The relation between excitation-contraction coupling and fine structure of a molluscan muscle,the radular retractor of the whelk,Buccinum undatum

The Buccinum radula is of the rachiglossate type with two outer rows of fierce hook-like attack teeth and a medial row of straight sharp-pointed shredding teeth. Individual cells of the radular retractor muscle are 10–12 m in diameter and separated at the closest by gaps of only 40 nm, providing areas of potential electrical contact. The cell membranes are heavily invested with long finger-like invaginations, associated with sarcoplasmic reticular cisternae, and surface caveolae; the latter are associated with the numerous dense body membrane attachment plaques found in this muscle. The radular retractor muscle possesses a significant sarcoplasmic reticulum of peripheral cisternae and deeper vesicles associated with mitochondria. The surface caveolae may result from myofilament force exerted via attachment plaques at the cell membrane, while deeper invaginations may constitute a rudimentary transverse tubular system to relay surface depolarization to associated sarcoplasmic reticular cisternae inducing calcium release to effect excitation-contraction coupling. The radular retractor muscle possesses the usual thick paramyosin and thin actin myofilaments, the latter associated with dense bodies and attachment plaques presumably to transduce force to the cell membrane. The mitochondria are unusually large and packed into dense central clusters surrounded by large deposits of glycogen granules. The nerve endings on the radular retractor muscle fibres show four different types of transmitter vesicle, presumably related to the four kinds of agonist action in this muscle, cholinergic, serotonergic, peptidergic and purinergic. All nerve endings have mixed vesicle populations, clear evidence of co-transmission. In this muscle we see a modification of usual smooth muscle structure to effect fast sustained contractions, an ultrastructural configuration functionally designed for the muscle's central role in the feeding cycle.Abbreviations ABRM anterior byssus retractor muscle - EC coupling excitation-contraction coupling - RP radular protractor muscle - RR radular retractor muscle - SR sarcoplasmic reticulum - T-system transverse tubular system     

Analysis of human crystalline lens accommodation

The behavior of the human crystalline lens during accommodation is analytically studied. The lens is modeled as a closed axisymmetrical membrane shell of varying thickness enclosing an incompressible liquid. To simulate zonular tension associated with lenticular accommodation, an axisymmetrical radial force or displacement is imposed around the shell equator. Two second-order, simultaneous, nonlinear governing differential equations are derived. Numerical results, obtained from the investigation of human lens profiles of three independently published MRI images and a drawing of a microphotograph, demonstrate that when zonular traction within the physiological force range of the ciliary muscle is exerted, both central lens thickness and central optical power increase. Qualitatively, these increases are independent of lens shape. However, the magnitude of these changes is dependent on the initial profile of the lens and is enhanced by the "natural" variation in capsular thickness. Only when a pulling force significantly exceeds the force capacity of the ciliary muscle does the lens flatten and its central thickness and optical power decrease.     

Daily and circadian variation in the electroretinogram of the domestic fowl: effects of melatonin

Visual and circadian function are integrally related in birds, but the precise nature of their interaction is unknown. The present study determined whether visual sensitivity measured electroretinographically (ERG) in 7-week-old cockerels varies over the time of day, whether this rhythm persists in constant darkness (DD) and whether exogenous melatonin affects this ERG rhythmicity. ERG b-wave amplitude was rhythmic in LD and persisted in DD with peak amplitude during mid- to late afternoon in LD and mid-subjective day in DD, indicating that the ERG rhythm is endogenously generated. No daily or circadian variation in a-wave amplitude was observed, and ERG component latency and durations were not rhythmic. Intramuscular injection of 10 g/kg melatonin at ZT10 in LD significantly decreased b-wave amplitude but had no effect on a-wave. Intraocular injection of 600 pg melatonin, however, had no effect on any aspect of the ERG. These data indicate that a circadian clock regulates ocular sensitivity to light and that melatonin may mediate some or all of this effect. The level at which melatonin modulates retinal sensitivity is not known, but the present data suggest a central site rather than a direct effect of the hormone in the eye.Abbreviations DD constant darkness - ERG electroretinography - EW Edinger-Westphal nuclei - IMEL iodomelatonin - IO isthmooptic nucleus - LD light-dark cycle - SCG superior cervical ganglion - SCN suprachiasmatic nuclei - vSCN visual suprachiasmatic nucleus     

Cerebral motoneurons mediating tentacle retraction in the land slug Ariolimax columbianus

(1) Tentacle retraction in the land slug Ariolimax columbianus can be elicited by stimulation of all nerves and connectives of the ipsi- and contralateral cerebral ganglia. (2) Six neurons in the left cerebral ganglion were classified as tentacle retraction motoneurons because their action potentials are followed one-for-one with constant delay by action potentials in the left tentacle retractor nerve and their depolarization causes retraction of the ipsilateral tentacle. The motoneurons can be identified by size, pattern of pigmentation, position, and physiological characteristics. (3) Each retractor motoneuron discharges at a rather constant rate and has more than one source of excitatory input, but no IPSPs were observed. No synaptic connections between the six retractor motoneurons were found. The nerve action potentials that correspond to each motoneurons are distinguishable by waveform and size rank. (4) Each motoneuron elicits visible contractions in a particular region of the ipsilateral retractor muscle, but the motor fields of some motoneurons overlap. Some motoneurons mediate relatively rapid contractions while others cause slower responses. (5) There is one-for-one correspondence between action potentials of the largest unit recorded extracellularly in the retractor nerve and exciatory junction potentials recorded from the retractor muscle. No evidence of a peripheral neural plexus was found in serial sections of the retractor muscle.     

Ultrastructure of a muscle spindle-analogous receptor organ in the mandible of Oncopeltus fasciatus (Insecta,Heteroptera) with remarks on the homology of the mandibular muscles

Summary A non-ciliary muscle receptor organ in the first mandibular retractor muscle of Oncopeltus fasciatus is described. The organ consists of two specialized muscle fibres of the first retractor, which are embedded in a thickened layer of connective tissue. The sensory innervation is supplied by three multiterminal sense cells sending several dendrites to the receptor muscle fibres. Naked dendritic terminals are attached to the muscle surface or connective tissue fibrils. The far-reaching analogy of the receptor to the intrafusal chain-fibres of vertebrate muscle spindles is remarkable. The existence of a muscle receptor organ in the first mandibular retractor may serve as an argument in favor of the homology of this muscle with the musculus tentorio-mandibularis of orthopteroid insects.Supported by a grant from the Deutsche Forschungsgemeinschaft     

The larval morphology of the marine bryozoan Bowerbankia gracilis (Ctenostomata: Vesicularioidea)

Summary The larval morphology of the marine bryozoan Bowerbankia gracilis has been investigated by light and electron microscopy. The barrel-shaped larva (200 m long and 150 m in diameter) is light yellow without any apparent eyespots, although it is positively phototactic during its brief free-swimming existence. The primary morphological characteristics of the larva are: (1) a large corona that forms most of the larval surface, (2) a small apical disc without blastemas, (3) a deep pallial sinus lined by an extensive pallial epithelium, (4) an internal sac without regional specializations, and (5) a polypide rudiment in the oral hemisphere. This organization is characteristic of larvae of the ctenostome superfamily Vesicularioidea, and differs radically from the organization of all other bryozoan larvae examined. The major morphological differences occur in the size and organization of the apical disc, the pallial epithelium, and the internal sac. In most bryozoans, these regions of the larval epithelium represent rudiments of the polypide and the body wall epidermis of the ancestrula. The oral polypide rudiment, the extensive pallial epithelium, and the reduced internal sac in vesicularioid larvae indicate that their pattern of metamorphosis also differs radically from the metamorphoses of other bryozoans.Figure Abbreviations AB aboral - acr axial ciliary rootlet - ad apical disc - anc aboral nerve cord - ANT anterior - arm apical retractor muscle - b basal body - bf basal foot process - c corona - cc ciliated cleft - ce centriole - ci cilium - cl cupiform layer of the polypide rudiment - cp ciliary pit - cr ciliary rootlet - enr equatorial neural ring - g glandular cells of the pyriform organ - gl glycocalyx - go Golgi complex - gr granule - hcr horizontal ciliary rootlet - ic intercoronal cell - igf inferior glandular field - ip infrapallial cells - is internal sac - jp juxtapapillary cells - l lipid droplets - L lateral - m mesenchyme - m Type I mesenchyme cell - m Type II mesenchyme cell - m Type III mesenchyme cell - mb median band of the polypide rudiment - mc marginal cells of the apical disc - mi mitochondria - mr microridge - mv microvilli - nn nerve nodule - np neural plate - nu nucleus - O oral - oce oral ciliated epithelium - op opening to the internal sac - ovc oral vesicular collarette - p papilla of the pyriform organ - pa pallial cell - pe pallial epithelium - po pyriform organ - POS posterior - pp parasagittal patches of undifferentiated cells - pr polypide rudiment - rer rough endoplasmic reticulum - sc supracoronal cells - sg secretory granules - sgf superior glandular field - sp suprapallial cells - tc terminal cone - tf transitional filaments - u undifferentiated cells - va vacuole - vc vesicular cell - wc wedge-shaped cells of the apical disc - y yolk granule - za zonula adhaerens Caption Abbreviations Gp Glutaraldehyde-phosphate - Os Osmium     

Histophysiological studies on the corpus allatum of Leucophaea maderae

Summary On the basis of the occurrence, at the light microscopic level, of alkaline and acid phosphatases, the pigment epithelium covering the posterior surface of the iris in the albino rabbit can be divided into two zones not previously described, viz. a central zone close to the pupil, approximately corresponding to the area occupied by the iridic sphincter muscle, and a peripheral zone extending to the ciliary body. The central zone which is in intimate relation with the lens was found to have a high content of both phosphatases. At the fine structural level it exhibits a marked pinocytotic activity in the epithelium at the interdigitations between adjacent cells. Electron microscopy revealed that acid phosphatase is localized to the walls of the pinocytotic vesicles. Alkaline phosphatase is in evidence at the surface membrane folds and at microvillous processes between the epithelial cells and the adjoining muscle cells. Unlike the distribution of the acid phosphatase, that of the alkaline phosphatase does not differ fundamentally in the two zones at the fine structural level.In a series of dehydrogenases studied, staining with a view to succinic-, isocitric- and glucose-6-phosphate dehydrogenases revealed an evenly distributed content of enzyme throughout the epithelium. As to the lactic- and -hydroxybutyric dehydrogenases, contents seem to be lower in the pupillary than in the peripheral zone.     

Antennal circulatory organs in Onychophora,Myriapoda and Hexapoda: Functional morphology and evolutionary implications

Summary A comparative investigation of the antennal circulatory organs in representatives of the Onychophora, all subtaxa of the Myriapoda and numerous taxa of the Hexapoda (comprising a total of 54 species) revealed an unexpected diversity in structure and function.In the Onychophora, antennal vessels exist which are connected to the enlarged anterior end of the aorta dorsal to the brain.In the Chilopoda, Diplopoda and Symphyla, antennal vessels exist which originate from the dorsal vessel caudal to the brain. They extend under the optic lobes, lateral to the circumoesophageal connectives, into the antennae.In the Hexapoda, the investigations include representatives of all higher taxa, apart from the Paraneoptera and the Holometabola. Generally, antennal vessels exist. In the Diplura, they originate from the anterior end of the aorta in front of the brain. In all other insects the antennal vessels are separate from the dorsal vessel. Their proximal ends form ampullary enlargements which are attached to the frontal cuticle near the antenna bases. They communicate via valved ostia with the haemolymph sinus in front of the brain. In the Archaeognatha, Zygentoma, Odonata, certain Plecoptera and the Notoptera, no muscles are connected to these organs. In all other groups the ampullae are pulsatile as a result of associated muscles (antennal hearts). These muscles diverge widely in their attachments and act either as compressors (Dermaptera) or dilators of the ampullae (Embioptera, Blattopteroidea, Orthopteroidea, and some Plecoptera).In the Collembola and Ephemeroptera, special antennal circulatory organs are lacking. In some forms the anatomical arrangement of the inner organs, in conjunction with short diaphragms at the antenna bases, apparently leads to a channelling of haemolymph flow. This condition may be explained by the very short antennae of these insects and is considered as a convergent and apomorphic state in these taxa.The antennal vessels are supposed to be homologous within the Tracheata and to represent the lateral arteries of the antenna segment. An origin from the dorsal vessel is considered an ancestral state, which was lost in the stem lineage of the Ectognatha. Specific space constraints within the cephalic capsule are discussed as the possible reason for this loss. The evolution of pulsatile antennal circulatory organs in the Neoptera is the result of the association of muscles with the proximal ampullary ends of the antennal vessels. The attachments and innervation of these muscles indicate a derivation from precerebral pharyngeal dilators.Abbreviations Amp ampulla - Ant antenna - ant anterior - AN antennal nerve - Ao aorta - AV antennal vessel - Br brain - BrSi brain sinus - CC corpora cardiaca - CoeC circumoesophageal connectives - CM compressor muscle of ampulla - CT connective tissue - Dia diagphragm - do dorsal - DM dilator muscle of ampulla - DM1 ampullo-ampullary dilator muscle - DM2 ampullo-pharyngeal dilator muscle - DM3 ampullo-frontal dilator muscle - DM Acc accessory dilator muscle of ampulla - DV dorsal vessel - EB elastic band - FbDM fronto-buccal pharynx dilator muscle - FG frontal ganglion - FSa frontal sac - FSe frontal septum - FSi frontal sinus - Lb labium - LV lateral vessel of aorta - MA mouth-angle - Nr nervus recurrens - Oc ocellus - Oe oesophagus - OeSi oesophageal sinus - Ost ostium - Ph pharynx - Pl labial palpus - RM retractor muscle of mouth-angle - RMl lateral retractor of mouth-angle - RMm medial retractor of mouth-angle - SceSi supracerebral sinus - SD salivary duct - T tentorium     

Morphological characteristics of eyes and retinas of two sardines (Sardinops melanostictus and Etrumeus sadina,Clupeidae) and an anchovy (Engraulis japonicus,Engraulididae)

The morphology of the eyes and distribution of retinal ganglion cells in two sardine species (Sardinops melanostictus and Etrumeus sadina, Clupeidae) and the Japanese anchovy (Engraulis japonicus, Engraulididae) were investigated anatomically and histologically. The eyes of the sardines faced a slightly dorsolateral direction with the visual field extended obliquely upward. In contrast, the eyes in the anchovy were almost laterally directed. It was hypothesized that the sardines may have an advantage in receiving more downward irradiance compared with the anchovy. The lens muscle was larger in these three species than in many other teleosts, and its surface was entirely melanin‐pigmented. Also, the lens muscle directly and tightly adhered to the backside surface of the iris. The relative area of the lens muscle to the area of the lens, a referential value of the relative power of visual accommodation were notably larger in the species studied than in other teleost values that have been previously reported. A higher M/L% value of these clupeid fishes could facilitate fast and wide ranging visual accommodation and was considered to be associated with maintaining and/or re‐establishing school formations quickly. Analysis of topographical distributions of cells in the ganglion cell layer showed that cell density was highest in the ventrotemporal quadrant of the retina (temporal of the optic cleft) in all three species. Another potentially important role for the black‐pigmented lens muscle may be to block the specialized retinal area from intense sunlight that scatters and irradiates upward or laterally in the surface waters that they inhabit. Thus, the sardine and anchovy may take advantage of efficient detection of visual signals in the frontal‐upward direction and further improve visibility of the target in this direction. J. Morphol. 276:415–424, 2015. © 2014 Wiley Periodicals, Inc.     

Cerebral cortical and brainstem areas related to the central control of lens accommodation in cat and monkey.

1. Studies on the central nervous system related to lens accommodation in cat and monkey were reviewed. 2. During the last decade, a considerable amount of neurophysiological data on the peripheral innervation of the ciliary muscle, properties of parasympathetic oculomotor neurons and mesencephalic reticular neurons have accumulated. 3. Neurophysiological and anatomical evidence supporting the contribution of the cerebellum to lens accommodation has been obtained. 4. Recently, cerebral cortical neurons in the parieto-occipital cortex with activities related to lens accommodation were found in cat and monkey.     

Spermiogenesis,sperm structure and fertilization in the palaeonemertean Cephalothrix rufifrons (Nemertini,Anopla)

Summary The spermatozoan from testes of Cephalothrix rufifrons consists of an elongated, straight head 13–14 m long with a flattened anterior acrosome and a 12.5-m-long nucleus. Placed along one side of the nucleus, is a single tubular 7-m-long mitochondrion. There is no midpiece, but immediately posterior to the nucleus are two centrioles. The tail is at least one and a half times the length of the head. Mature sperm cells were also found in the oviducts of mature females which, combined with the modified structure of the sperm cell, indicates that sperm is transferred during pseudocopulation.Abbreviations A acrosome - C centriole - D gonoduct - DC distal centriole - E epidermis - F flagellum - I intestine - LM longitudinal muscle layer - L lateral nerve - M nitochondrion - MT microtubules - N nucleus - O oocyte - PC proximal centriole - R rhynchocoel - S spermatozoa - SC spermatocyte - SP spermatid     

Spatial tuning of neurons in the inferior colliculus of the big brown bat: effects of sound level, stimulus type and multiple sound sources

We examined factors that affect spatial receptive fields of single units in the central nucleus of the inferior colliculus of Eptesicus fuscus. Pure tones, frequency- or amplitude-modulated sounds, or noise bursts were presented in the free-field, and responses were recorded extracellularly. For 58 neurons that were tested over a 30 dB range of sound levels, 7 (12%) exhibited a change of less than 10° in the center point and medial border of their receptive field. For 28 neurons that were tested with more than one stimulus type, 5 (18%) exhibited a change of less than 10° in the center point and medial border of their receptive field.The azimuthal response ranges of 19 neurons were measured in the presence of a continuous broadband noise presented from a second loudspeaker set at different fixed azimuthal positions. For 3 neurons driven by a contralateral stimulus only, the effect of the noise was simple masking. For 11 neurons driven by sound at either side, 8 were unaffected by the noise and 1 showed a simple masking effect. For the remaining 2, as well as for 5 neurons that were excited by contralateral sound and inhibited by ipsilateral sound, the peak of the azimuthal response range shifted toward the direction of the noise.Abbreviations E/E excitation at either ear - I/E inhibition at the ipsilateral ear, excitation at the contralateral ear - O/E no effect from the ipsilateral ear, excitation at the contralateral ear - FM downward frequency modulation - FM upward frequency modulation - IC inferior colliculus - ICC central nucleus of the inferior colliculus - ILD interaural level difference - ITD interaural time difference - PT pure tone - SAM sinusoidally amplitude modulated sounds - SFM sinusoidally frequency modulated sounds     

Tactile hairs and leg reflexes in wandering spiders: physiological and anatomical correlates of reflex activity in the leg ganglia

Intracellular recordings and Lucifer-yellow fillings were used in a wandering spider,Cupiennius salei Keys., to identify central neuronal correlates of local reflex activity in muscle c2, which inserts on the leg coxa. Here we describe related neuronal elements in the hindleg neuromere of the fused, subesophageal-ganglion complex:

Innervation du muscle rétracteur antérieur du byssus (ABRM) de Mytilus edulis L.

Summary Detection of nerve structures containing 5-HT were described in the anterior byssus retractor muscle (ABRM) in Mytilus edulis L. after using the fluorescence microscope technique of Falck. We are able to confirm our previous results and assumptions given by histology and electron microscope studies: the neuromuscular en passage junctions, largely distributed within the ABRM, contain 5-HT.     

Mechanisms controlling vocalization-evoked stapedius muscle activity in chickens (Gallus gallus)

Summary The mechanisms involved in the vocalization-evoked stapedius muscle contraction in the chicken (Gallus gallus) were studied. The stapedius muscle EMG response is constantly associated with vocalization elicited by electrically stimulating the mesencephalic calling area. Stimulation of discrete points within the mesencephalic calling area elicits stapedius muscle EMG activity at low stimulus intensities, but does not evoke vocalization. The stapedius muscle EMG response remains unchanged after exclusion of both the syringeal and vagal afferent inputs. It is concluded that stapedius muscle activity is not driven by a neural reflex originating within the syrinx, but is elicited by a central drive.EBS-elicited stapedius muscle activity, identical in all respects to that obtained in an intact preparation, is present when vocalization is prevented by synringeal muscle denervation and tracheal occlusion. This rules out the possibility that stapedius muscle activation could be due to vocalization-linked afferent impulses other than vagal and syringeal ones. Stimulation of discrete points within the mesencephalic calling area can elicit separately vocalization and stapedius muscle activity. This finding is discussed in terms of the existence of two midbrain neuronal populations, projecting to the XIIth nucleus (controlling the syrinx) and to the VIIth nucleus (controlling the stapedius).Abbreviations EBS electrical brain stimulation - EMG electromyogram - ICo nucleus intercollicularis - MLd nucleus mesencephalicus lateralis pars dorsalis - OM tractus occipitomesencephalicus     

Coding of sound location and frequency in the auditory midbrain of diurnal birds of prey,families accipitridae and falconidae

Summary The coding of sound frequency and location in the avian auditory midbrain nucleus (nMLD) was examined in three diurnal raptors: the brown falcon (Falco berigora), the swamp harrier (Circus aeruginosus) and the brown goshawk (Accipiter fasciatus). Previously this nucleus has been studied with free field stimuli in only one other species, the barn owl (Tyto alba).We found some parallels between the organisation of nMLD in the diurnal raptors and that reported in the barn owl in that the central region of nMLD was tonotopically organised and contained cells that did not encode location, and the lateral region (nMLDl) contained cells which were sensitive to stimulus position. However, unlike the barn owl, which has units with circumscribed receptive fields, cells sensitive to stimulus location had large receptive fields which were restricted in azimuth but not in elevation (hemifield units). Such cells could not provide an acoustic space map in which both azimuthal and elevational dimensions were represented, but there was a tendency for units with contralateral borders to be found superficially, and those with ipsilateral borders to be found deep, in nMLDl. Hemifield units displayed receptive field properties consistent with the directional properties of the tympana in the presence of sound transmission through the interaural canal, if there is a central mechanism which is sensitive to interaural intensity differences.Abbreviations nMLD nucleus mesencephalicus lateralis pars dorsalis - SPL sound pressure level re 20 Pa - nMLDl lateral region of nMLD - ICC central nucleus of the inferior colliculus - ICX external nucleus of the inferior colliculus - IID interaural intensity difference - EI excitatory inhibitory     

Ultrastructure and functional morphology of male genital organs and spermatophore formation inProtodrilus (Polychaeta,Annelida)

Summary The structure and functional morphology of lateral organs and sperm ducts, as well as the mechanisms of spermatophore formation and transfer, are investigated by means of light and electron microscopy in the genusProtodrilus. The sperm ducts are simple, ciliated, intercellular gonoducts with a funnel section surrounded by a thin muscle layer and a tube section opening externally in the anterior region of the lateral organs. No glands are present in the sperm ducts. The lateral organs are formed by long epidermal invaginations enclosing an elongate lumen into which numerous cilia project and a large number of glands open. Five to ten different gland types with strikingly distinctive secretory granules are found in the different species. In addition, special supporting cells, the so-called sponge cells, sensory cells and an underlying nervous tissue are developed in the lateral organs. It is stated that apart from some similarities to the ventral atrium ofNerilla antennata no corresponding organs are known within the Annelida. It is argued that inProtodrilus the spermatophores are formed by the lateral organs as there are a high number of glands opening into the lumen of the organ. The possible origin and genesis of the male gonoducts as well as the mode of spermatophore transfer inProtodrilus is discussed.Abbreviations used in the figures bl basal lamina - cc coelomic cell - ci ciliated cell - cir ciliary root - cr ciliary ring - cu cuticle - cv bs contractile ventral blood sinus - d dissepiment/septum - dbs dorsal blood sinus - es euspermatozoa - f funnel - fi filament - g gut - glo gland openings - lgl lateral organ gland - lm longitudinal muscle - lo lateral organ - lu lumen - mi mitochondrion - mt microtubules - mu muscle - mv microvilli - mvc microvillar crown - n nucleus - ne nervous tissue - o opening - ps paraspermatozoa - rer rough endoplasmatic reticulum - s spermatozoa - sc sponge cell - sg salivary gland - spd sperm duct - spdo sperm duct opening - t tube - tm transverse muscle - vc ventral ciliary band     

The nervous system of the actinotroch larva of Phoronis muelleri (Phoronida)

Summary The nervous system of the actinotroch larva of Phoronis muelleri has been investigated with the transmission electron microscope (TEM). Attempts have been made to localize all of the major nerves and to reveal the cytoarchitecture of the apical ganglion. The nervous system is intraepithelial in position and consists of an apical ganglion, located on the epistome, with at least four different cell types, including monopolar sensory cells and mono- or multipolar neuron-like cells. From the anterior part of the apical ganglion three median nerves extend to the edge of the epistome; two of these nerves connect to nerves which follow the edge of the epistome all the way to the junction of the epistome and the mesosome. From the posterior part of the ganglion extend two lateral nerves which continue along the tentacular ring. Each tentacle has three nerves located on the frontal side which connect to the nerve ring along the tentacles. Along the posterior ciliary band is a minor nerve ring. In addition, a nerve net is found on the epistome, mesosome, and metasome, but no longitudinal nerves were observed between the posterior ciliary band and the apical ganglion. All nerve cells were found in the apical ganglion and none was observed along the nerves. Sensory cells (probably mechanoreceptors) are located in two rows on each tentacle; sensory organs such as eyes and statocysts were not observed.Abbreviations ac accessory centricle - aen anterior epistome edge nerve - af abfrontal cells - bl basal lamina - bl.c blastocoel coelomocyte - ci cilium - co collar - cp cell process - cr ciliary root - ec ₁ epistome edge cell type 1 - mne mouth nerve ring - mo mouth - mp metasomal pouch - ms mesosome - mt metasome - mu muscle - n nerve process - ne nerve - np neuropil - nu nucleus - pc ₁ posterior ciliary band cell type 1 - ec ₂ epistome edge cell type 2 - ec ₃ epistome edge cell type 3 - epi epidermis - es epistome - ese epistome edge - fc frontal cell - gc ₁ type 1 ganglion cells - gc ₂ type 2 ganglion cells - gc ₃ type 3 ganglion cells - ge gut epithelium - ij intermediate junction - laf lateroabfrontal cell - lc lateral cell - lfc laterofrontal cell - lgc lateral ganglion cell - me metacoel epithelium - lne longitudinal median epistome nerves - pc ₂ posterior ciliary band cell type 2 - pc procoel - pe procoel epithelium - pen posterior epistome edge nerve - pr posterior ciliary band - p.rec proximal recess of procoel epithelium - prne nerve ring along posterior ciliary band - sj septate junction - sne secondary nerve along the tentacular ring - t tentacle - tr tentacular ring - trne horseshoe-shaped nerve along the tentacular ring     

The ciliary photoreceptor in the teleplanic veliger larvae of Smaragdia sp. and Strombus sp. (Mollusca,Gastropoda)

The cerebrally innervated eyes of the veliger larvae of Smaragdia sp. and Strombus sp. are composed of a lens, a cornea, and an everse retina. The retina contains two different types of cells, ciliary sensory cells and supportive cells which bear one or two cilia. It is suggested that: (a) the ciliary photoreceptors of these teleplanic veliger larvae are correlated with a long pelagic life in the ocean, which can last up to twelve months, and (b) that structural details of the photoreceptors can change during ontogenesis (ciliary vs rhabdomeric). Furthermore, the cilia of the supportive cells apparently tranport lens material and thus play an important role in lens formation. A decomposition mechanism of pigment granules is examined.Abbreviations bb basal body - bp basal plate - c cilium - cc corneal cell - cm ciliary membranes - cw ciliary whorl - ecm extracellular matrix - gr electron-dense granules - l lens - lb lamellar body - mp membranous pieces - mt microtubules - mv microvilli - n nucleus - oc optic cavity - on optic nerve - pg pigment granule - sc sensory cell - sj septate junction - spc supportive cell - v vesicles     

Glycation of human lens proteins from diabetic and (nondiabetic) senile cataract patients

Glycation (nonenzymatic glycosylation) in the human lens (cortex and nucleus) in senile (nondiabetic) and diabetic cataracts was studied by measuring the extent of early and late glycation products, the content of free -amino groups and the formation of disulfide bonds in the soluble lens proteins. There was a significant (p<0.001) increase in early and late glycation in the lens nucleus compared to the cortex in both the senile and diabetic groups. Overall these changes were much larger in the diabetic group. The concentration of free -amino groups was decreased in the senile nucleus as well as in the diabetic nucleus when compared with the senile and diabetic cortex (p<0.001). Disulfide bond content was in the order of diabetic nucleus > diabetic cortex > senile nucleus > senile cortex. Glycation of the lens proteins is a generalized feature which is enhanced in the diabetic lens compared to senile lens proteins and is associated with a decrease in free -amino groups and an increase in disulfide bonds formation in the lens proteins.