Subretinal injections in rodent eyes: effects on electrophysiology and histology of rat retina.

PURPOSE: To describe a reliable and fast method for subretinal injection in rodents and to assess the effect of the procedure on retinal function and histology. METHODS: Corneas of rodents were punctured with a 28 gauge hypodermic insulin needle avoiding the lens. The injection procedure can be observed with the aid of a dissecting microscope and methylcellulose solution on the eye. A 33 gauge blunt needle was inserted into the eye through the corneal puncture and guided toward the subretinal matrix. Addition of fluorescein to the injection mixture facilitated immediate evaluation of the injection. Rat eyes were either non-injected (controls), received only a corneal puncture or were injected with fluorescent microspheres or PBS-fluorescein mixture. Retinal function and integrity were assessed through electroretinographic (ERG) analysis and postmortem histology. RESULTS: The anterior injection procedure provided a fast and simple method for subretinal injections. In rats a successful subretinal delivery was achieved in more than 90%, with less than 5% of the injected eyes developing cataracts. No significant differences in b-wave ERG amplitudes in rodent eyes over a five-week period were observed between non-injected control eyes and subretinally injected eyes (1 to 10 microl of PBS-fluorescein or 2 microl fluorescent microspheres). Histological analysis revealed that re-attachment of the rat retina occurred in approximately 1 day post-injection and the phagocytotic ability of RPE cells remained intact. CONCLUSIONS: This method was easily learned and required a minimum of equipment and animal preparation. With experience, 10 to 30 eyes could be injected per h. Furthermore, the injection procedure did not compromise the lens, retina or retinal pigment epithelium (RPE).

Strongly linked current flow in polycrystalline forms of the superconductor MgB2.

The discovery of superconductivity at 39 K in magnesium diboride, MgB2, raises many issues, a critical one being whether this material resembles a high-temperature copper oxide superconductor or a low-temperature metallic superconductor in terms of its behaviour in strong magnetic fields. Although the copper oxides exhibit very high transition temperatures, their in-field performance is compromized by their large anisotropy, the result of which is to restrict high bulk current densities to a region much less than the full magnetic-field-temperature (H-T) space over which superconductivity is found. Moreover, the weak coupling across grain boundaries makes transport current densities in untextured polycrystalline samples low and strongly sensitive to magnetic field. Here we report that, despite the multiphase, untextured, microscale, subdivided nature of our MgB2 samples, supercurrents flow throughout the material without exhibiting strong sensitivity to weak magnetic fields. Our combined magnetization, magneto-optical, microscopy and X-ray investigations show that the supercurrent density is mostly determined by flux pinning, rather than by the grain boundary connectivity. Our results therefore suggest that this new superconductor class is not compromized by weak-link problems, a conclusion of significance for practical applications if higher temperature analogues of this compound can be discovered.

Reciprocity between light intensity and rhodopsin concentration across the rat retina.

1. If a purpose of photostasis - absorption of a constant number of photons by the retina, regardless of incident light levels - is to maintain rods at saturation during the light period, then in retinal regions where light intensity is low, rhodopsin concentration should be high, and vice versa. 2. Our ocular transmission photometric measurements revealed that the distribution of light intensity across the rat retina was not as simple as had been thought and, furthermore, that the local concentration of rhodopsin had a high negative correlation with the light intensity. 3. The reciprocity between these two parameters leads to nearly uniform rates of photon absorption in rods across the retina.

Research project on the treatment of anorexia and bulimia: an integrative, multidimensional approach.

This research project tries to test a therapeutic strategy that could improve the prognosis of anorexic and bulimic syndrome, by reducing their tendency to chronicity. The hypothesis is that, whenever we deal with complex, multifactoral syndromes, such as anorexia and bulimia, a therapy based upon the association of different kinds of treatments (medical-biological-nutritional treatments plus family therapy) helps to obtain better results than one type of treatment only (medical-biological-nutritional alone). The selection of the samples (experimental and control samples), the materials and methods of the research project, and the follow-up series are described.

Traumatic vesicourethral fistula: unusual case of male urinary incontinence.

The usual cause of urinary incontinence secondary to pelvic trauma is damage to the sphincter mechanism in the prostatic urethra. A case is presented of an unusual and correctable cause of incontinence, vesicourethral fistula. This complication can probably be prevented by adequate debridement, drainage, and diversion.