Morphological study of the eye bulb of the hammerhead shark, Sphyrna lewini (Elasmobranch: Carcharhinidae) / Estudio morfológico del bulbo ocular del tiburón martillo, Sphyrna lewini (Elasmobranch: Carcharhinidae)

The hammerhead sharks shows a head laterally expanded with eyes and nostrils on the edges, which gives the species a hammer appearance. Another strand of studies indicates that the hypothesis of head shape alterations for better adaptions in the sensorial system with the development of structures associated to binocular sight and others sensorial organs. Given the variety of characteristics, the study aim was to describe the anatomical constitution of the hammerhead shark eye bulb. The bulb and its annexes exenteration was performed, and further dissection; the morphological description of the muscle insertions and eye bulb components were based on direct observation and were further photographed and catalogued. The eye bulb fragments and its annexes were histological technical. Between the sclera and the choroid it was possible to observe, by the electronical scanning microscopy, the thin layer called supra-choroid, in this region, spaces often filled by lymphatic vessels allied to a matrix formed by loose conjunctive tissue are found. In the choroid, a layer which is rich in blood vessels, loose conjunctive tissue and collagen fibers, was observed, besides pigmentary cells full of melanin in its interior, which result in its layer's dark color. Ciliary body is a choroid's dilatation; it has the aspect of a thick ring in finger-like shape, pigmented, covering the sclera surface and containing pigmentary cells. The crystalline capsule, which shows an acellular covering that, is hyaline and homogeneous. In the electronical scanning microscopy, it was observed that the capsule is extremely thick especially in the anterior face. The capsule is very elastic, constituted mainly by thin lamellae of collagenous fibers, as illustrated by the electronically scanning microscopy. Anatomic variations related mainly to the position of the eye bulb in the skull, fibrous tunica and lens call the attention and must be related to its habitat.

El tiburón martillo tiene la cabeza lateralmente expandida con los ojos y la nariz en sus márgenes. Estudios indican que alteraciones de la forma de la cabeza de estos animales son adaptaciones que mejoran el desarrollo del sistema sensorial y estructuras asociadas a la visión binocular y otros órganos sensoriales. Dada la variedad de características, el objetivo del estudio fue describir la constitución anatómica del bulbo ocular. Se disecó el bulbo ocular junto a sus anexos. La descripción morfológica de las inserciones musculares y componentes del bulbo ocular se basaron en la observación directa, siendo éstas fotografiadas y catalogadas. Entre la esclera y la coroides se observó através de microscopía electrónica de barrido, una delgada capa supra-coroides, y vasos linfáticos junto a la matriz formada por tejidos conectivos. La coroides, era abundante en vasos sanguíneos y fibras de tejido conectivo. Se observaron escasas células pigmentarias llenas de melanina, lo que se asemeja a un anillo en forma de dedo, de manera que cubren la superficie de la esclera y células que contienen pigmentos. En la cápsula del lente, fue posible observar un recubrimiento celular, hialino y homogéneo. En la microscopía electrónica de barrido, se observó una cápsula muy gruesa, principalmente en la región frontal. La cápsula elástica,estaba constituida por láminas delgadas, principalmente, por fibras de colágeno. Se concluyó que el bulbo ocular de estos animales posee variaciones anatómicas relacionadas, principalmente, con la posición del bulbo ocular en el cráneo, túnica fibrosa y lente, lo que puede estar directamente relacionado con su hábitat.

A six-rhabdomere, open rhabdom arrangement in the eye of the chrysanthemum beetle Phytoecia rufiventris: some ecophysiological predictions based on eye anatomy

We are describing a rhabdom organization of the eye of the chrysanthemum beetle Phytoecia rufiventris that to date has not been described from any other insect. In cerambycid beetles free rhabdomeres, forming a circular, open rhabdom, surround a central rhabdom made up of the rhabdomeres of one or two cells. In Phytoecia rufiventris the central rhabdomeres are missing throughout the eye and the microvilli of the outer 6 rhabdomeres are regularly oriented in three directions. Following the classification of rhabdom types suggested by Wachmann (1979), we suggest to name the rhabdom arrangement seen in the retina of Phytoecia rufiventris [quot ]Grundmuster 3[quot ]. This pattern ought to facilitate polarization sensitivity and movement perception, features that agree with the behavioural repertoire of Phytoecia rufiventris.

Ocular lesions and experimental choline deficiency

Previous studies have shown ocular haemorrhages in choline-deficient rats. The aim of this paper is to study further the relationship between ocular and renal lesions and biochemical alterations in rats fed a choline-deficient diet. Fifty one weanling male Wistar rats, were divided into two groups. Thirty one ofthem were fed a choline-deficient diet and the rest was fed a choline- supplemented diet ad libitum. Animalsfrom both groups were killed between the fifth and the eighth day. Urea, creatinine and homocysteine concentrations in blood were determined. Eyes were used for light microscopy study; high resolution lightmicroscopy and the study of the retina as “rétine a plat”. Kidneys were studied by light microscopy. Cholinesupplementedrats did not show ocular or renal lesion. Choline-deficient rats that showed renal lesions, tubular or cortical necrosis, did not always have ocular changes. There were no ocular changes in the only cholinedeficient rat without renal lesion. The ocular changes consisted mainly in haemorrhage in both cameras andciliary and vitreous bodies. Correlations between ocular and renal lesion (r=0.72, p<0.0001, CI 95%: 0.48-0.86); ocular lesion and creatinine (r=0.86, p<0.0001, CI 95%: 0.72-0.93) and ocular lesion and urea (r=0.70, p<0.0001, CI 95%: 0.44-0.85) were positive. Choline-deficiency induces ocular haemorrhagic lesions after the development of renal necrosis. The ocular pathology could be due to the immaturity of the ocular vasculature at this age. The hyaloid, choroid and retinal system are involved

Estudios previos han demostradohemorragia ocular en ratas deficientes en colina. El objetivo de este trabajo es profundizar en la relación entre las alteraciones oculares, renales y bioquímicas en ratas deficientes en colina. Cincuenta y una ratas Wistar macho recién destetadas fueron divididas en dos grupos: treinta y una fueron alimentadas con una dieta colino deficiente y el resto con colina suplementada ad-libitum. Los animales de ambos grupos fueron sacrificados entre el quinto y el octavo día. Se midió la concentración de urea, creatinina y homocisteína en sangre. Los ojos fueron estudiados por microscopía de luz, microscopía óptica de alta resolución y para el estudio de la retina como retina plana. Los riñones fueron estudiados por microscopía de luz. Las ratas suplementadas con colina no mostraron lesiones oculares o renales. Las colino deficientes que mostraron lesiones renales, necrosis tubular o cortical, no siempre tuvieron cambios oculares. No se encontraron cambios oculares en la única rata deficiente en colina sin lesión renal. Los cambios oculares consistieron principalmente en hemorragia enambas cámaras, cuerpo ciliar y vítreo. La correlación entre la lesión ocular y renal (r=0.72, p<0.0001, CI 95%:0.48-0.86), lesión ocular y creatinina (r=0.86, p<0.0001, CI 95%: 0.72-0.93) y lesión ocular y urea (r=0.70,p<0.0001, CI 95%: 0.44-0.85) fue positiva. La deficiencia de colina induce lesiones oculares luego del desarrollode la necrosis renal. La patología ocular podría ser debida a la inmadurez de los vasos oculares. El sistemahialoide, coroideo y retinal están involucrados

Study of efficacy of intravitreal injection of ciprofloxacin versus vancomycin and ceftazidime in treating experimental endophthalmitis

Endophthalmitis is a severe inflammation of the interior of the eye caused by the introduction of contaminating microorganisms. The aim of this study was to compare the efficacy of intravitreal injection of vancomycin and ceftazidime versus ciprofloxacin in an experimental model of Staph. Epidermidis induced endophthalmitis in rabbits. The study was conducted on the right eyes of 35 pigmented rabbits, 5 of which were used as control group. All remaining 30 eyes were inoculated with 3 x 10[6] CFU / 0.1 ml of Staph. epidermidis then, they were divided into 3 equal groups. 24 hours postinoculation, group I: was given no treatment, group II received a combined intravitreal injection of vancomycin [1 mg /0.1 ml] and ceftazidime [2.25 mg / 0.1 ml], and group III received an intravitreal injection of ciprofloxacin [100 micro g/ 0.1 ml]. From each group, 72 hours postinoculation, 5 rabbits were used for clinical examination and then they were sacrificed, their right eyes were enucleated, and vitreous colony count was done. The other 5 rabbits were also sacrificed, their right eyes were enucleated, and histologlcal examination by LM and TEM was performed. The clinical examination revealed that the conjunctival injection and the corneal oedema were significantly less in group II in comparison to group I and III. The bacterial colony count was markedly decreased in group II in comparison to group I and III with a significant difference. Histological examination by LM and TEM revealed that the endophthalmitis group [group I] showed complete loss of architecture of the retina and choroid with disruption of the Bruch's membrane. Multiple degenerated cells and red blood cells were seen infiltrating the degenerated retina. On the contrary, the retinal structure was preserved to a great extent in group II, [vancomycin and ceftazidime group] except for focal areas of disorganization in the photoreceptor layer and mild invasion by inflammatory cells. Eyes treated with ciprofloxacin showed degeneration of the pigmented epithelial cells and the photoreceptor cell layers, pyknosis and karyolysis of the outer nuclear layer and infiltration of the all retinal layers with mononuclear cellular infiltration. Intravitreal injection of vancomycin [1 mg / 0.1 ml] and ceftazidime [2.25 mg / 0.1 ml] was more effective than ciprofloxacin [100 micro g / 0.1 ml] in improving the clinical signs, decreasing the bacterial colony count, and preserving the retinal structure in Staph. epidermidis endophthalmitis

Fine-structural details of the photoreceptor membranes in the ocellus of the scale-insect parasite Centrodora sp. (Hymenoptora; Aphenelidae): a case of gene transfer between host and parasite?

Only one insect (the scale insect Eriococcus sp.) is known, in which photoreceptive lamellae appear to have replaced the usual arthropod rhabdom microvilli. We are now reporting the presence of photoreceptive membranes, which also appear to resemble lamellae rather than microvilli, but they are in the ocellus of the tiny wasp Centrodora sp., which parasitizes scale insect eggs. The apparently optically homogenous lens of the Centrodora ocellus measures approximately 10 µm in diameter and, thus, operates at the limits of diffraction. We calculated that the lens is capable of focusing a parallel bundle of rays on the retina of the ocellus.

Microanatomical characteristics of marginal ommatidia in three different size-classes of the semi-terrestrial isopod Ligia exotica (Crustacea / Isopoda)

The aims of this paper have been (a) to characterize marginal ommatidia from different eye regions through a detailed description of their distinct ultrastructural features in three different size-classes of L. exotica, and (b) to compare microanatomical characteristics of the marginal ommatidia with those of ommatidia of the same eye, but located further centrally. On the basis of transverse as well as longitudinal sections we conclude that new ommatidia are added from a crescentic dorso-anterio-ventral edge of the eye and that maturing ommatidia go through a sequence in which originally the nuclei of cone-, pigment-, and retinula cells are arranged in three separate layers. At the beginning of the microvillar development, the organization of the corresponding rhabdomeres is still quite different (much less regular) from that of those rhabdomeres that make up the mature rhabdom. Marginal ommatidia always possess smaller diameters than more centrally located ones and retinal screening pigment granules are most apparent in the retinula cells only after the first microvilli have appeared. The diameters of rhabdom microvilli (approx. 55 nm) do not differ in ommatidia from the five investigated eye regions in small specimens (< 1.5 cm body length), but show a tendency to be slightly wider in the anterior (= frontal or rostral) regions of the eye (approx. 65 nm) in larger specimens (> 2.0 cm body length).

The postembryonic development of the ocellar system of Triatoma infestans Klug (Heteroptera: Reduviidae)

Simple eyes or ocelli coexist with compound eyes in many adult insects. The change in the morphology of the ocelli along the five larval instars of Triatoma infestans was studied by light and scanning electron microscopy. Our analysis showed that the development of the ocelli of these bugs occurs gradually along the larval life. The photoreceptor layer is present from the second-instar onwards. The cornea appears first at the imaginal stage and grows up to the 18-20th day after the last ecdysis, associated to an increase in the retinal mass. Findings are discussed in a comparative fashion and in relation to the functionality of the ocellar system in T. infestans

Análisis morfométrico automatizado del ojo contralateral en queratopatía bulosa pseudofáquica / Automated morphometric analysis of contralateral eye in pseudophagic bullous keratopathy

Con el fin de caracterizar la presencia de alteraciones endoteliales que pudiesen facilitar el desarrollo de queratopatía bulosa después de una cirugía de catarata se estudiaron 12 pacientes con queratopatía bulosa pseudofáquica en un ojo, mientras que el contralateral se encontraba sano. Todos los pacientes fueron sometidos a microscopia especular de contacto con análisis morfométrico automatizado de las imágenes obtenidas. La edad promedio del grupo de estudio fue de 71.0 años (D.E. 11.9), mientras que la densidad celular media fue de 1090 células por mm2 (D.E. 875), y el área promedio, 680 mm2 (D.E. 392). El coeficiente de variación fue 7.7, teniendo una poligonalidad de 58 por ciento de células hexagonales. Se identificaron dos subgrupos: uno con valores cercanos a la media obtenida y otro con valores por debajo de la desviación estándar. La diferencia de medidas (t student) fue estadísticamente significativa para los dos subgrupos (p < 0.05). Consideramos que en un alto porcentaje de pacientes con queratopatía bulosa pseudofáquica existe una enfermedad endotelial subyacente, lo que ocasiona el desarrollo de esta entidad al someter al endotelio a un evento quirúrgico.

Hallazgos histopatológicos y ultraestructurales de apoptosis en rehabilitación / Histopathologics and ultraestructurally find of apoptosis in retinoblastoma

Se realiza un estudio histopatológico de 53 globos oculares a 3 de los cuales se le realiza estudio ultraestructural, recibidos de la Sección de Oftalmología del Instituto de Anatomía Patológica de la Universidad Central de Venezuela de pacientes con el diagnóstico histológico de Retinoblastoma en un lapso comprendido entre 1990 y 1995, con el objeto de establecer la presencia de apoptosis y la relación que existe entre ella y el grado de evolución del tumor. La apoptosis es un mecanismo de muerte celular programada que se encuentra relacionada con una gran variedad de factores intra y extracelulares, sin embargo, el mecanismo que inicia el proceso es aún desconocido, se ha demostrado que la apoptosis juega un papel muy importante en la limitación y crecimiento del tumor pudiendo existir una correlación positiva entre la presencia de esta y un mejor pronóstico y evolución clínica de pacientes con retinoblastoma. Se realiza un estudio comparativo orientado a correlacionar los hallazgos establecidos en la literatura y los observados en nuestros casos de retinoblastoma