Role of the optic lobes in the regulation of the locomotor activity rhythm of Drosophila melanogaster: behavioral analysis of neural mutants

The locomotor activity patterns of the Drosophila melanogaster brain mutants optomotor blind (omb), lobula plateless (lop), minibrain (mnb), small optic lobes (sol), sine oculis (so), and the double mutants mnb;so and sol;so, all of which show reductions in the optic lobes, were investigated and compared with those of the wild-type. In none of the mutants was the number of arrhythmic flies significantly higher than in the wild-type, indicating that the optic lobes are not the sole site of a pacemaker controlling the locomotor activity rhythm. However, these mutations greatly influence the stability of the circadian system, in that the number of flies simultaneously showing two or more circadian components increased as the optic lobe defects became more severe. In flies with the strongest reduction of the optic lobes, two free-running circadian components were found almost exclusively. This suggests a two-oscillator control of the locomotor activity. Eyeless mutants also expressing a neural mutation were entrained by light:dark (LD) cycles, but their activity pattern in LD was changed compared to the wild-type and the eyeless mutant so.     

Additive Gene Actions on the Fiber Number in the Anterior Optic Tract of Drosophila Melanogaster

The influence of mutations in seven neurological genes on the number of fibers in the anterior optic tract (AOT) of Drosophila melanogaster has been investigated. It is shown that the number of fibers in the AOT can be drastically reduced in single and especially in multiple mutants. However, no evidence for synergistic interactions between the sample of mutations used in the sine oculis (so), reduced optic lobes (rol), minibrain (mnb), and small optic lobes (sol) genes was obtained at the level of the AOT. The rol^KS222 and so mutations eliminate similar fiber sets in the AOT, which are distinctly different from those eliminated by sol^KS58 and mnb¹.     

A Golgi analysis of the accessory optic fibers terminating in the medial terminal nucleus of the mouse accessory optic system

Fibers of the accessory optic tract (AOT) terminating in the medial terminal nucleus (MTN) were observed in the mouse by the rapid Golgi method. The AOT fibers, which entered the MTN from its ventromedial aspect, were divided into thick and fine fiber groups, the thick fibers emitting many terminal collaterals of various calibers, and the fine ones generating fine terminal branches. The possibility exists that the neurons sending AOT fibers to the MTN might be eterogenous in nature.     

Bilateral reorganization of the rat optic tract following enucleation of one eye at birth

In albino rats with one eye removed at birth (NE rats), electron microscopic studies were made on the optic tract (OT) to count the fibers and to measure their thickness. In addition, experiments were made in NE rats to know the physiological properties of the optic pathway such as conduction velocity, synaptic delay and so on. The number of fibers in the OT of NE rats was compared with that constituting the crossed and uncrossed pathways of normal adult rats. In NE rats the fiber count increased by about 30,000 in the OT ipsilateral to the remaining eye while it decreased by about the same amount in the contralateral OT. The axonal cross section area of OT fibers was measured as an index for fiber thickness. No marked abnormalities were found in the OTs of NE rats with regard to the morphological dimension. Relay cells (P-cells) of the LGN were recorded by electrical stimulation of the optic pathway. The uncrossed projection of NE rats to the LGN was characterized by the following points: (1) P-cells responding to stimulation of the uncrossed fibers were encountered in NE rats much more frequently than in normal adult rats. (2) Synaptic delays assumed to be involved in trans-synaptic activation of P-cells by the uncrossed fibers were calculated at larger values than for P-cells activated by the crossed fibers in NE rats and normally grown rats.     

Perlecan participates in proliferation activation of quiescent Drosophila neuroblasts.

Drosophila neuroblasts act as stem cells. Their proliferation is controlled through cell cycle arrest and activation in a spatiotemporal pattern. Several genes have been identified that control the pattern of neuroblast quiescence and proliferation in the central nervous system (CNS), including anachronism (ana), even skipped (eve) and terribly reduced optic lobes (trol). eve acts in a non-cell-autonomous manner to produce a transacting factor in the larval body that stimulates cell division in the population of quiescent optic lobe neuroblasts. ana encodes a secreted glial glycoprotein proposed to repress premature proliferation of optic lobe and thoracic neuroblasts. trol was shown to act downstream of ana to activate proliferation of quiescent neuroblasts either by inactivating or bypassing ana-dependent repression. Here, we show that trol codes for Drosophila Perlecan, a large multidomain heparan sulfate proteoglycan originally identified in extracellular matrix structures of mammals. The results suggest that trol acts in the extracellular matrix and binds, stores, and sequesters external signals and, thereby, participates in the stage- and region-specific control of neuroblast proliferation.     

Effects of eye removal on receptors of α-bungarotoxin in the optic lobes of chick brain

The existence of receptors with high affinity for α-bungarotoxin and the pharmacologic properties of a nicotinic ACh receptor has been shown in the optic tectum of chick brain. In the present study eyes were removed from chicks at embryonic day 3 (E3), or at post-hatching day 3 (P3). In both cases, the total number of receptors for I¹²⁵-αBT which developed in the deafferented optic lobe was about 50% of the number in normal lobes.     

Molecular screening of 980 cases of suspected hereditary optic neuropathy with a report on 77 novel OPA1 mutations

We report the results of molecular screening in 980 patients carried out as part of their work‐up for suspected hereditary optic neuropathies. All the patients were investigated for Leber's hereditary optic neuropathy (LHON) and autosomal dominant optic atrophy (ADOA), by searching for the ten primary LHON‐causing mtDNA mutations and examining the entire coding sequences of the OPA1 and OPA3 genes, the two genes currently identified in ADOA. Molecular defects were identified in 440 patients (45% of screened patients). Among these, 295 patients (67%) had an OPA1 mutation, 131 patients (30%) had an mtDNA mutation, and 14 patients (3%), belonging to three unrelated families, had an OPA3 mutation. Interestingly, OPA1 mutations were found in 157 (40%) of the 392 apparently sporadic cases of optic atrophy. The eOPA1 locus‐specific database now contains a total of 204 OPA1 mutations, including 77 novel OPA1 mutations reported here. The statistical analysis of this large set of mutations has led us to propose a diagnostic strategy that should help with the molecular work‐up of optic neuropathies. Our results highlight the importance of investigating LHON‐causing mtDNA mutations as well as OPA1 and OPA3 mutations in cases of suspected hereditary optic neuropathy, even in absence of a family history of the disease. © 2009 Wiley‐Liss, Inc.     

The accessory optic system of the rabbit, cat, dog and monkey: a whole-mount HRP study

Summary The three-dimensional fiber pathways of the accessory optic system in the rabbit, cat, dog and monkey were studied in whole-mounted preparations of the diencephalon and the midbrain, without sectioning, by anterograde labeling of retinal axons with horseradish peroxidase (HRP). HRP histochemical studies on alternate serial coronal sections were also performed. The rabbit accessory optic system exhibited two fasciculi (the inferior fasciculus, and the superior fasciculus consisting of the anterior fibers and the posterior fibers) and three terminal nuclei (the medial terminal nucleus, and the anterior and posterior porcions of the lateral terminal nucleus), but lacked the dorsal terminal nucleus. In the cat and dog, only the posterior fibers of the superior fasciculus were detected. The inferior fasciculus and the anterior fibers of the superior fasciculus were absent. The medial terminal nucleus and the posterior portion of the lateral terminal nucleus were commonly observed in the cat and dog. The cat accessory optic system possessed the dorsal terminal nucleus, and the dog accessory optic system possessed the anterior portion of the lateral terminal nucleus. The monkey (Macaca fuscata) accessory optic system consisted of the posterior fibers of the superior fasciculus, but blacked the inferior fasciculus and the anterior fibers of the superior fasciculus. Most of the posterior fibers terminated in the well-developed posterior portion of the lateral terminal nucleus located on the upper surface of the cerebral peduncle. A small number of posterior fibers projected to the poorly-developed medial terminal nucleus. Based on these findings, species differences in the mammalian accessory optic system were discussed.     

Binocular interaction in the fetal cat regulates the size of the ganglion cell population

During fetal development of the cat's visual system there is a marked overproliferation of optic nerve axons. In utero binocular interaction contributes to the severity of fiber loss since removal of an eye during gestation attenuates axon loss in the remaining optic nerve. The purpose of the present study was to determine whether this reduced loss of optic nerve fibers is due to a failure of retraction by supernumerary axon branches or to a reduction in ganglion cell death. To resolve this issue, we compared the number of ganglion cells and optic nerve fibers in adult cats which had one eye removed at known gestational ages. Retinal ganglion cells were backfilled with horseradish peroxidase and counts were made from retinal wholemounts. The axon complement was assessed with an electron microscopic assay. In the retinas of a normal cat we estimated 151,000 and 152,000 ganglion cells. The optic nerves of two other normal cats contained approximately 158,000 and 159,000 axons. In comparison, an animal enucleated on embryonic day 42 had 180,000 ganglion cells and 178,000 optic nerve fibers, while in an animal enucleated on embryonic day 51 the corresponding estimates were 182,000 and 190,000. The close agreement between cell and fiber counts indicates that axonal bifurcation does not contribute appreciably to the axon surplus in the optic nerve of prenatally enucleated cats. These results demonstrate that prenatal binocular interaction regulates the size of the mature retinal ganglion cell population.     

常染色体显性视神经萎缩的分子遗传学研究进展

常染色体显性视神经萎缩 (Autosomal Dominant Optic Atrophy , ADOA), 亦称Kjer型，是一种常见的遗传性视神经病变。该病常在儿童期发病（平均发病年龄为7岁），发病率约1:10 000-1:50 000，表现为隐匿性渐进性视力减退，双颞侧视盘苍白，中心或旁中心暗点，色觉障碍(常表现为蓝黄色盲)。组织病理学表现为：视网膜神经节细胞退行性变。 OPA1编码一种保守的动力相关GTPase，OPA1突变是ADOA发病的主要原因，目前已发现117个ADOA相关OPA1突变，包括：31.6%缺失和插入突变， 16.2%无义突变，25.6%错义突变和28.8%剪接突变。这些突变分布于OPA1基因编码区，但多数位于GTPase区。另外，本病还与OPA3 (19q13.2-q13.3)、OPA4 (18q12.2-12.3)及OPA5 (22q12.1-q13.1)基因突变有关。个体间的表型差异表明：其他遗传因素，个人因素以及环境因素可能与ADOA发病有关。     

下丘脑生长抑素神经元的发生

实验用免疫组化ＰＡＰ漂浮法研究了下丘脑生长抑素免疫反应阳性神经元的发生发育规律。结果表明生长抑素免疫反应阳性神经元的发生发育规律可归为三种模式；（１）生长抑素阳性神经元或纤维逐渐增至成年大鼠水平、代表核区为室周核和正中隆起；（２）阳性神经元或纤维数目很快增至峰值，然后又降至成年大鼠水平，该模式最普遍，大多数核区阳性神经元或纤维的发生都属于该模式。     

Course of the accessory optic fascicular fibers in the rat

The courses of fibers in the dorsal and lateral fasciculi of the accessory optic tract were studied in the rat by means of a selective silver impregnation method for degenerating nerve fibers and Mesulam's HRP method. The results indicate that except for a moderate number of fibers entering the dorsal terminal nucleus and the lateral terminal nucleus respectively, all optic fibers constituting the dorsal and lateral fasciculi descend the lateral surface of the brain to terminate in the medial terminal nucleus. No ascending optic nerve fiber to the dorsal or lateral terminal nucleus is included in these fasciculi.     

A patient with two mitochondrial DNA mutations causing PEO and LHON

We report a 22-year-old man with PEO and optic atrophy. PEO developed before the onset of optic atrophy. The patient showed mitochondrial myopathy with cytochrome c oxidase deficient fibers.In skeletal muscle the patient was homoplasmic for the mtDNA G11778A Leber hereditary optic neuropathy (LHON) mutation and heteroplasmic for the mtDNA 5 kb “common” deletion mutation. In blood only the homoplasmic LHON mutation was identified.The occurrence of two pathogenic mtDNA mutations is exceedingly rare. The clinical findings in this patient indicate that the combination of the two mtDNA mutations resulted in the expected combined phenotype since the mtDNA deletion mutation accounted for the PEO and the mtDNA G11778A point mutation for the optic atrophy.     

Functional organization of vestibular and visual inputs to neck and forelimb motoneurons in the frog.

1. Intracellular responses in neck and forelimb motoneurons to electrical stimulation of the vestibular nerve, the optic tectum, and the optic nerve were studied in frog. 2. Stimulation of the anterior branch of the vestibular nerve typically produced EPSPs, bilaterally, in neck, shoulder (DOR), and forelimb extensor (TRI, RAD) motoneurons, and bilateral IPSPs in forelimb adductor (PED) and flexor (ULN, COR) motoneurons. 3. Latencies of PSPs recorded in neck, shoulder, and proximal extensor motoneurons (TRI) were mostly in the disynaptic range, whereas many of those recorded in distal extensor (RAD) and in adductor and flexor motoneurons involved three synapses. 4. Lesion of the vestibulospinal fibers greatly reduced the vestibular nerve-evoked field potentials in the spinal cord and the occurrence of PSPs in forelimb motoneurons. These results as well as the latency measurements suggest that the pathway linking vestibular nerve and forelimb motoneurons mainly consists of vestibulospinal fibers, though involvement of other structures for production of later PSPs could not be completely ruled out. Hemisection of the brain stem at its most caudal level showed that the pathway to the contralateral motoneurons crosses at the level of brain stem as well as in the spinal cord. 5. Stimulation of the optic tectum produced EPSPs, IPSPs, and a mixture of EPSPs and IPSPs in neck, shoulder, and forelimb motoneurons, bilaterally. Most frequently, a combination of an excitation and inhibition was observed. The pathway from the optic tectum to neck and limb motoneurons is at least dysnaptic in nature. 6. Stimulation of the optic nerve produced IPSPs and a mixture of EPSPs and IPSPs in neck and forelimb motoneurons. Impulses originating from the optic nerve descend as far as to lumbar motoneurons producing EPSP-IPSP sequences bilaterally. 7. Interaction studies suggested that the vestibular and optic pathways to neck and forelimb motoneurons are separate from each other so that the site of integration of vestibular and visual input occurs at the level of motoneurons. 8. Evidence for electronic coupling among forelimb motoneurons and electrical synaptic transmission in th pathway linking vestibular nerve and forelimb motoneurons is presented.     

Origin of leucine-enkephalin fibers and their two main afferent pathways in the bed nucleus of the stria terminalis in the rat

Summary The destruction of th central amygdaloid nucleus (Ce), which contains a large group of neurons with leucine-enkephalin (L-ENK)-like immunoreactivity (L-ENKI), resulted in a marked ipsilateral reduction of these fibers in the bed nucleus of the stria terminalis (BST) suggesting that L-ENKI neurons in the Ce project ipsilaterally to the BST. This was supported by the finding that injection of biotin-wheat germ agglutinin into the BST labeled many neurons in the Ce. Simultaneous staining with antiserum showed that some of these neurons are L-ENKI. The L-ENKI fibers from the Ce reach the BST via two pathways; one from the ventral amygdalofugal pathway (VA), which terminate in the ventral subdivision of the BST pars lateralis (BSTL), and the other from the stria terminalis (ST), which terminates in the lateral subdivision of the BSTL, because (1) accumulation of L-ENKI structures appeared in the axons of these two systems on the amygdaloid side, (2) transection or destruction of the ST alone caused only a slight reduction of ENKI fibers in the lateral subdivision of the BSTL ipsilaterally and (3) transection or destruction of VA alone markedly reduced the number of L-ENKI fibers in the ventral subdivision of the ipsilateral BSTL. Thus, the VA L-ENKI fiber system is the major source of L-ENKI fibers in the ventral subdivision, while the ST L-ENKI fiber system is a minor source of the L-ENKI fibers in the lateral subdivision. The presence of an intrinsic L-ENKI system in the BST which may innervate the lateral subdivision was also suggested.Abbreviations used in Figures ac anterior commissure - AHy anterior hypothalamic nucleus - AM anteromedial thalamic nucleus - AV anteroventral thalamic nucleus - BST bed nucleus of stria terminalis - BSTL BST pars lateralis - BSTM BST pars medialis - Ce central amygdaloid nucleus - f fornix - GP globus pallidus - HDB horizontal limb of diagonal band of Broca - ic internal capsule - l lateral subdivision of the BSTL - LH lateral hypothalamus - LPO lateral preoptic area - LS lateral septal nucleus - m medial subdivision of the BSTL - Mfb medial forebrain bundle - MPO medial preoptic area - MS medial septal nucleus - ox optic chiasma - Re reuniens thalamic nucleus - Rt reticular thalamic nucleus - SI substantia innominata - sm stria medularis thalami - st stria terminalis - v ventral subdivision of the BSTL - va ventral amygdalofugal pathway - VDB vertical limb of diagonal band of Broca - VP ventral pallium - 2n optic nerve - 3v third ventricle     

Rescuing axons from degeneration does not affect retinal ganglion cell death

After a traumatic injury to the central nervous system, the distal stumps of axons undergo Wallerian degeneration (WD), an event that comprises cytoskeleton and myelin breakdown, astrocytic gliosis, and overexpression of proteins that inhibit axonal regrowth. By contrast, injured neuronal cell bodies show features characteristic of attempts to initiate the regenerative process of elongating their axons. The main molecular event that leads to WD is an increase in the intracellular calcium concentration, which activates calpains, calcium-dependent proteases that degrade cytoskeleton proteins. The aim of our study was to investigate whether preventing axonal degeneration would impact the survival of retinal ganglion cells (RGCs) after crushing the optic nerve. We observed that male Wistar rats (weighing 200-400 g; n=18) treated with an exogenous calpain inhibitor (20 mM) administered via direct application of the inhibitor embedded within the copolymer resin Evlax immediately following optic nerve crush showed a delay in the onset of WD. This delayed onset was characterized by a decrease in the number of degenerated fibers (P<0.05) and an increase in the number of preserved fibers (P<0.05) 4 days after injury. Additionally, most preserved fibers showed a normal G-ratio. These results indicated that calpain inhibition prevented the degeneration of optic nerve fibers, rescuing axons from the process of axonal degeneration. However, analysis of retinal ganglion cell survival demonstrated no difference between the calpain inhibitor- and vehicle-treated groups, suggesting that although the calpain inhibitor prevented axonal degeneration, it had no effect on RGC survival after optic nerve damage.     

A novel 65 kDa RNA-binding protein in squid presynaptic terminals

A polyclonal antibody (C4), raised against the head domain of chicken myosin Va, reacted strongly towards a 65 kDa polypeptide (p65) on Western blots of extracts from squid optic lobes but did not recognize the heavy chain of squid myosin V. This peptide was not recognized by other myosin Va antibodies, nor by an antibody specific for squid myosin V. In an attempt to identify it, p65 was purified from optic lobes of Loligo plei by cationic exchange and reverse phase chromatography. Several peptide sequences were obtained by mass spectroscopy from p65 cut from sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) gels. BLAST analysis and partial matching with expressed sequence tags (ESTs) from a Loligo pealei data bank indicated that p65 contains consensus signatures for the heterogeneous nuclear ribonucleoprotein (hnRNP) A/B family of RNA-binding proteins. Centrifugation of post mitochondrial extracts from optic lobes on sucrose gradients after treatment with RNase gave biochemical evidence that p65 associates with cytoplasmic RNP complexes in an RNA-dependent manner. Immunohistochemistry and immunofluorescence studies using the C4 antibody showed partial co-labeling with an antibody against squid synaptotagmin in bands within the outer plexiform layer of the optic lobes and at the presynaptic zone of the stellate ganglion. Also, punctate labeling by the C4 antibody was observed within isolated optic lobe synaptosomes. The data indicate that p65 is a novel RNA-binding protein located to the presynaptic terminal within squid neurons and may have a role in synaptic localization of RNA and its translation or processing.     

The distribution of crossed and uncrossed optic fibers in the different layers of the lateral geniculate nucleus in the tree shrew (Tupaia glis)

Summary The laminar distribution of crossed and uncrossed optic fibers was studied in the lateral geniculate nucleus (LGN) in the tree shrew (Tupaia glis) following unilateral enucleation. For the investigation of the termination of optic fibers the transneuronal degeneration method and experimental EM were employed. By using formvar film-coated slot grids, all six layers of the LGN could be studied in a single ultrathin section. Degeneration of crossed optic fibers was observed in layers 1, 3, 4 and 5 of the contralateral LGN. The uncrossed retinofugal fibers supply layers 2 and 6 of the LGN. The degeneration in layer 4 was less pronounced than that in the other layers. Ipsilateral and contralateral optic fibers were well separated. Filamentous as well as dark types of degeneration were found in the LGN after enucleation. The optic terminals (RL boutons) were seen only in the synaptic glomeruli.