KymoRod: a method for automated kinematic analysis of rod‐shaped plant organs

A major challenge in plant systems biology is the development of robust, predictive multiscale models for organ growth. In this context it is important to bridge the gap between the, rather well‐documented molecular scale and the organ scale by providing quantitative methods to study within‐organ growth patterns. Here, we describe a simple method for the analysis of the evolution of growth patterns within rod‐shaped organs that does not require adding markers at the organ surface. The method allows for the simultaneous analysis of root and hypocotyl growth, provides spatio‐temporal information on curvature, growth anisotropy and relative elemental growth rate and can cope with complex organ movements. We demonstrate the performance of the method by documenting previously unsuspected complex growth patterns within the growing hypocotyl of the model species Arabidopsis thaliana during normal growth, after treatment with a growth‐inhibiting drug or in a mechano‐sensing mutant. The method is freely available as an intuitive and user‐friendly Matlab application called KymoRod.     

Apical end organ structure and histochemistry in plerocercoids of Proteocephalus ambloplitis

The end organ of Proteocephalus ambloplitis pleroceroids was studied by light microscopy and histochemistry. The end organ consists of a spherical sac filled with an amorphous, granular secretory product. The lining of the end organ is devoid of an epithelial cell layer. Protease was detected within the end organ by a gelatin-silver film technique. No aminopeptidase activity was detected. The end organ was PAS positive and diastase-fast. A positive test was obtained for neutral mucopolysaccharides and protein. The end organ is thought to assist migration of larvae through host tissue.     

Evolution of photosensory pineal organs in new light: the fate of neuroendocrine photoreceptors

Pineal evolution is envisaged as a gradual transformation of pinealocytes (a gradual regression of pinealocyte sensory capacity within a particular cell line), the so-called sensory cell line of the pineal organ. In most non-mammals the pineal organ is a directly photosensory organ, while the pineal organ of mammals (epiphysis cerebri) is a non-sensory neuroendocrine organ under photoperiod control. The phylogenetic transformation of the pineal organ is reflected in the morphology and physiology of the main parenchymal cell type, the pinealocyte. In anamniotes, pinealocytes with retinal cone photoreceptor-like characteristics predominate, whereas in sauropsids so-called rudimentary photoreceptors predominate. These have well-developed secretory characteristics, and have been interpreted as intermediaries between the anamniote pineal photoreceptors and the mammalian non-sensory pinealocytes. We have re-examined the original studies on which the gradual transformation hypothesis of pineal evolution is based, and found that the evidence for this model of pineal evolution is ambiguous. In the light of recent advances in the understanding of neural development mechanisms, we propose a new hypothesis of pineal evolution, in which the old notion 'gradual regression within the sensory cell line' should be replaced with 'changes in fate restriction within the neural lineage of the pineal field'.     

Isolation from Cholinergic Synapses of a Protein That Binds to Membranes in a Calcium-Dependent Manner

A protein that binds to membranes in a calcium-dependent manner between calcium concentrations of 10(-5) and 10(-6) M has been isolated in large amounts (20 mg/kg tissue) from the entirely cholinergic electric organ of Torpedo marmorata. The protein bound reversibly to membrane fractions in a calcium-specific and saturable manner. The protein also bound to lipids isolated from Torpedo electric organ and to clathrin-coated vesicles prepared from pig brain. The protein bound to a Triton X-100-sensitive site. It had an apparent subunit molecular weight of 32,000 by polyacrylamide gel electrophoresis and of 35,900 by amino acid analysis; a broad isoelectric range of 4.8 to 5.5; and 27% of its amino acids after hydrolysis were observed to be aspartic and glutamic acids. Synaptosomes derived from electric organ were enriched in the protein which is probably localised within the nerve ending. It was localised in the synaptic region of the electric organ by means of immunofluorescence. In the electric lobe, discrete patches of fluorescence were seen within the cell bodies that innervate the electric organ. The protein may be involved in the recognition of membranes within the cholinergic neurone. Proteins with similar purification properties were found in all tissues investigated so far, and polypeptides of subunit molecular weight 32,000 were identified in bovine adrenal medulla and guinea pig brain synaptosomes.     

Vessel and blood specification override cardiac potential in anterior mesoderm

Organ progenitors arise within organ fields, embryonic territories that are larger than the regions required for organ formation. Little is known about the regulatory pathways that define organ field boundaries and thereby limit organ size. Here we identify a mechanism for restricting heart size through confinement of the developmental potential of the heart field. Via fate mapping in zebrafish, we locate cardiac progenitors within hand2-expressing mesoderm and demonstrate that hand2 potentiates cardiac differentiation within this region. Beyond the rostral boundary of hand2 expression, we find progenitors of vessel and blood lineages. In embryos deficient in vessel and blood specification, rostral mesoderm undergoes a fate transformation and generates ectopic cardiomyocytes. Therefore, induction of vessel and blood specification represses cardiac specification and delimits the capacity of the heart field. This regulatory relationship between cardiovascular pathways suggests strategies for directing progenitor cell differentiation to facilitate cardiac regeneration.     

The tympanal hearing organ of the parasitoid fly Ormia ochracea (Diptera, Tachinidae, Ormiini)

Tympanate hearing has evolved in at least 6 different orders of insects, but had not been reported until recently in the Diptera. This study presents a newly discovered tympanal hearing organ, in the parasitoid tachinid fly, Ormia ochracea. The hearing organ is described in terms of external and internal morphology, cellular organization of the sensory organ and preliminary neuroanatomy of the primary auditory afferents. The ear is located on the frontal face of the prothorax, directly behind the head capsule. Conspicuously visible are a pair of thin cuticular membranes specialized for audition, the prosternal tympanal membranes. Directly attached to these membranes, within the enlarged prosternal chamber, are a pair of auditory sensory organs, the bulbae acusticae. These sensory organs are unique among all auditory organs known so far because both are contained within an unpartitioned acoustic chamber. The prosternal chamber is connected to the outside by a pair of tracheae. The cellular anatomy of the fly's scolopophorous organ was investigated by light and electron microscopy. The bulba acustica is a typical chordotonal organ and it contains approximately 70 receptor cells. It is similar to other insect sensory organs associated with tympanal ears. The similarity of the cellular organization and tympanal morphology of the ormiine ear to the ears of other tympanate insects suggests that there are potent constraints in the design features of tympanal hearing organs, which must function to detect high frequency auditory signals over long distances. Each sensory organ is innervated by a branch of the frontal nerve of the fused thoracic ganglia. The primary auditory afferents project to each of the pro-, meso-, and metathoracic neuropils. The fly's hearing organ is sexually dimorphic, whereby the tympanal membranes are larger in females and the spiracles larger in males. The dimorphism presumably reflects differences in the acoustic behavior in the two sexes.     

Differential scaling within an insect compound eye

Environmental and genetic influences cause individuals of a species to differ in size. As they do so, organ size and shape are scaled to available resources whilst maintaining function. The scaling of entire organs has been investigated extensively but scaling within organs remains poorly understood. By making use of the structure of the insect compound eye, we show that different regions of an organ can respond differentially to changes in body size. Wood ant (Formica rufa) compound eyes contain facets of different diameters in different regions. When the animal body size changes, lens diameters from different regions can increase or decrease in size either at the same rate (a ‘grade’ shift) or at different rates (a ‘slope’ shift). These options are not mutually exclusive, and we demonstrate that both types of scaling apply to different regions of the same eye. This demonstrates that different regions within a single organ can use different rules to govern their scaling, responding differently to their developmental environment. Thus, the control of scaling is more nuanced than previously appreciated, diverse responses occurring even among homologous cells within a single organ. Such fine control provides a rich substrate for the diversification of organ morphology.     

The tympanal hearing organ of the parasitoid fly Ormia ochracea (Diptera,Tachinidae, Ormiini)

Tympanate hearing has evolved in at least 6 different orders of insects, but had not been reported until recently in the Diptera. This study presents a newly discovered tympanal hearing organ, in the parasitoid tachinid fly, Ormia ochracea. The hearing organ is described in terms of external and internal morphology, cellular organization of the sensory organ and preliminary neuroanatomy of the primary auditory afferents. The ear is located on the frontal face of the prothorax, directly behind the head capsule. Conspicuously visible are a pair of thin cuticular membranes specialized for audition, the prosternal tympanal membranes. Directly attached to these membranes, within the enlarged prosternal chamber, are a pair of auditory sensory organs, the bulbae acusticae. These sensory organs are unique among all auditory organs known so far because both are contained within an unpartitioned acoustic chamber. The prosternal chamber is connected to the outside by a pair of tracheae. The cellular anatomy of the fly's scolopophorous organ was investigated by light and electron microscopy. The bulba acustica is a typical chordotonal organ and it contains approximately 70 receptor cells. It is similar to other insect sensory organs associated with tympanal ears.The similarity of the cellular organization and tympanal morphology of the ormiine ear to the ears of other tympanate insects suggests that there are potent constraints in the design features of tympanal hearing organs, which must function to detect high frequency auditory signals over long distances. Each sensory organ is innervated by a branch of the frontal nerve of the fused thoracic ganglia. The primary auditory afferents project to each of the pro-, meso-, and metathoracic neuropils. The fly's hearing organ is sexually dimorphic, whereby the tympanal membranes are larger in females and the spiracles larger in males. The dimorphism presumably reflects differences in the acoustic behavior in the two sexes.     

Morphological and histological organization of the pyriform appendage of the tetrabranchiate Nautilus pompilius (Cephalopoda,Mollusca)

The pyriform appendage, an organ only found in nautiloid cephalopods was investigated with histological, histochemical and ultrastructural methods in order to characterize the anatomical and the cytological structure of this organ. The pyriform appendage is situated within the genital septum and lies in close contact with the ventricle of the heart. The proximal side ends blindly near the gonad whereas the distal side is developed into a duct. The duct was observed to open into the mantle cavity in juvenile and adult Nautilus pompilius of both sexes. Injections of India ink in the heart demonstrate that the organ is supplied with hemolymph from an artery that extends from the heart. The pyriform appendage is a hollow organ consisting mainly of glandular tissue. The lumen is covered with a columnar epithelium, the tunica mucosa, consisting of only one cell type containing vacuoles with different inclusions. Underneath the tunica mucosa is the tunica muscularis, which is embedded in connective tissue and folded, enlarging the internal surface. A cuboidal tunica serosa surrounds this organ. The vacuoles and the secretory products contain neutral mucopolysaccharides, glycoproteins and glycolipids. Acid phosphatase and serotonin were localized in the tunica mucosa. Acetylcholinesterase, catecholamines and the tetrapeptide FMRF‐amide were demonstrated within the nerve endings of the tunica muscularis indicating a dual “cholinergic‐aminergic” neuroregulation, possibly modulated by FMRF‐amide. These findings suggest that the pyriform appendage is not a rudimentary organ but instead has distinct biological functions in nautiloid cephalopods, possibly in intraspecific communication. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.     

Histological,histochemical and electron microscopical studies on the nervous apparatus of the pineal organ in the tiger salamander,Ambystoma tigrinum

Summary 150–190 photoreceptor cells form a basic structural component of the pineal organ of Ambystoma tigrinum. Most of the outer and inner segments of these cells project into the lumen horizontally. Only 10 percent of the total number of photoreceptor cells are located within the pineal roof which is composed of a single cell layer. The photoreceptor cells are connected with nerve cells by synapses displaying characteristic ribbons. Different types of synaptic contacts, i.e. simple, tangential, dyad, triad and invaginated, are found. They are embedded in extended neuropil zones. A particular type of synapse indicates the presence of interneurons. The basal processes of some photoreceptor cells leave the pineal organ and make synaptic contacts with nervous elements located within the area of the subcommissural organ. Employing the method of Karnovsky and Roots (1964) for histochemical demonstration of acetylcholinesterase (AChE) approximately 70 neurons (intrapineal neurons) can be discerned in the pineal organ of Ambystoma tigrinum. In analogy to the distribution of photoreceptor cells only few nerve cells are observed in the roof portion of the pineal organ. Evidently, two different types of AChE-positive intrapineal neurons are present. About 40–50 AChE-positive neurons (extrapineal neurons) are scattered in the area of the subcommissural organ. In this area two types of nerve cells can be distinguished: 1) neurons which send pinealofugal (afferent) axons toward the posterior commissure and 2) neurons which emit pinealopetal (efferent) axons into or toward the pineal organ.The nervous pathways connecting the pineal organ with the diencephalomesencephalic border area are represented by a distinct pineal pedicle and several accessory pineal tracts.Granular nerve fibers run within the posterior commissure and establish synaptic contacts in the commissural region adjacent to the pineal organ. Some of these granular elements enter the pineal organ.The morphology of the nervous apparatus of the pineal organ of Ambystoma tigrinum is discussed in context with evidence from physiological experiments.In partial fulfillment of the requirements for the degree of Dr. med., Faculty of Medicine, Justus Liebig University, GiessenThe author is indebted to Professors A. Oksche and M. Ueck for their interest in this study. Thanks are due to Professor Ch. Baumann, Giessen, and Professor H. Langer, Bochum, for stimulating discussions. The technical assistance of Miss R. Liesner is gratefully acknowledgedDedicated to Professor Berta Scharrer on the occasion of her 70th birthday. Supported by grants from the Deutsche Forschungsgemeinschaft to A.O. and M.U.     

Beyond the ABCs: ternary complex formation in the control of floral organ identity

The production of a flower requires several events to occur. A floral meristem must form, boundaries must be set to enable discrete primordia to arise and the primordia must adopt the correct organ identity. Homeotic mutants, whose organs adopt inappropriate identities for their position within the flower, have helped the construction of a simple combinatorial model to explain how floral organ identity is defined. However, recent experiments suggest that the regulation of floral organ identity is more complex than was previously apparent. The simple interactions are becoming more complex and the universal applicability of the model less clear.     

Organization of the vomeronasal organ in a plethodontid salamander

Salamanders in the family Plethodontidae show a unique behavior (nose-tapping) and have unique structures (nasolabial grooves) that may be used specifically to convey chemicals to the vomeronasal organ. The nasal structure of Plethodon cinereus was studied to determine if there is enhanced development of the vomeronasal organ compared with other salamander families that would correlate with use of these unique features. The vomeronasal organ in salamanders is found in a ventrolateral diverticulum of each main olfactory organ. P. cinereus has a more anteriorly placed vomeronasal organ within the diverticulum, and the posterior limit of each nasolabial groove is adjacent to the anterior limit of the vomeronasal organs. This suggests that the grooves deliver chemicals preferentially to the vomeronasal organs instead of to the main olfactory organs. In addition, the vomeronasal sensory epithelium is thickest anteriorly and is at its thinnest at about the level corresponding to the location of the vomeronasal organ in other salamander families. These adaptations suggest a specific mechanism of odorant delivery to the vomeronasal organ in plethodontid salamanders not found in other salamander families.     

Tegument and apical end organ fine structure in the metacestode and adult Proteocephalus ambloplitis

The tegument of plerocercoid and adult P. ambloplitis was examined. Differences in tegument structure existed between these two stages. Plerocercoids of P. ambloplitis lacked extensive vacuolization and unicellular gland cells characteristic of adult tegument. Plerocercoid microtriches were short and conoid; adult microtriches were lenticular with an extended, whip-like shaft. An inclusion, not previously reported from proteocephalid cestodes, is described. Adult tegument had ducts, originating from underlying unicellular glands, extending through the distal cytoplasm and opening to the exterior between microtriches.

The apical end organ cavity of P. ambloplitis contained numerous labyrinth-like spherical bodies. These structures appeared to be synthesized and secreted into the end organ by a thin cellular lining of the end organ. This lining was composed of discrete, filamentous cells believed to be modified subtegumental cell bodies. Spherical structures identical to those observed within the end organ cavity occurred within this cellular lining. The spherical bodies may be associated with enzymes necessary for tissue migration by the metacestode.     

Culture media from hypoxia conditioned endothelial cells protect human intestinal cells from hypoxia/reoxygenation injury

Remote ischemic preconditioning (RIPC) is a phenomenon, whereby short episodes of non-lethal ischemia to an organ or tissue exert protection against ischemia/reperfusion injury in a distant organ. However, there is still an apparent lack of knowledge concerning the RIPC-mediated mechanisms within the target organ and the released factors. Here we established a human cell culture model to investigate cellular and molecular effects of RIPC and to identify factors responsible for RIPC-mediated intestinal protection.     

A new sensory organ in “primitive” molluscs (Polyplacophora: Lepidopleurida), and its context in the nervous system of chitons

Introduction

Chitons (Polyplacophora) are molluscs considered to have a simple nervous system without cephalisation. The position of the class within Mollusca is the topic of extensive debate and neuroanatomical characters can provide new sources of phylogenetic data as well as insights into the fundamental biology of the organisms. We report a new discrete anterior sensory structure in chitons, occurring throughout Lepidopleurida, the order of living chitons that retains plesiomorphic characteristics.

Results

The novel “Schwabe organ” is clearly visible on living animals as a pair of streaks of brown or purplish pigment on the roof of the pallial cavity, lateral to or partly covered by the mouth lappets. We describe the histology and ultrastructure of the anterior nervous system, including the Schwabe organ, in two lepidopleuran chitons using light and electron microscopy. The oesophageal nerve ring is greatly enlarged and displays ganglionic structure, with the neuropil surrounded by neural somata. The Schwabe organ is innervated by the lateral nerve cord, and dense bundles of nerve fibres running through the Schwabe organ epithelium are frequently surrounded by the pigment granules which characterise the organ. Basal cells projecting to the epithelial surface and cells bearing a large number of ciliary structures may be indicative of sensory function. The Schwabe organ is present in all genera within Lepidopleurida (and absent throughout Chitonida) and represents a novel anatomical synapomorphy of the clade.

Conclusions

The Schwabe organ is a pigmented sensory organ, found on the ventral surface of deep-sea and shallow water chitons; although its anatomy is well understood, its function remains unknown. The anterior commissure of the chiton oesophagial nerve ring can be considered a brain. Our thorough review of the chiton central nervous system, and particularly the sensory organs of the pallial cavity, provides a context to interpret neuroanatomical homology and assess this new sense organ.     

Neuralized functions cell autonomously to regulate Drosophila sense organ development

Neurogenic genes, including NOTCH: and DELTA:, are thought to play important roles in regulating cell-cell interactions required for DROSOPHILA: sense organ development. To define the requirement of the neurogenic gene neuralized (neu) in this process, two independent neu alleles were used to generate mutant clones. We find that neu is required for determination of cell fates within the proneural cluster and that cells mutant for neu autonomously adopt neural fates when adjacent to wild-type cells. Furthermore, neu is required within the sense organ lineage to determine the fates of daughter cells and accessory cells. To gain insight into the mechanism by which neu functions, we used the GAL4/UAS system to express wild-type and epitope-tagged neu constructs. We show that Neu protein is localized primarily at the plasma membrane. We propose that the function of neu in sense organ development is to affect the ability of cells to receive Notch-Delta signals and thus modulate neurogenic activity that allows for the specification of non-neuronal cell fates in the sense organ.     

Making bigger plants: key regulators of final organ size

Organ growth in plants is controlled by both genetic factors and environmental inputs. Recent progress has been made in identifying genetic determinants of final organ size and in characterizing a pathway that may link organ growth with environmental conditions. Some identified growth regulatory factors act downstream of plant hormones, while others appear to be components of novel signaling pathways. Additional characterization of these proteins is needed before we can understand how growth-promoting and growth-restricting inputs are integrated to coordinate growth within a developing organ. Some parallels in the mechanisms used by plants and animals to regulate organ size are suggested by the identification of KLUH, a noncell-autonomous regulator of organ growth, and by similarities in the target of rapamycin (TOR)-signaling pathway.