A simple,rapid protocol for adventitious shoot development from mature cotyledons of glycine max cv bragg

Mature soybean cotyledons (Maturity group VII) were cultured on modified MS containing 0–2.5 μM indole-butyric acid (IBA); 0–10 μM 6-benzylaminopurine (BAP) and 0.7% agar. Embryonic axes of explants were removed prior to culture initiation and cultures were incubated at 24°C with 45–50 μE. s⁻¹.M⁻² of mixed irradiance with 16 h photoperiod. Shoot proliferation occurred at 0–2.5 μM IBA and 5–10 μM BAP, while in the presence of 2.5 μM IBA alone, only roots developed. Abnormal shoots were produced with 2.5 μM IBA and 5–7.5 μM thidiazuron. Adventitious shoot development started 7–14 d after culture initiation in the region where the embryonic axis was previously attached to the cotyledon and shoots were visible within 28 days. The presence of the embryonic axis inhibited shoot morphogenesis. The shoots were rooted on half strength MS inorganic salts plus vitamins, 2% sucrose, 0.5 μM NAA acid or 2.5–5 μM IBA, or 5–10 μM IAA, and 0.7% agar. Rooted plants were acclimatized under a mist in the greenhouse. This simple, rapid,in vitro adventitious shoot development protocol could be adapted for transformation/regeneration studies in soybean. Trade and company names are used in the publication solely to provide specific information. Mention of a trade or company name does not constitute a warranty or an endorsement by the U.S. Department of Agriculture to the exclusion of other products or organizations not mentioned.     

Evolutionary origin of aminoglycoside phosphotransferase resistance genes

Summary The protein sequences of seven 3-aminoglycoside phosphotransferases falling into the six identified types and three 6-aminoglycoside phosphotransferases were analyzed to give a rooted phylogenetic tree. This tree supports the origin of these groups of enzymes in an ancestor closely related to the actinomycetes, and that horizontal transfer of the resistance genes occurred, possibly via transposons. The implications for genetic engineering of a novel antibiotic are discussed.     

Single chloride channels in endosomal vesicle preparations from rat kidney cortex

Summary Endocytotic vesicles from rat kidney cortex, isolated by differential centrifugation and enriched on a Percoll gradient, contain both an electrogenic H⁺ translocation system and a conductive chloride pathway. Using the dehydration/rehydration method, we fused vesicles of enriched endosomal vesicle preparations and thereby made them accessible to the patch-clamp technique. In the fused vesicles, we observed Cl^– channels with a single-channel conductance of 73±2 pS in symmetrical 140mm KCl solution (n=25). The current-voltage relationship was linear in the range of –60 to +80 mV, but channel kinetic properties dependended on the clamp potential. At positive potentials, two sublevels of conductance were discernible and the mean open time of the channel was 10–15 msec. At negative voltages, only one substate could be resolved and the mean open time decreased to 2–6 msec. Clamp voltages more negative than –50 mV caused reversible channel inactivation. The channel was selective for anions over cations. Ion substitution experiments revealed an anion permeability sequence of Cl^–=Br^–=I^–>SO ₄ ^2– F^–. Gluconate, methanesulfonate and cyclamate were impermeable. The anion channel blockers 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS, 1.0mm) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 0.1mm) totally inhibited channel activity. Comparisons with data obtained from radiolabeled Cl^–-flux measurements and studies on the H⁺ pump activity in endocytotic vesicle suspensions suggest that the channel described here is involved in maintenance of electroneutrality during ATP-driven H⁺ uptake into the endosomes.     

Different long-term effects of bilateral and unilateral nucleus basalis lesions on rat cerebral cortical neurotransmitter content

Young adult rats received either unilateral or bilateral ibotenic acid infusions in their nucleus basalis, destroying most of the cholinesterase-staining neurons in that region. Cerebral cortex levels of choline acetyltransferase, somatostatin, neuropeptide Y, and monoamines were then assayed 2.5 and 10 months after bilateral lesions, or, 2.5, 10, and 14 months after unilateral lesions. Entorhinal and cerebral cortex levels of several amino acid transmitters were also measured. As expected, choline acetyltransferase activity was decreased in the frontal cortex ipsilateral to the ibotenic acid infusion in unilaterally or bilaterally lesioned animals. Parietal cortex concentrations of somatostatin and neuropeptide Y were altered by lesioning in a complicated, time-dependent manner. Thus, while unilateral lesions transiently decreased or had no effect on these neuropeptide levels, bilateral lesions elevated the level of each neuropeptide by over 100% at 10 months. Other cortical transmitter systems investigated appeared to be less affected by nucleus basalis-lesions. Unilateral lesions had no effect on prefrontal cortex norepinephrine, serotonin, or dopamine content at 14 months post-lesioning. These different neurochemical effects of unilateral and bilateral nucleus basalis lesions may be important for developing a model for the trans-synaptic effects of cortical cholinergic deafferentation.     

Geitler's “Plattenband” in the diatomSynedra cf.ulna in the light of TEM investigations

The ultrastructure of the diatomSynedra cf.ulna was examined paying special attention to the Plattenband (platelet band). This structure was first described byGeitler in 1948 on the basis of LM observations and denotes a linear array of dictyosomes along the apical axis of the cell. The present investigation confirmsGeitler's observations in all essential details and demonstrates that the dictyosomes are arranged along polarized nuclear extensions running towards the cell poles. Laterally the extensions are accompanied by a number of microtubules. In large cells the total length of the nucleus thus may reach 400 µm and more. Since only the central part of the nucleus is DNA-positive with DAPI and acridine orange, the nuclear nature of the backbone of the Plattenband cannot be recognized by LM techniques. TEM investigation of serial apical and transapical sections, however, prove unambiguously the identity with extended parts of the nucleus.Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

Identification of two general diffusion channels in the outer membrane of pea mitochondria.

Reconstitution experiments were performed on lipid bilayer membranes in the presence of detergent solubilized mitochondrial membranes of pea seedlings (Pisum sativum). The addition of the detergent-solubilized material to the membranes resulted in a strong increase of the membrane conductance. To identify the proteins responsible for membrane activity the detergent extracts were applied to a hydroxyapatite (HTP) column and the fractions were tested for channel formation. The eluate of the column contained a protein which migrated as a single band with an apparent molecular mass of 30 kDa on SDS-PAGE. This channel was identified as the porin of pea mitochondria since it formed voltage-dependent channels with single-channel conductances of 1.5 and 3.7 nS in 1 M KCl and an estimated effective diameter of about 1.7 nm. Further elution of the column with KCl containing solutions yielded fractions which resulted in the formation of transient channels in lipid bilayer membranes. These channels had a single-channel conductance of 2.2 nS in 1 M KCl and had also the characteristics of general diffusion pores with an estimated effective diameter of 1.2 nm. Zero-current membrane potential measurements suggested that pea porin was anion-selective in the open state. The selectivity of the second channel was investigated by the measurement of the reversal potential. It was also slightly anion-selective. Its possible role in the metabolism of mitochondria is discussed.     

Deterministic versus Individualistic community structure: a test from invasion by Nothofagus menziesii in southern New Zealand

Abstract. The Clements' Deterministic model of plant communities implies that a change in one species, especially a change in the physiognomic dominant, would have profound effects on the remainder of the community. Gleason's Individualistic model suggests there would be little effect. These alternative models are tested by examining the forest composition on both sides of a boundary along which the tree Nothofagus menziesii is slowly invading. Classification of forest composition, excluding N. menziesii, gave little evidence of an effect of N. menziesii on the lower strata: understorey vegetation types were distributed across the boundary. Some differences were found at individual sites, but these were often inconsistent between sites. Ordination, also excluding N. menziesii, similarly showed that none of the first three understorey axes reflected any effect of N. menziesii. The fourth axis was correlated with the presence of N. menziesii, but only when canopy trees were included. It is concluded that specific composition of the canopy in these montane New Zealand evergreen forests has little effect on the understorey, supporting Gleason's Individualistic concept of the community.     

Purification and some properties of a novel microbial lactate oxidase

 Geotrichum candidum was found to produce a lactate oxidase. The enzyme was purified by gel filtration and ion-exchange chromatography. The purified lactate oxidase showed a molecular mass of 50 kDa under denaturing and about 400 kDa under non-denaturing conditions. Transmission electron micro-scopy analysis confirmed an octameric structure. FMN was found to be a cofactor for this enzyme. Polarographic studies confirmed an oxygen uptake by the lactate oxidase. The enzyme showed specificity towards the L isomer of lactate and did not oxidise pyruvate, fumarate, succinate, maleate and ascorbate. It was stable at alkaline pH and also for 15 min at 45°C. The addition of glycerol and dextran 500 000 to the enzyme sample enhanced storage stability. Received: 28 September 1995/Received revision: 10 January 1996/Accepted: 15 January 1996