Subjective Estimation of the Trajectory Length of Fused Auditory Image Movement

The perceived trajectory length of the movement of a fused auditory image (FAI) against the background of interaural intensity differences was estimated in eight subjects upon dichotic stimulation through headphones. FAI movement was created by gradually changing the interaural delay (ΔT) between clicks in binaurally presented series of clicks from 0 to ±630 μs. When the FAI moved from the left to the right, an increase in interaural intensity difference (ΔI) from 0 to +13 dB (in the right channel of stimulation) significantly shortened the FAI trajectory because of a greater lateralization of the start point of FAI movement as compared to its end point. In the case of an oppositely directed movement (from the right to the left), the movement trajectory significantly decreased when ΔI increased from 0 to −13 dB (i.e., in the left stimulation channel), which was also explained by the greater lateralization of the start point of FAI movement as compared to its end point.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 3, 2005, pp. 32–38.Original Russian Text Copyright © 2005 by Varyagina.     

Yeasts and filamentous fungi carried by the gynes of leaf-cutting ants

Insect-associated microbes exhibit a wide range of interactions with their hosts. One example of such interactions is the insect-driven dispersal of microorganisms, which plays an essential role in the ecology of several microbes. To study dispersal of microorganisms by leaf-cutting ants (Formicidae: Attini), we applied culture-dependent methods to identify the filamentous fungi and yeasts found in two different body parts of leaf-cutting ant gynes: the exoskeleton and the infrabuccal pocket. The gynes use the latter structure to store a pellet of the ants’ symbiotic fungus during nest founding. Many filamentous fungi (n = 142) and yeasts (n = 19) were isolated from the gynes’ exoskeleton. In contrast, only seven filamentous fungi and three yeasts isolates were recovered from the infrabuccal pellets, suggesting an efficient mechanism utilized by the gynes to prevent contamination of the symbiotic fungus inoculum. The genus Cladosporium prevailed (78%) among filamentous fungi whereas Aureobasidium, Candida and Cryptococcus prevailed among yeasts associated with gynes. Interestingly, Escovopsis, a specialized fungal pathogen of the leaf-cutting ant-fungus symbiosis, was not isolated from the body parts or from infrabuccal pellets of any gynes sampled. Our results suggest that gynes of the leaf-cutter ants Atta laevigata and A. capiguara do not vertically transmit any particular species of yeasts or filamentous fungi during the foundation of a new nest. Instead, fungi found in association with gynes have a cosmopolitan distribution, suggesting they are probably acquired from the environment and passively dispersed during nest foundation. The possible role of these fungi for the attine ant–microbial symbiosis is discussed.     

Habitat choice by juvenile cod (Gadus morhua L.) on sandy soft bottoms with different vegetation types

Habitat choice by juvenile cod (Gadus morhua L.) on sandy bottoms with different vegetation types was studied in laboratory. The experiment was conducted day and night in flow-through tanks on two different size-classes of cod (7–13 and 17–28 cm TL). Four habitats, typical of shallow soft bottoms on the Swedish west coast:Fucus vesiculosus, Zostera marina, Cladophora sp. and bare sand, were set up pair-wise in six combinations. The main difference between habitats in this study was vegetation structure, since all parameters except vegetation type was considered equal for both sides of the experimental tanks and natural prey was eliminated. The results showed a difference in habitat utilization by juvenile cod between day (light) and night (dark). During day time the fishes showed a significant preference for vegetation, while nocturnally no significant choice of habitat was made. Both size-classes preferredFucus, considered the most complex habitat in this study, when this was available. The smaller size-class seemed to be able to utilize the other vegetation types as well, always preferring vegetation over sand. Larger juvenile cod, on the other hand, appeared to be restricted toFucus. This difference in habitat choice by the two size-classes might be due to a greater dependence on shelter from predation by the smaller juveniles, causing them to associate more strongly with vegetation. The larger juveniles avoidedCladophora, since they might have difficulties in entering the compact structure of this filamentous algae. Availability of vegetation at day time, as a predation refuge, as well as of open sandy areas for feeding during night, thus seems to be important for juvenile cod. It is concluded that eutrophication-induced changes in habitat structure, such as increased dominance by filamentous algae, could alter the availability of predation refuges and foraging habitats for juvenile cod.     

Lipid Fatty Acid Composition and Thermophilicity of Cyanobacteria

An analysis of lipid fatty acid composition in several unicellular and filamentous forms of mesophilic and thermophilic cyanobacteria was performed. At 47°C (the temperature of thermophilic cyanobacteria maintenance in the collection), the unicellular thermophilic Synechococcus strains were devoid of polyenoic acids as distinct from the mesophilic forms of this genus at the temperature of 20°C (the temperature of this cyanobacterial maintenance in the collection). In the thermophilic Synechococcus elongatusIPPAS B-267 strain, a decrease in temperature did not result in the occurrence of C18 polyenoic acids, but the quantitative relationship between the saturated and unsaturated fatty acids (S/U ratio) was decreased twofold. In contrast, the culturing of mesophilic strains at 25–32°C resulted in an increase in the S/U ratio due to an increase in the proportion of the 16:0 acid. In the Synechococcus IPPAS B-434 strain, this treatment resulted in a decrease in the relative content of monoenoic, mainly hexadecenoic, acids. The cyanobacterium Gloeobacter violaceus, which lacks thylakoids, and whose photosystems are formed in a cell membrane, contained polyenoic acids. The filamentous thermophilic cyanobacterium Phormidium laminosum, at the maintenance temperature of 47°C, did contain polyenoic acids, but their proportion was considerably lower than that in the filamentous mesophilic forms, such as Tolypothrix sp. and Spirulina platensis. A relative content of hexadecenoic acids in Ph. laminosum was higher than in the mesophilic forms. A possible role of hexadecenoic acids in the processes of adaptation of cyanobacteria to high temperatures is discussed. A relationship between the characteristics of fatty acid composition fixed by evolution and the changes caused by adaptation to a particular environment is considered.     

Extract of <Emphasis Type="Italic">Microcystis</Emphasis> water bloom affects cellular differentiation in filamentous cyanobacterium <Emphasis Type="Italic">Trichormus variabilis</Emphasis> (Nostocales,Cyanobacteria)

Cyanobacteria produce a wide spectrum of biologically active compounds such as microcystins, whose effects on photoautotrophic organisms and role in the aquatic ecosystems have been most intensively discussed and studied. In our study, we examined effects of semipurified Microcystis extract containing microcystins (0.2–20 nM corresponding to 0.2–20 μg L⁻¹) on age-induced cell differentiation of filamentous cyanobacterium Trichormus variabilis. The heterocyst and akinete formation was significantly decreased after exposure to extract containing 2 or 20 nM of microcystins within 10 days of exposure. To our knowledge, this is the first information about effects of metabolites produced by planktonic cyanobacteria on cell differentiation in filamentous cyanobacteria. Since the effects were induced by environmentally relevant concentrations of microcystins, our observations may indicate not only that microcystins or other bioactive peptides could affect conservation, overwintering, and nitrogen-fixation in filamentous cyanobacteria under environmental conditions but also contribute to the understanding of possible signaling function of cyanobacterial metabolites.     

The significance of peroxisomes in secondary metabolite biosynthesis in filamentous fungi

Peroxisomes are ubiquitous organelles characterized by a protein-rich matrix surrounded by a single membrane. In filamentous fungi, peroxisomes are crucial for the primary metabolism of several unusual carbon sources used for growth (e.g. fatty acids), but increasing evidence is presented that emphasize the crucial role of these organelles in the formation of a variety of secondary metabolites. In filamentous fungi, peroxisomes also play a role in development and differentiation whereas specialized peroxisomes, the Woronin bodies, play a structural role in plugging septal pores. The biogenesis of peroxisomes in filamentous fungi involves the function of conserved PEX genes, as well as genes that are unique for these organisms. Peroxisomes are also subject to autophagic degradation, a process that involves ATG genes. The interplay between organelle biogenesis and degradation may serve a quality control function, thereby allowing a continuous rejuvenation of the organelle population in the cells.     

Recent increase of filamentous algae in shallow Swedish bays: Effects on the community structure of epibenthic fauna and fish

A summary is presented of estimates of distribution and growth of filamentous algae and its effect on the structure and functioning of epibenthic fauna and fish communities in shallow bays on the Swedish west coast. As a consequence of coastal eutrophication vegetation cover has gradually increased during the last decade, and during 1990's most bays in the Skagerrak-Kattegat area were variously covered with filamentous algae during spring and summer (May–July). In some areas filamentous algae (mainlyCladophora andEnteromorpha) completely covered the bottom. In field studies it was demonstrated that increased cover and dominance of filamentous algae result in structural changes of the epibenthic fauna community. Field studies showed that species richness and biomass of epibenthic fauna increased in a sandy bay with a moderate increase (30 to 50%) of filamentous algae cover. At higher cover (90%), biomass of epibenthic fauna was reduced, however, to the same level as for the sandy habitat, although the dominant epibenthic species were different. Heavy growth of epiphytic filamentous algae on eelgrass resulted in reduced biomass and a shift in the species composition of the epibenthic fauna community. Fish assemblage structure was also related to changes in vegetation. In eelgrass beds, fish species numbers were reduced with increasing cover of epiphytic filamentous algae, and at rocky bottoms with kelp algae (dominated byFucus), fish biomass decreased with increasing cover of attached filamentous algae. Further, foraging efficiency of juvenile cod and settling success of plaice were reduced as a response to increasing dominance of filamentous algae.     

Synthesis of different pectinases by filamentous growingA. niger mutants

Mutants ofA. niger K 69/26, prepared by multistep mutagenesis (UV, MNNG, heating) have been screened for pectinase activities. Mutants with altered levels of certain pectinases, such as endo- and exopolygalacturonase (PG vis, red), pectinesterase (PE) and pectinlyase (PL), were isolated. The enzyme activities of the best mutants M 1348/126 were increased 2–3-fold compared to the parent strain after a 6-d cultivation of filamentous mycelium on a shaker. Further mutagenesis of mutants with decreased pectinase activities (e.g. Se3) produced revertants. PG (vis) synthesis of revertant Se5 was increased 1.7 times compared to the control strain K 69/26. Independent of these increased rates, the general level of pectinase activities synthesized by the filamentous mycelium ofA. niger mutants amounts to about 10–20% compared with those produced by aggregated mycelium. It appears that the enzyme synthesis related to mycelium structure is independent of the mechanism which regulates the level of pectinase synthesis within a specific morphological structure.     

Lakeside reed border characteristics at Lake Constance (Untersee): A comparison between 1981–1983 and 1994

Eutrophication and the associated proliferation offilamentous algae were often considered importantcauses of reed die-back that occurred in the sixtiesand seventies at Lake Constance. According to thishypothesis the reduction in lake water nutrientconcentrations during the eighties and nineties shouldhave reduced the abundance of filamentous algae andwhich should have reduced the supposed mechanicalimpact of filamentous algae on the lakeside reedstands. To examine whether this had actually occurred,the condition of the lakeside reed border at LakeConstance (Untersee) was surveyed in 1994 and resultswere compared to those of similar surveys carried outin the years 1981–83. The extent of mechanical damageto reed stalks, the amount of macrophyte wash and thedegree of shoreline erosion were assessed forshoreline segments of 25 m along a total shorelinelength of 65 km. The results showed that mechanicaldamage to reed stalks was generally higher in 1994than in 1981–83, while macrophyte wash and shorelineerosion were generally less severe. The decreasedamount of macrophyte wash was associated with a changein macrophyte species composition from a dominance offloating filamentous algae to a dominance of rootedPotamogetonaceaeand fragile Characeae,and therefore probably was due to the lower nutrientconcentrations of the lake. The opposite trends foundfor mechanical damage to reed stands and the amount ofmacrophyte wash between 1981–83 and 1994, as well asthe absence of relation between the two variables in1994, suggested that macrophyte wash had only a minoreffect on the condition of lakeside reed stands atLake Constance. Highly damaged reed stands and erodedcliffs were often located at wind exposed sites orclose to highly frequented shipping routes in 1994,suggesting that mechanical stress from waves wasresponsible for the damage. Due to the lakewardprogression of reed stands during the early nineties,reed stalks were, on average, located in deeper waterin 1994 than in 1981–83. This might have strengthenedthe mechanical stress from wave action even more andhave caused the higher frequency of mechanical damageto reed stalks. Other causes of damage such asmacrophyte wash, roosts of birds or bird swarmsprobably played a minor and only local role.     

Competitive ability of Daphnia under dominance of non-toxic filamentous cyanobacteria

It is generally assumed that Daphnia is more susceptible to the inhibitory effects of filamentous cyanobacteria than small cladocerans since daphnids have a larger gape size and filtrate the filaments, whereas small cladocerans do not. This study addresses the question whether food limitation has the potential to modify this scenario of cladoceran response to dominance of non-toxic filamentous cyanobacteria. Daphnia galeatawas grown under limited (0.1 mg C l^–1) and unlimited concentrations (1.0 mg C l^–1) of high-quality food algae both in the absence/presence of non-toxic filamentous Aphanizomenon flexuosum. As the effects of these cyanobacteria on D. galeatawere positive under food limiting conditions and negative at the high food density, it was concluded that D. galeatawas mainly affected by nutritional quality due to its ability to ingest the filaments, while mechanical interference with food collection was not important. In competition experiments between D. galeataand Bosmina longirostris, D. galeatawas the dominant species at regular additions of food (1.0 mg C l^–1) in the absence of Aphanizomenon. In the presence of these cyanobacteria, D. galeatawas inhibited during the first days of the experimental period. However, the negative effect at the initially high food density was outweighed by nutrition at food limiting conditions and the outcome in competitive dominance was not changed. The results demonstrate that the ability of D. galeata to ingest large-sized non-toxic cyanobacteria can be considered as advantageous under food limiting conditions.     

Herniation pits in human mummies: a CT investigation in the Capuchin Catacombs of Palermo, Sicily

Herniation pits (HPs) of the femoral neck were first described in a radiological publication in 1982 as round to oval radiolucencies in the proximal superior quadrant of the femoral neck on anteroposterior radiographs of adults. In following early clinical publications, HPs were generally recognized as an incidental finding. In contrast, in current clinical literature they are mentioned in the context of femoroacetabular impingement (FAI) of the hip joint, which is known to cause osteoarthritis (OA). The significance of HPs in chronic skeletal disorders such as OA is still unclear, but they are discussed as a possible radiological indicator for FAI in a large part of clinical studies.In this paleoradiological study we examined a sample of mummies from the Capuchin Catacombs of Palermo, Sicily, by a mobile computed tomography (CT) scanner. Evaluation of the CT examinations revealed HPs in six out of 16 (37.5%) adult male mummies.The first aim of this study was to compare the characteristics of HPs shown in our mummy collection to the findings described in clinical literature. Thereby CT evaluation revealed that their osseous imaging characteristics are in accordance, consisting of round to oval subcortical lesions at the anterior femoral neck, clearly demarcated by a sclerotic margin.The second aim was to introduce HPs to the paleoradiological and paleopathological methodology as an entity that underwent a renaissance from an incidental finding to a possible radiological indicator of FAI in the clinical situation. As FAI plays an important role in the development of OA of the hip, which is a very common finding in human skeletal remains, HPs should always be considered in paleoradiological evaluation of hip joint diseases.     

‘Morphological shifts’ in filamentous bacteria isolated from activated sludge processes

Summary This study aimed at isolating filamentous bacteria from full-scale activated sludge processes and studying them in pure culture. Three cultures were isolated using conventional microbiological techniques. The isolates were positively identified as Gordonia amarae, Thiothrix nivea and Type 1863/Acinetobacter spp., using fluorescent in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probes. However, a ‘morphological shift’ from filamentous to single-cell form was observed in pure culture. The application of fluorescent in situ hybridization (FISH) showed filamentous bacteria to be much more diverse in their ability to adapt to their changing enviroments. Pure culture studies of filamentous bacteria form the basis for application in full-scale activated sludge plants. It therefore remains important that the taxonomic status of filamentous bacteria be determined.     

Species-specific responses of dew fly larvae to mycotoxins

Abstract   The larval stages of saprophagous insects and filamentous fungi have been demonstrated to be serious competitors on decaying organic matter. When filamentous fungi appear to be competitively superior, fungal mycotoxins have frequently been suggested to constitute chemical weapons, causing high mortality among insect larvae. In this study, we tested whether typical fungal secondary compounds can indeed be considered as the underlying mechanism of interference competition between filamentous fungi and various saprophagous Drosophila species. In contrast to our expectation, we found no grand mycotoxin-specific effects, but insect survival appeared to be generally determined by complex interaction between toxin identity, toxin concentration and insect species. Three out of five drosophilids seemed to be equally affected by the mycotoxins used in this study, whereas two species showed toxin-specific changes in survival. Only two (Kojic acid and Ochratoxin A) out of seven mycotoxins caused insect-specific responses. Moreover, we discovered correlations between survival in toxin-free and spoiled substrates, which may indicate an interrelationship between intra-specific competitive ability and resistance to mycotoxins. We discuss the significance of mycotoxins as underlying mechanisms driving competitive insect–fungus interactions.     

The Fine Structure of Four “Species” of Amoeba*

The fine structure of Amoeba discoides, Amoeba dubia, and Amoeba amazonas was studied and compared with that of Amoeba proteus. The different kinds of amebas showed general similarities but differed in the ultrastructural details of their organelles. With respect to fine structure, A. discoides was indistinguishable from A. proteus, while both A. dubia and A. amazonas had distinctive features. The nuclei of all had a prominent honeycomb-like fibrous lamina, but A. dubia differed from the others in the distribution of nucleoli within the nucleus. The mitochondria of A. amazonas were unusual in having a variable pattern of cristae, some being plate-like and others tubular. Golgi bodies in A. amazonas had a greater proportion of vesicles and a smaller number of cisternae than those of the others, while Golgi bodies in A. dubia had highly flattened cisternae without a lining of filamentous material such as is found in the other types. The plasma membrane of A. dubia also lacked the prominent filamentous cell coat common to A. proteus and other amebas. The relation between the Golgi apparatus and the cell coat and the significance of the degree of development of the cell coat for pinocytosis and other phenomena is considered. The experimental use of these cells, including the formation of hybrids by nuclear transplantation is discussed.     

Decreased fibularis reflex response during inversion perturbations in FAI subjects

Investigate reflex responses in muscles throughout the lower limb and low back during sudden inversion perturbations in individuals with and without Functional Ankle Instability (FAI) while walking. Forty subjects participated in the study. Surface electromyogram recordings were obtained from the fibularis (FIB), gluteus medius (GM), erector spinae (ES), and sternocleidomastoid (SCM) of the injured/matched side as well as the uninjured/matched contralateral side (FIB_CLS, GM_CLS, or ES_CLS). Latency and amplitude data were collected while subjects were walking on a custom-built perturbation walkway. The onset of the short-latency stretch reflex of the FIB was significantly later in the injured side of the FAI individuals when compared to the control group (P = 0.009). Both the short and long latency reflex amplitude was significantly smaller in the FIB muscle in the FAI group than in the control group (P < 0.008). No significant differences in latency or amplitude reflex responses were identified between the two groups in the GM, ES, FIB_CLS, GM_CLS, or ES_CLS (P > .05). Interpretation of these results indicate that during a dynamic perturbation task individuals with FAI demonstrate longer fibularis muscle latencies on the injured side while no significant changes in the proximal muscle groups. Additionally, short and long latency reflex amplitude was significantly decreased in FAI individuals.     

Segmented filamentous bacteria in the rodent small intestine: Their colonization of growing animals and possible role in host resistance toSalmonella

The establishment and proliferation of a model population of autochthonous surface-associated microorganisms in the small bowel of growing rats (2–12 weeks of age) was studied. Segmented filamentous bacteria on the distal ileal villi were examined by scanning electron microscopy (SEM) and countedin situ by transect line analysis. In young animals, these bacteria first colonized the villous base, but occupied all areas on the villus by adult age. Their distribution on Peyer's patches was also noted.In growing animals, colonization of the ileal villi by filamentous bacteria was significantly correlated to the development of host resistance to fatal infection by orally-dosedSalmonella enteritidis. In animals givenSalmonella and examined by SEM and transmission EM (TEM), the pathogen was seen only on ileal tissue surfaces, predominantly the villous base, from which the autochthonous population was absent. Conversely, in animals with filamentous bacteria,Salmonella surface colonization was not observed. The results suggest a possible protective role for the surface flora in the small bowel.     

Isolation,characterization, and abundance of filamentous members of <Emphasis Type="Italic">Caldilineae</Emphasis> in activated sludge

Chloroflexi are currently believed to serve as backbone forming agents in the activated sludge of wastewater treatment plants (WWTPs). In this study, we isolated and characterized filamentous bacteria in the class Caldilineae of the phylum Chloroflexi in municipal WWTPs. Diversity analysis using Chloroflexi-specific 16S rRNA gene clone libraries showed that 97% of the clones belonged to the subdivision Anaerolineae comprising the two classes Anaerolineae (95%) and Caldilineae (2%). Clones of Caldilineae were related to a thermophilic filament Caldilinea aerophila with 93% 16S rRNA gene sequence similarity. We obtained filamentous isolates classified into the class Caldilineae showing the best match to C. aerophila with 89% 16S rRNA gene sequence similarity. Isolates showed no ability to assimilate glucose or N-acetylglucosamine or to degrade biopolymers which were observed in filamentous Chloroflexi of WWTPs. The assessment of relative abundance based on quantitative PCR of the 16S rRNA gene indicated that members of the class Caldilineae comprised 12–19% of the Chloroflexi in the activated sludge. Additionally, fluorescence in situ hybridization experiments showed that diverse filamentous Caldilineae inhabit the activated sludge of municipal WWTPs. These findings yield insight into the role of filamentous mesophilic Caldilinea in stabilizing flocs of activated sludge in a wide range of WWTPs.     

Presence of nucleosomes inPenicillium chrysogenum

We have studied the chromatin structure ofPenicillium chrysogenum. This fungus presents the typical nucleosomal repeat and the core DNA size characteristic of all the eukaryotes. The repeat length (about 180 base pairs) is in the range of those obtained for most fungi (160–180 base pairs) and shorter than in higher eukaryotes. Knowledge aboutP. chrysogenum chromatin structure opens the way to the study of the mechanisms of genetic regulation in this filamentous fungus.     

Hydrogen peroxide is involved in the sclerotial differentiation of filamentous phytopathogenic fungi

Aims: The purpose of this study was to investigate the role of H₂O₂ and the related oxidative stress markers catalase (CAT) and lipid peroxidation in the sclerotial differentiation of the phytopathogenic filamentous fungi Sclerotium rolfsii, Sclerotinia minor, Sclerotinia sclerotiorum and Rhizoctonia solani. Methods and Results: Using the H₂O₂‐specific scopoletin fluorometric assay and the CAT‐dependent H₂O₂ consumption assays, it was found that the production rate of intra/extracellular H₂O₂ and CAT levels in the sclerotiogenic fungi were significantly higher and lower, respectively, than those of their nondifferentiating counterpart strains. They peaked in the transition between the undifferentiated and the differentiated state of the sclerotiogenic strains, suggesting both a cell proliferative and differentiative role. In addition, the indirect indicator of oxidative stress, lipid peroxidation, was substantially decreased in the nondifferentiating strains. Conclusions: These findings suggest that the differentiative role of H₂O₂ is expressed via induction of higher oxidative stress in the sclerotiogenic filamentous phytopathogenic fungi. Significance and Impact of the Study: This study shows that the direct marker of oxidative stress H₂O₂ is involved in the sclerotial differentiation of the phytopathogenic filamentous fungi S. rolfsii, S. minor, S. sclerotiorum and R. solani, which could have potential biotechnological implications in terms of developing antifungal strategies by regulating intracellular H₂O₂ levels.