Cell and endophyte structure of the nitrogen-fixing root nodules ofCeanothus integerrimus H.and A.

Summary The nitrogen fixing root nodules ofCeanothus integerrimus were very similar in appearance to other non-legume nodules. Each nodule was a cluster of small lobes. Each lobe in cross section had a central vascular cylinder and a hypertrophied cortex. The cortex contained very large infected cells, with large nuclei; among these infected cells were scattered small, normal-appearing cortex cells. The actinomycete endophyte consisted of wavy hyphae 0.4 m in diameter which terminated in pear-shaped vesicles 1.6 m×2 m. The vesicles were not septate. The function of the vesicles was unknown. The infected cells had apparently normal nuclei, chloroplasts and mitochondria and were probably alive, except at the base of the nodule where both infected cells and the endophyte they contained were dead.     

The cytology of phytophthora infestans

Summary Phytophthora infestans has three kinds of somatic nuclei: an oval shaped nucleus (approx. 3.1×2.7 ) which stains diffusely except for a crescent shaped Feulgen positive cap which stains intensely; a granular nucleus whose contents are organized into a fairly constant number of stained bodies, and, a deeply staining condensed nucleus. The capped nucleus is thought to be metabolic or resting and the granular nucleus is thought to be dividing as it is most commonly found in hyphal tips. Attenuated forms of all three kinds of nuclei are found.Nuclear division is mitotic and intranuclear. Eight—ten chromosomes are seen at metaphase.Sporangia have a mean of 6.3 nuclei which is constant for age and strain of culture. Sporangia become multinucleate as a result of nuclear migration and not by division in the developing sporangium. Zoospores are usually uninucleate.The nuclear cap is persistent throughout nuclear division when it also divides. It is associated with flagella production and nuclear migration and has some of the properties of a blepharoplast.     

The formation of vesicles in the developmental cycle of the nodular endophyte of Hippophaë rhamnoides L.

Summary The mature vesicle of the Hippophaë rhamnoides root nodule endophyte is spherical, approximately 3–4 m in diameter and exhibits a high degree of apparently random septation. Electron micrographs are presented which show that this vesicular form in the endophytic development within the host cell originates as a swelling of the hyphal tip. The young vesicle is non-septate and in general attains a minimum diameter of 3 m before septation becomes evident. The number of septa then increases with vesicle maturity.     

Zur Feinstruktur der Elektrozeptorepidermis der Mormyridae (Teleostei,Pisces)

Zusammenfassung Die schwachelektrischen Mormyridae haben eine dreischichtige Epidermis, deren innere Schicht aus nur etwa 0,22 m dicken sechseckigen Zellen von ca. 60 m Durchmesser besteht. Die etwa 2 m dicken, linsenförmigen Kerne von 7,6 m Durchmesser liegen am Zellrand. Die Zellen sind zu Säulen aufgeschichtet. Ihr Rand ist ausgezackt und dort, wo er die Säulengrenze erreicht, auf etwa 0,34 m verdickt. In der Nähe der Säulengrenzen sind die Zellen über Desmosomen mit den Nachbarn in der eigenen und in der angrenzenden Säule verbunden. Diese Epidermisschicht ist auf die Körperpartien beschränkt, in denen auch Elektrorezeptoren ausgebildet sind.Die beiden anderen Epidermisschichten haben den üblichen Aufbau einer Fischepidermis, abgesehen vom Fehlen der Becherzellen.

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Ultrastructure of the electroceptor epidermis of the Mormyridae (Teleostei, Pisces)

Summary The weakly electric fish of the family Mormyridae have a three layered epidermis, with a medium layer consisting of hexagonal cells of only 0.22 m in thickness and about 60 m in diameter. The lens-shaped nuclei are about 2 m thick and 7.6 m in diameter and are situated near the border of the cells. The cells are piled up to hexagonal columns. Their margin is serrate and where it reaches the boundary of the column, it has a thickness of about 0.34 m. Close to the boundaries of the columns, the cells are linked to their neighbours within the column and of the adjoining column by desmosomes. This layer of the epidermis is confined to those regions of the body surface which also contain electroreceptors.The other layers of the epidermis have a structure as usual in fish, except for the lack of goblet cells.

     

Coated vesicles and other cytoplasmic components of growing root hairs of radish

Summary Root tips of radish,Raphanus sativus, were fixed in glutaraldehyde followed by osmium tetroxide. The fine structure of young root hairs, not exceeding about 130, in length, was studied to relate their apical growth pattern to their cytoplasmic organization. The cytoplasm in the terminal 3–5 it of the root hair is characterized by an electron dense matrix in which lie numerous smooth-surfaced vesicles, large irregularly-shaped fibrous inclusions, and clusters of ribosomes. Other organelles are largely or entirely excluded from this region. Farther than about 5, from the tip, the hair cytoplasm is filled with plastids, rough endoplasmic reticulum, mitochondria, and dictyosomes. The latter produce smooth vesicles similar in size and morphology to those present in the apical dome. Vesicles of a different kind appear in the peripheral cytoplasm along the entire length of the hair. These vesicles possess an alveolate or chambered coat about 20 m thick and have a diameter of about 85 m, including coat. They originate by evagination from the large, smooth-surfaced vesicles in the vicinity of dictyosomes. It is suggested that proteins and carbohydrates are concentrated in the dictyosomes and then segregated in the smooth vesicles released from the dictyosome cisternae. The coated vesicles which bud from the smooth vesicles may serve to isolate the proteins and transport them to the hair surface for participation in wall synthesis. The smooth vesicles are believed to convey carbohydrates to the region of active wall extension at the hair apex.This work was supported in part by grant GM-10493 from the National Institutes of Health. United States Public Health Service, to Dr. H. T. Bonnett, Jr., and grant RG-628 from the National Science Foundation to Dr. E. H. Newcomb.     

Freeze-fracture studies on the cockroach hemocyte membrane complex: Symmetric and asymmetric membrane particle distributions

Summary Freeze-fracture studies were conducted on the membranes of normal cockroach hemocytes. The plasmalemma is asymmetric with the A fracture face containing 80–100 Å membrane intercalated particles at a concentration of 2500/². The B fracture face contains 120–150 Å particles with a relatively low density (800/²). The nuclear envelope displays an asymmetry with the A fracture face containing 1500 particles/² and the B face containing 300/ ². No significant particle size differences were observed in nuclear envelope fracture faces. Two types of symmetric membranes were also found in these cells. Both A and B fracture faces of the membrane surrounding the numerous cytoplasmic inclusion bodies contain particle sizes and concentrations similar to the B face of the plasmalemma. A second type of symmetry was observed in cells apparently engaged in exocytosis. Vesicles (0.1 D) from this process were completely particle free on both fracture faces. Such particle free vesicles could be found in the cytoplasm, attached to the plasmalemma, or completely separated from the cell.Supported by a Pharmaceutical Manufacturers Association Foundation Fellowship.The author wishes to thank Ms. Annalena K. Charla for assistance in plate preparation, Dr. Julius Schultz and the Papanicolaou Cancer Research Institute for use of the freeze-etch device, and Dr. David Smith for the electron microscope facilities.     

Physicochemical and morphological characterization of two small polluted streams in southwest Germany

As a supporting component of the VALIMARproject, physicochemical investigations wereconducted monthly from 1995 to 1999 at theKrähenbach/Aich stream system (two samplingsites) and at the Körsch stream (sixsampling sites). Several physicochemicalparameters were analysed continuously bydataloggers during the entire sampling period.Moreover, a selection of the most importantmorphological parameters of the stream wererecorded in 1998.The results of these physicochemicalinvestigations demonstrated that theKrähenbach/Aich system could becharacterized as a natural rhithral submontanecarbonate stream system that is welloxygenated. Low temporal variations in pH,conductivity and chloride occurred at allsampling sites in the Krähenbach whichcoincided with the geological conditions atthis test stream. Because of relatively lowconcentrations of organic and inorganiccompounds during the entire study period thesites AB and AC in the Krähenbach/Aichsystem were classified as slightly polluted.The morphological assessment of the streamindicated a moderately affected status atboth of these streams.Physicochemical and morphologicalinvestigations along the Körsch streamsystem (KA to KE including the tributary streamSulzbach) indicated a highly affected rhithralsubmontane carbonate system characterized byhigh water velocity, flow rate and dissolvedoxygen. The Körsch, however, differssignificantly with respect to watertemperature, conductivity, pH, BOD₅,nutrients, and chloride concentrations from theKrähenbach. As a result of differentanthropogenic inputs (e.g. several sewageplants, agriculture activities and waste waterdumping) the Körsch sites KA to KD wereclassified as critically to heavilypolluted. The morphological assessmentindicated a clearly affected to damagedstatus. The upstream site KE could becharacterized as slightly polluted and itsmorphological structure as moderatelyaffected.     

The Sertoli cell of the water buffalo (Bubalus bubalis) during the spermatogenic cycle

Summary Ultrastructural features and morphometric evaluations of buffalo Sertoli cells are reported for the six phases of the spermatogenic cycle. The phases of the tubular seminiferous epithelium are identified according to characteristic cellular associations with completed spermiation as demarcation between two cycles. Average tubular diameter (245 m) and epithelial height (61 m) do not vary significantly during the cycle. The relative Sertoli cell volume in the seminiferous epithelium varies between 30% (phase 4) and 39% (phase 8). The calculated volume of a single Sertoli cell increases from a nadir of 7118 m³ in phase 3 abruptly to a maximum of 8968 m³ in phase 4 and is then gradually reduced during the following phases. The Sertoli cell surface area shows a similar trend: it amounts to 11105 m² in phase 3 and to 14260 m² in phase 4. The contact area of the Sertoli cell with adjacent cells and structures is subject to characteristic changes; from the expansion of basal Sertoli-Sertoli contacts it is concluded that the blood-testis barrier in the buffalo is particularly tight during phases 8, 1 and 2. The irregularly contoured nucleus contains a vesicular nucleolus, has a calculated volume from 465 m³ to 543 m³ and occupies 5 to 7% of the cell. Volume percentages of mitochondria (4%), Golgi apparatus and lysosomal bodies are rather constant during the cycle. Whorls and orderly arranged aggregates of the smooth endoplasmic reticulum occur in basal location as well as in close association with elongating spermatids. Smooth ER is the organelle that exhibits the most prominent changes during the Sertoli cell cycle: it occupies 5.79% in phase 3 and 20.9% in phase 4 of the total cellular volume. Phagocytosis of residual bodies is insignificant in this species and a lipid cycle is absent in buffalo Sertoli cells.     

The quantitative analysis of chromosome pairing and chiasma formation based on the relative frequencies of M I configurations

Whilst reliable estimates of chiasma frequencies can usually not be obtained, the probability (b) of a chromosome arm to be bound by at least one chiasma can often be determined. In the absence of interference this probability equals (1–e ^–2), where 2 is the average chiasma frequency of the chromosome arm and the average crossover frequency or map length. In the presence of interference is shown to retain its genetic meaning as an additive metric that may describe the chromosome arm or other distinctive chromosome segment in terms of genetic recombination. It is a form of potential map length, comparable to, but numerically different from the regular map length. It is termed provisionally crossing-over potential.A chromosome with armsm andn with crossing-over potentials and will form ring bivalents with a frequency (1–e ^–2).(1–e ^–2); open bivalents with a frequency (1–e ^–2).e ^–2+(1–e ^–2).e ^–2; univalent pairs with a frequencye ^–2.e ^–2. Estimates of these frequencies yield equations from which and may be solved. In rye (Secale cereale) their ratio (q) is approximately two and differs from the mitotic arm length ratio of 1.4, indicating localization of chiasmata in the long arms.Graphs are given to show how, with constantq, the relation between the probabilitiesb _m andb _n of the two arms being bound changes with changing averageb.Data are presented on chiasma frequencies in M I, and compared with the frequencies expected in the absence of interference to give an impression of the degree of interference. Apparent fusion of chiasmata simulates interference.     

Regeneration of plantlets through organogenesis in the Himalayan yellow poppy,Meconopsis paniculata

Plantlet formation through organogenesis in callus cultures of Himalayan yellow poppy,Meconopsis paniculata D.Don (Prain), a threatened taxon of ornamental value, is described. Hypocotyl segments from 3-month-old laboratory-raised seedlings produced callus on agar-solidified Murashige and Skoog medium (MS) containing 10 M -naphthaleneacetic acid and 1 M kinetin. Shoots differentiated best from callus on MS containing 10 M indolebutyric acid (IBA) and 1 M 6-benzyladenine. The regenerated shoots rooted best on MS medium containing 10 M IBA. From seed germination to differentiation of plantlets through the two-step organogenesis process required 28–29 weeks.Abbreviations 2,4-d 2,4-dichlorophenoxyacetic acid - FAA formalin-acetic acid-alcohol - BA 6-benzyladenine - IAA indole-acetic acid - IBA indolebutyric acid - GA₃ gibberellic acid - NAA -naphthaleneacetic acid - RH relative humidity     

In vitro organogenesis of elephant apple (Feronia limonia)

Elephant apple (Feronia limonia L.). was micropropagated on MS medium containing 4.4 M benzyladenine and 4.6 M kinetin using cotyledon explants taken from in vitro-grown seedlings. Adventitious buds formed on the cotyledon developed into shoots that were rooted in half-strength MS medium containing 0.57 M indoleacetic acid and 0.49 M indolebutyric acid. Plants were successfully established in soil.Abbreviations BA 6-benzyladenine - IAA 3-indoleacetic acid - IBA 3-indolebutyric acid - MS Murashige & Skoog     

Observations on the ultrastructure ofFrankia sp. in root nodules ofDatisca cannabina L.

Summary The fine structures of the microsymbiont inside the root nodules ofDatisca cannabina have been studied by light, by transmission- and by scanning-electron microscopy. The endophyte is prokaryotic and actinomycetal in nature. The hyphae are septate and branched, diameter 0.3–0.5 m. The tips of hyphae are swollen to form electron-dense, clubshaped to filamentous vesicles, ranging in diameter: 0.4–1.4 m. The endophyte penetrates through walls of the cortial cells. The infected zone is kidney shaped and confined to one side of the acentric stele. The orientation of infection is reversed from other actinorhizae exceptCoriaria. The hyphae are near the host cell wall and vesicles are directed towards the central vacuole. Vesicles are aseptate and no collapsing of the vesicle cell wall (void area) has been observed. Vesicle clusters structures are globular with an opening at one side of the cluster. The host cell is multinucleate or contains a lobed nucleus. Groups of mitochondria are located in between the hyphae, suggesting a strong association between the host and the endophyte for energy supply and amino acid production. The consequences of the inability to separate the mitochondria from the vesicle clusters in nodule homogenates in physiological studies have been discussed.Isolated vesicles clusters showed dehydrogenase activity, indicated by the presence of formazan crystals, after incubation with NADH and NBT. Strongest reducing activity was found within the vesicles. The possible role of filamentous vesicles in nitrogen fixation has been discussed.     

Inhibition of (+)[3H]SKF 10,047 binding to rat brain membranes by FAB fragments from a monoclonal antibody directed against the opioid receptor

Examination of the binding of (+)[³H]SKF 10,047 to rat brain membranes indicated that at a low concentration most of the binding was to the haloperidol-sensitive binding site. Titration curves exhibited a displacement potency order of haloperidol >(+)SKF 10,047 =1,3-diorthotolyl-guanidine(–)SKF 10,047 phencyclidine analogues. The effect of Fab fragments from a monoclonal antibody, OR-689.2.4, directed against the opioid receptor on the binding of(+)[³H]SKF 10,047 to rat brain membranes was examined. The specificity of this antibody for the opioid receptor has been determined by its ability to inhibit the binding of and opioid peptides to rat brain but not the binding of opioid ligands or nonopioid ligands specific for other receptors. The Fab fragments blocked and displaced specifically bound (+)[³H]SKF 10,047 in a titratable manner. Increasing the incubation time of the membranes with the Fab fragments increased the percent inhibition obtained. The Fab fragments acted as noncompetitive inhibitors of (+)[³H]SKF 10,047 binding. A(+)SKF 10,047 binding site in rat brain appears to share a common structural domain with and opioid receptors.     

On T-tubule openings at the sarcolemma of white fast-twitch muscle fibres in fish and frog

Summary In white muscle fibres of a teleost fish T-tubule openings may occur regularly at all Z-disc levels between adjacent peripheral myofibrils, the T-tubule openings thus occurring at a density of ca. 0.9 m^-2.In frog white fibres, T-tubule openings are infrequently seen in material fixed like the fish material. In material prepared according to the albumin method of Gray (1975, 1976 a, b) which renders the muscle fibres swollen, straight tubules or sometimes chains of vesicles instead are seen opening at the sarcolemmal surface. Such tubules occur at a higher density than expected from experiments with local activation of contraction. Lability and dynamics within the T-system normally and during fixation are discussed.     

Modelling of sulfur oxidation from elemental sulfur

An elemental S oxidation model has been developed which combines a maximum S release rate with modifiers for temperature and soil moisture conditions. This model has been combined with a pasture growth and CNSP nutrient cycling model to match S oxidation rate to pasture S demand. In two Southern Australian enviroments, 100m elemental S was superior to 200m particles whilst in Northern Australia the 200m particles were superior. These models can be used to match S release to plant demand.     

Triazole treatment of explant source provides stress tolerance in progeny of Geranium (Pelargonium hortorum Bailey) plants regenerated by somatic embryogenesis

Thehypothesis that chemically induced stress tolerance in plants can betransferredto a larger clonal population regenerated by somatic embryogenesis wasevaluatedusing the triazole compound paclobutrazol as a chemical inducer of stresstolerance in Geranium (Pelargonium horturum Bailey). Seedswere imbibed in 3.4, 10.2 or 17.0 M (1, 3, 5 mgL^–1) paclobutrazol for 24 h and germinatedfor 7 days. Hypocotyl explants were cultured in vitro toinduce somatic embryogenesis. Plants regenerated from somatic embryos wereexposed to heat stress at 56°C. Explants treated with3.4 M paclobutrazol yielded a substantially higher number ofsomatic embryos compared with untreated explants. In contrast, 17.0M paclobutrazol treatment inhibited embryogenesis producing asignificantly lower number of somatic embryos. There was no difference in theembryo number between control and 10.2 M treatment. Somaticembryos derived from 3.4 and 10.2 M paclobutrazol treatedexplants developed into plants at a faster rate than the control and 17.0M treatments. Plants derived from paclobutrazol-treatedexplants displayed a greater tolerance to heat stress compared with thecontrols. Observations in this study provide a technique for regeneratingplantsin tissue/cell culture with additional desirable traits such as stresstolerancewith minimal chemical contamination of the environment.     

Factors influencing shoot regeneration from cotyledonary explants ofCucumis melo

Cotyledonary explants of 4-day-oldCucumis melo cv. Hale's Best Jumbo in vitro seedlings showed maximum initiation of shoot buds when cultured onto a revised Murashige & Skoog medium supplemented with 5 M indole-3-acetic acid and 5 M benzylaminopurine and cultured at 25–29°C under low light intensity (5–30 mol m^-2 s^-1). Subculture of the shoot buds onto the same medium without auxin and supplemented with 3 M benzylaminopurine caused the development of shoots from 30% of the buds. The presence of abscisic acid significantly increased the number of explants producing shoot buds. Bud initiation was affected by genotype, seedling age, light intensity, and temperature. Addition of gibberellic acid, thidiazuron or silver nitrate to regeneration medium did not improve either bud initiation or shoot regeneration.     

Membrane vesicles of cellular dimensions fit in two geometric series

Summary Preparations of basal-lateral plasma membranes from rat intestinal epithelial cells were analyzed with the analytical centrifuge. In these preparations a number of well-defined membrane fractions were observed. The particle weights of these fractions appear to fit in two geometric series. Until now only relatively small vesicles up to a diameter of about 1 m were observed. In our preparation we have observed vesicles up to a diameter of 7.5 m. Therefore, even vesicles with the same size as the plasma membranes of intact cells fit in the two geometric series.     

Three dimensional reconstruction of the X-Y pair during pachytene in the rat (Rattus norvegicus)

The ultrastructure of the X-Y pair from rat spermatocytes has been reconstructed sterically by the study of serial sections. The X-Y pair of the rat at early pachytene contains two dense cores, a long and a short one, which form a synaptonemal complex 1.7 long at their common end. The long core (10.6 ) and the short core (4.5 ) correspond to X and Y, respectively. There is no RNA histochemically detectable in the X-Y pair. Nucleoli are independent of the X-Y pair. A low number of cells show nucleoli very near the X-Y pair but no continuity exists between these structures.     

Nitrogen fixation byRubus ellipticus J. E. Smith

Summary Nitrogenase activity as assayed by acetylene reduction was observed in detachedRubus ellipticus J. E. Smith root nodules collected in the field and tested under ambient conditions. The nitrogenase activity was 8.4 moles C₂H₄.gfr. wt nodule^–1.h^–1 or 24.0 moles C₂H₄.g dry wt nodule^–1.h^–1 being at a rate comparable with that measured in some other non-legumes assayed in Java at the same time under similar conditions. Nodule morphology bore little resemblance to the root nodules of other non-leguminous plants and nodule structure was different from the other rosaceous examples.The endophyte inhabiting the root nodules was actinomycetal.