Electron Microscopic Localization of ATPase Activity in the Cytopharyngeal Basket of the Ciliate Pseudomicrothorax dubius

The cytopharyngeal basket of Pseudomicrothorax dubius is used to ingest filamentous blue-green algae. The basket has three main components: a sheath of microfilaments, bundles of microtubules (the nemadesmata), and ribbons of microtubules. The ribbons of microtubules (nemadesmal lamellae) are adpressed to the food vacuole during ingestion. Cytochemical techniques show that both the lamellae and the microfilamentous sheath possess ATPase activity, but the reaction product appears under different conditions in the two cases. The presence of ATPase activity within the microtubular lattices of the feeding organelle suggests the capacity for active motility. Consequently the basket seems to have two motile systems, one may be used to constrict and dilate the cytopharynx while the other is used in the inward propulsion of the forming food vacuole.     

Anaerobic Fish Spoilage by Bacteria II. Kinetics of Bacterial Growth and Substrate Conversions in Herring Extracts

The time course of the conversions of chemical components in herring extracts during anaerobic growth of Proteus sp., str. NTHC 153, Aeromonas sp., str. NTHC 154, and Enterobacter sp., str. NTHC 151 (Strøm & Larsen 1979) has been studied. When the Proteus sp. or the Aeromonas sp. were inoculated into the herring extracts and incubated at 15°C under anaerobic conditions, the sugar components (i.e. mainly ribose, free and bound) were the first substrates utilized. These compounds were converted to acetate and CO₂ by the use of trimethylamine oxide (TMAO) as an external hydrogen acceptor. Growth of bacteria ceased when all TMAO was reduced to trimethylamine (TMA). By adding an extra amount of TMAO to the herring extracts an increased growth of the Proteus sp. and the Aeromonas sp. ensued. The increased growth occurred concomitantly with a further conversion of TMAO to TMA and of lactate to acetate and CO₂. The Enterobacter sp., which did not utilize lactate, did not give an increased growth in herring extracts enriched with TMAO.     

Vibration and sound communication in solitary bees and wasps

ABSTRACT. Females of solitary bees ( Colletes cunicularius L.) and of digger wasps ( Bembix rostrata L.) produce buzzing sounds and are known to secrete volatile odours when digging their way from the subterranean nests to the soil surface. The odours allow patrolling males to determine the approximate position of the digging virgin female. The buzzes are measured as substrate-borne sound (soil buzz vibrations) and as air-borne sound (soil buzz sounds). Play-back experiments suggest that the soil buzzes are used by the males as additional cues for localization. Faint buzz sounds are emitted regularly by the male during genital contact in copulation. They may serve to change the receptivity of the female. Intense and broadband buzz sounds are produced by bees of either sex, if restrained from moving, perhaps serving to deter predators.     

The Nuclear Apparatus of the Ditransversal Ciliate Homalozoon Vermiculare (Ciliophora, Rhabdophora) During Interphase and Division Ii. the Micronuclei and Some Observations On Conjugation

ABSTRACT. The nuclear apparatus of H. vermiculare consists of a single moniliform macronucleus and about 25 micronuclei. the micronuclei are about 3 μm in diameter and characterized by a meshwork of thick condensed chromatin. Mitosis is intranuclear and acentric as in all other ciliates. In metaphase, interpolar and chromosomal microtubules are abundant and the length of the micronuclei increases to about 5 μm. In late anaphase, interzonal microtubules become prominent and the spindle elongates to about 50 μ. In meta- and anaphase, the microtubules of the spindle are attached to the polar vesicles, and in anaphase, chromosomes become attached to it. In contrast to most other eukaryotes, micronuclear mitosis is not strictly bound to cell division in H. vermiculare. While most of the micronuclei divide prior to cytokinesis, others retain their interphasic shape or degenerate. In addition, some micronuclei divide in the interdivision period, i.e. between two successive divisions of the cell and macronucleus. Mating cells of H. vermiculare become joined to each other in the cilia-free region covering the cytostome. In the course of conjugation, the cell membranes and the underlying oral filamentous sheaths of both cells fuse, thus uniting the endoplasm of both cells in the mouth region. Synaptonemal complexes in the meiotic chromosomes are more distinct in H. vermiculare than in most other dilates. the micrographs presented here depict dearly the central filament, transverse elements, and other substructures.     

Molecular Characterization of the D Surface Protein Gene Subfamily in Paramecium tetraurelia

ABSTRACT. When Paramecium tetraurelia expresses the D serotype, detectable by serum tests, high molecular mRNA could be isolated, which corresponds to the molecular mass of the D surface protein. Using this D specific mRNA as a probe for screenings in different genomic libraries a subfamily of five very similar genes was found, named α-51D, _γ1-51D, _γ2-51D, δ-51D and ε-51D. Each of them is about 8-kb long, they show regions of identity to each other, and there is no evidence that any are defective genes or pseudogenes. Up to now serotype D is the only known serotype showing this phenomenon. Another novel feature is that two of the D isogenes are closely linked. The sequence for the entire coding region of the α-51D gene has been determined, as well as the upstream and downstream noncoding regions. Its deduced amino acid sequence shows the same characteristic cysteine periodicity displayed by all other immobilization antigen (i-ag) genes from Paramecium. However, in contrast to most other such genes, tandem repeats are missing from the 7599-bp long coding region of the α-51D gene. When the sequences of the type 51D genes are compared to each other, the similarity is very high and extends to coding as well as to noncoding regions. Similarity within noncoding regions is usually only observed for allelic i-ag genes. We conclude that the type D genes constitute a family of isogenes that are nonallelic. They contain slightly different consensus sequences with possible functions as regulatory regions.     

Palaeobotryllus from the Upper Cambrian of Nevada — a probable ascidian

Phosphatic microfossils etched from Upper Cambrian (Trempealeauan Stage) Limestones of the Whipple Cave Formation, Nevada, and other contemporaneous formations in western North America, are colonies, the individuals of which are arranged irregularly around one or more nuclei. No secondary growth has occurred. During their lifetime, however, the individuals partially filled their chambers with phosphatic matter. The highly differentiated morphology of the colonies is strikingly similar to the living ascidian tunicate Botryllus. Ecological conditions and size range of the fossils are likewise similar to those of the Ascidiacea. If recognized as an ascidian, Palaeobotryllus taylori n.g., n.sp. extends the known occurrence of Tunicata into the Upper Cambrian.     

Heterogeneity of Intermediate Filament Expression in Vascular Smooth Muscle: A Gradient in Desmin Positive Cells from the Rat Aortic Arch to the Level of the Arteria Iliaca Communis

The display of the two distinct intermediate filament proteins, desmin and vimentin, in rat vascular smooth muscle tissue was studied by immunofluorescence microscopy on frozen sections of aorta and other blood vessels. Vascular smooth muscle cells present in these vessels always appeared rich in vimentin. However, staining of sections covering six distinct but contiguous parts of the aorta showed that the number of desmin containing cells was low distal to the truncus brachiocephalicus, but increases until in distal parts of the aorta and in the arteria iliaca communis almost all cells appear positive for desmin. Thus blood vessels show heterogeneity of intermediate filament expression not only in cross-section but can also display heterogeneity along their length. Muscular arteries such as the renal artery and the arteria femoralis, as well as arterioles and veins including the vena jugularis and the vena cava also contain desmin. Thus it may be that low numbers of desmin-positive cells are typical of elastic arteries, while muscular arteries and other blood vessels are characterized by large numbers of desmin-positive cells. We discuss whether desmin-positive and desmin-negative vascular smooth muscle cells may perform different functions and raise the possibility that desmin expression may coincide with the turn on of a specially regulated contractility program.     

A Perspective on Protistan Nomenclature

ABSTRACT. The nomenclature of protists is more complicated than that of plants or animals because more than one code of nomenclature applies (i.e. the taxa may be ambiregnal), because of the frequent absence of type material, and because of changing perspectives of the phylogenetic relationships of various groups of protists. These factors often lead to uncertainty over the meaning of names of taxa. If nomenclatural instability is to be avoided, some changes in current practices are required. The nature of the problems and some possible changes are discussed.     

Effect of Low Relative Humidity on {delta}13C Value in Two C3 Grasses and in Panicum milioides, a C3-C4 Intermediate Species

When grown under conditions of low relative humidity, the C₃–C₄intermediate Panicum milioides, as well as the C₃ grasses Triticumaestivum and Poa pratense, exhibited ¹³C values which were upto 2–7%o less negative than the ¹³C values of the correspondingplants grown at high relative humidity. At both humidity levels,there was no evidence of a substantial contribution of phosphoenolpyruvatecarboxylase to carbon gain in Panicum milioides     

Slow response of soil organic matter to the reduction in atmospheric nitrogen deposition in a Norway spruce forest

Global nitrogen (N) deposition rates in terrestrial environments have quadrupled since preindustrial times, causing structural and functional changes of ecosystems. Different emission reduction policies were therefore devised. The aim of our study was to investigate if, and over what timescale, processes of soil organic matter (OM) transformation respond to a decline in atmospheric N deposition. A N‐saturated spruce forest (current N deposition: 34 kg ha^?1 yr^?1; critical N load: 14 kg ha^?1 yr^?1), where N deposition has been reduced to 11.5 kg ha^?1 yr^?1 since 1991, was studied. Besides organic C and organic and inorganic N, noncellulosic carbohydrates, amino sugars and amino acids were determined. A decline in organic N in litter indicated initial effects at plant level. However, there were no changes in biomarkers upon the reduction in N deposition. In addition, inorganic N was not affected by reduced N deposition. The results showed that OM cycling and transformation processes have not responded so far. It was concluded that no direct N deposition effects have occurred due to the large amount of stored organic N, which seems to compensate for the reduction in deposited N. Obviously, the time span of atmospheric N reduction (about 14.5 years) is too short compared with the mean turnover time of litter to cause indirect effects on the composition of organic C and N compounds. It is assumed that ecological processes, such as microbial decomposition or recycling of organic N and C, react slowly, but may start within the next decade with the incorporation of the new litter.