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.     

Effect of oxygen on growth and respiration of potato tuber callus

Growth and oxygen uptake of potato callus is faster in an oxygen-enriched atmosphere (70% oxygen, v/v; oxygen-callus) than in air (20% oxygen, v/v; air-callus). Especially the non-mitochondrial, so-called residual respiration is increased in oxygen-callus. The capacities of the mitochondrial respiratory pathways (cytochrome pathway, V_cyt and alternative pathway, V_alt) are also higher in this callus. In both callus types only a small part of the alternative pathway capacity is used in uninhibited respiration. The lower oxygen uptake of air-callus at normal air oxygen pressures is partially due to diffusional impedance. Measurement of the respiratory parameters of air-callus in oxygen-saturated medium leads to higher values than measurement in air-saturated medium, although these values are still lower than those of oxygen-callus.ATP-production was calculated from the oxygen-uptake data and compared with the dry weight production of the callus to give values of 10.0 and 10.8 g dry weight produced.-mol ATP^-1, for air-callus and oxygen-callus respectively. As no harmful side-effects are observed, cultivation of callus under elevated oxygen pressures may be useful, when rapid callus-growth is necessary.Abbreviations AA antimycin A; A; - BHAM benzohydroxamate - DW dry weight - FW fresh weight - 8-OHQ 8-hydroxyquinolin - RC respiratory control - SHAM salicylhydroxamate     

Endocrine cells in the human fetal small intestine

Summary In this report we describe the time of appearance and ultrastructural features of enteroendocrine cells (EECs) in the human fetal small intestine (SB) between 9 and 22 weeks gestation. Thirteen distinctive EECs were identified in fetal SB. Two of these, not found in normal adult SB, appeared within the stratified epithelium of the proximal SB at 9–10 weeks. They were arbitrarily termed primitive and precursor cells. As in all fetal EECs, the pale cytoplasm of the primitive cell contains a distinctive population of secretory granules (SGs). Primitive cell SGs average 200–330 nm; some have dense cores with lucent halos while others are filled with a homogeneous dense or flocculent material. The SGs of the precursor cells are larger, averaging up to 1 m in diameter and their contents vary in electron density. A third group of cells not described in normal adult SB was arbitrarily termed transitional cells. These have two populations of SGs; one resembles the SGs of the precursor cells, and the other resembles the SGs of some of the specific adult type EECs. Transitional EC, S, I and G cells are seen. In addition, mature appearing EC, S, G, I, L, D, and D₁ cells were identified by 12 weeks of gestation. The primitive, precursor, and transitional cells may represent sequential developmental precursors of adult type EECs.Supported by Research Grant AM-17537 from the National Institutes of Health, Besthesda, MarylandThe authors would like to thank Ms. Linda Barstein for her excellent technical assistance     

A comparison of male and female recombination frequency in wheat using RFLP maps of homoeologous group 6 and 7 chromosomes

A novel approach was used to compare male and female recombination rates in wheat. Doubled haploid lines were developed from an F₁ using two distinct approaches: the anther-culture technique and the Hordeum bulbosum system, from which sets of lines were developed from male and female meioses, respectively. The genotype of the lines was established at RFLP and isozyme markers polymorphic on chromosomes of homoeologous groups 6 and 7, and male and female linkage maps were calculated using this information. The markers in one segment of chromosome 6B exhibited disturbed segregation frequencies in the anther-culture population. The male and female maps differed significantly in recombination frequency between some markers on two chromosomes, and these were consistent in direction within chromosomes and inconsistent in direction between chromosomes. In two of the four chromosomes studied the male map was much longer than the female map. These results suggest that significant differences may exist in male and female recombination frequencies in bread wheat which are specific to certain chromosomal segments but are inconsistent in direction between chromosomes. Other factors, such as environmental influences, may also be important in creating differences.     

DNA variations in regenerated plants of pea (Pisum sativum L.)

Summary The aim of this study was to determine whether DNA variations could be detected in regenerated pea plants. Two different genotypes were analyzed by cytogenetic and molecular techniques: the Dolce Provenza cultivar and the 5075 experimental line. Dolce Provenza regenerated plants showed a reduction in DNA content, particularly at the level of unique sequences and ribosomal genes. Moreover, regeneration was associated with an increase in DNA methylation of both internal and external cytosines of the CCG sequence. On the other hand, the DNA content of the 5075 line remained stable after regeneration. DNA reduction was found only in 5075 plants regenerated from callus cultures maintained for long incubation periods (about a year). The DNA variations observed are discussed both in relation to the genotype source and the role of tissue-culture stress.     

Flora Palinologica Italiana,Sezione Aeropalinologica: S 205 -Pinus pinea L. (Pinaceae)

Summary According to the program Palynological Italian Flora, Aeropalynological section, the pollen morphological card ofPinus pinea L. is presented. The study is carried out on pollen coming from three Italian localities and regards fresh and acetolyzed pollen. For each sample, measurements are carried out on 30 fresh pollen grains in glicerol jelly with fuchsin and on 30 acetolyzed pollen grains in water/glicerol (1/1); general observations regard 1000 fresh and 1000 acetolyzed pollen grains/sample. Some observations on the main differences between fresh and acetolyzed pollen are mentioned.

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Riassunto Nell'ambito della Flora Palinologica Italiana, Sezione Aeropalinologica, è presentata la scheda morfopalinologica diPinus pinea L. nella versione su polline fresco e polline acetolizzato, su tre campioni di diversa provenienza. Vengono notate le principali differenze tra polline fresco e polline acetolizzato.

     

Intercellular junctions in nerve-free hydra

Summary Epithelial cells of nerve-free hydra contain septate and gap junctions. In thin sections the gap junctions are characterized by a gap of 3–4 nm. Freeze-fracture demonstrates the presence of septate junctions and two further types of structures: (i) the E-type or inverted gap junctions with particles in an en plaque conformation appearing as a raised plateau on the E-face or as a depression on the P-face; (ii) structures morphologically similar to gap junctions in rat liver, containing particles on the P-face and corresponding pits on the E-face, both having hexagonal packing with a lattice constant of 8 nm. We propose that these structures are also gap junctions.     

An increase in the “inhibitor-β” content of detached wheat leaves following a period of wilting

Summary Wheat seedlings were grown under a 14-hour photoperiod and the first leaves excised at the end of the eighth dark period. The effect of treatments causing wilting on the inhibitor- content of such leaves was studied.When leaves were rapidly wilted (i.e. to a 6% fresh weight loss) and extracted immediately, the amount of inhibitor- per leaf was found to be the same as in fresh turgid leaves. However, when the leaves were maintained in a wilted condition in darkness for a period of 110 minutes, there was a marked increase in inhibitor- content.The greater the degree of wilting (i.e. up to about a 9% loss in fresh weight) the greater the eventual inhibitor- content. Moreover, the increment in inhibitor- was shown to be temperature dependent.The time lapse requirement and the temperature dependency of the inhibitor- formation suggest an enzymic conversion from a precursor.If a similar phenomenon occurs during the wilting of intact plants then the increase in this growth inhibitor might play a role in some of the physiological changes which accompany water stress.     

Lipid profile of rat myelin subfractions

Myelin from adult rat brains was separated on a discontinuous sucrose gradient into three subfractions. Analysis of light, heavy and membrane fraction lipid classes was performed by HPTLC and densitometry while fatty acid composition was determinated by GLC. The more interesting results observed are: i) the membrane fraction resembles in its lipid and fatty acid composition other cell membranes (particulary oligodentrocytes); ii) light and heavy myelin are quite similar between them but the former has a higher content of sphingomyelin, a lower hydroxy/nohhydroxy cerebrosides ratio and a lower content of monoenoic fatty acids than the heavy subfraction. The results obtained could explain the different structures observed in each myelin subfraction since fatty acid composition, hydroxy fatty acids, sphingomyelin and cholesterol play a key role in the stability and structure of membranes.     

Ultrastructure of the new neuromuscular junctions formed during reinnervation of rat soleus muscle by a “foreign” nerve

Summary In rats the fast fibular nerve was transposed to the slow soleus muscle outside the original innervation band. Formation of new neuromuscular junctions was induced by cutting the soleus nerve after different periods of time. The morphological maturation of these junctions was studied by electron microscopy.New neuromuscular junctions do not form when the original innervation is left intact.Three to five days after denervation, vesicle-laden terminal boutons contact muscle fibers with only the basal lamina of the latter intervening. Three weeks after denervation, most boutons are larger and postsynaptic folds are present, although younger stages are also seen. Sixteen weeks after denervation, the neuromuscular junctions appear mature. This corresponds well with electrophysiological findings in the same material.The fully developed neuromuscular junctions sixteen weeks after denervation possess postsynaptic folds similar to those of normal fast muscle fibers. This suggests that the fast fibular nerve rather than the slow soleus muscle fibers determines the morphology of the postsynaptic folds.Possible trophic neuromuscular interactions are discussed.The authors are indebted to Mrs. Jorunn Line Vaaland, Miss Bjørg Riber, and Miss Berit Branil for technical assistance. Dr. T. Lømo and Dr. C. Slater have contributed constructive criticism and advice     

The relationships between the structure of paddy levees and the plant species diversity in cultural landscapes on the west side of Lake Biwa,Shiga, Japan

Paddy levees form networks of narrow linear habitats and play various roles in cultural landscapes. Traditional landscapes on the west side of Lake Biwa consist of paddy field terraces and both stone and soil levees that have been maintained by paddy field management using local resources. Paddy levees in this study site are principally classified into five different types. Our study points out how differences in paddy levee structure as well as in management practices influence the plant species. Seventeen paddy levee transects were split into four habitat types based on their species components by TWINSPAN. Spatial characteristics and physical structures of paddy levees depended on natural conditions and human activities. The species–area curves of each levee type showed a clear distinction: the soil, stone and abandoned curves were steep, while the concrete and consolidated ones were gentle. The vegetation on consolidated levees was utterly different from the vegetation on traditional levee types from the aspect of species richness and species components. Soil type levees contained various woody plant species and included more diverse and indigenous plant species than abandoned type levees.     

Das organische Gerüstwerk der Kalkschale des Schwanen-Eies

Zusammenfassung Kegel und Säulen der Schwanen-Eischale hinterlassen am Querschliff nach Entkalkung mit EDTA organisches (mucoproteides) Material als ein zusammenhängendes Gerüst, das sich mit Thionin metachromatisch färbt; ohne Demineralisierung oder wenigstens Anätzung bleibt Thionin an Schliffen und Bruchkanten der Schale wirkungslos. Das Lichtmikroskop zeigt an Schliffen nichts von dem organischen Material, es wurde während des Kristallwachstums fein zerteilt in Gitterlücken des Schalencalcits eingeschlossen. Es findet sich am stärksten angehäuft an den äueren und inneren Oberflächen der Kristall-individuen. In den Kegeln ist das Gerüst radial ausgebildet als die Loculi der Keile, und konzentrisch geschichtet, entsprechend den Lagen der Globularinklusionen, um deren jede herum Verdichtung der organischen Substanz statthat. In den inneren Säulen folgt das organische Gerüst dem Rhombenmuster; die äueren Säulen sind arm an organischer Substanz, hier verbleibt nach der Entkalkung eine dünne laterale Oberflächenschicht.

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Summary The cones and columns of the swans egg shell leave behind after decalcification with EDTA an organic (mucoproteid) material in form of a continuous frame work stainable metachromatically with thionine. Without demineralisation or at least etching, thionine proves ineffectual in ground sections or breaking edges of the shell. In ground sections the light microscope demonstrates nothing of the organic material: it was inclosed during the crystal growth in submicroscopical lattice gaps of the calcite individuals. The organic material is chiefly accumulated in the outer and inner surfaces of the crystals. In the cones the organic frame work is developed radially as the loculi of the wedges and concentrically layered corresponding with the globular inclusions, concentrated in the circumference of each. In the inner columns the organic material follows to the rhomb pattern. The outer columns after decalcification only leave behind a thin lateral organic sheath.

     

Quantitative relationship between active sodium transport,expansion of endoplasmic reticulum and specialized vacuoles (“scalloped sacs”) in the outermost living cell layer of the frog skin epithelium (Rana temporaria)

Summary When an isolated frog skin (Rana temporaria) is exposed to a hydrostatic pressure difference between inside and outside bathing solutions (inside pressure higher than outside) of 20–50 cm of H₂O and if under these conditions the skin is short-circuited electrically, small vacuoles appear light-microscopically in the outermost living cell layer in the epithelium. The number of such vacuoles shows a linear dependency on the rate of active sodium transport as measured by the short-circuit current. Electron-microscopically, the vacuoles are interpreted as previously undescribed organelles, the scalloped sacs which are about 0.5 in diameter, with a wrinkled surface and bounded by a unit membrane. This organelle is in intimate contact with sacs and tubules of smooth endoplasmic reticulum. The observed increase in the number of scalloped sacs usually is accompanied by a significant expansion of the whole system of endoplasmic reticulum. Some of the vacuoles seen light-microscopically must indeed be expanded cisternae of endoplasmic reticulum. The findings are discussed in light of the possibility that the scalloped sacs and the endoplasmic reticulum may be involved in active transport of sodium ions.     

X-ray microanalysis of calcium binding sites in Paramecium

Summary In Paramecium cells Ca⁺⁺-stimulated triggering of the exocytosis of secretory vesicles (trichocysts) was achieved by ionophores X-537 A or A 23187. Under triggering conditions electron dense deposits were present in some resting trichocysts and regularly in discharging trichocysts; upon subsequent fixation deposits occurred on the trichocyst membrane (on the inner side or within the membrane) and on the inner lamellar sheath from where deposits seemed to radiate into the secretory materials. Similar results were obtained with glutardialdehyde fixation alone which also triggers exocytosis but only at low concentrations. Element analysis by energy dispersive x-ray microanalysis ascertained the presence of Ca and P in deposits occurring in trichocysts. Those resting trichocysts which were devoid of deposits did not contain Ca or P enriched. Hence, an abrupt Ca⁺⁺-influx into individual trichocysts just before exocytosis seems to be involved in the triggering mechanism, possibly in combination with the sudden activation of an ATPase systemlocalized at those sites of the trichocysts which primarily contain the deposits. When paramecia were treated only with Ca⁺⁺ and then fixed with OsO₄ plus oxalate or merely with glutardialdehyde, electron scattering deposits were formed also on the inner side of the cell membrane and within the ciliary shaft (but rarely in trichocysts). Deposits obtained on cilia (including ciliary granule plaques) also contained Ca, P and S. Cells contain osmiophilic calcium-storing vacuoles which were selectively rich in Ca and S but devoid of P.     

Triggering and predisposing factors in the “Red” decline syndrome of Norway spruce (Picea abies)

Summary Analysis of 62 mature Norway spruce (Picea abies provenance Viborg) trees growing in a Danish plantation was undertaken along with analysis of their nutrient contents (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B and Na), in each of the three youngest needle age classes, from branches of four exposure directions near the tree top. The aim was to investigate if one among the studied possible predisposing factors was also a triggering factor in the 1989 outbreak of the Red Norway spruce decline in Denmark. Neither nutrient imbalance or deficiency, nor excessive N-deposition or salt-stress were indicated as triggering factors in 1989. The Red syndrome, noticeable for the bright red colour of the current-year needles, was found to be an extension of the European type Novel Decline. Red syndrome is similar to previously reported phenomena of top-dying and sub top-dying, in that it had fewer needle age classes and significantly higher contents of mobile cations (and Ca) in the younger needle classes. Tree ring analysis suggested that the Red syndrome was initiated in the early 1980s, when the trees experienced adverse climatic conditions. Because of this long-term development of the Red Norway spruce decline syndrome, it is concluded that a triggering factor is of minor importance relative to the multitude of predisposing factors.     

Some observations on the fine structure of the myotendinous junction in myotomal muscles of the tadpole tail

Summary Myotendinous junctions in the myotomal tail muscles of the tadpole of Rana rugosa were examined by electron microscopy. At the site of the myotendinous junction, the sarcolemma is covered on its sarcoplasmic aspect by the connecting filament layer and the attachment layer, and on the extracellular aspect by the intermediary layer and the external lamina, with associated collagen fibrils. The intermediary layer consists of filamentous structures which closely resemble microfibrils (Hanak and Böck, 1971), spine-like or thread-like profiles (Korneliussen, 1973) and intermediary layer (Nakao, 1975a, b) in the myotendinous junctions of other vertebrate skeletal muscles.Particularly interesting is the fact that all the coverings and linings of the sarcolemma, including the external lamina, are completely absent in the terminal segment of the finger-like sarcolemmal invagination characteristic of the myotendinous junction. Furthermore, special types of coupling between a sac of sarcoplasmic reticulum and a part of the sarcolemmal invagination are frequently observed. These couplings always occur along the region of the sarcolemma where the external lamina is absent. The couplings show features similar to those of the triad, such as SR feet , scalloped SR membranes and granular content of the SR sac, suggesting that they are analogous and functionally similar to the triad and other equivalent structures.     

A model for light adaptation: Producing Weber's law with bleaching-type kinetics

An adaptation model having two stages is introduced and its mathematical properties are examined. The two stages are the adaptive process (parameter K _b), which has bleaching-type kinetics, and the response function (parameters K _r and n), which incorporates response saturation. In order to study the increment threshold functions generated by the adaptation model the concept of a detector is required. It is demonstrated that without an adaptive process the compression hypothesis, in the form of the difference equation, produces increment threshold functions which saturate and do not obey Weber's law. It is then shown that an adaptive process with bleaching-type kinetics can prevent saturation and produce Weber's law behavior provided that the adaptive strength of the system exceeds the detector sensitivity.     

Model of neural visual system with self-organizing cells

This paper describes a model of a neural visual system of a higher animal, in which the capability of pattern recognition develops adaptively. To produce the adaptability, we adopted self-organizing cells, and with them modeled feature-detecting cells which were discovered by Hubel and Wiesel and whose plasticity was found by Blakemore and Cooper. Combining the self-organizing cells and the learning principle of a Perceptron-type system, we constructed a model of the whole visual system. The model is also equipped with an eye movement control mechanism for gazing, which reduces the number of selforganizing cells required for pattern recognition, thus contributing to their quick self-organization. Computer simulation and an experiment using a hardware simulator showed that self-organizing cells quickly become sensitive to the features often seen and that the resulted system can classify patterns with a rather small number of feature-detecting cells.     

Elektronenmikroskopische Untersuchungen über Bildung und Struktur der Zygotenwand beiMicrasterias papillifera (Desmidiaceae)

Zusammenfassung Die Feinstruktur von Mesospor und Endospor reifer Zygoten vonMicrasterias papillifera wurde untersucht. Das für die Resistenz der Zygoten gegenüber ungünstigen Umweltbedingungen wichtige Mesospor besteht aus vier Schichten von unterschiedlicher Elektronendichte. Es ist insgesamt 460–500 nm dick. Die Schichten Mes a und Mes c bestehen aus akkrustierten, dicht gepackten globulären Elementen eines Stoffes, der dem Sporopollenin ähnlich ist. Die Schicht Mes b zeigt ein fibrilläres Grundgerüst, wahrscheinlich aus Zellulose, in das Stoffe inkrustiert sind, die nicht mit denen der Schichten Mes a und Mes c identisch, aber gegen Abbauversuche ähnlich résistent sind.Die Schicht Mes d ist eine Übergangsschicht zum Endospor. Zwischen die Zellulose-Mikrofibrillen in Streutextur sind isolierte Partikel des Materials der Schicht Mes c eingestreut. Das etwa 650 nm dicke Endospor ist eine Zelluloseschicht mit Streutextur. Es wird als Wand der sogenannten Keimblase bei der Zygotenkeimung nach Sprengung von Exospor und Mesospor stark gedehnt.

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Electron microscopical investigations on the structure and formation of the zygote wall inMicrasterias papillifera (Desmidiaceae) II. The structure of the mesospore and the endospore

Summary The mesospore (460–500 nm thick) which is responsible for the resistance of the zygote against desiccation during its resting period, consists of four layers of different electron density. The layers Mes a and Mes c are composed of densely packed amorphous globular elements of a substance resembling sporopollenine. The layer Mes b has a fibrillar, probably cellulosic frame. It is incrusted by a substance which is not identical with that of Mes a or Mes c but which shows a comparable resistance against degradation.The layer Mes d contains isolated particles such as in Mes c and cellulose microfibrils of the endospore. The endospore (650 nm thick) has foliate texture. This layer surrounds the protoplast after it has escaped from the ruptured exospore and mesospore during zygospore germination.

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Der Deutschen Forchungsgemeinschaft dank ich f:ur Sachbeihilfe.     

Niche,habitat, and related ecological concepts

Summary Darwin's phrase place in natural economy, andSpencer's term correspondence can be regarded as first attempts to express the organism-environment relationships. The same concept has more recently been approached from the point of view of (1) life-form, (2) external activities, and (3) habitat. Though all these points are interlocking, they have been stressed differently in the writings of American and European ecologists. It is proposed that the term niche would be most useful and rational if applied to the total of relationships between a living organism (population, species) and its complete environment, both biotic and abiotic.