Conspicuous Modifications Research Articles

Fate and migration of enhanced rock weathering products through soil horizons; implications of irrigation and percolation regimes

Terrestrial enhanced rock weathering (ERW) is reckoned as a robust method to contribute to stabilizing atmospheric carbon and combat global warming. The method is particularly a matter of interest in agricultural soil, offering a vast opportunity for the application of crushed silicate minerals and secondary carbonate accumulation and migration. Although the applicability of this practice is well acknowledged, its impact on the geochemical alteration of soil vertical profile, particularly deeper layers, is less discussed in the literature. Moreover, the effect of irrigation and percolation regimes, as influenced by ambient conditions, is also not well-reported and characterized. In the present study, we utilized a high amendment rate (50 t/ha) of wollastonite skarn, a fast-weathering silicate mineral, to uncover the alterations in topsoil and subsoil as well as effluent water over a through a soil column experiment over five months, under more controlled (indoor) and less controlled (outdoor) ambient and irrigation conditions. The results indicate more conspicuous modification of parameters in shallow layers of soil compared to deeper ones, explicitly in the rain-fed setup. Silicate amendment induced an increase of 6.53 and 2.85 tCO2/ha (in the form of pedogenic carbonate (PC)) over the profile of soil (0–60 cm) under periodic and rain-fed water regimes, respectively. The silicate treatment was also found to be effective toward rising pH and electrical conductivity of topsoil (0–15 and 15–30 cm layers) and leachate, and a measurably greater release of Ca2+ and Mg2+ in the column effluent. We estimate a carbon drawdown ratio (carbonate/bicarbonate) of ≈15:1 in this study, showing that PC formation is a more significant weathering indicator than leachate bicarbonate export in the shorter term for a fast-weathering mineral in pH-neutral soils and moderate irrigation regime. Such observations are valuable for developing carbon drawdown quantification methods suitable for a variety of agricultural lands and global regions.

A decreased expression of interferon stimulated genes in peri-implantation endometrium of embryo transfer recipient sows could contribute to embryo death

Pig pregnancy succeeds thanks to a well-coordinated system ruling both maternal immune activation and embryonic antigen tolerance. In physiological pregnancies, the maternal immune system should tolerate the presence of hemi-allogeneic conceptuses from the pre-implantation phase to term, while maintaining maternal defence against pathogens. Allogeneic pregnancies, as after embryo transfer (ET), depict high embryo mortality during the attachment phase, calling for studies of the dynamic modifications in immune processes occurring at the maternal-foetal interface, for instance, of interferon (IFN)-stimulated genes (ISGs). These ISGs are generally activated by IFN secreted by the conceptus during the process of maternal recognition of pregnancy (MRP) and responsible for recruiting immune cells to the site of embryo attachment, thus facilitating cell-antigen presentation and angiogenesis. We performed RNA-Seq analysis in peri-implantation (days 18 and 24) endometrial samples retrieved from artificially inseminated sows (hemi-allogeneic embryos (HAL) group) or sows subjected to ET (allogeneic embryos (AL) group) to monitor alterations of gene expression that could be jeopardising early pregnancy. Our results showed that endometrial gene expression patterns related to immune responses differed between hemi- or allogeneic embryo presence, with allogeneic embryos apparently inducing conspicuous modifications of immune-related genes and pathways. A decreased expression (P < 0.05; FC < −2) of several interferon ISGs, such as CXCL8, CXCL10, IRF1, IRF9, STAT1, and B2M, among others was detected in the endometrium of sows carrying allogeneic embryos on day 24 of pregnancy. This severe downregulation of ISGs in allogeneic pregnancies could represent a failure of ET-embryos to signal IFN to the endometrium to warrant the development of adequate immunotolerance mechanisms to facilitate embryo development, thus contributing to elevated embryo death.

Optimization of Liquid Hot Water Pretreatment and Fermentation for Ethanol Production from Sugarcane Bagasse Using Saccharomyces cerevisiae

Sugarcane bagasse can be considered a potential raw material in terms of quantity and quality for the production of alternative biofuels. In this research, liquid hot water (LHW) was studied as a pretreatment process to enhance the digestibility of pretreated material for further conversion into bioethanol. Different variables (temperature, residual time, and acid concentration) were determined to predict the optimized condition. LHW pretreatment showed an impact on the hemicellulose structure. The optimized condition at 160 °C for 60 min with 0.050 M acid concentration reached the highest glucose yield of 96.86%. Scanning electron microscopy (SEM) showed conspicuous modification of the sugarcane bagasse structure. The effect of LHW pretreatment was also demonstrated by the changes in crystallinity and surface area analysis. FTIR techniques revealed the chemical structure changes of pretreated sugarcane bagasse. The prepared material was further converted into ethanol production with the maximized ethanol concentration of 19.9 g/L.

Straight to Low-Sinuosity Drainage Systems in a Variscan-Type Orogen—Constraints from Tectonics, Lithology and Climate

A holistic-modular approach has been taken to study the evolution of three straight to low-sinuosity drainage systems (=SSS) in an uplifted basement block of the Central European Variscides. The development of the SSS is described by means of a quadripartite model. (1) The geological framework of the SSS: Forming the lithological and structural features in the bedrock as a result of different temperature, pressure and dynamic-metamorphic processes. (2) Prestage of SSS: Forming the paleo-landscape with a stable fluvial regime as a starting point for the SSS. (3) Proto-SSS: Transition into the metastable fluvial regime of the SSS. (4) Modern SSS: Operation of the metastable fluvial regime Tectonics plays a dual role. Late Paleozoic fold tectonic creates the basis for the studied SSS and has a guiding effect on the development of morphotectonic units during the Neogene and Quaternary. Late Cenozoic fault tectonics triggered the SSS to incise into the Paleozoic basement. The change in the bedrock lithology has an impact on the fluvial and colluvial sediments as well as their landforms. The latter reflects a conspicuous modification: straight drainage system ⇒ higher sinuosity and paired terraces ⇒ hillwash plains. Climate change has an indirect effect controlling via the bedrock the intensity of mechanical and chemical weathering. The impact on the development of the SSS can be assessed as follows: Tectonics &gt;&gt; climate ≅ bedrock lithology. The three parameters cause a facies zonation: (1) wide-and-shallow valley (Miocene), (2) wide-angle V-shaped valley (Plio-Pleistocene), (3) acute-angle V-shaped valley (Pleistocene), (4) V-shaped to U-shaped valleys (Pleistocene-Holocene). Numerical data relevant for the hydrographic studies of the SSS are determined in each reference area: (1) Quantification of fluvial and colluvial deposits along the drainage system, (2) slope angles, (3) degree of sinuosity as a function of river facies, (4) grain size distribution, (5) grain morphological categorization, (6) grain orientation (“situmetry”), (7) channel density, (8) channel/floodplain ratios. Thermodynamic computations (Eh, pH, concentration of solubles) are made to constrain the paleoclimatic regime during formation of the SSS. The current model of the SSS is restricted in its application to the basement of the Variscan-Type orogens, to an intermediate crustal maturity state.

Post-γ -irradiation effects on structural, optical and morphological properties of chemical vapour deposited MWCNTs

In this work, the effect of γ-irradiation with 1.25 MeV average energy (Co-60) was studied on the structural, optical and morphological properties of chemical vapour deposited MWCNTs at 10–60 kGy dose. The XRD spectra with the peak at 2θ ~ 26.08° of (002) plane confirm the MWCNTs formation and conspicuous modifications were observed after γ- irradiation. The UV–Vis studies show that the UV lower wavelength shifts towards the higher region with increasing γ- dose, bandgap decreasing from 3.57 eV to 3.33 eV (372 nm–347 nm) because of the generation of charge trapping of the radiolytic holes or electrons, which change the valence and conduction bandgap in electronic states. The FTIR results provided confirmation of the attachment of hydroxyl and carboxyl functional groups to the MWCNTs sidewalls whereas after γ- irradiation caused significant changes in the structure of the sidewalls of MWCNTs. The Raman spectra confirmed the ID/IG ratio decreases after γ- irradiation which is due to the enhancement in defects through the interaction between MWCNTs and photons during γ-irradiation. The TEM and FESEM results confirmed the inter-mingling or agglomeration of the network of nanotubes having varying diameters of about 40–60 nm on account of the interaction of γ-ray. SAED pattern shows a dispense halo pattern due to the presence of amorphous carbon.

Does over-dominance of &lt;i&gt;Bambusa&lt;/i&gt; &lt;i&gt;bambos&lt;/i&gt; (L.) Voss. alter abundance and richness of Arbuscular Mycorrhizal fungal community in forests?

Some areas under the Tropical Moist Evergreen Forests (TMEF), the major forest type in the Intermediate Zone of Sri Lanka, are heavily dominated by a native bamboo species, Bambusa bambos (L.) Voss. altering the hierarchical status and structure. The study evaluated whether the over-abundance of B. bambos has modified the arbuscular mycorrhizal fungal (AMF) communities in soil. Soil samples collected from bamboo-dominated (BM) and non-bamboo (NB) forest patches in three different locations viz., Moragolla, Maragomuwa and Galboda, were enumerated for AMF spores using wet sieving and decanting method. A total of 1,577 and 898 AMF spores were documented from BM and NB forest patches, respectively. A total of 14 different morphotypes belonged to the genera, Glomus, Scutellospora, Gigaspora and Acaulospora, were identified. Glomus was the dominant genus in all study sites, while Acaulospora the least. The mean abundance and richness of AMF spores were higher in BM than in NB, with the most notable difference observed at Maragomuwa. These site-specific variations may perhaps due to the differences in vegetation characteristics, edaphic properties and disturbance regimes. However, the community structure of AMF showed no conspicuous modifications due to the over-abundance of B. bambos. The findings reiterated the general understanding that any changes to the above-ground vegetation may incur impacts on the AMF. However, AMF community structure shows resilience to influences imposed by the dominance of a single species.

Deciphering the binding mode and mechanistic insights of pentadecylidenemalonate (1b) as activator of histone acetyltransferase PCAF

Histone acetyltransferases (HATs) is one among the conspicuous posttranslational modification in eukaryotic cells. p300/CBP Associated Factor (PCAF) and CREB-binding protein (CBP) are the two highly homologous HAT family which are vastly implicated in several diseases like cancer, diabetes, etc. Pentadecylidenemalonate, a simplified analog of anacardic acid, was reported as first mixed inhibitor/activator of HATs which inhibits p300/CBP and activates PCAF. It was appointed earlier as a valuable biological tool to understand the mechanism of lysine acetyltransferases due to its powerful apoptotic effect. In this study, pentadecylidenemalonate was taken for deciphering the binding mode, key interacting residues as well as mechanistic insights on PCAF and CBP as activator and inhibitor, respectively. This study is highly believed to help in rational design on antineoplastic drugs against PCAF.Communicated by Ramaswamy H. Sarma

Identification and examination of inconspicuous carnivore modifications

Bone modifications are associated with a broad range of agents, including carnivores, stone tools, sediments, etc., and can be categorized as one of two types: conspicuous or inconspicuous. Contrary to the larger, more easily identifiable conspicuous modifications, inconspicuous modifications are small, shallow and almost unnoticeable without the aid of a hand lens and strong light, making them harder and more time consuming to identify. This has led to arguments for their omission from tooth mark counts, even though their presence on the bones of archaeological and paleontological faunal assemblages have been recognized and mentioned in literature as having interpretive potential.This study employs visible light microscopy and high resolution scanning electron microscopy to present evidence that positively identifies inconspicuous carnivore modifications as abrasions that also have diagnostic morphology which differentiates them from abrasion created by other taphonomic agents. These inconspicuous carnivore marks may also be associated with the presence of soft tissue and so may help reconstruct the amount of flesh present at specific stages of carcass consumption. This study shows the interpretive potential of ICA may be substantial, requiring their inclusion in tooth mark counts for more accurate reconstructions of past carnivore behavior.Furthermore, understanding the etiology and implications of inconspicuous carnivore marks may provide a new way to interpret faunal assemblages that exhibit such marks, such as those associated with FLK Zinjanthropus, Tanzania. Such interpretations may be able to help develop stronger inferences regarding methods of hominin carcass acquisition.

Feeding structures in the ray-finned fishEurynotus crenatus(Actinopterygii: Eurynotiformes): implications for trophic diversification among Carboniferous actinopterygians

ABSTRACTThe Permo-Carboniferous eurynotiforms show conspicuous modifications to postcranial and cranial morphology relative to primitive actinopterygian conditions, and represent an important early example of functional experimentation within ray-finned fishes. Although eurynotiforms are represented by abundant articulated fossil material, the internal anatomy of the group is not well known. Microcomputed tomography (μCT) ofEurynotus crenatusfrom the early Carboniferous (Viséan) Wardie Shales Member of the Gullane Formation of Wardie, Scotland provides detailed information on the jaws, palate and dentition. The lower jaw is deep and bears a well-developed convex dental plate on the prearticular/coronoids. The dentary bears a dorsally directed posterior process and lacks any obvious marginal dentition. The prearticular bears a low coronoid process. Apart from the first and second dermopalatines, and a likely accessory vomer, bones of the palate are tightly sutured or fused. The upper dental plate comprises a longitudinal, concave horizontal dental surface that occludes with the convex lower toothplate, and a more vertical region consisting of anastomosing ridges. The parasphenoid has a narrow anterior corpus and a broad posterior stalk that bears a pronounced midline notch. The smooth, irregularly punctated surfaces of the dental plates are formed by closely packed teeth with conjoined crowns, providing clues to the evolution of the more monolithic toothplates ofAmphicentrumfrom the peg-like teeth reported in the earliest and most anatomically generalised eurynotiforms. The feeding apparatus shows many qualitative and quantitative features consistent with the processing of hard prey items.Eurynotusand its relatives show the first clear example of jaw and dental structures consistent with durophagy among actinopterygians. The origin of the group in the early Carboniferous is suggestive of diversification into newly available ecological roles in the aftermath of the end-Devonian extinction.

Squeeze Casting of Semiolid A356 Alloy

The rheo-squeeze casting (rheo-SQC) combining the rheocasting and the SQC was developed, in which semisolid slurry was produced by the low superheat pouring with a shearing field (LSPSF) process. The three-dimensional morphology of the primary α-Al phase and the rest spacing of slurry prepared by LSPSF process have been reconstructed and visualized, and the microstructures of squeeze cast A356 alloy have been obtained. Based on the three-dimensional microstructure reconstructed, their three-dimensional characterizations such as solid volume fraction and equivalent diameter of the extracted primary α-Al phase of the slurry were measured and calculated. And the microstructures of cross-section of squeeze cast product were investigated. Compared and analyzed the typical microstructure characteristics of parts in different positions produced by SQC and rheo-SQC, the results show that the primary α-Al phase was in the form of enriched dendrites across the whole section of parts produced by SQC. Nevertheless, in the relative case of the rheo-SQC, the whole formations of dendrites have been inhibited effectively, revealing a conspicuous modification in morphology and refinement of the primary α-Al phase. In addition, the solid fraction decreased from the centre to the verge of products along the slurry flow orientation.

Climate variance influence on the non-stationary plankton dynamics

We examined plankton responses to climate variance by using high temporal resolution data from 1988 to 2007 in the Western English Channel. Climate variability modified both the magnitude and length of the seasonal signal of sea surface temperature, as well as the timing and depth of the thermocline. These changes permeated the pelagic system yielding conspicuous modifications in the phenology of autotroph communities and zooplankton. The climate variance envelope, thus far little considered in climate-plankton studies, is closely coupled with the non-stationary dynamics of plankton, and sheds light on impending ecological shifts and plankton structural changes. Our study calls for the integration of the non-stationary relationship between climate and plankton in prognostic models on the productivity of marine ecosystems.

New Late Pleistocene megafaunal assemblage with well-supported chronology from the Pampas of southern South America

Late Pleistocene outcrops exposed in Buenos Aires province, Argentina, represent one of the most informative sources about the paleoecology of South American megafauna. However, there are no records of an accurately dated carnivore–herbivore taphocenosis. This paper presents preliminary results of a recent excavation at the margins of the Salado River, on sediments attributed to the Luján Formation (Late Pleistocene–Early Holocene). The fossiliferous strata consist of greenish brown sandy-clays deposited in a small paleopond environment that was filled by fluvial sediments, exhibiting abundant organic matter, gypsum and carbonate concretions. Fieldwork yielded an association of extinct large-sized mammals that include the horse Hippidion principale, the saber-tooth cat Smilodon populator (at least one adult and one juvenile associated specimen), a giant ground sloth Megatherium americanum, and the glyptodont Doedicurus clavicaudatus. Four 14C dates were performed on organic matter (12,100 ± 100 14C BP), a femur of S. populator (13,400 ± 200 14C BP), and a cervical vertebra of Hippidion principale (12,860 ± 120 14C BP), and a pelvis of D. clavicaudatus (12,380 ± 190 14C BP) situating the site within 12,500 and 13,500 years, approximately. Remarkably, some of the recovered specimens exhibit conspicuous bone modifications (furrows, pits, punctures, striations and crenulated margins) attributed to the activity of a medium-large carnivore. The association between bones of herbivore mammals with conspicuous modifications produced by a large carnivore, and the presence of cub and adult remains of Smilodon, link this felid with at least part of the excavated association.

Calcium imaging in single neurons from brain slices using bioluminescent reporters

Responses of three bioluminescent Ca(2+) sensors were studied in vitro and in neurons from brain slices. These sensors consisted of tandem fusions of green fluorescent protein (GFP) with the photoproteins aequorin, obelin, or a mutant aequorin with high Ca(2+) sensitivity. Kinetics of GFP-obelin responses to a saturating Ca(2+) concentration were faster than those of GFP-aequorin at all Mg(2+) concentrations tested, whereas GFP-mutant aequorin responses were the slowest. GFP-photoproteins were efficiently expressed in pyramidal neurons following overnight incubation of acute neocortical slices with recombinant Sindbis viruses. Expression of GFP-photoproteins did not result in conspicuous modification of morphological or electrophysiological properties of layer V pyramidal cells. The three sensors allowed the detection of Ca(2+) transients associated with action potential discharge in single layer V pyramidal neurons. In these neurons, depolarizing steps of increasing amplitude elicited action potential discharge of increasing frequency. Bioluminescent responses of the three sensors were similar in several respects: detection thresholds, an exponential increase with stimulus intensity, photoprotein consumptions, and kinetic properties. These responses, which were markedly slower than kinetics measured in vitro, increased linearly during the action potential discharge and decayed exponentially at the end of the discharge. Onset slopes increased with stimulus intensity, whereas decay kinetics remained constant. Dendritic light emission contributed to whole-field responses, but the spatial resolution of bioluminescence imaging was limited to the soma and proximal apical dendrite. Nonetheless, the high signal-to-background ratio of GFP-photoproteins allowed the detection of Ca(2+) transients associated with 5 action potentials in single neurons upon whole-field bioluminescence recordings.

Homospermidine in transgenic tobacco results in considerably reduced spermidine levels but is not converted to pyrrolizidine alkaloid precursors

Homospermidine synthase is the first specific enzyme in the biosynthesis of pyrrolizidine alkaloids. Whereas the substrates putrescine and spermidine are part of the highly dynamic polyamine pool of plants, the product homospermidine is incorporated exclusively into the necine base moiety of pyrrolizidine alkaloids. Recently, the gene encoding homospermidine synthase has been shown to have been recruited several times independently during angiosperm evolution by the duplication of the gene encoding deoxyhypusine synthase. To test whether high levels of homospermidine suffice for conversion, at least in traces, to precursors of pyrrolizidine alkaloids, transgenic tobacco plants were generated expressing homospermidine synthase. Analyses of the polyamine content revealed that, in the transgenic plants, about 80% of spermidine was replaced by homospermidine without any conspicuous modifications of the phenotype. Tracer-feeding experiments and gas chromatographic analyses suggested that these high levels of homospermidine were not sufficient to explain the formation of alkaloid precursors. These results are discussed with respect to current models of pathway evolution.

A new species of Seira Lubbock (Collembola: Entomobryidae) from Brazil with sexually dimorphic legs

A new species of Seira Lubbock, S. bicolorcornuta sp. nov., from Alto do Moura, Pernambuco State, Brazil, is described and illustrated. The males of this species have conspicuous modifications on the first pair of legs. This condition and other morphological features indicate a clear relationship between S. bicolorcornuta sp. nov. and S. raptora Zeppelini &amp; Bellini. The distribution and chaetotaxic patterns of both species are discussed.

Efeitos de fertilização na biomassa e qualidade nutricional do zooplâncton utilizado para alimentação de alevinos na estação de hidrobiologia e piscicultura de Furnas, MG

This investigation aimed to evaluate the effects of organic matter (pig manure) and nutrients on the structure of zooplankton in plankton tanks at Furnas hatchery station. Zooplankton is commonly used as food resource of Hoplias lacerdae fry. Total lipid levels, density and biomass of zooplankton were analyzed in two plankton tanks twice a week during 60 days. Water temperature, pH, dissolved oxygen and electric conductivity were also monitored daily. Chlorophyll-a, total phosphorus, ammonium and total kejdahl nitrogen (TKN) were measured on a weekly basis. In the first thirty days, nutrient fertilization was performed every five days. In the last thirty days, there was no external input of nutrient or organic material. The interruption of external nutrient load caused a clear and conspicuous modification in most physical and chemical variables as well as in the zooplankton. There was an abrupt and conspicuous reduction in the conductivity, ammonium , TKN, total phosphorus and chlorophyll. On the other hand, dissolved oxygen and pH increased. Biomass of total zooplankton also showed a brief peak following the interruption of external nutrient flux. During this period, the cladocera Moina and the rotifer Brachionus calyciflorus became the dominant zooplanktons. At the end of the study, the ciclopods became once more the dominant organisms, although there was a higher proportion of immature stages. Levels of total lipids of zooplankton remained at lower levels (6-10%) throughout the covered period, suggesting that zooplankton was eating food particles of lower nutritional quality. Nevertheless, the study demonstrates that nutrient input is essential for maintaining zooplankton at adequate levels. However, lower lipid levels also suggest that the quality, quantity and frequency of this nutrient input showed be thoroughly revised.

Very Long-chain Polyunsaturated Fatty Acids Are the Major Acyl Groups of Sphingomyelins and Ceramides in the Head of Mammalian Spermatozoa

Very long-chain (C24 to C34) polyunsaturated fatty acids (VLCPUFA) are important constituents of sphingomyelin (SM) and ceramide (Cer) in testicular germ cells. In the present paper we focused on the SM and Cer and their fatty acids in spermatozoa and their main regions, heads and tails. In bull and ram spermatozoa, SM was the third most abundant phospholipid and VLCPUFA were the major acyl groups ( approximately 70%) of SM and Cer. In rat epididymal spermatozoa the SM/Cer ratio was low in the absence of and could be maintained high in the presence of the cation chelator EDTA, added to the medium used for sperm isolation. This fact points to the occurrence of an active divalent cation-dependent sphingomyelinase. Bull and rat sperm had an uneven head-tail distribution of phospholipid, with virtually all the VLCPUFA-rich SM located at the head, the lower SM content in the rat being determined by the lower sperm head/tail size ratio. Most of the SM from bull sperm heads was readily solubilized with 1% Triton X-100 at 4 degrees C. The detergent-soluble SM fraction was richer in VLCPUFA than the nonsoluble fraction and richer in saturated fatty acids. Cer was produced at the expense of SM, thus decreasing severalfold the SM/Cer ratio in rat spermatozoa incubated for 2 h in presence of the sperm-capacitating agents, calcium, bicarbonate, and albumin. The generation of Cer from SM in the sperm head surface may be an early step among the biochemical and biophysical changes known to take place in the spermatozoon in the physiological events preceding fertilization.

The Wake-Promoting Hypocretin/Orexin Neurons Change Their Response to Noradrenaline after Sleep Deprivation

Sleep deprivation is accompanied by the progressive development of an irresistible need to sleep, a phenomenon whose mechanism has remained elusive. Here, we identified for the first time a reflection of that phenomenon in vitro by showing that, after a short 2 h period of total sleep deprivation, the action of noradrenaline on the wake-promoting hypocretin/orexin neurons changes from an excitation to an inhibition. We propose that such a conspicuous modification of responsiveness should contribute to the growing sleepiness that accompanies sleep deprivation.

Extracellular matrix synthesis, proliferation and death in mechanically stimulated human gingival fibroblasts in vitro

Gingival tissues are constantly exposed to the effect of physical forces. Mechanical stimuli are regulators of connective tissue homeostasis and sustained mechanical stimulation may lead to modifications in cell activity and extracellular matrix (ECM) composition. This study examined in vitro ECM synthesis, proliferation, and death in mechanically stimulated human gingival fibroblastlike cells. Four primary human cell strains were established and subjected to intermittent stretching in FX-3000 Flexercell Strain Unit for 10 days, 45 min/day, at 1 Hz, 10% strain, and cell proliferation, cell death, and synthesis of collagens types I, III, and V, matrix metalloproteinase 1, elastin, and tenascin were assessed. In some of the cell strains mechanical stimulation led to changes in synthesis of the ECM molecules, proliferative activity, and death of stimulated cells as shown by statistically significant differences between the experimental and unstimulated control cultures. Although not seen in every culture investigated, these findings suggest that prolonged mechanical stimulation might lead to conspicuous modifications in the metabolic activity of gingival fibroblasts and cause changes in the ECM composition of the gingival connective tissue. The results indicate a pronounced interindividual variation in reactions of gingival fibroblasts to mechanical stimulation.

Sperm ultrastructure and spermiogenesis in two Exogone species (Polychaeta, Syllidae, Exogoninae)

Abstract. The spermatozoa of Exogone naidina and E. dispar are characterized by a prominent bell‐shaped acrosome, a spheroidal nucleus, and a conventional flagellum. During spermiogenesis, the acrosomal vesicle undergoes conspicuous modifications leading to its final bell shape with a posterior opening. The subacrosomal material initially shows radiating filaments but in mature sperms it appears as a meshwork of electron‐opaque material. The acrosomal axis is oblique with respect to the main longitudinal sperm axis. The chromatin is arranged in electron‐opaque strands in the early spermatids, then becomes amorphous, and is finally organized in filaments in mature sperms. Centrioles are orthogonally arranged beneath the nucleus and fibers radiate from the distal centriole to contact the plasma membrane and the single mitochondrion. The latter is located eccentrically on the side of the nucleus opposite the acrosome. A disk‐shaped structure is evident beneath the distal centriole. The flagellar axoneme has a 9+2 microtubule pattern. A conspicuous glycocalyx surrounds the flagellar plasma membrane, and an electron‐lucent space is present between these two structures at the distal tip of the flagellum. We compare the sperm morphology of these two species of Exogone with that described in other members of the subfamily Exogoninae. The fine structure of these two species supports the occurrence of an ent‐aquasperm type within Exogoninae, in accordance with the brood strategy present within this subfamily. The mode of reproduction is of taxonomic importance for defining subfamilies within Syllidae, and is likely also of phylogenetic significance. Because epitoky is probably plesiomorphic, the ent‐aquasperm type found in Exogoninae can be considered a derived feature within Syllidae.