Search

The objective of this study was to develop a bioprocess for lactose hydrolysis in diverse dairy matrices, specifically skim milk and cheese whey, utilizing column reactors employing a core-shell enzymatic system featuring β-galactosidase fused to a Cellulose Binding Domain (CBD) tag (β-galactosidase-CBD). The effectiveness of reactor configurations, including ball columns and toothed columns operating in packed and fluidized-bed modes, was evaluated for catalyzing lactose hydrolysis in both skim milk and cheese whey. In a closed system, these reactors achieved lactose hydrolysis rates of approximately 50% within 5 h under all evaluated conditions. Considering the scale of the bioprocess, the developed enzymatic system was capable of continuously hydrolyzing 9.6 L of skim milk while maintaining relative hydrolysis levels of approximately 50%. The biocatalyst, created by immobilizing β-galactosidase-CBD on magnetic core-shell capsules, exhibited exceptional operational stability, and the proposed bioprocess employing these column reactors showcases the potential for scalability., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: To evaluate the mechanism, clinical characteristics, management and visual outcome of ocular trauma following penetrating keratoplasty (PK)., Methods: Twenty-six patients (13 men, 13 women) who suffered surgical wound dehiscence after PK because of ocular blunt trauma between 1994 and 2001 were included in this retrospective study. Graft dehiscence was managed with primary wound closure in all patients. Visual acuity, intraocular pressure, and funduscopy were evaluated in the follow-up., Results: The mean age at trauma was 50+/-24 years (range 9-88 years). Mean interval between transplantation and trauma was 45.5+/-64 months (range 1 month to 20 years). Globe rupture occurred at the graft-host junction in all patients. Nine of 13 phakic eyes (69.2%) presented lens expulsion. Eight of nine pseudophakic eyes (88.9%) had lost their implants. Retinal detachment occurred in seven eyes (27%) within 3 months following the trauma. Five patients (19.2%) underwent vitreous surgery for posterior segment damage. Two eyes (7.7%) were regrafted. At the last examination, only seven eyes (27%) had visual acuity of 20/200 or better., Conclusions: Traumatic wound dehiscence may occur, and the prognosis is poor after the injury. Globe rupture at the graft-host junction showed persistence of wound weakness even a long time after PK. Prevention of ocular trauma should be performed following PK.

Unlabelled: Interesting results have been reported on the use of pars plana vitrectomy with adventitial sheathotomy for the decompression of branch retinal vein occlusions (BRVO). Recent onset BRVO responsible for a visual acuity of 20/40 or less have been estimated to be good candidates for this procedure. We report on the results of the prospective evaluation of three eyes (in three patients) with recent onset BRVO which underwent surgical decompression. Three men, aged 40, 50, and 68 years presenting with BRVO for 4, 4, and 3 weeks respectively, underwent surgical decompression. Initial visual acuity was 20/80, 20/80, and 20/200. After 11, 10, and 9 months follow-up, visual acuity was 20/80, 20/200, and 20/200. In two eyes, an increase of the area of retinal non-perfusion was treated with peripheral laser photocoagulation. No cataract, retinal tears or retinal detachment were observed., Conclusion: although feasible, sheathotomy did not lead to a significant visual improvement in our patients. Dissection of the arteriovenous crossing could have induced vascular trauma. Furthermore, vitrectomy with posterior hyaloid detachment alone could be of benefit in the treatment of branched retinal vein occlusions. A prospective randomised trial is needed to assess the effectiveness and the safety of this procedure and to determine the best candidates for surgery.

Background: Migration and proliferation of lens epithelial cells (LECs) are based on interactions between cellular integrins and extracellular matrix proteins (ECMs). We were able to design polymers substituted with COO- and SO3- groups that counteract LEC proliferation through modification of the integrin/ECM interaction. The objective of this study was to compare the cell proliferation-inhibiting properties of differently substituted copolymers with those of a homopolymer., Methods: Polymers were synthesized by radical polymerization and characterized by nuclear resonance spectroscopy. Second-passage rabbit LECs were cultured either on PMMA homopolymers (control) or on substituted PMMA copolymers. Cells were counted on days 2, 7, and 17. Cell vitality was evaluated by trypan blue staining. Experiments were run in quadruplicate. Statistical analysis was performed using the Wilcoxon test and the Mann-Whitney U-test., Results: Compared with control, cells cultured on copolymers grew to significantly lower cell numbers. The inhibitory effect became evident at day 2 after seeding and persisted throughout the experiment. Different ratios of COO-/SO3- substitutions yielded different grades of inhibition. No toxic effect was seen on rabbit LECs., Conclusions: The tested copolymers inhibit cell proliferation and are nontoxic. Further evaluation could lead to the development of new intraocular lens materials that prevent secondary cataract.

Background: The intrastromal corneal ring (ISR) is a refractive device recently introduced for clinical application that is implanted in the mid-peripheral corneal stroma in order to correct myopia without invasion of the central optical zone. First clinical results of intracorneal ring segment implantation were published recently. These results reveal striking similarities to our own experimental data, only briefly published up to now. The aim of this study is to present the refractive and histopathological data of ISR implants in rabbits and to compare these results with the clinical data actually available., Methods: Expansion/constriction effects were evaluated with a ring of constant size (7.5 x 0.5 x 0.2 mm) in channels of 7.0, 7.5, or 8.0 mm in diameter, volume effects by implantation of 7.5-mm rings with varying thickness (0.2, 0.3, 0.4 mm) into a channel of 7.5 mm, respectively. Refractive power was measured preoperatively and at day (D) 7, D14, D30 for the first and the second experiment, plus D60, D90 for the second experiment. Histological evaluations of the induced morphological changes were additionally performed at all time intervals., Results: Significant (P<0.05) flattening of the cornea was obtained in all but the first (constant ring, 7.0-mm channel) implants postoperatively at D7 and/or D14, with mean dioptric changes up to -5.03+/-2.92 compared with controls. However, from D30 on, there was no statistically significant difference between operated and control eyes. Biomicroscopy and histology of the implanted eyes revealed good biocompatibility, with only rare major complications such as stromal abscess or massive neovascularization., Conclusions: Although our implantation technique differs slightly from that employed in the recent FDA studies, our results tend to confirm the maximal achievable refractive change of about -5 dpt with this procedure. Furthermore, this study is the first to demonstrate that in rabbits, ISR implantation has only a shortterm effect on refractive power. Our results indicate that long-term refractive follow-up may be necessary in human eyes prior to the introduction of ISRs as a routine procedure in refractive surgery.

Intrastromal ring (ISR) implantation is a promising concept in refractive corneal surgery. In theory, it has two main advantages: eccentric corneal surgery and reversibility after ISR explanation. We present our first experimental data on histobiocompatibility after implantation of a 0.2/1.0 mm vaulted polymethylmethacrylate (PMMA) ISR of 7.5 mm diameter with a specially designed "puzzle lock" using a suction-guided stromal channelling device. Ninety-six rabbit eyes were implanted and enucleated after a 24-h to 8-month follow-up to be period and processed for histology (n = 51), scanning electron microscopy (n = 30) and transmission electron microscopy (n = 9). In this study, the histological data are reported. Two main histopathological phases of stromal reaction were observed: (1) up to 3 months: mild inflammation, mostly mononuclear cell reaction with some macrophages; (2) over 3 months: moderate fibrosis surrounding the ISR filling irregularities of the stromal channel. Mild scarring and rare circumscribed vascularization occurred at the sutured peripheral insertion site of the ISR. Persistent epithelial atrophy without erosion or ulceration was regularly observed over the bulging shoulder of the ISR. There was no significant endothelial surgical trauma due to ISR placement. Major complications occurred in 11 cases (11.5%): stromal abscess starting from the incision (n = 8) and massive neovascularization (n = 3). However, the incidence of complications regressed with improved surgical technique. In conclusion, there is good middle-term tolerance of the PMMA ring with a transparent central cornea.

In our experimental study on 53 rabbits we compared the amount of corneal endothelial damage caused by radial keratotomy (RK) referred to (1) the number of incisions (4, 8, or 16), (2) the postoperative interval (0 h, 48 h) and (3) the direction of the incision [centripetal (cp), centrifugal (cf)]. The endothelial damage was quantified by means of the Janus green photometry technique. Morphological changes were evaluated by scanning electron microscopy (SEM). Depending on the group examined, we found endothelial damage extending over 3-7% of an analysed surface of 64 mm2. One perforation caused endothelial damage of up to 17% of the surface examined. Increasing the number of incisions from 4 to 8 or 16 resulted in a statistically significant increase in the amount of endothelial damage (4.2%, 5.1%, 5.8%; P less than 0.05). At 0 h it was significantly higher than after 48 h (5.5%, 4.6%; P less than 0.05). The direction of the incision had no statistically significant influence in our study (zp: 5.2%, zf: 4.9%). The morphological changes in the rabbit corneal endothelium examined directly after the RK procedure were ruptures in the cell membranes, loss of cells, and posterior corneal protrusions beneath the incisions. After 48 h, we found fewer damaged cells and no denuded Descemet's membranes, but larger polymorphy of the cells and a numerical increase in the microvilli of the cells surrounding the damaged cells. Our results support the crucial argument against RK: the alteration and destabilization of healthy corneal tissue up to the endothelium.

Four cases of macular dystrophy in siblings were studied, 2 brothers and 2 sisters (49, 52, 55, 57 years old). The two youngest had an associated cornea guttata. We performed histologic, transmission, and scanning electron microscopic studies, and in addition a morphometric analysis of Descemet's membrane and of guttata excrescences. Previous studies have been confirmed and the problem of the relationship between the two conditions of macular dystrophy and guttate excrescences is emphasised.

There is in the ciliary epithelium a barrier which prevents the passage of plasma proteins into the posterior chamber of the eye. The anatomical site of this blood-aqueous barrier is at the zonulae occludentes (tight junctions) located between the lateral plasma-membranes of the nonpigmented epithelial cells. Using the freeze-fracture technique we have studied these junctions in the pars plicata. As in many epithelia, they are formed by an anastomosing network of ridges on the fracture PF face and by a complementary set of furrows on the fracture EF face of plasma membranes. Features of these junctions are the presence of frequent parallel and closely associated double or triple ridges, and a few small gap junctions, associated with tight junctional elements of the zonulae occludentes. We also show that the number of junctional strands (ridges and furrows from apex to base) varies from a few strands to about 15, according to their position around the nonpigmented epithelial cells. These observations suggest that the rabbit's ciliary epithelium is to be classified among the 'tight' or 'very tight' epithelia (Claude and Goodenough, 1973). After paracentesis, we observed no breakdown of the zonulae occludentes. This supports the hypothesis that the site of leakage of the plasma proteins is elsewhere than ciliary epithelium.

Endothelial cells of the microvasculature (arterioles, fenestrated capillaries, and small venules) of the rabbit ciliary body have been examined in freeze-fracture replicas in ultrahigh vacuum and at very low temperatures, with special regard to their junctional boundaries. The junctional complexes of fenestrated capillaries and venular endothelium are discontinuous and do not seal the interendothelial clefts. They cannot be compared with zonulae occludentes or tight junctions, while the junctions in the arteriolar endothelium are continuous and well organized, suggesting a very low degree of paracellular permeability. It would be of interest to know if these structural differences at the junctional level in each segment of the microvasculature correspond to different paracellular permeability properties.

A host versus graft reaction is induced by the injection of sensitized lymphocytes into the anterior chamber of rabbit eyes. The reaction of these lymphocytes against the corneal endothelium is studied with S.E.M. and T.E.M. On the first and second days the transformation of lymphocytes into active cells with uropods is observed. These immunologic cells destroy the endothelium, but the endothelial cells regenerate quickly. On the sixth day there appear macrophages coming from the host, indicating that the lesions are being cleaned. These experiments present a good model for the study of the interaction between immunologic cells and an organized cellular structure.

The study of the development of the cornea in the chick embryo by transmission and scanning electron microscopy allows us to observe the differences between the aspect of thin sections and the surface of the cells. When studied with the T.E.M. both endothelium and epithelium have a rather normal and mature aspects on the 9th day of development. Observed with the S.E.M., the aspect of the surface of the epithelium becomes mature no earlier than on the 19th day, whereas the development of the endothelium is completed only after hatching. The development of apical junctional complexes occurs at a later stage in the organisation of the endothelial layer.

The iridocorneal angle of the chick embryo was examined by scanning electron microscopy from the 7th day to the 19th day of development. The mesodermal tissue situated between the corneal endothelium and the iris differentiated into trabecular cells. These cells formed a strip on the 9th day and enlarged on the 13th day to form long cellular fibres. The trabecular meshwork was recognizable on the 15th day and reached full development only on the 19th day. The development of the trabecular meshwork was probably much earlier than is usually described. It began with differentiation of the corneal endothelial cells and these cells acquired a multipolar cell body with long cellular processes. The last stage is probably regulated to avoid an abnormal development of the angle structure. These results can be correlated with those obtained in the morphological examination of the structure of the angle in congenital glaucoma and the "cleavage syndrome" of the anterior chamber.

One systemic injection of retinal tissue or extract mixed with Freund's complete adjuvant induces uveo-retinitis in several animal species: guinea pig [6], rabbit [5, 7], monkey [4] and rat [8]. Rod outer segments may be used as the pathogenic antigenic preparation [1, 3, 9]. This study reports on the conditions of induction of experimental autoimmune uveo-retinitis (EAU) in rats (susceptible strains of rats, optimal doses of antigen and adjuvant) and the histopathological features of the lesions in the early stages of the disease. In several species one systemic injection of retinal tissue or extract mixed with Freund's complete adjuvant induces an ocular inflammatory disease, whose main features are an inflammatory infiltration of the uvea and a destruction of the external layers of the retina. With adequate doses of guinea pig retinal extract and adjuvant, the disease was induced in all cases in albino rats of the Lewis strain. The vascular and tissular lesions, and the infiltrates with a predominance of PMN's and basophils seem to be the result of immune complexe deposition.

The ability of the human corneal endothelium to regenerate is studied with the scanning electron microscope through examples of corneal diseases and penetrating keratoplasties. This study does not lead to final conclusions on the possibilities of regeneration of the human corneal endothelium but allows us to say that: --regeneration occurs through size increasing and deformation of the remaining cells. --the increase in number and size of surface microvilli may simply indicate a state of cell activation. --the presence of two nuclei in one cell is probably obtained by amitotic division but no complete mitosis has been seen. --Displacement of endothelial cells is a real progression and the cell is able to overcome obstacles. --the fibroblastic transformation of the endothelial cells is present in man but this may simply represent the migrating form of the cells.