Anatomical circuitry of lateral inhibition in the eye of the horseshoe crab,
            <i>Limulus polyphemus</i>

Fahrenbach, Wolf H.

doi:10.1098/rspb.1985.0060

Cited by 33 publications

(5 citation statements)

References 63 publications

(78 reference statements)

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“…The lateral eye contains a number of different cell types, most of which receive input from OCT-containing efferent fibers (Fahrenbach, 1985). At this stage of our investigation it is not clear which of these cells contain the 122 kDa phosphoprotein.…”

Section: Cellular Distribution Of the 122 Kda Subtrate Protein And Itmentioning

confidence: 44%

Octopamine- and cyclic AMP-stimulated phosphorylation of a protein in Limulus ventral and lateral eyes

Edwards¹,

Battelle²

1987

J. Neurosci.

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The biogenic amine octopamine (OCT) fulfills most of the criteria as a neurotransmitter of efferent fibers that project to lateral and ventral eyes of the horseshoe crab, Limulus polyphemus. OCT is synthesized by and released from the efferent fibers, and OCT mimics many of the effects of endogenous efferent activity. OCT stimulates an increase in intracellular adenosine 3′,5′-monophosphate (cAMP) in both ventral and lateral eyes, and many of the physiological effects of OCT in these eyes appear to be mediated via cAMP-dependent mechanisms. Here we show that OCT, acting apparently through an OCT-specific receptor, stimulates the increased phosphorylation of a protein with an apparent molecular weight of 122 kDa in both ventral and lateral eyes. This protein is also phosphorylated in response to 8-bromo cAMP and forskolin, suggesting that its phosphorylation involves activation of a cAMP-dependent protein kinase. We present evidence that the 122 kDa protein may be widely distributed in the Limulus visual system but that its phosphorylation in intact tissue in response to OCT, or agents acting through cAMP, may be restricted to portions containing photoreceptor cell bodies. The 122 kDa protein is quantitatively a major cellular protein in the photoreceptor cell body enriched portions of the ventral eye, its isoelectric point is between pH 6.2 and 6.4, and it is associated with both cell membranes and the cytoplasm. The function of this protein is not yet known. It may be important in mediating one or more of the effects of octopamine on Limulus vision.

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Section: Cellular Distribution Of the 122 Kda Subtrate Protein And Itmentioning

confidence: 44%

Octopamine- and cyclic AMP-stimulated phosphorylation of a protein in Limulus ventral and lateral eyes

Edwards¹,

Battelle²

1987

J. Neurosci.

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“…Indeed, this approach has often been successfully applied to study the three-dimensional structure of relatively small portions of neurons such as dendritic segments, dendritic spines, axon initial segments or axon terminals (e.g., Porter and White, 1986; White, 1989; Fariñas, and DeFelipe, 1991; Harris, 1999; Merchán-Pérez et al, 2009). Extensive reconstructions of single neurons (e.g., White and Rock, 1980; Megías et al, 2001) or full reconstructions of small nervous systems or synaptic circuits (Fahrenbach, 1985; White et al, 1986) have also been performed, although for technical reasons these studies are rather scarce. The major limitation is that obtaining long series of ultrathin sections is extremely time-consuming and difficult, often making it impossible to reconstruct large volumes of tissue.…”

Section: Discussionmentioning

confidence: 99%

Counting synapses using FIB/SEM microscopy: a true revolution for ultrastructural volume reconstruction

et al. 2009

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The advent of transmission electron microscopy (TEM) in the 1950s represented a fundamental step in the study of neuronal circuits. The application of this technique soon led to the realization that the number of synapses changes during the course of normal life, as well as under certain pathological or experimental circumstances. Since then, one of the main goals in neurosciences has been to define simple and accurate methods to estimate the magnitude of these changes. Contrary to analysing single sections, TEM reconstructions are extremely time-consuming and difficult. Therefore, most quantitative studies use stereological methods to define the three-dimensional characteristics of synaptic junctions that are studied in two dimensions. Here, to count the exact number of synapses per unit of volume we have applied a new three-dimensional reconstruction method that involves the combination of focused ion beam milling and scanning electron microscopy (FIB/SEM). We show that the images obtained with FIB/SEM are similar to those obtained with TEM, but with the advantage that FIB/SEM permits serial reconstructions of large volumes of tissue to be generated rapidly and automatically. Furthermore, we compared the estimates of the number of synapses obtained with stereological methods with the values obtained by FIB/SEM reconstructions. We concluded that FIB/SEM not only provides the actual number of synapses per volume but it is also much easier and faster to use than other currently available TEM methods. More importantly, it also avoids most of the errors introduced by stereological methods and overcomes the difficulties associated with these techniques.

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“…Helmstaedter et al, 2013;Ding et al, 2016), which share a common circuit design (Borst and Helmstaedter, 2015), and the numerically simple synaptic circuits of certain invertebrates (Bargmann and Marder, 2013). Arthropod visual systems have played a major role, because their composition inherited from the overlying compound eye is modular, with older accounts from the optic lamina in various species: the water flea Daphnia magna (Macagno et al, 1973), the horseshoe crab Limulus polyphemus (Fahrenbach, 1985) and the fruit fly Drosophila melanogaster (Meinertzhagen and O'Neil, 1991) (Fig. 1), all of which depend on a repeating retinotopic composition of cartridges (see Glossary).…”

Section: Em Plays An Essential Rolementioning

confidence: 99%

Of what use is connectomics? A personal perspective on theDrosophilaconnectome

Meinertzhagen

2018

Journal of Experimental Biology

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The brain is a network of neurons and its biological output is behaviour. This is an exciting age, with a growing acknowledgement that the comprehensive compilation of synaptic circuits densely reconstructed in the brains of model species is now both technologically feasible and a scientifically enabling possibility in neurobiology, much as 30 years ago genomics was in molecular biology and genetics. Implemented by huge advances in electron microscope technology, especially focused ion beam-scanning electron microscope (FIB-SEM) milling (see Glossary), image capture and alignment, and computer-aided reconstruction of neuron morphologies, enormous progress has been made in the last decade in the detailed knowledge of the actual synaptic circuits formed by real neurons, in various brain regions of the fly It is useful to distinguish synaptic pathways that are major, with 100 or more presynaptic contacts, from those that are minor, with fewer than about 10; most neurites are both presynaptic and postsynaptic, and all synaptic sites have multiple postsynaptic dendrites. Work on has spearheaded these advances because cell numbers are manageable, and neuron classes are morphologically discrete and genetically identifiable, many confirmed by reporters. Recent advances are destined within the next few years to reveal the complete connectome in an adult fly, paralleling advances in the larval brain that offer the same prospect possibly within an even shorter time frame. The final amendment and validation of segmented bodies by human proof-readers remains the most time-consuming step, however. The value of a complete connectome in is that, by targeting to specific neurons transgenes that either silence or activate morphologically identified circuits, and then identifying the resulting behavioural outcome, we can determine the causal mechanism for behaviour from its loss or gain. More importantly, the connectome reveals hitherto unsuspected pathways, leading us to seek novel behaviours for these. Circuit information will eventually be required to understand how differences between brains underlie differences in behaviour, and especially to herald yet more advanced connectomic strategies for the vertebrate brain, with an eventual prospect of understanding cognitive disorders having a connectomic basis. Connectomes also help us to identify common synaptic circuits in different species and thus to reveal an evolutionary progression in candidate pathways.

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Anatomical circuitry of lateral inhibition in the eye of the horseshoe crab, Limulus polyphemus

Cited by 33 publications

References 63 publications

Octopamine- and cyclic AMP-stimulated phosphorylation of a protein in Limulus ventral and lateral eyes

Octopamine- and cyclic AMP-stimulated phosphorylation of a protein in Limulus ventral and lateral eyes

Counting synapses using FIB/SEM microscopy: a true revolution for ultrastructural volume reconstruction

Of what use is connectomics? A personal perspective on theDrosophilaconnectome

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