A new mutation protocol for obtaining auxotrophic mutants of the yeastPhaffia rhodozyma

Summary A new mutation strategy, which involves -irradiation of cells followed by a selective enzymatic enrichment step, was worked out to obtain auxotrophic mutants from the astaxanthin-producing yeast P. rhodozyma. Under the optimized conditions described, different mutants suitable for strain improvement were isolated.     

Cell competence forAgrobacterium-mediated DNA transfer inPisum sativum L.

Distribution and properties of pea (Pisum sativum L.) cells, competent forAgrobacterium-mediated transformation were analysed byin situ histochemical detection of GUS (-glucuronidase) activity, 4 d after inoculation with engineeredAgrobacterium tumefaciens. The vector system consisted of the hypervirulent disarmed strain EHA101 and the binary plasmid pIBGUS, carrying an intron-containing, 35S-promotor drivengusA (oruidA) gene and two selectable marker genes. Cells competent for transformation were mainly restricted to the dedifferentiating cells neighbouring the vascular system of cotyledon and epicotyl explants. A standardized assay was developed, allowing determination and quantification of factors influencing number and distribution of competent cells. In etiolated seedlings, competence for transformation decreased with the distance of the epicotyl explant from the shoot apex and was specifically induced by the exogenous application of auxins. Transient expression ofgusA afterAgrobacterium-mediated DNA transfer was dramatically reduced upon application of cell-cycle and DNA replication inhibitors aphidicolin, colchicine and nalidixic acid. GUS expression after direct DNA transfer of double-stranded plasmid DNA (via PEG into protoplasts or via particle bombardment of epicotyl segments) was independent of cell-division/DNA replication.A GUS-positive mutant of EHA101 was constructed to allowin situ analysis of attaching bacteria within the plant tissue. Attachment and invasion was inhibited by well-developed cuticula but was restored after chloroform treatment of the tissue surface. Moreover, no correlation was found between distribution of attaching bacteria and the pattern of transformation-competent cells.     

Conservation of highly repetitive DNA in cetaceans

It is controversial whether odontocetes (toothed whales) and mysticetes (whalebone whales) have a common ancestry. Cetacean karyological uniformity, which is unique among mammalian orders, suggests a monophyletic origin; however, several anatomical authorities have maintained that odontocetes and mysticetes are diphyletic. We investigated the issue using Southern blot hybridization. Two labelled restriction fragment probes from the DNA of the sei whale (a mysticete) were hybridized to restricted DNA of cetacean species representing all extant families except the Eschrichtiidae, the gray whales. The probes hybridized to specific restriction fragments in all odontocete and mysticete materials. Hybridizations showed preservation of hybridization homologies and a striking conservation of the length of highly repeated DNA sequences. The results are compatible with a common ancestry of odontocetes and mysticetes.     

Visual unit,EEG and sustained potential shift responses to biologically significant stimuli in the brain of toads (Bufo bufo)

Summary Visual unit activity, EEG changes and sustained potential shifts (SPS) were recorded from the toad tectum whilst the animal was presented with a visual stimulus. Telencephalic EEGs were also recorded.On the surface of the tectum, retinal unit activity preceded a sustained negative shift in potential and an increase in the amplitude and dominant frequency of the EEG. In deeper layers of the tectum, T5 units with configurational selectivity for wormlike stimuli were found. The activity of these units followed a pronounced SPS and EEG change.Visual unit activity was most pronounced during the negative-going phase of the synchronised EEG, when there was also a small decrease in amplitude of neuronal spikes. Similarities between the latencies and durations of EEGs and SPSs, and their response decrements, on repeated stimulus presentation, implies a close relationship between them not shared by the visual units studied. The specific activity of tectal units is discussed in relation to the correlated EEG and SPS changes, which may form part of an adaptive sensitizing mechanism.Abbreviations EEG electroencephalogram - ERF excitatory receptive field - SPS sustained potential shift - T4, T5 tectal neurons     

Are the funnel-canal organs the “campaniform sensilla” of the shore crab Carcinus maenas (Crustacea,Decapoda)?

Summary The topography of the funnel-canal organs of Carcinus maenas (Decapoda, Crustacea) and their stimulus-receiving cuticular and sensory apparatus were studied in the light and electron microscopes.About 4000 funnel-canal organs are situated within the exoskeleton of Carcinus. Almost all of them are on the distal segments of the walking legs, in particular on the epicuticular cap at the tip of the dactyl. They were not found to be arranged in groups or sensilla fields, and no sex-specific differences were observed.Characteristic features of the funnel-canal organs are as follows: (a) There is a terminal pore (0.5×0.8 m diameter) in the cuticle, at the tip of a small projection. It is closed by a plug of electron-dense material. (b) The terminal sections of the dendrites are enclosed in a dendritic sheath up to ca. 10 m below the pore. (c) The dendrites, 3–24 in number, end below the plug; none of the dendrites exhibits a tubular body; two of the dendrites are distinguished from the others by the greater number of microtubules in their outer segments.The structural characteristics, in particular the gustatory pore and the number of dendrites, are typical of bimodal receptors in arthropods. In such receptors, as in the contact chemoreceptors of insects and arachnids, mechano-and chemosensitive sensory cells are combined.This interpretation of the function of the funnel-canal organs is supported by electrophysiological data of other authors.The morphological parameters we find for the funnelcanal organs, in comparison with those of insect campaniform sensilla, provide clear evidence against the reclassification of the funnel-canal organs as crustacean campaniform organs proposed by Shelton and Laverack (1968).Supported by the Deutsche Forschungsgemeinschaft (W.G., SFB 45/A1)We thank Professor Dr. F.G. Barth for valuable discussion and Mr. K. Grommet for drawing the Figs. 1 and 6c     

A modification of the amidoblack-TCA-staining for quantitative microspectrometrical determination of proteins in tissue sections

Summary Conditions are described by which cells and fresh frozen tissues, following fixation with ethanol-ether, and after staining with the amidoblack (AB)-TCA-staining method, show a modified dye/protein ratio of 0.9 moles AB/10⁵ g protein compared to 8.5 moles AB/10⁵ g protein (Schauenstein et al. 1980) as in a previously used method. In contrast to the AB-TCA-method, which leads to extremly high and unmeasurable extinctions in tissue sections, staining with the modified AB-TCA-23st-method with 10 m tissue sections produces easily measurable extinction values.A correlation of the microspectrometrically determined mean total extinction values of different cell types and nuclei after staining with the tetrazonium method (Nöhammer 1978; Nöhammer and Desoye 1981) and on the other hand with the AB-TCA 23st-method has been found. The microspectrometrically determined extinctions after AB-TCA 23st-staining can be calculated; an extinction of 0.04248 corresponds to 1 pgm protein.Dedicated to Prof. Dr. E. Schauenstein on the occasion of his 65th birthday     

The H2 18O enrichment in the leaf water of tropic trees: Comparison of species from the tropical rain forest and the semi-arid region in Brazil

Summary The H₂ ¹⁸O enrichment,, in the water of leaves from four Brazilian trees, was studied. In all trees the leaf water showed a periodic variation in, with a maximum in the early afternoon and a minimum around 6 a.m. In general was found to be either higher or lower than the stationary enrichment which is supposed to depend only on the relative atmospheric humidity. This effect is due to the slow response of the system to variations of the humidity. For a special case, where steady-state conditions could be anticipated, the kinetic enrichment was obtained to 20 ± 3, which agrees with theoretical predictions.     

The paramedial neurosecretory cells of the suboesophageal ganglion of the cricket,Teleogryllus commodus (Walk.)

Summary Ovariectomy, performed immediately after the final hatch, caused a reduction of stainable (neurosecretory?) material in the paramedial neurosecretory cells (PNC) (A-type) of the suboesophageal ganglion in 10 day-old females of Teleogryllus commodus (Walk.). A concomitant increase in nuclear volume and in the incorporation of ³⁵S-cysteine indicates increased synthesis of neurosecretory material. From these findings it is concluded that more stainable material is secreted in the cerebral neurohaemal organ after Ovariectomy. A functional relationship between the PNC and the ovaries is suggested.     

Effects of isoniazid (INH) on the oogenesis of mice

Summary Mutagenic damages in female germ, cells of mice have been tested with the dominant, lethal assay and the cytogenetic analysis of unfertilized M II-oocytes. Concluding one can say that from the experimental data presented here do not show any mutagenic effect of INH on oogenesis of different strains of mice can be stated.