The propagation and dispersal of misinformation in ecology: Is there a relationship between citation accuracy and journal impact factor?

The biological and physico-chemical structure of near bottom habitats located under densely growing submerged vegetation, and their significance in the functioning of whole aquatic ecosystems, are very little known due to difficulties in sampling. Corer-type samplers, believed to be the best in littoral studies, do not work properly in such places, because their tube opening is easily clogged by plant shoots, acting as a stopper. In order to overcome this problem, an alteration to the shape of the tube ending is proposed. This can be done by its trimming at an accurate angle, or by fitting (permanently or interchangeably) a metal collar made of stainless steel to its end, so that the ending would resemble the shape of a needle. The modification can be applied to virtually all corer samplers. It was found to be efficient while sampling sediment cores for the purposes of both hydrobiological and paleolimnological studies on heavily overgrown macrophyte-dominated water ecosystems.     

Silage studies IX biochemical changes in microbe-free silage

Summary If the aseptic plant material is regarded as a substrate for preservative microbial activity, it may be said that both the nitrogen and carbohydrate components undergo changes due to the influence of native enzymes in the plant material. These changes may very well be reflected in the microbial activity in a silage.It is interesting to compare the findings of this investigation, which show that during the days immediately after ensilage practically no changes take place when no bacteria are present. In a non-sterile ensilage, on the other hand, it is during this early stage that the briskest bacterial activity takes place.The chances of, say, an acid-forming microbial process actually lowering the pH in order that preservation of the material may take place are directly counteracted by the action of native enzymes of the vegetable material. During the days immediately after ensilage, however, if other conditions are favourable, microbial activity may clearly determine the whole course of events, and may possibly even inactivate the processes of the plant material itself.As is evident from the experiments described above, the activities inherent in the ensiled material itself are of no mean proportions. Further study of the mutual relationship of the ensilage and the various microbial fractions is therefore particularly necessary in order to be able to understand a number of processes of fundamental importance in biological preservation of plant material.     

Ontogeny of hormone-secreting cells of the rat pituitary gland: An immunocytochemical study on dissociated cells

Summary An immunocytochemical study was undertaken in foetal, prepubertal and mature rats to determine the time of differentiation of various types of adenohypophyseal cells during development. Freshly dissociated pituitary cells from foetal (18–21 days postconception), neonatal (from birth up to 30 days) and adult rats (more than 8 weeks) were characterized using immunocytochemical methods. All types of hormone-producing cells were present at day 18 postconception, although only 20% of the cells were immunolabelled. Adrenocorticotropin (ACTH)-secreting cells accounted for the highest number of hormone-positive cells. Growth hormone-secreting cells increased remarkably from day 18 postconception onwards. Prolactin-secreting cells were not seen in the foetal adenohypophysis and did not start to increase until 10 days after birth, whereas by that time the number of ACTH, thyrotropin, follicle-stimulating and luteinizing hormone-secreting cells had stopped increasing. By day 30 after birth, 80–95% of the cells were immunoreactive.     

Butyrophilin,an apical plasma membrane-associated glycoprotein characteristic of lactating mammary glands of diverse species

Lipid globule membranes were isolated from human and bovine milk and from the milk of sheep, goat, pig, rat and guinea pig, and their polypeptide compositions were analyzed. The major polypeptides with molecular weights similar to that of bovine butyrophilin were separated by gel electrophoresis, isolated and characterized with respect to isoelectric point, molecular weight, immunological cross-reactivity and peptide composition after proteolytic cleavage. We show that in all species examined these proteins are similar to bovine butyrophilin in (i) their relative insolubility in buffers of low and high ionic strength and in non-denaturing detergents, (ii) the occurrence of several isoelectric variants, and (iii) patterns of peptides obtained by protease digestion. It is concluded that closely related proteins are major constituents of the cytoplasmic coat structures associated with milk lipid globule membranes of many species, and we propose the name butyrophilins for this group of proteins. Bovine and human butyrophilins are glycosylated with relatively large amounts of glucosamine, mannose, glucose and galactose but little fucose, sialic acids or galactosamine. Most if not all of the sugar residues are associated with an acetone-soluble peptide fragment of $\text{M}{}_{\mathrm{<mtext>r</mtext>}}$ 12 000–16 000 focusing at about pH 4.0. We suggest that this fragment contains a membrane-spanning peptide sequence and is involved in the attachment of the cytoplasmic coat to the membrane of the milk lipid globule.     

The effect of cardiotoxin on (Ca2+ + Mg2+)-ATPase of the erythrocyte and sarcoplasmic reticulum

The effects of cardiotoxin on the ATPase activity and Ca2+-transport of guinea pig erythrocyte and rabbit muscle sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPase (E.C.3.6.1.3) were investigated. Erythrocyte (Ca2+ + Mg2+)-ATPase was inhibited by cardiotoxin in a time- and dose-dependent fashion and inhibition appears to be irreversible. Micromolar calcium prevented this inhibitory effect. Specificity for (Ca2+ + Mg2+)-ATPase inhibition by cardiotoxin was indicated since a homologous neurotoxin had no effect. Cardiotoxin did not affect (Ca2+ + Mg2+)-ATPase activity from sarcoplasmic reticulum, but Ca2+-transport was 50% inhibited. This inhibition was not due to an increased Ca2+-efflux and could be the result of an intramolecular uncoupling of ATPase activity from Ca2+-transport. Inhibition of Ca2+-transport by cardiotoxin could not be prevented by millimolar concentrations of Ca2+. It is suggested that the biological effects of cardiotoxin could be a consequence of inhibition of plasma membrane (Ca2+ + Mg2+)-ATPases.     

Versuche zur Frage der Erhaltungszüchtung beim Kulturchampignon

Zusammenfassung 1. Die Arbeit befaßt sich mit Fragen der Erhaltungszüchtung beim Kulturchampignon. Von den drei Möglichkeiten der Vermehrung, Mycelteilung, Gewebekultur und Aussaat, wird die Mycelteilung untersucht.2. Es wurden zu diesem Zweck Vielsporkulturen (viele Kerntypen) und Einsporkulturen (nur 2 Kerntypen) miteinander verglichen.3. Eine Ein- und eine Vielsporkultur wurden bei Kultur auf Agar-Nährboden fortlaufend durch Mycelteilung vermehrt. Während die Einsporkultur auch nach 40maliger Teilung keine Mycelveränderung zeigte, traten bei der Vielsporkultur nach 13maliger Vermehrung Degenerationserscheinungen in Form von langsam wachsendem belagartig anliegendem Mycel auf. Später bildete sich teilweise wieder schneller wachsendes Mycel.In Ertragsprüfungen zeigte die Vielsporkultur in der höchsten geprüften Vermehrungsstufe (27. V.) einen starken Ertragsabfall. Bei der Einsporkultur trat kein Ertragsrückgang ein.4. Beide Stämme wurden auch durch Überimpfungen von Körnern vermehrt. Nach achtmaliger Vermehrung war kein Ertragsabfall nachzuweisen. Der in einem zweiten Versuch mit der Einsporkultur allein festgestellte Ertragsrückgang nach 15 Vermehrungen konnte nicht statistisch gesichert werden.5. Von einer Schale der 22. Vermehrung der Vielsporkultur, die belagartige langsamwachsende und fädige schnellwachsende Sektoren enthielt, wurden von beiden Mycelarten Stücke abgeimpft. Es war dadurch möglich, die verschiedenen Wuchstypen voneinander zu trennen. Jedoch bildeten sich manchmal wieder fädige Sektoren im belagartigen Typ und umgekehrt. Insgesamt wurde sechsmal hintereinander Mycel der verschiedenen Typen abgeimpft (6 Teststufen).6. Die Trennung der verschiedenen Wuchstypen wird mit Kernentmischung erklärt. Die Frage bleibt offen, ob Kerne vom Typ des langsam wachsenden Mycels schon von der Aussaat an in der Vielsporkultur waren oder erst später durch Mutation oder Modifikation entstanden. In diesem Falle hätten sich die Degenerationserscheinungen genausogut in der Einsporkultur wie in der Vielsporkultur zeigen können.7. Daß die Entmischung unvollkommen war, liegt vermutlich an den großen Mycelstücken, die abgeimpft wurden. In Fortsetzung der Versuche wird mit zerkleinertem Mycel gearbeitet. Dann werden einzelne Zellen, die unter dem Phasenkontrastmikroskop als kernarm bestimmt wurden, übergeimpft.8. Vier Viel- und vier Einsporkulturen wurden in Wachstumstesten bei Auslese auf schnell- und lang-samwachsendes Mycel miteinander verglichen. Es wurden von jedem Stamm aus zehn Kulturschalen die am wenigsten durchsponnene Schale (l-Gruppe) und die am weitesten durchsponnene Schale (s-Gruppe) ausgelesen und vermehrt. Von der l-Gruppe wurde fünfmal hintereinander aus der am wenigsten durchsponnenen Schale, von der s-Gruppe genausooft aus der am weitesten durchsponnenen Schale Mycel auf zehn neue Schalen abgeimpft.Die Differenz zwischen dem durchschnittlichen Myceldurchmesser der l- und s-Gruppe war unterschiedlich und vergrößerte sich nicht mit der Zahl der Überimpfungen. Die l-Gruppen der Vielsporkulturen wuchsen immer langsamer als die s-Gruppen, während es bei den Einsporkulturen auch umgekehrte Fälle gab. Auch war die Differenz zwischen der l-und s-Gruppe im Mycelwachstum bei den Vielsporkulturen doppelt so häufig statistisch gesichert als bei den Einsporkulturen.Für die Erhaltungszüchtung kann daraus gefolgert werden, daß sich Vielsporkulturen bei Vermehrung durch Teilung leichter verändern können als Einsporkulturen.9. Mycelkulturen auf drei verschiedenen Nährböden (Biomalz-Agar, Weizen-Agar und Kompost-Agar) zeigten je nach Nährboden unterschiedliches Wachstum. Auf Biomalz-Agar wuchsen die Kulturen am langsamsten. Auf Kompost-Agar, dem nährstoff-reichsten der drei Nährböden, waren die Unterschiede im Aussehen des Mycels am deutlichsten ausgeprägt.Es wird über einige Arbeiten anderer Autoren berichtet, in denen ein großer Einfluß des Nährbodens auf das Mycel festgestellt wurde.Die Ursachen dieses Einflusses werden diskutiert.Für die Erhaltungszüchtung wird gefolgert, daß die Stammkulturen auf einem möglichst nährstoffreichen Substrat, z. B. Kompost, gehalten werden sollten.10. In Untersuchungen des schlecht wachsenden belagartigen Mycels auf Krankheitsbefall konnten weder Bakterien noch Schadpilze nachgewiesen werden. Die Virusteste (Fusionsversuche, Wärmeschock) fielen unterschiedlich aus. Das Material wird noch mit Hilfe der Elektronenmikroskopie genauer untersucht werden. Über das Ergebnis wird später berichtet.

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Experiments on maintenance of strains of the cultivated mushroomI. Propagation by mycelium transfer

Summary 1. The paper deals with problems of maintaining strains of the cultivated mushroom. There are three possibilities for propagation: Transfer of mycelium, tissue culture and multispore culture. Of these the transfer of mycelium was investigated.2. Multispore cultures (many types of nuclei) and monospore cultures (only two types of nuclei) were compared.3. Mono- and multispore cultures were continuously propagated on agar media by transfers of mycelium. After 40 transfers the monospore culture showed no change in the mycelium. In the multispore culture degenerative symptoms in the form of slowly growing, matted mycelium appeared after 13 transfers, though the faster growing mycelium reappeared later in some cases. After the last (27th) transfer tested, the multispore culture showed a strong decrease in yield; none was found in the monospore culture.4. Both strains were also propagated by grain transfer. After eight transfers there was no decrease in yield, and the one noticed after 15 transfers in a repeat experiment with the monospore culture proved to be statistically not significant.5. From a petri dish containing, after the 22nd transfer of the multispore culture, matted, slow growing and stringy, fast growing mycelia, pieces of both kinds were taken. Thus it was possible to separate the two types of growth. However, sometimes stringy sectors reappeared in the matted type, and vice versa. Mycelia of the different types were transferred six consecutive times.6. The separation of the various types is explained by a separation of types of nuclei. The question whether nuclei of the type of the slow growing mycelium were already present in the multispore culture before starting the culture or originated later by mutation or modification remains open.In case of a modification or mutation the degeneration symptoms could have occurred in the monospore culture as well as in the multispore culture.7. The reason for an incomplete separation could be the transfer of large pieces of mycelium. In further experiments disintegrated mycelium will be used. Then single cells selected under phase contrast microscope as poor in nuclei will be transferred.8. Four multi- and four monospore cultures were compared for growth rates by selection for fast and for slow growing mycelium. For each strain the least overgrown (l-group) and the most overgrown (s-group) were chosen from ten culture plates and subcultured by five successive transfers to ten fresh plates.The difference in average diameter of mycelium from the l-group and s-group varied and did not increase with the number of transfers. The mycelium of the l-groups of multispore cultures always grew slower than that of the s-groups; in monospore cultures the opposite also occurred. The difference between the l- and s-group in the multispore culture was twice as often significant as in the monospore culture. From this one can conclude that, in propagation with frequent transfer, multispore cultures change more easily than do monospore cultures.9. Mycelium cultures on three different media (biomalt agar, wheat agar, compost agar) showed different growth rates. The slowest growth was found on biomalt agar. On compost agar, richest in nutrients, the difference in appearance of the mycelium was most obvious. Papers by other authors who found a great influence of the medium on the mycelium and the reasons for this influence are discussed. For the maintenance of strains original cultures should be kept on a substrate rich in nutrients, i.e. compost.10. Tests for bacteria and fungi on slow growing, matted mycelium were negative. Tests for virus (fusion tests, heat shock) showed different results. Results of electron microscopic studies on this material will be reported later.

     

Determination of mercury in human serum and packed blood cells by neutron activation analysis

A method is described for the determination of mercury in human blood serum and packed blood cells employing neutron activation analysis. Great attention was devoted to the collection and manipulation of the samples. The accuracy and precision of the method were tested by analyzing biological reference materials and by comparing the concentrations measured in a number of serum samples to those obtained by another, independent technique (cold vapor atomic absorption spectrometry) in the same samples. The article reports the levels measured in blood serum and packed blood cells samples from 15 adult volunteers, as well as the figures determined in a “second-generation” biological reference material (freeze-dried human serum), prepared and conditioned at the University of Ghent.     

Using XAD resins to study the effects of reduced organic micropollutant concentrations in River Rhine and Meuse water on phytoplankton growth

Laboratory incubation experiments were used to study the effect of reduced concentrations of organic micropollutants in water from the rivers Rhine and Meuse on the specific growth rate of the river phytoplankton community. Before incubation, part of the water sampled was treated with XAD-4 and XAD-8 resins to absorb dissolved organic compounds. Four dilutions were made by mixing untreated water with XAD-treated water in the ratios 100:0 (control), 70:30, 40:60 and 0:100. The phytoplankton specific growth rate increased significantly with the increased fraction treated with XAD in all but one incubation experiment. In these experiments, the specific growth rate was on average 9% higher in the fraction in which 100% was treated with XAD than in the controls. In the Rhine and Meuse river water, phytoplankton growth seemed to be inhibited by organic compounds. This inhibition was ascribed to the presence of dissolved organic micropollutants. Removing organic micropollutants using XAD resins to study the toxic effects of these compounds on field phytoplankton communities can be concluded to be a promising tool for risk assessment of micropollutants but needs to be supported by additional methodological research.     

Vertical migration of adult Ixodes rubicundus,the Karoo paralysis tick (Acari: Ixodidae)

Mortality due to Karoo paralysis amongst livestock is of considerable economic importance in South Africa. Indications are that the extent of vertical migration of adult ticks, to reach questing positions on grasses, is influenced by sudden climatic chages. Such influences as well as selection of questing substrates were investigated under controlled conditions. Vertical migration of adult Ixodes rubicundus on copper rods was determined in a square metal arena within a closed glass container in a room in which temperature and light could be controlled. Significantly more female and male ticks migrated vertically on 1.5 mm diameter rods than on 4.0 mm rods and on 450 mm long rods than on 100 mm rods. More ticks of both sexes migrated vertically at RH>80% than at RH<50% and at 12°C than at 21°C. More female than male and more older than younger ticks migrated vertically in all experiments. The results of this study contribute towards an understanding of the epidemiology of Karoo paralysis.