Ultrastuctural and cytochemical study of spermatogenesis in Scrobicularia plana (Mollusca,Bivalvia)

The ultrastructure of the mature spermatozoa and spermatogenesis of the bivalve Scrobicularia plana are described. Support cells extend from the basal lamina to the lumen of the testis and are laterally connected to the germinal epithelium. Germ cells present intercellular bridges and flagella since the spermatogonial stage. While spermatogonia and spermatocytes appear connected to support cells by desmosome-like junctions, elongated spermatids are held at the acrosomal region by support cell finger-like processes. During spermiogenesis, the acrosomal vesicle differentiates from a golgian saccule and then migrates to the nuclear apex. A microtubular manchette arising from centrioles surrounds the acrosomal vesicle, the nucleus, and the mitochondria at the time these three organelles start their elongation, disappearing after that. The mature spermatozoon of S. plana lacks a distinct midpiece because the mitochondria extend from the region of the pericentriolar complex along the nucleus anteriorly for approximately 1.4 μm. The features of this bivalve type of modified spermatozoon are compared with those of other animal groups having similar modifications.     

3D genome organization in the central nervous system,implications for neuropsychological disorders

Chromosomes in eukaryotic cell nuclei are highly compacted and finely organized into hierarchical three-dimensional (3D) configuration. In recent years, scientists have gained deeper understandings of 3D genome structures and revealed novel evidence linking 3D genome organization to various important cell events on the molecular level. Most importantly, alteration of 3D genome architecture has emerged as an intriguing higher order mechanism that connects disease-related genetic variants in multiple heterogenous and polygenic neuropsychological disorders, delivering novel insights into the etiology. In this review, we provide a brief overview of the hierarchical structures of 3D genome and two proposed regulatory models, loop extrusion and phase separation. We then focus on recent Hi-C data in the central nervous system and discuss 3D genome alterations during normal brain development and in mature neurons. Most importantly, we make a comprehensive review on current knowledge and discuss the role of 3D genome in multiple neuropsychological disorders, including schizophrenia, repeat expansion disorders, 22q11 deletion syndrome, and others.     

Nucleolar apparatus in the macronucleus of Didinium nasutum (Ciliata): EM and 3D reconstruction

The three-dimensional (3D) organization of nucleoli in the somatic nuclei (macronuclei) of recently fed and starved Didinium nasutum was reconstructed on the basis of serial ultra-thin sections. It was shown that nucleoli, looking on the single sections like individual separate structures, appeared to be parts of the large complicated branchy nucleolar networks. A 30 h starvation did not lead to disintegration of this network, but stimulated formation of numerous vacuoles in the granular component of nucleoli, which becomes more condensed. Unlike starved D. nasutum, in fed ciliates numerous holes appeared in the fibrillar component located at the periphery of nucleoli. These holes may presumably serve as channels for transporting newly synthesized rRNA. To our knowledge, this is the first report of a 3D reconstruction of the nucleolar apparatus in ciliates.     

2,3-Dimethylpyrazine (3DP) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) generated by the Maillard reaction in foods affect autonomic nervous activity and central nervous activity in human

ABSTRACT

This study investigated the effect of the odors generated by the glycine/glucose Maillard reaction and the potent odorants 2,3-dimethylpyrazine (3DP) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) on the human mood and integrative physiological activity. The score of certain subjective moods, especially anger-hostility, and tension-anxiety were decreased significantly after inhalation of the Maillard reaction sample and DMHF, and fatigue-inertia mood was also significantly decreased by DMHF, suggesting a sedative effect of these odors on mood, while 3DP had no effect. Miosis rate and fingertip temperature increased significantly following inhalation of the odor from the Maillard reaction sample and both potent odorants, suggesting that the parasympathetic nervous system dominates through suppression of the sympathetic activity. The physiological relaxing effect of these odors was also confirmed by decreased flicker frequency value and decreased oxyhemoglobin in the prefrontal cortex.     

Larval development of the shell and the shell gland inMytilus (Bivalvia)

Summary In the newly hatched larva ofMytilus galloprovincialis the larval shell field almost totally invaginates to form a shell gland. Only very few cells remain outside and they meet at one point. Only these cells secrete the pellicle, which in the beginning is protected by the glycocalyx and the microvilli of the surrounding cells. The invaginated cells do not participate in pellicle secretion. The secretion partly passes through infoldings of the apical cell membrane. Mineralization of each valve begins along the hinge line, continues to the valve margins and includes the valve centre.     

Ontogeny and evolution within the Myophorellidae (Bivalvia): Paedomorphic trends

The role of heterochronic phenomena in molluscan evolution is insufficiently understood but potentially significant. The aim of this paper is to explore some paedomorphic trends in the evolution of the Myophorellidae (Bivalvia: Trigoniida). Early ontogeny of general shell shape and ornamentation of one species of Steinmanella was analyzed and compared to data obtained for three species of Myophorella: two belonging to the subgenus M. (Promyophorella) (one from the Jurassic and one from the Cretaceous) and one belonging to the Jurassic M. (Myophorella). For general shell shape, a geometric morphometric analysis was performed on lateral views of the shells. Regarding ornamentation, flank costal disposition on the marginal carina, tubercle separation and relative development of the sub-commarginal subset of flank costae were quantified. A qualitative analysis was also performed. A two-trend shell shape development is considered as primitive. The first trend is marked by a relative reduction of the posterior margin together with a relative elongation of the shell. A tangential opisthogyrate growth component characterizes the second trend. There is a transitional stage where both trends interact. Early flank ornamentation is characterized by two or three sub-commarginal costae, continuous through the area, after which oblique costae with fine tubercles start to form. The subgenus M. (Myophorella) evolved by paedomorphic retention of juvenile shell shape and ornamentation, resulting in a large shell with coarse tubercles. Shell morphology in Steinmanella evolved by paedomorphic suppression of the primitive second trend in the development of the shell, resulting in an orthogyrate shell shape, and the retention of juvenile ornamentation (coarse tubercles, more sub-commarginal costae, juvenile rates of costal disposition). The paedomorphic (most likely by deceleration) retention of juvenile shell morphology within the Myophorellidae seems to have been recurrent within the group, resulting in many cases of convergence, and obscuring the phylogenetic relationships among its species.     

Accuracy of computer-aided geometric 3D reconstruction based on histological serial microgrinding preparation

Purpose: For our research on computer-optimised and automated cochlear implant surgery, we pursue a model-based approach to overcome the limitations of currently available clinical imaging modalities. A serial cross section preparation procedure has been developed and evaluated concerning accuracy to serve for modelling of a digital anatomic atlas to make delicate soft tissue structures available for pre-operative planning.

Methods: A special grinding tool was developed allowing the setting of a specific amount of abrasion as equidistant slice thickness was considered a crucial step. Additionally, each actual abrasion was accurately measured and used during three-dimensional reconstruction of the serial cross-sectional images obtained via digital photo documentation after each microgrinding step. A well-known reference object was prepared using this procedure and evaluated in terms of accuracy.

Results: Reconstruction of the whole sample was achieved with an error less than 0.4%, and the edge lengths in the direction of abrasion could be reconstructed with an average error of 0.6 ± 0.3 mm; both prove the realisation of equidistant abrasion. Using artificial registration fiducials and a custom-made algorithm for image alignment, parallelism and rectangularity could be preserved with average errors less than 0.4° ± 0.3°.

Conclusion: We present a systematic, practicable and reliable method for the geometrically accurate reconstruction of anatomical structures, which is especially suitable for the middle and inner ear anatomy including soft tissue structures. For the first time, the quality of such a reconstruction process has been quantified and successfully proven for its usability.     

Mathematical and experimental insights into the development of the enteric nervous system and Hirschsprung's disease

The vertebrate enteric nervous system is formed by a rostro-caudally directed invasion of the embryonic gastrointestinal mesenchyme by neural crest cells. Failure to complete this invasion results in the distal intestine lacking intrinsic neurons. This potentially fatal condition is called Hirschsprung's Disease. A mathematical model of cell invasion incorporating cell motility and proliferation of neural crest cells to a carrying capacity predicted invasion outcomes to imagined manipulations, and these manipulations were tested experimentally. Mathematical and experimental results agreed. The results show that the directional invasion is chiefly driven by neural crest cell proliferation. Moreover, this proliferation occurs in a small region at the wavefront of the invading population. These results provide an understanding of why many genes implicated in Hirschsprung's Disease influence neural crest population size. In addition, during in vivo development the underlying gut tissues are growing simultaneously as the neural crest cell invasion proceeds. The interactions between proliferation, motility and gut growth dictate whether or not complete colonization is successful. Mathematical modeling provides insights into the conditions required for complete colonization or a Hirschsprung's-like deficiency. Experimental evidence supports the hypotheses suggested by the modeling.     

Abundance,Population Structure and Production of Scrobicularia plana and Abra tenuis (Bivalvia: Scrobicularidae) in a Mediterranean Brackish Lagoon,Lake Ichkeul,Tunisia

Abundance, growth and production of the deposit‐feeding bivalves were studied in the Ichkeul wetland, northern Tunisia, from July 1993 – April 1994. Scrobicularia plana (Da Costa , 1778) occurred at annual mean densities (biomasses) of 299 ± 65 to 400 ± 100 individuals/m² (22.54 ± 3.00 to 34.27 ± 3.96 g ash‐free dry mass (AFDM)/m²) depending on the study area. The annual mean density of Abra tenuis (Montagu , 1803) amounted to 640 ± 74 individuals/m² during the whole study period, in contrast the biomass rose from 2.87 g AFDM/m² in July to 10.29 g AFDM/m² in April. Both species were largely dominated by age class I. Although not very successful, recruitment presented a two‐period pattern: the main period at the beginning of spring, and a secondary one in late summer/autumn. S. plana rarely exceeded 40 mm and lived for only 2 years, while most individuals of A. tenuis lived for only 15–18 months growing to a length of 12 mm. The annual bivalve deposit‐feeder production for the whole lagoon system (90 km²) was 8.24 g AFDM/m² (5.26 g C/m², 0.65 g N/m²). The annual P/ ratio was about 0.4 and therefore in the same order of magnitude as estimates from other brackish coastal waters. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Palaeohistology and external microanatomy of rauisuchian osteoderms (Archosauria: Pseudosuchia)

Abstract: The presence of postcranial dermal armour is plesiomorphic for Archosauria. Here, we survey the external microanatomy and histology of postcranial osteoderms (i.e. dorsal paramedian and caudal osteoderms) of rauisuchians, a widely distributed assemblage of extinct predatory pseudosuchians from the Triassic. The osteoderms of eight rauisuchian taxa were found to be rather compact bones, which usually lack significant bone remodelling or large areas of cancellous bone. The presence of highly vascularized woven or fibrolamellar bone tissue deposited in the core areas indicates higher growth rates during earlier life stages, whereas a more compact parallel‐fibred bone matrix indicates reduced growth rates in later development. This pattern of change corroborates earlier studies on long bone histology. With the exception of a bone tissue found in the sample of Batrachotomus kupferzellensis, which might be the result of metaplastic ossification, the general mode of skeletogenesis is comparable with intramembraneous ossification. The lack of cancellous bone tissue and remodelling processes associated with bone ornamentation, as well as the predominantly intramembraneous mode of ossification, indicates that rauisuchian osteoderm formation differs profoundly from that of the osteoderms of the only extant pseudosuchian lineage, the crocodylians.     

Development and validation of a generic 3D model of the distal femur

The development and validation of a virtual generic 3D model of the distal femur using computer graphical methods is presented. The synthesis of the generic model requires the following steps: acquisition of bony 3D morphology using standard computed tomography (CT) imaging; alignment of 3D models reconstructed from CT images with a common coordinate system; computer graphical sectioning of the models; extraction of bone contours from the image sections; combining and averaging of extracted contours; and 3D reconstruction of the averaged contours.

The generic models reconstructed from the averaged contours of six cadaver femora were validated by comparing their surface geometry on a point to point basis with that of the CT reconstructed reference models. The mean errors ranged from 0.99 to 2.5 mm and were in agreement with the qualitative assessment of the models.     

New insights into the control of neurotrophic growth factor receptor signaling: Implications for nervous system development and repair

Neurotrophic growth factors control neuronal development by activating specific receptor tyrosine kinase positive signaling pathways, such as Ras‐MAPK and PI3K‐Akt cascades. Once activated, neurotrophic factor receptors also trigger a cascade of molecular events, named negative receptor signaling, that restricts the intensity of the positive signals and modulates cellular behavior. Thus, to avoid signaling errors that ultimately could lead to aberrant neuronal physiology and disease, negative signaling mechanisms have evolved to ensure that suitable thresholds of neuronal stimulation are achieved and maintained during right periods of time. Recent findings have revealed that neurotrophic factor receptor signaling is tightly modulated through the coordinated action of many different protein regulators that limit or potentiate signal propagation in spatially and temporally controlled manners, acting at specific points after receptor engagement. In this review, we discuss progress in this field, highlighting the importance of these modulators in axonal growth, guidance, neural connectivity, and nervous system regeneration.     

Architecture of the nervous system in mystacocarida (Arthropoda,crustacea)—An immunohistochemical study and 3D reconstruction

Mystacocarida is a species‐poor group of minute crustaceans with unclear phylogenetic affinities. Previous studies have highlighted the putative “primitiveness” of several mystacocarid features, including the architecture of the nervous system. Recent studies on arthropod neuroarchitecture have provided a wealth of characters valuable for phylogenetic reconstructions. To permit and facilitate comparison with these data, we used immunohistochemical labeling (against acetylated α‐tubulin, serotonin and FMRFamide) on the mystacocarid Derocheilocaris remanei, analyzing it with confocal laser‐scanning microscopy and 3D reconstruction. The mystacocarid brain is fairly elongated, exhibiting a complicated stereotypic arrangement of neurite bundles. However, none of the applied markers provided evidence of structured neuropils such as a central body or olfactory glomeruli. A completely fused subesophageal ganglion is not present, all segmental soma clusters of the respective neuromeres still being delimitable. The distinct mandibular commissure comprises neurite bundles from more anterior regions, leading us to propose that it may have fused with an ancestral posterior tritocerebral commissure. The postcephalic ventral nervous system displays a typical ladder‐like structure with separated ganglia which bears some resemblance to larval stages in other crustaceans. Ganglia and commissures are also present in the first three limbless “abdominal” segments, which casts doubt on the notion of a clear‐cut distinction between thorax and abdomen. An unpaired longitudinal median neurite bundle is present and discussed as a potential tetraconate autapomorphy. Additionally, a paired latero‐longitudinal neurite bundle extends along the trunk. It is connected to the intersegmental nerves and most likely fulfils neurohemal functions. We report the complete absence of serotonin‐ir neurons in the ventral nervous system, which is a unique condition in arthropods and herein interpreted as a derived character. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Qualitative and Quantitative analysis of 3D predicted arachidonate 15-lipoxygenase-B (15-LOX-2) from Homo sapiens

15-Lipoxygenase-2 protein has been reported to play an important role in normal development of prostate, lung, skin, and cornea tissues. It behaves as a suppressor of prostate cancer development by restricting cell cycle progression and implicating a possible protective role against tumor formation. On the basis of the above report, we selected 15-LOX-2 protein to study the structural classification and functional relationship with associated protein network at computational level. Sequence alignment and protein functional study shows that it contains a highly conserved LOX motif. PLAT domain with PF01477 and LH2 domain with PF00305 were successfully observed. Arachidonate 5-lipoxygenase (PDB ID: 3O8Y) was selected as a template with 42% identity. 3D structure was successfully predicted and verified. Qualitative analysis suggests that the predicted model was reliable and stable with best quality. Quantitative study shows that the model contained expected volume and area with best resolution. Predicted and best evaluated model has been successfully deposited to PMDB database with PMDB ID PM0078035. Active site identification revealed GLU(369), ALA(370), LEU(371), THR(372), HIS(373), LEU(374), HIS(376), SER(377), HIS(378), THR(385), LEU(389), HIS(394), PHE(399), LYS(400), LEU(401), ILE(403) and PRO(404) residues may play a major role during protein-protein, protein-drug and protein-cofactor interactions. STRING database result indicated that IL (4), GPX (2 and 4), PPARG, PTGS (1 and 2), CYP (2J2, 2C8, 4A11 and 2B6), PLA (2G2A, 2G4A, 2G1B and 2G6) and A LOX (5, 15, 12 and 12B) members from their respective gene families have network based functional association with 15-LOX-2.     

Expression of vitamin D receptors in the superior cervical ganglia of rats

We investigated the role of vitamin D in the sympathetic nervous system including the distribution of vitamin D receptors (VDR), 1α-hydroxylase and 24-hydroxylase (CYP24) in neuronal subpopulations and satellite glia in the superior cervical ganglia (SCGs) of rats using immunohistochemistry. VDR immunoreactivity was observed in the cytoplasm and nucleus of nearly all neurons in the SCG. Intensity of VDR fluorescence was significantly greater in the cytoplasm of neuropeptide Y (NPY) negative somata compared to NPY positive neurons. Immunoreactivity for 1α-hydroxylase also was observed in the cytoplasm of all neurons of the SCG, but the intensity of fluorescence was less in the nuclei. To the contrary, the immunoreactivity for CYP24 was stronger in the nuclei, although it was present at lower intensity also in the cytoplasm of neurons. VDR and 1α-hydroxylase immunofluorescence was observed in many non-neuron cells, except satellite glial cells, which exhibited weak CYP24 immunofluorescence. Expression of VDRs and key metabolizing enzymes indicated the importance of vitamin D in the autonomic nervous system and the ability of sympathetic neurons to activate and deactivate vitamin D for its autocrine and paracrine roles.     

Morphometry and microanatomy of the barbels of the common sawshark Pristiophorus cirratus (Pristiophoridae): implications for pristiophorid behaviour

The internal anatomy of the barbels of the common sawshark Pristiophorus cirratus was examined with light microscopy to clarify their sensory role. No sensory structures such as taste buds (chemoreception), ampullae of Lorenzini (electroreception) or free neuromasts (lateral line mechanoreception) could be located in the barbels. The presence of bundles of nerve fibres, however, indicates a tactile function for the barbels. Conveyance of information regarding potentially damaging stimuli (nociception) and temperature (thermoception) cannot be excluded at this stage. It is hypothesized that the barbels are used by P. cirratus to locate prey in both the water column and on the substratum via wake detection and sensing changes in surface texture. The barbels may also be involved in the detection of water currents for rheotaxis. Regression analyses on P. cirratus morphometric data showed that the width of the rostrum at two sections (the barbels and the rostrum tip) does not significantly correlate with total length. The regression analyses also suggested that the barbels of P. cirratus may be lateralised.     

The myosepta in Branchiostoma lanceolatum (Cephalochordata): 3D reconstruction and microanatomy

Zoomorphology - Myosepta have been subject to comparative and evolutionary studies in aquatic groups of the Craniata, because they are likely to play a role in transmission of muscular forces to...     

Basal ganglia and functions of the autonomic nervous system

1. The aim of this mini-review was to describe an underrecognized but important aspect of the basal ganglia diseases, the dysfunction of the autonomic nervous system that patients suffer owing to the degenerative process affecting these structures, mainly Parkinson's disease.2. We analyze the most prevalent autonomic abnormalities in these patients from an experimental and clinical point of view.