for the mass propagation of this difficult-to-root eucalypt.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic acid - IBA -indole-3-butyric acid - 2-iP isopentyl adenine - Kn kinetin - MS Murashige-Skoog - NAA -naphthalene acetic acid - PVP polyvinylpyrrolidone     

Regional and subcellular distribution of taurine-synthesizing enzymes in the rat central nervous system

The distribution of cysteine oxidase (CO) and cysteine sulfinate decarboxylase (CSD) was examined in 12 regions of the rat central nervous system (CNS). The distribution of CO activity, expressed as mol of cysteine sulfinate formed per h per g, was the following: hypothalamus, superior and inferior colliculi, 94–99 mol/h/g; olfactory bulbs, cerebral cortex, striatum, and hippocampus, 44–51 mol/h/g; cerebellum, 71 mol/h/g; pons-medula and spinal cord, 94 and 60 mol/h/g, respectively. The distribution of CSD activity expressed as mol of cysteine sulfinate decarboxylated per h per g was the following: hypothalamus and colliculi, 14–21 mol/h/g; olfactory bulbs, cerebral cortex, striatum, hippocampus, and cerebellum, 8–13 mol/h/g; pons-medulla, 7.3; and spinal cord, 3.6 mol/h/g. No CSD activity was detected in sciatic nerve. The subcellular distribution of CO and CSD activities was studied in hypothalamus, colliculi, and cerebral cortex. CO activity was localized in synaptosomes, mitochondria, and microsomes. CSD was primarily confined to the crude mitochondrial fraction and after subfraction, recovered mainly in the synaptosomal fraction.     

Determination of copper, manganese and zinc in human liver

Autopsied liver tissue samples collected from 42 males and 31 females were analyzed for copper, manganese and zinc using atomic absorption spectrometry (AAS). With the exception of two liver samples for which the copper levels were determined to be 74.8 and 104.0 g/g (dry weight), hepatic copper concentrations were found to range from 1.7 to 32.4 g/g with a mean concentration of 14.2 g/g and standard deviation of 7.0 g/g. Manganese concentrations (with the exception of one sample having 12.9 g/g) ranged from 0.22 to 4.6 g/g with a mean of 2.26 ± 1.00 g/g. Hepatic zinc levels averaged 118.3 ± 44.4 g/g and ranged from 38.5 to 231.3 g/g. There were no apparent trends for the levels of any metals versus age nor were there any differences in average hepatic metal concentrations for males and females. © Rapid Science 1998.     

Maturation of optics and resolution in adult dung beetle superposition eyes

Summary The maturation of the morphology and refractive-index gradients of the crystalline cones and cornea of the superposition compound eye of the nocturnal dung beetle Onitis aygulus was traced as a function of age following adult ecdysis. Intracellular recordings from retinula cells were also made to trace the maturation of angular sensitivity, thereby determining the resolution of the eye at each age. Maturation proceeded quickly during the first 3 days following ecdysis, and then more slowly, with full maturation attained by the end of the second week. The main experimental results obtained during the first 2 weeks after ecdysis were: (1) the mean length of the crystalline cones increases from 67 m to 79 m; (2) the mean thickness of the cornea increases from 36 m to 50 m; (3) the mean refractive index along the axis of the crystalline cones increases from 1.459 to 1.511 in the distal cone region, from 1.434 to 1.501 in the waist region and from 1.425 to 1.486 in the proximal region; (4) the shape of the refractive-index gradient becomes more parabolic; (5) the mean rhabdom cross-sectional area increases from 190 m² to 230 m²; (6) the angular-sensitivity function narrows, with the acceptance angle decreasing from 22 ° to 4 °. An optical ray tracing model predicts an image quality limited only by the immaturity of the optics, a prediction confirmed by the electrophysiological results. The results are compared to optical maturation in day-active moths and skipper butterflies (which mature very quickly) and discussed in relation to ecological efficiency.     

The eyes of mesopelagic crustaceans

Summary In Streetsia challengeri left and right eyes have fused and become a single cylindrical photoreceptor, which occupies the basal half of a forward directed head projection. This unusual compound eye consists of approximately 2500 ommatidia, which are arranged in such a way that the animal has almost circumferential vision, but cannot look ahead or behind. It is thought that the eye operates on light-guide principles, and that the crystalline cones are the major dioptric component. Ommatidia in anterior-posterior rows show a greater overlap of visual fields than dorso-ventrally arranged ommatidia. Cone layer and retinula are separated by a 4 m thick screen-membrane, which contains tiny pigment granules of 0.15 m diameter. Cells of unknown function and origin, containing unusual multitubular organelles, are regularly found near the proximal ends of the crystalline cone threads. The twisted rhabdoms measure 18–20 m in diameter, and consist of microvilli 0.05 m in width, which belong to five retinula cells and which show no trace of disintegration. The position of interommatidial screening pigment, the density of retinula cell vesicles and inclusions, and the narrowness of the perirhabdomal space all suggest that the eyes have been light-adapted at the time of fixation for electron microscopy. The retinula cell nuclei lie on the proximal side of the heavily pigmented basement membrane. A tapetum or basal retinula cells are not developed. It is concluded that the eye optimally combines acuity with sensitivity, and that for distance estimation parallax may be important.Address until January 25th 1978: Scott Base, Ross Dependency, Antarctica (C/-Chief Post Office, Christchurch, New Zealand)     

Cadmium, lead, and zinc removal by expression of the thiosulfate reductase gene from Salmonella typhimurium in Escherichia coli

The thiosulfate reductase gene (phsABC) from Salmonella typhimuriumwas expressed in Escherichia coliin order to produce sulfide from inorganic thiosulfate and precipitate metals as metal sulfide complexes. The sulfide-engineered strain removed significant amounts of heavy metals from the medium within 24 h: 99% of zinc up to 500 M, 99% of lead up to 200 M, 99% of 100 M and 91% of 200 M cadmium. In a mixture of 100 M each of cadmium, lead, and zinc, the strain removed 99% of the total metals from solution within 10 h. Cadmium was removed first, lead second, and zinc last. These results have important implications for removal of metals from wastewater contaminated with several metals.     

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.     

Regeneration from long-term cell suspension cultures of tepary bean (Phaseolus acutifolius)

Plant regeneration has been achieved from long-term cell suspension cultures established from leaf derived callus of tepary bean (Phaseolus acutifolius). The proportion of densely cytoplasmic cells in suspension culture increased when cultured in the L-6 medium with 54 M NAA and 2 M KN. Filtration of the cells at each of five consecutive subcultures resulted in the isolation of a plant regenerating cell line (TB 686), which is being maintained in L-6 medium with 4.5 M 2,4-D and 2.3 M zeatin. Differentiated green cell aggregates were obtained when cells from maintenance medium were transferred to the same medium with 10 M BA. Embryo-like structures developed from these aggregates on L-6 medium with 2.3 M zeatin, 0.69 M GA₃ and 1.5 M NAA. Plantlets regenerated from these structures when they were cultured on L-6 medium with 7.0 M NAA and 1.0 M KN. Plant regeneration from the cell line remained relatively constant for 270 days. Regenerated plants were grown to maturity in the greenhouse.Abbreviations BA Benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - GA₃ Gibberellic acid - IPA Isopentenyladenine - KN Kinetin - NAA Naphthaleneacetic acid - AA Amino acid medium (Toriyama and Hinita, 1985) The research was sponsored by United States Agency for International Development, Washington D.C., Cooperative Agreement DAN-4137-A-00-4053-00     

Influence of plant growth regulators,basal media and carbohydrate levels on the in vitro development of Pinus ponderosa (Dougl. ex Law.) cotyledon explants

Applications of in vitro screening techniques for Pinus ponderosa resistance to Peridermium harknessii could be beneficial in a tree breeding program. Plant growth regulators, basal media formula and carbohydrate levels were examined to determine the various effects each would have on excised cotyledon growth and development. Proliferating green callus was initiated from cotyledon explants on SH basal medium containing 4.4 M BA:5.4 M NAA and 1% sucrose. Subsequent subculturing onto LS medium supplemented with 44.0 M BA: 5.4 M NAA and 2% sucrose improved callus maintenance. The highest frequency of caulogenesis from cotyledon explants occurred on a modified GD medium containing 44.0 M BA: 0.054 M NAA and 4% glucose. The influence of nitrogen source, osmoticum and medium salt concentrations are discussed relative to callus initiation and caulogenesis.Abbreviations BA 6-benzyladenine - NAA -naphthaleneacetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - 2,4-D 2,4-dichlorophenoxyacetic acid - CD Campbell & Durzan - GD Gresshoff & Doy - LP Le Poivre - LS Linsmaier & Skoog - MC McCown - SH Schenk & Hildebrandt     

Zum Feinbau des Komplexauges von Stylops spec. (Insecta,Strepsiptera)

Zusammenfassung Unter den Cornealinsen des Komplexauges von Stylops befindet sich ein Kristallkegel vom pseudoconen Typ, der von zahlreichen Pigmentzellen umhüllt wird. An seinem proximalen Ende liegen 6 meist pigmentfreie Zellen (Sempersche Zellen).Das Ommatidium besteht aus etwa 60 Retinulazellen. Ihre distal kranzartig miteinander verbundenen Mikrovillisäume bilden ein einziges offenes Rhabdom, das extrazelluläres (?) granuläres Material und die Basis der Semperschen Zellen umgibt. Stellenweise wird das Rhabdom samt granulärem Material von homogen erscheinenden distalen Ausläufern einzelner Retinulazellen überlagert. Proximad zerfällt das Rhabdom zunehmend in kleinere Rhabdomteile. Im zentralen Teil des Ommatidiums liegen 1–2 auffallend große Retinulazellen, die meist weniger elektronendicht erscheinen und kleinere Pigmentgrana haben.Die einzelnen Ommatidien werden von ungemein zahlreichen, sehr pigmentarmen Stützzellen umhüllt. Diese werden — wie die basalen Teile der Retinulazellen — teilweise durch Gliazellfortsätze isoliert.Bei Stylops, einem Vertreter der Strepsipteren, handelt es sich nicht um ocelläre Komplexaugen (Strohm, 1910), auch nicht um eucone Ommatidien (Kinzelbach, 1967), sondern um Ommatidien vom pseudoconen Typ. Zumindest der Bau des Rhabdoms ähnelt dem des Larvenauges (Stemma), dessen rezeptorischer Teil entgegen den Annahmen früherer Autoren in der Imago nicht reduziert wird.

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On the fine structure of the compound eye of Stylops spec. (Insecta, Strepsiptera)

Summary In the compound eye of Stylops a crystalline cone of the pseudocone type is found beneath the corneal lens. It is enveloped by several pigment cells. At the proximal part of the cone there are 6 cells (Semper cells) mostly pigment-free.The ommatidium consists of approximately 60 retinula cells. Their rhabdomeres distally rim-like connected to another form a single open rhabdom which encircles extracellular granular material as well as the bases of the Semper cells. Here and there the rhabdom plus granular material is overlain with distal protrusions of single retinula cells which appear to be homogeneous. Towards the proximal part the rhabdom increasingly divides up into smaller rhabdomal segments. One or two conspicuous large retinula cells were found in the central part of the ommatidium, appearing to be less electron-dense and containing pigment granules of a smaller size. Each ommatidium is surrounded by numerous cells (Stützzellen) lacking in pigment. These cells are partially insulated from another—as well as the basal parts of retinula cells—by protrusions of glia cells.Our investigations show that the eyes of Stylops (as a representative of Strepsiptera) are not of the ocellar complex eye type. At least the structure of the rhabdom resembles to that of the larval eye (stemma), the receptor part of which is not reduced in the imago.

Herrn Prof. Dr. Helmcke danke ich für die freundliche Unterstützung am Raster-Elektronenmikroskop.     

Effects of the growth regulator 4PU-30 on growth,K+ content,and alkaloid production in tobacco callus cultures

Growth, K⁺ content, and alkaloid production were compared in nonorganogenetic callus cultures ofNicotiana tabacum cv. Burley 21 grown at 25°C in the dark on two different media: a basal medium with 1 M -naphthaleneacetic acid and 1 M kinetin, and one with 1 M -naphthaleneacetic acid and 1 M 4PU-30 (N-(2-chloro-4-pyridyl)-N-phenylurea). These callus tissues behaved differently not only in growth and K⁺ content but also in alkaloid production. In comparison to cultures grown with kinetin, those grown with 4PU-30 showed a significantly higher fresh weight and dry weight and K⁺ content during the growth period studied. The data clearly indicate a positive correlation between K⁺ uptake rate stimulated by 4PU-30 and cell enlargement rate. However, the alkaloid biosynthesis in the callus tissues was activated by the supply of kinetin and diminished by that of 4PU-30. It thus appears that cellular enlargement of meristematic tissue stimulated by 4PU-30 limited alkaloid production.     

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     

Callus growth and plant regeneration in diverse cultivars of cucumber (Cucumis sativus L.)

The growth and differentiation of callus tissues derived from cotyledons of ten cultivars ofCucumis sativus L. were investigated. Cotyledonary explants from all ten cultivars formed callus tissue on Murashige and Skoog (MS) medium supplemented with 0.5 M 2,4-dichlorophenoxyacetic acid and 5 M 6-benzylaminopurine. Fresh weight of the callus tissues averaged 1 to 8 g per flask after five weeks of culture. Shoot development was achieved in three cultivars, Hukchinju, Manchoonchoungjang and Seoul, on MS medium supplemented with 0.5 M -naphthaleneacetic acid and 5 M 6-benzylaminopurine. Reducing the 6-benzylaminopurine concentration to 0.01 M resulted in root formation on callus tissues and on shoots transferred to this medium. All cultivars gave the same response in tests of root formation, but shoot regeneration from callus culture of cucumber cotyledons was dependent on genotype with cultivar Manchoonchoungjang exhibiting the best shoot differentiation capability among the genotypes examined. Examination of mitotic metaphase from the regenerants revealed that all were tetraploid.     

Nutrient limitation in Ellis Fjord,eastern Antarctica

The occurrence of high chlorophyll-a concentrations (up to 11.6gl^–1) at shallow depths within Ellis Fjord, eastern Antarctica, during spring and summer, coincided with the development of a stratified water column. Macronutrient concentrations during periods of high chlorophyll-a levels were very low. Phosphate concentrations decreased to 0.2 M, nitrate to 0.4 M and silicate to 3.9 M. High rates of nutrient depletion early in the season can be explained by strong sea-ice algal mat development. An SiNP uptake ratio of 25.513.81 indicates a strong demand for silicate. Minimum silicate levels were below those necessary for maximum diatom growth and probably contributed to the successional shift from diatoms to phytoflagellates.     

Silver nitrate and aminoethoxyvinylglycine affect <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated apple transformation

In Fuji, the production of ethylene was increased with the addition of AgNO₃ and inhibited with the addition of 10 M aminoethoxyvinylglycine (AVG). The addition of 80 M AgNO₃ to transformed explants of Fuji cultured on selection medium resulted in increased ethylene production (20 l l^–1) at 3 weeks. Under examining the effect of AgNO₃ in Fuji, the 40 M AgNO₃ showed with higher 33.8% and 6.5% in the efficiency of regeneration and transformation. However, ethylene production in Gala explants treated with 10M AgNO₃ (3 l l^–1) decreased after 2 weeks compared with the control (5 l l^–1). Although the regeneration efficiency of Gala with 10 M AgNO₃ was higher (41.1%) than the control (20.1%), there was no significant difference in the transformation efficiency at the same concentration. Shoot regeneration of Fuji and Gala was completely inhibited with 10 M AVG. These results suggest that the addition of AgNO₃ affects the efficiency of Agrobacterium-mediated gene transfer in Fuji.Eun Soo Seong, Ill Min Chung- These two Authors Contributed equally to this work     

The gibberellin synthesis inhibitors,ancymidol and flurprimidol,promote in vitro rooting of white pine microshoots

Summary Ancymidol and flurprimidol were tested for their ability to induce in vitro rooting on axillary proliferated shoots of white pine (Pinus strobus L.). Shoots were treated for 30 days (pulse) with growth regulators, then subcultured to 0.5X medium for conifer morphogenesis without growth regulators. A pulse treatment containing 5 M ancymidol and 0.54 M naphthaleneacetic acid resulted in 43% rooted shoots, whereas a pulse treatment with 0.54 M naphthaleneacetic acid alone resulted in 7% root formation. Flurprimidol also stimulated rooting of white pine shoots, but was less effective than ancymidol. No detrimental effects on shoot growth were observed with the gibberellin synthesis inhibitors at the 5 M concentration used. Some rooted shoots were successfully acclimatized to the greenhouse.Abbreviations ancymidol -cyclopropyl-(4-methoxyphenyl)-5-pyrimidinemethanol - flurprimidol -(1-methylethyl--[4-trifluromethoxy)phenyl]-5-pyridinemethanol - GA gibberellin - MCM medium for conifer morphogenesis - NAA 1-naphthaleneacetic acid