Fungi,leaves, and the theory of island biogeography

Species dynamics of fungi (filamentous fungi and yeasts) on apple leaves were studied within the framework of the theory of island biogeography by following immigration and extinction patterns on individual apple leaf islands over time. Total fungi were censused on unmanipulated leaves collected throughout two seasons; filamentous fungi only were monitored additionally for several weeks in one season on newly created, axenic, model (seedling) islands introduced to the orchard, and on surface-sterilized, preexisting leaves. Analyses based on both the natural and the surface-sterilized systems showed that an equilibrium in species number was reached and turnover in species composition occurred in both. Immigration and extinction events were strongly related to number of species present on each island. The balance between immigration and extinction implies that species number on leaves and real (oceanic) islands is determined by a common mechanism, and emphasizes the need to regard leaf microbial communities as dynamic.     

Experiments on the water budget of densely and sparsely needled spruces [Picea abies (L.) Karst.] in a declining stand

Summary The osmotic potentials of needles were compared from numerous trees that had been classified according to needle loss along an altitude profile. With the increasing degree of damage of the trees, the maximum and minimum values deviated more strongly above and below the common mean of all samples. The level of water content of the needles unequivocally reflected the vitality of the trees. Experiments covering a whole vegetation period were performed on a tree pair selected from a natural stand. They were designed to demonstrate differences in water balance between the healthy and damaged state of the trees. For the damaged tree, measurements of the water potentials of single needles showed a greater reduction of potential during the course of the day compared to the healthy tree. Recovery in the evenings was slower and often incomplete. The osmotic potentials of damaged and healthy shoots measured in individual needles also differed both predawn and especially after transpiration stress. Depending on weather and soil desiccation, the differences were more or less pronounced. In the damaged tree, the rises in potential after saturation of the twigs fell far short of the healthy tree. Reduction of water potential, osmotic potential and relative water content under comparable stress conditions suggest a reduced tolerance of drought by damaged trees. In the context of earlier experiments this result was ascribed to a lack of stomatal control, and long-term pollution effects were thus explained as a specific disturbance of hydroregulation.     

Electron microscopic and cytochemical study on the role of Golgi elements and plasma membrane of enterocytes in the intestinal lipid transport

Summary Intestinal lipid absorption and transport were investigated in albino rats. The observations point towards the existence of a continuity between plasma membrane invaginations and elements of the Golgi complex on its mature face. They also suggest a segregation of lipid droplets by paired Golgi membranes and plasma membrane invaginations. The following way for lipid transport is deduced: lipid droplets moving inside the smooth endoplasmic reticulum accumulate progressively and are condensed in Golgi cisternae of the forming face. Their limiting membrane ruptures and liberated lipid droplets are segregated by paired Golgi membranes of the mature face or by plasma membrane invaginations. Subsequently the inner of the two segregating membranes disappears while the lipid droplet is moved towards the intercellular space inside a canal communicating with this space. The suggestion is made that the Golgi apparatus is of double origin: one component representing a terminal plication of the endoplasmic reticulum; the second one—a terminal plication of the plasma membrane invagination. This concept explains the ultrastructural and histochemical differences between Golgi membranes of the forming and mature faces of the complex.     

Charles Darwin's theory of evolution: A review of our present understanding

The paper characterizes Darwin's theory, providing a synthesis of recent historical investigations in this area. Darwin's reading of Malthus led him to appreciate the importance of population pressures, and subsequently of natural selection, with the help of the wedge metaphor. But, in itself, natural selection did not furnish an adequate account of the origin of species, for which a principle of divergence was needed. Initially, Darwin attributed this to geographical isolation, but later, following his work on barnacles which underscored the significance of variation, and arising from his work on botanical arithmetic, he supposed that diversity allowed more places to be occupied in a given region. So isolation was not regarded as essential. Large regions with intense competition, and with ample variation spread by blending, would facilitate speciation. The notion of place was different from niche, and it is questioned whether Darwin's views on ecology were as modern as is commonly supposed. Two notions of struggle are found in Darwin's theory; and three notions of variation. Criticisms of his theory led him to emphasize the importance of variation over a range of forms. Hence the theory was populational rather than typological. The theory required a Lamarckian notion of inheritable changes initiated by the environment as a source of variation. Also, Darwin deployed a use/habit theory; and the notion of sexual selection. Selection normally acted at the level of the individual, though kin selection was possible. Group selection was hinted at for man. Darwin's thinking (and also the exposition of his theory) was generally guided by the domestic-organism analogy, which satisfied his methodological requirement of a vera causa principle.     

Immature erythroid cells with novel morphology and cytoskeletal organization in adultXenopus

Summary Nucleated erythrocytes of non-mammalian vertebrates are a useful model system for studying the correlation between changes in cell shape and cytoskeletal organization during cellular morphogenesis. They are believed to transform from spheres to flattened discs to ellipsoids. Our previous work on developing erythroblasts suggested that pointed cells containing incomplete, pointed marginal bands (MBs) of microtubules might be intermediate stages in the larval axolotl. To test whether the occurrence of such pointed cells was characteristic of amphibian erythrogenesis, we have utilized phenylhydrazine (PHZ)-induced anemia in adultXenopus. In this system, circulating erythrocytes are destroyed and replaced by erythroblasts that differentiate in the blood, making them experimentally accessible. Thus, we followed the time-course of morphological and cytoskeletal changes in the new erythroid population during recovery. During days 7–9 post-PHZ, pointed cells did indeed begin to appear, as did spherical and discoidal cells. The percentage of pointed cells peaked at days 11–13 in different animals, subsequently declining as the percentage of elliptical cells increased. Since degenerating old erythrocytes were still present when pointed cells appeared, we tested directly whether pointed ones were old or new cells. Blood was removed via the dorsal tarsus vein, and the erythrocytes washed, fluorescently tagged, and re-injected. In different animals, 2–8% of circulating erythrocytes were labeled. Subsequent to induction of anemia in these frogs, time-course sampling showed that no pointed cells were labeled, identifying them as new cells. Use of propidium iodide revealed large nuclei and cytoplasmic staining indicative of immaturity, and video-enhanced phase contrast and anti-tubulin immunofluorescence showed that the pointed cells contained pointed MBs. The results show that pointed cells, containing incomplete, pointed MBs are a consistent feature of amphibian erythrogenesis. These cells may represent intermediate stages in the formation of elliptical erythrocytes.Abbreviations MB marginal band - MS membrane skeleton - PHZ phenylhydrazine     

Allospecific T cell recognition of HLA-A2 antigens: Evidence for group-specific and subgroup-specific epitopes

Interleukin 2-dependent alloreactive cytotoxic T cell lines, with activity predominantly directed against the HLA-A2 antigen, have been generated in vitro by stimulating blood mononuclear cells from donors nonimmune to the Epstein-Barr (EB) virus with appropriate numbers of EB virus-transformed B cells from A2-homozygous individuals. Such effector cells were tested against a panel of EB virus-transformed target cell lines all expressing the serologically defined A2 antigen but typed into common A2 and variant A2 subgroups on the basis of their recognition by A2-restricted EB virus-specific cytotoxic T cells. Variant A2 responder cells cocultivated with common A2-bearing stimulators gave rise to effector T cell lines which recognized only the common A2-bearing subgroup of targets. By contrast, responder cells from A2-negative donors stimulated with common A2-bearing cells produced effector T cell lines in which the strong lysis of common A2-bearing targets was accompanied by a lower, but still significant, lysis directed against all targets within the variant A2 subgroup. In both cases, lysis of the target cells was blocked equally well by the anti-A2-specific monoclonal antibody MA2.1 as by the monoclonal antibody W6/32 specific for HLA-A, -B, and -C determinants. This suggests that HLA-A2 molecules possess at least two distinct sets of epitopes capable of inducing alloreactive T cell cytotoxicity: first, epitopes probably associated with T cell-restricting sites, which generate subgroup-specific responses, and second, epitopes shared by all A2 molecules, and perhaps associated with serologically defined sites, which generate pan A2 group-specific responses.Abbreviations used in this paper EB Epstein-Barr - IL-2 Interleukin 2 - UM unfractionated mononuclear - AET aminoethylisothiouroniumbromide hydrobromide     

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.

     

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.     

Einige Bemerkungen über die Ersatzgeschlechtstiere vonReticulitermes

Zusammenfassung An Laboratoriumszuchten vonReticulitermes lucifugus Rossi undReticulitermes flavipes Kollar (aus den Hamburger Befallsgebieten) werden Beobachtungen zur Biologie der Ersatzgeschlechtstiere mitgeteilt. Für die Durchführung dieser Beobachtungen wurden besondere Schaunester eingerichtet. Folgende Punkte der beobachteten Verhaltensweisen werden hier hervorgehoben: Die Nymphen der Ersatzgeschlechtstiere sammeln sich stets in Herden von 80–100 Einzeltieren und werden von einer Gruppe Arbeiter (als Hütehunde) bewacht. Die Arbeiter halten die Nymphen auf einem engen Raum zusammen und versuchen andere Nestgenossen von den Nymphen fernzuhalten. Alle ein bis zwei Tage wechseln die Herden ihren Standort. Das Weiterziehen geschieht gleichfalls in Form von Herden.Die Ernährung der Nymphen geschieht auf stomodealem Wege durch die Arbeiter. *** DIRECT SUPPORT *** A0180089 00007     

Recurrent inversion of visual orientation in the walking fly,Drosophila melanogaster

Summary Movement-induced visual orientation in flies depends largely upon predictable responses which establish simple optomotor balance or complex pseudo search in the appropriate visual environment. Less conspicuous course diverting spontaneous actions of the flies become important in pattern-induced visual orientation. The apparently stochastic spontaneous actions of the houseflyMusca domestica still allow powerful probabilistic predictions of orientation during stationary flight (Reichardt and Poggio 1981). The predominance of non-stochastic spontaneous actions such as body saccades, focussing and shift of visual attention, plasticity of response components etc. in the fruitflyDrosophila melanogaster (Heisenberg and Wolf 1979–1980) accounts for complementary behavioural options which reduce the relevance of probabilistic predictions of orientation in this fly.The conjecture of complementary options is based on a striking antagonism between orientation towards a visual object (fixation), and orientation in the opposite direction (anti-fixation), in the walking fly. Forced choice in a multiple-Y-maze quite definitely elicits fixation in the wild type, and antifixation in the optomotor blind mutantomb ^H31 (Fig. 3). However, these effects cannot be attributed to a continuous predominance of attraction in the wild type and repellence in the mutant. This is shown under comparable conditions of free choice in an arena: The flies of either strain alternate between fixation and anti-fixation of an inaccessible visual object (Fig. 4a), and keep running to and fro between two of these objects in Buridan's paradigm (Fig. 4b, c), even if the objects are not alike (Fig. 4d). The sequence of approach, retreat and transition may be repeated a few thousand times to the point of exhaustion (Fig. 5). The process resembles the recurrent alternation of ambiguous figures such as the Necker cube in human perception. The recurrent transition between competitive objects counteracts the accumulation of spontaneous preferences, and is likely to explain the apparent lack of pattern-discrimination under operant and non-operant conditions of continued free choice inDrosophila. The conspicuous dichotomy of fixation and anti-fixation in the same environment is, as yet, incompatible with the phenomenological theory of visually controlled orientation in larger flies.Abbreviation S.E.M. standard error of the mean     

Taurine- and FMRFamide-dependent modulation of receptor- and voltage-gated currents by cerebrolysine in molluscan neurons

The action of cerebrolysine, a biogenic stimulator, on the receptor- and voltage-gated ionic currents was studied in identifiedHelix pomatia neurons. Cerebrolysine reversibly suppressed the acetylcholine (ACh)- and glutamate (GLU)-induced chloride currents in some neurons (LP11, B4, E12) with a latency of 9±3 sec, while not affecting these currents in other neurons. The suppressing effect of cerebrolysine on the voltage-gated sodium and calcium currents was also selective. There were fast and slow phases, with latencies of 52±8 sec and 5±1 min, respectively, in the cerebrolysine effect on the voltage-gated sodium current. The effect of cerebrolysine on the sodium current during the fast suppression phase could be simulated with FMRFamide (10^–5 M), while those exerted on the ACh- and GLU-induced currents could be simulated with taurine (10^–6 M). The effects of cerebrolysine and the above substances were non-additive. These facts allow us to suggest that both taurine and FMRFamide (or its fragment) are involved in the mechanism of posttraumatic and postsurgical curative effects of cerebrolysine.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 190–196, May–June, 1994.     

The supramolecular organization of red algal cell membranes and their participation in the biosynthesis and secretion of extracellular polysaccharides: a review

Summary The relationship between the supramolecular organization of red algal cell membranes and the biosynthesis and secretion of the cell wall skeletal and matrix polysaccharides is reviewed. Freeze-fracture studies have revealed that organized macromolecular structures — linear terminal complexes and tetrads — are present on the plasma membrane and on membranes of the endomembrane system. The linear terminal complexes seem to be involved in the biosynthesis, assembly, and orientation of the cellulose microfibrils and the tetrads in the synthesis of the matrix polysaccharides. It is shown how the research on the supramolecular organization of cell membranes has increased the knowledge on the biosynthesis and secretion of the extracellular crystalline and non-crystalline polysaccharides in red algae. In this review, the progress to date is discussed.Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

Line source models for active fibers

It is shown that the utility of usual circular line source models is highly questionable. A line source model related to arbitrary cross-sections is given and essential differences between the source strength of the circular and non-circular model are found in the case of fairly flat elliptic fibers.     

Effect of Intercalators on the Properties of Liquid-Crystalline Dispersions of Nucleic Acid–Chitosan Complex

Molecules of deoxyribonucleic acid and synthetic polydeoxyribonucleotides (NA) in the particles of liquid-crystalline dispersions resulting from interaction with chitosan are accessible to interaction with intercalators. The intercalation is accompanied by alteration in the direction of spatial twist of cholesterics of NA–chitosan complexes. This effect is absent in the case of classical cholesterics produced from NA molecules via phase exclusion, i.e., the cholesteric structure of NA–chitosan complex is very labile as distinct from classical cholesteric NA.     

Biometeorological comfort index

The paper aims to represent and scale biometeorological sensations through a thermal index which comprises the effects of temperature, humidity and wind. The cooling power of a measured combination of wind speed and air temperature is equated with that due to the combination of a reference wind speed (related to the air movement experienced by a person walking in still air), and a derived aerodynamic temperature. A biometeorological temperature which is the average of such an aerodynamic temperature and a conventionally measured wet bulb temperature is shown to afford a better measure of comfort in Spain than some other, alternative indices.     

Further cytogenetic analyses of the Croatian triploid shallot “Ljutika” (Allium cepa var.viviparum, Alliaceae) and its comparison with the Indian triploid “Pran”

Feulgen and silver-stained karyotypes and meiosis of two triploid viviparous onion forms (Allium cepa var.viviparum), the Croatian Ljutika and the Indian Pran, were comparatively analyzed. The results of chromosome measurements show that Ljutika and Pran are karyologically not identical, although significant similarities were found in the morphology of their chromosomes. Five geographically distant clones of Ljutika showed good agreement in the number and gross morphology of the chromosomes and in the number and position of NORs and interphase nucleoli. Heterotrivalents were predominant in meiosis of Ljutika but a relatively high frequency of higher multivalents together with univalents and bivalents were also observed. The relationship between Ljutika and Pran and their possible origin are discussed.     

Differential immunostaining for substance P in Huntington's Diseased and normal spinal cord: significance of serial (optimal,supra-optimal and end-point) dilutions of primary anti-serum in comparing biological specimens

Summary Using immunocytochemistry (ICC), the number of immunoreaction products (IRPs) visualized for the peptide substance P (SP) appears reduced within the human spinal cord (also substantia nigra) taken at autopsy from cases diagnosed with Huntington's disease (HD) compared with the non-HD cases (Vacca 1983). The reductions of SR-IRPs become apparent in the HD specimens when primary anti-SP serum is applied to the tissue sections at supra-optimal dilutions; that is, dilutions greater than the optimal dilutions which visualize maximal numbers of SP-IRPs and concomitantly give maximal staining intensity. Curiously, the application of optimal dilutions to the HD and non-HD specimens visualizes equivalent numbers of SP-IRPs; therefore, the qualitative and quantitative differences between the specimens become masked. Applying supra-optimal dilutions of the anti-SP serum unmasks the difference, and also reveals different end-points for the immunostain deposited in each type of specimen. In both the HD and non-HD specimens, two sizes of SP-IRPs could be identified, large (3 m) and small (0.7 m). Presumably they mark two different categories of axons defined by caliber (e.g.; C-type and A ), or origin (e.g., sensory intrinsic, or supraspinal). Alternatively the large SP-IRPs label tangentially-cut or large axons and nerve terminals. In the present report, counts of the large and small SP-IRPs visualized in the HD and the non-HD specimens have been plotted against the serial dilutions (optimal, supra-optimal and endpoint) of the primary anti-SP serum used for ICC. The graphs which result, describe a titration curve characteristic for the large SP-IRPs in each specimen. Applying supra-optimal dilutions of the primary antibody, causes the numbers of large and small SP-IRPs to decrease differentially. The numerical decrease probably largely reflects the concentration of immunoreactive antigen in different anatomic or metabolic tissue compartments. Alternatively, or perhaps to a lesser degree, the small and large SP-IRPs represent cross-reacting components which have different staining end-points, and may have biological significance in HD. Criteria are given for the proper use of ICC, and have significance regarding the use of commercial kits especially for pathological diagnosis.     

On the heterogeneity of the slow reassociating (“unique”) DNA

Summary The slow reassociating fraction of mouse DNA (unique DNA), when allowed to reassociate in 0.14 m sodium phosphate buffer at 50 °C showed a biphasic melting curve with a transition at 78–80 °C. On the basis of this feature, the slow reassociating DNA was separated preparatively into two fractions: unique DNA I and II. Their duplexes showed differences with respect to thermal stability, S1 nuclease resistance and rate of reassociation. About one third of the sequences in each fraction were fraction-specific. The conclusion was drawn that for unique DNA I these should be the low repetitive or single copy related sequences (multigene families) and for unique DNA II—the unrelated single copy sequences or recent families of low repetitive not yet diverged sequences.     

Psychological changes associated with self-regulatory treatments of irritable bowel syndrome

The psychological side effects of self-regulatory treatment (a combination of relaxation, thermal biofeedback, and cognitive therapy) for irritable bowel syndrome (IBS) were compared among 20 successfully treated patients, 12 unsuccessfully treated patients, and 9 patients who merely monitored symptoms for 12 weeks. Pretreatment and posttreatment scores on the Beck Depression Inventory, State-Trait Anxiety Inventory, and Psychosomatic Symptom Checklist were examined. Successfully treated patients had significant (p<.01) reductions on all measures and significantly greater reductions on depression and state anxiety than the symptom monitoring group. Interestingly, the failures also showed a significant (p=.027) reduction in trait anxiety and no significant increases on other measures.     

Die Richtungen des Nahrungsflusses im Darmtrakt der Kleinzikade Euscelidius variegatus KBM. (Jassidae)

Zusammenfassung Der Verlauf des Nahrungsflusses im Darmtrakt der Kleinzikade Euscelidius variegatus wird nach Verfütterung von farbstoffhaltiger Nährlösung ermittelt. Es wird der Beweis erbracht, daß die aufgenommene Nahrungsmenge in der Filterkammer geteilt wird und die beiden Anteile den Darmtrakt auf zwei verschiedenen Wegen in Richtung Rektalblase passieren. Ein Anteil der aufgenommenen Nährlösung wird über einen Kurzschlußweg in der Filterkammer sowohl über den Filterkammerdarm als auch über die Kryptonephridien direkt in den Enddarm gepumpt, während die in der Magentasche der Filterkammer verbleibenden Nahrungsanteile über einen langen Verdauungsweg zum After gelangen. Hierbei wird der Magentascheninhalt in den Magen gedrückt. Von dort aus passiert er den Mitteldarm und erreicht über den Enddarm den After. Der Kurzschlußweg und der Verdauungsweg können gleichzeitig benutzt werden. Der Kurzschlußweg wird von der Nahrung jedoch in viel kürzerer Zeit durchströmt als der längere Verdauungsweg.

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The directions of the flow of food in the alimentary trad of the leafhopper Euscelidius variegatus KBM. (Jassidae)

Summary The leafhopper Euscelidius variegatus is fed with synthetic food, coloured with 1% Azorubin-S. Its flow in the alimentary tract has been studied. It has been found that the sucked-in food is divided into two parts in the filter chamber, each taking different way in the alimentary tract for its flow. One part of the food is pumped into the hindgut via the short circuit way going through the filter chamber once over the Filterkammerdarm and also over the kryptonephries. That part of the food, which remains in the pocket of the filter chamber takes the long digestion way to the anus over stomach, midgut and hindgut. Both the ways could be used at the same time. But the food takes much shorter time for its passage through the short circuit way as compared to the time needed for the long digestion way.