Decrease in reducing power of aqueous humor originating from glaucomatous rabbits.

AIM: To evaluate changes in the reducing power of aqueous humor (AH) with cyclic voltammetry (CV) and HPLC-EC. METHODS: NZW Rabbits exhibiting a sporadic mutation causing bilaterally buphthalmus eyes were set for intra ocular pressure (IOP) and eye size measurements. AH was obtained under anesthesia, from congenital glaucomatic rabbits (CGR, n=6) and age-matched controls (CON; n=6). The AH samples were analysed by CV and HPLC-EC. RESULTS: CGR IOP was found to be significantly higher than in CON (33.5+/-1.1 and 14.2+/-1.0 mmHg, respectively), eye size was 18.25 and 13.9 cm, respectively. CV analysis revealed two anodic currents representing two groups of low molecular weight antioxidant (LMWA). The two anodic potentials were equal for the two tested groups, indicating the same components of LMWA. The first anodic current of CGR was only 30% of the CON rabbits (2.11 vs7.17 microA/mg protein, t-test: P<0.05). As the main hydrophilic components of the first anodic current are known to be uric acid (UA) and ascorbic acid (AA), they were analysed for exact content by HPLC-EC. UA and AA levels were significantly lower in the CGR group (UA: 17.1+/-3.2 and 189.1+/-75.70 microM/mg, AA: 1.1+/-0.3 and 4.8+/-2.0 microM/mg protein respectively). CONCLUSIONS: Changes in the reducing power, as indicated by CV analysis, of CGR AH, is probably a result of chronic oxidative stress caused by the pathology. The differences in the first anodic wave are mainly due to a fall in the concentration of UA and AA.

The influence of helium-neon laser irradiation on the viability of skin flaps in the rat.

Low energy helium-neon (He-Ne) laser irradiation has been shown to induce various therapeutic effects. We investigated its effect on the viability of skin flaps in the rat. Thirty rats underwent skin flap elevation and were then divided into three equal groups. Group I (control) was not irradiated. Groups II and III were irradiated for 5 days postoperatively, Group II to the transition zone (between the live and expected necrotic areas) and Group III to the transitional and distal zones; total energy, 2.9 J/cm(2)for each rat. Ten days after the last treatment larger surviving areas were demonstrated macroscopically in Groups II and III (P< 0.01 and 0.001, respectively). Histological examination showed tremendous proliferation of capillaries (P

Histopathological changes in iridocorneal angle of inherited glaucoma in rabbits.

BACKGROUND: We examined morphologically the angular region of eyes affected by inherited glaucoma in rabbits genetically developed by crossbreeding in order to investigate the etiologic changes in the iridocorneal angle and to establish whether this strain of rabbit is a suitable animal model of goniodysgenetic glaucoma in humans. METHODS: The angular regions of both normal and glaucomatous eyes from four rabbits having unilateral inherited glaucoma were observed with light and electron microscopy. RESULTS: In the glaucomatous eyes angular region, the aqueous plexus corresponding to Schlemm's canal in humans was open and located far peripherally to the peripheral margin of the anterior chamber angle, although the plexus of one glaucomatous eye was poorly developed with a small lumen. In the angular meshwork, which corresponds to the trabecular meshwork in humans, a thick abnormal tissue with round cells embedded in the extracellular matrix was located just beneath the plexus. A large amount of extracellular matrix of basal lamina-like material was observed in the thick tissue. In the normal eyes, the angular region consisted of well-developed trabecular sheets with neither a thick tissue nor accumulations of extracellular matrix in the angular meshwork. CONCLUSION: The findings observed in the glaucomatous eyes are much the same as those observed in goniodysgenetic glaucoma in humans, suggesting that this strain of inherited glaucoma rabbits is a suitable animal model of goniodysgenetic glaucoma in humans. The present study also supports the hypothesis that the presence of a thick subcanalicular tissue due to maldevelopment of the iridocorneal angle is one of the main causes of this type of glaucoma.

Link between optic nerve regrowth failure and macrophage stimulation in mammals.

The adult mammalian central nervous system (CNS) fails to regenerate its axons following injury. A comparison between its postinjury response and that of axons of nervous systems capable of regeneration reveals major differences with respect to inflammation. In regenerative systems, a large number of macrophages rapidly invade the injured site during the first few hours and days after the injury. Following their activation/differentiation through interaction with the host tissue, they play a central role in tissue healing through phagocytosis of cell debris and communication with cellular and molecular elements of the damaged tissue. Relative to the peripheral nervous system (PNS), macrophage recruitment in the adult mammalian CNS is delayed and is restricted in amount and activity. It was recently proposed that in injured mammalian CNS tissue, implantation of macrophages stimulated by prior co-culture with segments of peripheral (sciatic) nerves can compensate, at least in part, of the restricted postinjury inflammatory reaction. In the present study, this experimental paradigm is further explored and shows that there is no conflict between the systemic use of anti-inflammatory compounds and treatment with stimulated macrophages to promote regrowth of neuronal tissue.

Peripheral nerve-stimulated macrophages simulate a peripheral nerve-like regenerative response in rat transected optic nerve.

We have previously demonstrated that the failure of the mammalian central nervous system (CNS) to regenerate following axonal injury is related to its immunosuppressive nature, which restricts the ability of both recruited blood-borne monocytes and CNS-resident microglia to support a process of repair. In this study we show that transected optic nerve transplanted with macrophages stimulated by spontaneously regenerating nerve tissue, e.g., segments of peripheral nerve (sciatic nerve), exhibit axonal regrowth at least as far as the optic chiasma. Axonal regrowth was confirmed by double retrograde labeling of the injured optic axons, visualized in their cell bodies. Transplanted macrophages exposed to segments of CNS (optic) nerve were significantly less effective in inducing regrowth. Immunocytochemical analysis showed that the induced regrowth was correlated with a wide distribution of macrophages within the transplanted-transected nerves. It was also correlated with an enhanced clearance of myelin, known to be inhibitory for regrowth and poorly eliminated after injury in the CNS. These results suggest that healing of the injured mammalian CNS, like healing of any other injured tissue, requires the partnership of the immune system, which is normally restricted, but that the restriction can be circumvented by transplantation of peripheral nerve-stimulated macrophages.

Micromorphology of the dorsal ocelli of the Oriental hornet.

The development of vision in animals throughout evolution has been reviewed by Sir Stewart Duke-Elder, whose survey of the sense of sight ranges from lowly Crustaceans to mammals and man. According to Duke-Elder each ocellus is formed by the "fusion of two or more ocelli, each with its own retina and pigment cup". This process of 'ocellation' probably occurred independently in a number of phyla. So far as Hymenoptera are concerned, at least in Bombus, only the median ocellus has retained any evidence of its 'dual' origin. In hornets, there are three ocelli which are organized on the dorsal part of the head and receive their innervation from the optical lobes that are located in the protocerebrum. Proceeding from the exterior to the interior, the ocelli are generally composed of a cornea, followed by corneogenic cell layers and then by a layer of sensory cells from which emerges the ocellar nerve. Thus, in wasps and hornets the ocelli consist of a group of visual cells beneath a common lens and they possibly accentuate the response to light stimuli that are perceived by the compound eyes. Recently, the ocelli have been ascribed roles in orientation and navigation. In honeybees the sensitivity of the ocelli to light at various wavelengths was compared with that of the compound eyes, and was found to be different, to wit: in the ocellus there were two peaks--one of UV light at a wavelength of 335-340 nm and the other of green light at 490 nm, whereas in compound eye the peaks were at 350 nm and 540 nm. From all the foregoing, it would seem that the role of the ocelli in insects in general and in hornets in particular is not yet sufficiently clear. The present study was undertaken to elucidate the structure of the ocelli in the Oriental hornet and possibly also their function.

Reattachment of extraocular muscles using fibrin glue in a rabbit model.

PURPOSE: Reattaching extraocular muscles by the conventional suturing method may be complicated by scleral perforation. The attachment of extraocular muscles, using fibrin sealants, avoids such risk. The authors evaluated the use of fibrin sealant in a laboratory rabbit model. METHODS: Fifty-eight eyes of 29 rabbits were used in the study. In both eyes of each rabbit, the superior rectus muscle was disinserted, recessed, and either sutured or reattached to the globe by fibrin sealant. Two groups of eyes were compared. In one group (42 eyes), the recessed muscle was reattached using fibrin sealant. In the second group (16 eyes), sutures were used to reattach the recessed muscle to the globe. The insertion of the superior rectus muscle was examined 14 days after surgery, and histopathologic evaluation was performed 6 weeks after the surgery. RESULTS: Although in the sutured muscle group no slippage from the original placement was found, it was found in the group in which fibrin glue was used. The muscle slippage was greater at the small muscle recessions and smaller at the large muscle recessions. For muscle recession of 6 mm or more, the average muscle slippage was 0.12 +/- 0.28 mm, which was not statistically different from the suture group (P = 0.0828). CONCLUSIONS: Fibrin sealant was found to be effective for extraocular muscle reattachment only in large muscle recessions. However, in small muscle recessions the glue was not strong enough to overcome the contractive strength of the muscle.

Complete transection of rat optic nerve while sparing the meninges and the vasculature: an experimental model for optic nerve neuropathy and trauma.

In this study we present a method to achieve a complete transection of optic nerve axons in adult rat, while preserving the vasculature and retaining the continuity of the meninges. Under deep anesthesia, the optic nerve of adult rat is exposed. Using specially designed instruments built from disposable glass microsampling pipettes, a small opening is created in the meninges of the optic nerve, 2-3 mm behind the eye globe. A glass dissector is introduced through the opening and is used to cut all the axons through the whole width of the nerve. Complete transection of the optic nerve axons was achieved, while retaining the continuity of the meninges and avoiding damage to the nerve's vascular supply. Transection was confirmed by transillumination showing a complete gap in the continuity of the nerve axons, and by both morphological and electrophysiological criteria. Nerve transection performed by the conventional technique leads to neuroma formation and hampers regeneration. Crush injury may cause nerve ischemia, which is detrimental to axonal recovery. Both of these disadvantages are avoided by the method of transection presented here. The opening created in the 'meningeal tube' can be used to inject substances that may be of benefit in recovery, rescue and/or regeneration of the injured axons. The model is particularly suitable for in vivo studies on nerve regeneration, and especially for screening of putative therapeutic agents.

Transplantation of activated macrophages overcomes central nervous system regrowth failure.

Macrophages have long been known to play a key role in the healing processes of tissues that regenerate after injury; however, the nature of their involvement in healing of the injured central nervous system (CNS) is still a subject of controversy. Here we show that the absence of regrowth in transected rat optic nerve (which, like all other CNS nerves in mammals, cannot regenerate after injury) can be overcome by local transplantation of macrophages preincubated ex vivo with segments of a nerve (e.g., sciatic nerve) that can regenerate after injury. The observed effect of the transplanted macrophages was found to be an outcome of their stimulated activity, as indicated by phagocytosis. Thus, macrophage phagocytic activity was stimulated by their preincubation with sciatic nerve segments but inhibited by their preincubation with optic nerve segments. We conclude that the inability of nerves of the mammalian CNS to regenerate is related to the failure of their macrophages recruited after injury to acquire growth-supportive activity. We attribute this failure to the presence of a CNS resident macrophage inhibitory activity, which may be the biochemical basis underlying the immune privilege of the CNS. The transplantation of suitably activated macrophages into injured nerves may overcome multiple malfunctioning aspects of the CNS response to trauma, and thus may be developed into a novel, practical, and multipotent therapy for CNS injuries.

Prevention of posterior capsular opacification by cryolysis and the use of heparinized irrigating solution during extracapsular lens extraction in rabbits.

We tried applying a specially-designed cryoprobe to the posterior capsule as well as adding heparin, an anticoagulative, anti-inflammatory compound, to the anterior chamber irrigation solution in an attempt to inhibit secondary cataract formation following a planned extracapsular lens extraction in 36 rabbits. The first group received both cryo treatment and heparin; a second group received heparin without cryo treatment; a third group received neither heparin nor cryo treatment. Complete opacification of the lens developed 3 months after the operation in all the rabbits not treated with heparin, and in 50% of those that received heparin. The addition of cryo treatment to the heparin-treated rabbits further reduced opacification by 20%. We conclude that in rabbits, cryo treatment, combined with intracameral administration of heparin during surgery, has a significant inhibitory effect on secondary cataract formation.