The Eyes and the Photonegative Behaviour of Nephtys (Annelida, Polychaeta)

1. The photoreceptors found in the Nephtyidae are: (a) Two pairs of vacuolated cells lying in pigment cups, with accessory cells, embedded in the posterior part of the supra-oesophageal ganglion. (b) One or two cells, which may or may not be vacuolated, on either side, lying a little anterior to the ganglion. (c) Undifferentiated epidermal cells surrounded by pigment granules may be photosensitive. 2. There are both morphological and behavioural grounds for concluding that the prostomial eyes of Nephtys are homologous with the eyes of Nereis, and that they are involved in the same types of behaviour. 3. The frequency with which Nephtys swims is, within limits, a linear function of the light intensity. Although the ganglionic eyes are directional receptors the worm does not orientate itself in a light beam; presumably the light reaching them is too diffuse. In the very small species N. cornuta, the eyes are close to the surface of the brain and the worm does orientate itself in a light beam. 4. Swimming is an essential prelude to burrowing, and the brighter the light the more frequently the worm swims and the sooner it is buried. Activity in light can be inhibited by stimulating receptors on the dorsal surface of the animal by contact.

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Hedgehog organises the pattern and polarity of epidermal cells in the Drosophila abdomen

Development ◽

10.1242/dev.124.11.2143 ◽

1997 ◽

Vol 124 (11) ◽

pp. 2143-2154 ◽

Cited By ~ 16

Author(s):

G. Struhl ◽

D.A. Barbash ◽

P.A. Lawrence

Keyword(s):

Anterior Part ◽

Posterior Part ◽

Cell Types ◽

Epidermal Cells ◽

Concentration Gradients ◽

Cell Pattern ◽

Different Cell Types ◽

Adult Drosophila

The abdomen of adult Drosophila, like that of other insects, is formed by a continuous epithelium spanning several segments. Each segment is subdivided into an anterior (A) and posterior (P) compartment, distinguished by activity of the selector gene engrailed (en) in P but not A compartment cells. Here we provide evidence that Hedgehog (Hh), a protein secreted by P compartment cells, spreads into each A compartment across the anterior and the posterior boundaries to form opposing concentration gradients that organize cell pattern and polarity. We find that anteriorly and posteriorly situated cells within the A compartment respond in distinct ways to Hh: they express different combinations of genes and form different cell types. They also form polarised structures that, in the anterior part, point down the Hh gradient and, in the posterior part, point up the gradient - therefore all structures point posteriorly. Finally, we show that ectopic Hh can induce cells in the middle of each A compartment to activate en. Where this happens, A compartment cells are transformed into an ectopic P compartment and reorganise pattern and polarity both within and around the transformed tissue. Many of these results are unexpected and lead us to reassess the role of gradients and compartments in patterning insect segments.

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A study of digit fusion in the mouse embryo

Development ◽

10.1242/dev.49.1.259 ◽

1979 ◽

Vol 49 (1) ◽

pp. 259-276

Author(s):

Elaine Maconnachie

Keyword(s):

Embryonic Development ◽

Mouse Embryo ◽

Dorsal Surface ◽

Ventral Surface ◽

Epidermal Cells ◽

Mouse Limb ◽

Epithelial Fusion

During the embryonic development of the mouse limb separation of the digits is followed by their union. This is a true, though temporary, epithelial fusion, a fused layer of epidermal cells remaining intact until separation takes place after birth. The periderm cells in the line of fusion are displaced to the dorsal or ventral surface of the foot. On the dorsal surface these displaced cells form a prominent interdigital ridge of elongated, intertwined cells which remains until the periderm is shed. During the fusion of the eyelids, and also of the pinnae to the scalp, a similar ridge of periderm cells is formed.

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Neuroimaging in Alzheimer’s Disease

Bioinformatics ◽

10.4018/978-1-4666-3604-0.ch023 ◽

2013 ◽

pp. 427-431 ◽

Cited By ~ 1

Author(s):

Hidenao Fukuyama

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Posterior Part ◽

Lewy Body Disease ◽

New Drugs ◽

Amyloid Protein ◽

Dementia Patients ◽

Positron Emission ◽

Occipital Lobes ◽

The Brain

The diagnosis of Alzheimer’s disease (AD) is often based on clinical and pathological data. Positron emission tomography (PET) using the tracer 18F-FDG revealed findings specific to AD-mainly the posterior part of the brain and the association cortices of the parietal and occipital lobes were affected by a reduction in glucose metabolism. Recent advances in the development of tracers for amyloid protein, which is the key protein in the pathogenesis of AD, enables the pattern of deposition of amyloid protein in the brain to be visualized. Various tracers have been introduced to visualize other aspects of AD pathology. Recent clinical interests on dementia have focused on the early detection of AD and variation of Parkinson’s disease, namely dementia with Lewy body disease (DLB), because the earlier the diagnosis, the better the prognosis. The differential diagnosis of mild AD or mild cognitive impairment (MCI) as well as DLB has been studied using PET and MRI as part of the NIH’s Alzheimer disease Neuroimaging initiative (ADNI). At present, many countries are participating in the ADNI, which is yielding promising results. This chapter’s study will improve the development of new drugs for the treatment of dementia patients by enabling the evaluation of the effect and efficacy of those drugs.

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Bacterial Symbionts in Pogonophora

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400070417 ◽

1982 ◽

Vol 62 (4) ◽

pp. 889-906 ◽

Cited By ~ 69

Author(s):

Eve C. Southward

Keyword(s):

Life History ◽

Blood Vessels ◽

Blood Supply ◽

Posterior Part ◽

Gram Negative Bacteria ◽

Bacterial Symbionts ◽

Small Species ◽

Gram Negative

Prokaryote organisms, with characteristics of Gram-negative bacteria, occur intracellularly in Pogonophora, as described here for seven small species. The tissue containing the bacteria lies between the two longitudinal blood vessels in the posterior part of the trunk and has a special blood supply. This tissue is probably homologous with the so-called trophosome tissue of the much larger vestimentiferan pogonophores, which also contains bacteria, and the term can be applied to all pogonophores. The presence of such bacteria-containing trophosome tissue may be a characteristic of the phylum. In both large and small species examined the bacteria appear to be chemoautotrophs and probably assist the nutrition and/or metabolism of their hosts. It is not yet certain if the bacterium-containing cells do originate from mesoderm or endoderm, but, if the latter, then the trophosome represents the remains of the missing gut. The trophosome tissue situated internally, and transfer of bacteria must take place early in the life history, in the egg or embryo.

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Nocturnal hatching in the monogenean skin parasiteEntobdella hippoglossifrom the halibut,Hippoglossus hippoglossus

Parasitology ◽

10.1017/s0031182000045704 ◽

1974 ◽

Vol 68 (2) ◽

pp. 161-172 ◽

Cited By ~ 23

Author(s):

Graham C. Kearn

Keyword(s):

Light Intensity ◽

Blue Light ◽

Epidermal Cells ◽

Free Swimming ◽

Skin Mucus ◽

Hippoglossus Hippoglossus ◽

Monogenean Parasite ◽

The Relationship

When eggs of the monogenean parasiteEntobdella hippoglossi, from the skin of the halibut (Hippoglossus hippoglossus), are incubated at 7 °C in alternating 12 h periods of dim blue light (intensity about 3 nW/cm2) and darkness, free-swimming larvae are recovered mostly at the end of the first 2 h of the period of darkness. Larvae do not emerge in significant numbers when the eggs are mechanically disturbed during the light or dark periods, or when the eggs are placed in shadow for periods of 5–25 min during the illumination period. The treatment of fully developed eggs with washings from halibut or from sole or with halibut skin mucus failed to produce hatching.The free-swimming life of the larvae at 7 °C is in excess of 24 h and within 4 h of hatching at 4 °C some larvae are able to attach themselves to halibut skin and shed their ciliated epidermal cells.The relationship between the hatching pattern of the eggs of the parasite and the behaviour of the halibut is discussed.

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ERK-Regulated Double Cortin-Like Kinase (DCLK)-Short Phosphorylation and Nuclear Translocation Stimulate POMC Gene Expression in Endocrine Melanotrope Cells

Endocrinology ◽

10.1210/en.2011-0067 ◽

2011 ◽

Vol 152 (6) ◽

pp. 2321-2329 ◽

Cited By ~ 3

Author(s):

Miyuki Kuribara ◽

Bruce G. Jenks ◽

Thomas F. Dijkmans ◽

Daan de Gouw ◽

Debbie T. W. M. Ouwens ◽

...

Keyword(s):

Gene Expression ◽

Light Intensity ◽

Skin Color ◽

Cell Activation ◽

Nuclear Translocation ◽

Erk Signaling ◽

White Background ◽

Its Gene ◽

Pomc Gene ◽

The Brain

We tested whether double cortin-like kinase-short (DCLK-short), a microtubule-associated Ser/Thr kinase predominantly expressed in the brain, is downstream of the ERK signaling pathway and is involved in proopiomelanocortin gene (POMC) expression in endocrine pituitary melanotrope cells of Xenopus laevis. Melanotropes form a well-established model to study physiological aspects of neuroendocrine plasticity. The amphibian X. laevis adapts its skin color to the background light intensity by the release of α-MSH from the melanotrope cell. In frogs on a white background, melanotropes are inactive but they are activated during adaptation to a black background. Our results show that melanotrope activation is associated with an increase in DCLK-short mRNA and with phosphorylation of DCLK-short at serine at position 30 (Ser-30). Upon cell activation phosphorylated Ser-30-DCLK-short was translocated from the cytoplasm into the nucleus, and the ERK blocker U0126 inhibited this process. The mutation of Ser-30 to alanine also inhibited the translocation and reduced POMC expression, whereas overexpression stimulated POMC expression. This is the first demonstration of DCLK-short in a native endocrine cell. We conclude that DCLK-short is physiologically regulated at both the level of its gene expression and protein phosphorylation and that the kinase is effectively regulating POMC gene expression upon its ERK-mediated phosphorylation.

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An Integrated Molar/Molecular Model of the Brain

Psychological Reports ◽

10.2466/pr0.1972.30.2.343 ◽

1972 ◽

Vol 30 (2) ◽

pp. 343-368 ◽

Cited By ~ 12

Author(s):

Alan Einar Hendrickson

Keyword(s):

Action Potentials ◽

Short Term Memory ◽

Molecular Model ◽

Spike Trains ◽

Mass Action ◽

Small Species ◽

Short Term ◽

Term Memory ◽

Anaesthetic Agents ◽

The Brain

A model of the brain is presented at both molecular and molar levels. Communication between neurons is thought to be a kind of telegraph code, with the information being coded as the permutation of four possible interval values between successive action potentials in spike trains. A small species of RNA molecule is thought to be the memory molecule, and the four possible nucleotide bases of RNA correspond to the four possible interval values. The model is shown to account for generalization, speed of retrieval, mass action, long- and short-term memory, forgetting, operant and classical conditioning, intelligence, reaction time, the action of anaesthetic agents, and some aspects of personality. Some evidence from multidisciplinary sources is presented in support of the major features of the model.

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Course of the Peripheral Gustatory Nerves

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348947708600219 ◽

1977 ◽

Vol 86 (2) ◽

pp. 251-258 ◽

Cited By ~ 5

Author(s):

Heinz Rollin

Keyword(s):

Facial Nerve ◽

Medulla Oblongata ◽

Trigeminal Nerve ◽

Soft Palate ◽

Cranial Nerve ◽

Anterior Part ◽

Posterior Part ◽

Greater Superficial Petrosal Nerve ◽

The Brain

The multiple variations of the course of the gustatory nerves still considered possible are discussed. Recent investigations lead to the conclusion that there is only one path for the gustatory fibers for each gustatory area: 1) from the anterior part of the tongue via the tympanic cord and facial nerve to the medulla oblongata; 2) for the posterior part of the tongue in the IX cranial nerve; and 3) from the soft palate via the greater superficial petrosal nerve to the facial nerve. The trigeminal nerve carries no gustatory fibers to the brain.

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