Mix and Match Color Vision: Tuning Spectral Sensitivity by Differential Opsin Gene Expression in Lake Malawi Cichlids

Mix and Match Color Vision: Tuning Spectral Sensitivity by Differential Opsin Gene Expression in Lake Malawi Cichlids
Authors: Juliet W.L. Parry, Karen L. Carleton, Tyrone Spady, Aba Carboo, David M. Hunt,
and James K. Bowmaker.
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Summary
Cichlid fish of the East African Rift Lakes are renowned for their diversity and offer a unique opportunity to study adaptive changes in the visual system in rapidly evolving species flocks [1, 2]. Since color plays a significant role in mate choice [3–6], differences in visual sensitivities could greatly influence and even drive speciation of cichlids. Lake Malawi cichlids inhabiting rock and sand habitats have significantly different cone spectral sensitivities [7, 8]. By combining microspectrophotometry (MSP) of isolated cones, sequencing of opsin genes, and spectral
analysis of recombinant pigments, we have established the cone complements of four species of Malawi cichlids. MSP demonstrated that each of these species predominately expresses three cone pigments, although these differ between species to give three spectrally different cone complements. In addition, rare populations of spectrally distinct cones were found. In total, seven spectral classes were identified. This was confirmed by opsin gene sequencing, expression, and in vitro reconstitution. The genes represent the four major classes of cone opsin genes that diverged early in vertebrate evolution [9]. All four species possess a long-wave-sensitive (LWS), three spectrally distinct green-sensitive (RH2), a bluesensitive (SWS2A), a violet-sensitive (SWS2B), and an
ultraviolet-sensitive (SWS1) opsin. However, African cichlids determine their spectral sensitivity by differential expression of primarily only three of the seven available cone opsin genes. Phylogenetic analysis suggests that all percomorph fish have similar potential.

Introdução à Teoria Geral da Administração

Introdução à Teoria Geral da Administração
Autor: Idalberto Chiavenato
Edição: 7ª
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Equações que mudaram o mundo.

Equações que mudaram o mundo.
Autor: Ian Stewart.
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Análise para Licenciatura G. Ávila completo

Análise para  Licenciatura
Autor: G. Ávila.

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The number, morphology, and distribution of retinal ganglion cells and optic axons in the Australian lungfish Neoceratodus forsteri (Krefft 1870)

The number, morphology, and distribution of retinal ganglion cells and optic axons in the Australian lungfish Neoceratodus forsteri (Krefft 1870)

Authors:HELENA J. BAILES, ANN E.O. TREZISE, and SHAUN P. COLLIN

Abstract

Australian lungfish Neoceratodus forsteri may be the closest living relative to the first tetrapods and yet little is known about their retinal ganglion cells. This study reveals that lungfish possess a heterogeneous population of ganglion cells distributed in a horizontal streak across the retinal meridian, which is formed early in development and maintained through to adult stages. The number and complement of both ganglion cells and a population of putative amacrine cells within the ganglion cell layer are examined using retrograde labelling from the optic nerve and transmission electron-microscopic analysis of axons within the optic nerve. At least four types of retinal ganglion cells are present and lie predominantly within a thin ganglion cell layer, although two subpopulations are identified, one within the inner plexiform and the other within the inner nuclear layer. A subpopulation of retinal ganglion cells comprising up to 7% of the total population are significantly larger (>400 micrometer/m²) and are characterized as giant or alpha-like cells. Up to 44% of cells within the retinal ganglion cell layer represent a population of presumed amacrine cells. The optic nerve is heavily fasciculated and the proportion of myelinated axons increases with body length from 17% in subadults to 74% in adults. Spatial resolving power, based on ganglion cell spacing, is low (1.6–1.9 cycles deg^-1, n =2) and does not significantly increase with growth. This represents the first detailed study of retinal ganglion cells in sarcopterygian fish, and reveals that, despite variation amongst animal groups, trends in ganglion cell density distribution and characteristics of cell types were defined early in vertebrate evolution.

Keywords: Visual streak, Spatial resolving power, Amacrine cells, Optic nerve, Dipnoi

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Displaced Amacrine Cells Disappear from the Ganglion Cell Layer in the Central Retina of Adult Fish during Growth

Displaced Amacrine Cells Disappear from the Ganglion Cell Layer in the Central Retina of Adult Fish during Growth
Authors: Andreas F. Mack, Christl Su¨ssmann, Bernhard Hirt, and Hans-Joachim Wagner

PURPOSE. Fish grow throughout life, including enlargement of eye and retina. Retinal growth involves several mechanisms of adjustment, such as cell addition and dendritic growth. To discover possible other means with which the animals adjust to changing eye size, the distribution of displaced amacrine cells (DACs) and ganglion cells (GCs) was analyzed in the retina of three sizes of a South American cichlid, the blue arcara Aequidens pulcher.
METHODS. DACs were identified by staining with antibodies specific for the calcium-binding protein parvalbumin. They were also weakly positive for staining against choline acetyl transferase (ChaT). GCs were labeled retrogradely with rhodamine dextran. Densities for both DACs and GCs were lower in the retinas of large fish. To distinguish changes due to eye size from specific adjustments, the proportions of DACs to GCs were examined, rather than the absolute cell densities, in various retinal regions in cryostat sections and wholemount preparations from fish of the three sizes.
RESULTS. The analyses suggest that, in small and large fish, DACs and GCs were produced in similar proportions (ratio of DACs to GCs, 0.62) in the retinal periphery where new retinal tissue was added by the germinal zone. However, in the central retina of large fish, this proportion was shifted toward GCs (DAC-GC ratio as low as 0.25).
CONCLUSIONS. During growth of the eye, the proportion of DACs in the ganglion cell layer decreases, indicating that these cells are eliminated from the ganglion cell layer by some unknown
mechanism. (Invest Ophthalmol Vis Sci. 2004;45: 3749–3755) DOI:10.1167/iovs.04-0190 

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Morphology and Circuitry of Ganglion Cells

Morphology and Circuitry of Ganglion Cells
Author: Helga Kolb

General Morphology

Ganglion cells are the final output neurons of the vertebrate retina. The ganglion cell collects the electrical messages concerning the visual signal from the two layers of nerve cells preceding it in the retinal wiring scheme. A great deal of preprocessing has been accomplished by the neurons of the vertical pathways (photoreceptor to bipolar to ganglion cell chain), and by the lateral pathways (photoreceptor to horizontal cell to bipolar to a macrine to ganglion cell chain), before presentation to the ganglion cell, and so it represents the ultimate signaler to the brain of retinal information. Ganglion cells are larger on average than most preceding retinal inter neurons and have large diameter axons capable of passing the electrical signal, in the form of transient spike trains, to the retinal recipient areas of the brain many millimeters or centimeters distant from the retina. The optic nerve collects all of the axons of the ganglion cells, and this bundle of more than a million fibers (in humans, at least) then passes information to the next relay station in the brain for sorting and integrating into additional information-processing channels.

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Progressive Diplopia and Facial Weakness in a 62-Year-Old Woman

Progressive Diplopia and Facial Weakness in a 62-Year-Old Woman 

Diplopia progressiva e fraqueza facial em uma mulher de 62 anos de idade.

Monika R. Kolloori, MD, Luis J. Mejico, MD, Joseph Corbo, MD, PhD, Aseem Sharma, MD, Melissa W. Ko, MD 

Dr. Kolloori: 
A 62-year-old woman presented to a local emergency department with horizontal diplopia that she first noted upon awakening the previous day. She had experienced a mild headache the prior evening but was otherwise well and denied any constitutional symptoms, concurrent or recent illnesses, jaw claudication, or eye pain. She had a history of hypercholesterolemia. Physical examination revealed normal vital signs. The patient’s visual acuity, intraocular pressures, and funduscopy were normal, and she had a mild abduction deficit of the left eye. Hematologic studies including complete blood count, metabolic panel, and sedimentation rate were normal. Noncontrast computed tomography (CT) of the head and magnetic resonance imaging (MRI) of the brain with and without contrast were performed.

Este artigo aborda a doença de Lyme, transmitida pelo carrapato e que provoca entre outras coisas febre, calafrios, fadiga, dores no corpo e dor de cabeça pode acompanhar a erupção cutânea, dor nas articulações, inflamação ocular. Causada pela bactéria Borrelia burgdorferi (http://www.minhavida.com.br/saude/temas/doenca-de-lyme). Este artigo aborda alguns outros sintomas da doença de Lyme em uma mulher de 62 anos, que muitas vezes são confundidos com casos de linfoma.

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Ebola and the need for restructuring pharmaceutical incentives.

Ebola and the need for restructuring pharmaceutical incentives.

Ebola e a necessidade de reestruturação dos incentivos farmacêuticos.

Abraar Karan1, Thomas Pogge2

1David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
2Yale University, Department of Philosophy, New Haven, CT, USA

The Ebola outbreak in West Africa has claimed the lives of over 9000 people largely due to a combination of poor health care infrastructure in affected countries, traditional beliefs and cultural practices, including the consumption of bushmeat and certain burial rituals that have amplified transmission, and the lack of therapeutic interventions such as medications and vaccinations [1,2].
Ebola virus was discovered in 1976, and since then there have been over 30 outbreaks, the majority occurring in Sub-Saharan Africa, yet development of medications has been negligible [3]. Moreover, while the current epidemic has spurred a new race to develop Ebola vaccines and treatment
regimens, the current patent system makes it unlikely that people in the most afflicted nations will have access to such vaccines or medications when they are brought to market without the assistance of development aid initiatives from the United Nations (UN), World Health Organization, the
GAVI Alliance and other multinational global entities.

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Phylogeography: retrospect and prospect

Phylogeography: retrospect and prospect

Author: John C. Avise

ABSTRACT
Phylogeography has grown explosively in the two decades since the word was coined and the discipline was outlined in 1987. Here I summarize the many achievements and novel perspectives that phylogeography has brought to population genetics, phylogenetic biology and biogeography. I also address future directions for the field. From the introduction of mitochondrial DNA assays in
the late 1970s, to the key distinction between gene trees and species phylogenies, to the ongoing era of multi-locus coalescent theory, phylogeographic perspectives have consistently challenged conventional genetic and evolutionary paradigms, and they have forged empirical and conceptual bridges between the formerly separate disciplines of population genetics (microevolutionary analysis) and phylogenetic biology (in macroevolution). 

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