[Effect of glucocorticoid receptor blockade on pulmonary and renal vascular permeability in scalded rats]

With glucocorticoid receptor (GR) blockade by RU38486, a competitive antagonist of GR, the change in contents of FITC labeled albumin (FITC-albumin) in pulmonary and renal tissue in scalded rats have been measured to study the changes in vascular permeability. The result showed that the contents of FITC-albumin in pulmonary and renal tissue in the scalded rats were markedly higher than those of the controls (lung: P < 0.05, kidney: P < 0.001). When the scalded rats were given GR blockade, the contents of FITC-albumin in pulmonary and renal tissue were significantly higher than those of rats with scald only (P < 0.05). The results indicated: (1) the pulmonary and renal vascular permeability in scalded rats was markedly enhanced; (2) GR blockade might aggravate the increase in vascular permeability caused by scald, so that the protective effect of glucocorticoid (GC) on vascular permeability seemed to be reversed.

Overexpressing sperm surface beta 1,4-galactosyltransferase in transgenic mice affects multiple aspects of sperm-egg interactions

Sperm surface beta 1,4-galactosyltransferase (GalTase) mediates fertilization in mice by binding to specific O-linked oligosaccharide ligands on the egg coat glycoprotein ZP3. Before binding the egg, sperm GalTase is masked by epididymally derived glycosides that are shed from the sperm surface during capacitation. After binding the egg, sperm-bound oligosaccharides on ZP3 induce the acrosome reaction by receptor aggregation, presumably involving GalTase. In this study, we asked how increasing the levels of sperm surface GalTase would affect sperm-egg interactions using transgenic mice that overexpress GalTase under the control of a heterologous promoter. GalTase expression was elevated in many tissues in adult transgenic animals, including testis. Sperm from transgenic males had approximately six times the wild-type level of surface GalTase protein, which was localized appropriately on the sperm head as revealed by indirect immunofluorescence. As expected, sperm from transgenic mice bound more radiolabeled ZP3 than did wild-type sperm. However, sperm from transgenic animals were relatively unable to bind eggs, as compared to sperm from wild-type animals. The mechanistic basis for the reduced egg-binding ability of transgenic sperm was attributed to alterations in two GalTase-dependent events. First, transgenic sperm that overexpress surface GalTase bound more epididymal glycoside substrates than did sperm from wild-type mice, thus masking GalTase and preventing it from interacting with its zona pellucida ligand. Second, those sperm from transgenic mice that were able to bind the zona pellucida were hypersensitive to ZP3, such that they underwent precocious acrosome reactions and bound to eggs more tenuously than did wild-type sperm. These results demonstrate that sperm-egg binding requires an optimal, rather than maximal, level of surface GalTase expression, since increasing this level decreases sperm reproductive efficiency both before and after egg binding. Although sperm GalTase is required for fertilization by serving as a receptor for the egg zona pellucida, excess surface GalTase is counterproductive to successful sperm-egg binding.

[Auto-analysis of corneal endothelium with photoelectrical scans and computer]

A quantitative analysis of corneal endothelial cells was made with photoelectrical scans and computer in 67 eyes. No difference was found as regards to the mean cell area and density between the endothelial analysis system and routine square counting. On the other hand, we analyzed corneal endothelial cells between 30 eyes wearing hard contact lens and 30 eyes of age- and sex-matched nonwearing control. The parameters, including cell density individual cell area, area, mean cell area, standard deviation, coefficient of variation of cell size (CV), maximum cell, minimum cell, the ratio of the maximum to minimum cell, and percentage of the hexagoal cells, were automatically displayed. The cell density and mean cell area also showed no significant difference (P > 0.05) between the wearers and nonwearing control, but the CV and the frequency of the hexagonal cells showed significant difference (P < 0.01). The ratio of maximum to minimum cell, the polymegethism and pleomorphism were obviously increased in the wearers. It is highly suggested that computer analysis system is of great value in evaluating corneal endothelial cells.

Egg cortical granule N-acetylglucosaminidase is required for the mouse zona block to polyspermy

The mammalian egg must be fertilized by only one sperm to prevent polyploidy. In most mammals studied to date, the primary block to polyspermy occurs at the zona pellucida, the mammalian egg coat, after exocytosis of the contents of the cortical granules into the perivitelline space. The exudate acts on the zona, causing it to lose its ability to bind sperm and to be penetrated by sperm previously bound to the zona. However, the cortical granule components responsible for the zona block have not been identified. Studies described herein demonstrate that N-acetylglucosaminidase is localized in cortical granules and is responsible for the loss in sperm-binding activity leading to the zona block to polyspermy. Before fertilization, sperm initially bind to the zona by an interaction between sperm surface GalTase and terminal N-acetylglucosamine residues on specific oligosaccharides of the zona glycoprotein ZP3 (Miller, D. J., M. B. Macek, and B. D. Shur. 1992. Nature (Lond.). 357:589-593). These GalTase-binding sites are lost from ZP3 after fertilization, an effect that can be duplicated by N-acetylglucosaminidase treatment. Therefore, N-acetylglucosaminidase, or a related glycosidase, may be present in cortical granules and be responsible for ZP3's loss of sperm-binding activity at fertilization. Of eight glycosidases assayed in exudates of ionophore-activated eggs, N-acetylglucosaminidase was 10-fold higher than any other activity. The enzyme was localized to cortical granules using immunoelectron microscopy. Approximately 70 or 90% of the enzyme was released from cortical granules after ionophore activation or in vivo fertilization, respectively. The isoform of N-acetylglucosaminidase found in cortical granules was identified as beta-hexosaminidase B, the beta, beta homodimer. Inhibition of N-acetylglucosaminidase released from activated eggs, with either competitive inhibitors or with specific antibodies, resulted in polyspermic binding to the zona pellucida. Another glycosidase inhibitor or nonimmune antibodies had no effect on sperm binding to activated eggs. Therefore, egg cortical granule N-acetylglucosaminidase is released at fertilization, where it inactivates the sperm GalTase-binding site, accounting for the block in sperm binding to the zona pellucida.

Sperm require beta-N-acetylglucosaminidase to penetrate through the egg zona pellucida

Fertilization in the mouse is initiated by sperm beta 1,4-galactosyltransferase (GalTase) binding to terminal N-acetylglucosamine residues on the zona pellucida glycoprotein ZP3. Binding of ZP3 induces exocytosis of the sperm acrosome, whose contents are believed to digest a penetration slit in the zona matrix through which sperm reach the egg. As a consequence of acrosomal exocytosis, GalTase is redistributed to the lateral aspect of the sperm head, where its function remains unknown. In this location, GalTase could conceivably impede zona penetration by binding to N-acetylglucosamine residues exposed on zona pellucida glycoproteins. Therefore, in this study we investigated the presence and function of acrosomal glycosidases capable of removing the GalTase-binding site from zona pellucida glycoproteins. beta-N-acetylglucosaminidase was found at very high levels in sperm, being more than 20-fold higher than other glycosidases assayed. The specific isozymic variant was identified as beta-hexosaminidase B. beta-N-acetylglucosaminidase was localized to sperm acrosomes by biochemical and indirect immunofluorescence studies and was released during the acrosome reaction, as expected for an enzyme involved in zona penetration. To determine if, in fact, acrosomal beta-N-acetylglucosaminidase facilitated penetration through the zona, an assay was developed using eggs that were rendered incapable of triggering the block to polyspermy. A specific competitive inhibitor of beta-N-acetylglucosaminidase activity, PUGNAC, inhibited sperm penetration of the zona in a dose-dependent manner, whereas a closely related beta-glucosidase inhibitor, PUGLU, had no effect on zona penetration or on beta-N-acetylglucosaminidase activity. Neither glycosidase inhibitor affected sperm motility or induction of the acrosome reaction. These results demonstrate that beta-N-acetylglucosaminidase is found in sperm acrosomes and is released during the acrosome reaction, at which time it facilitates sperm penetration through the zona. These results also imply that sperm have developed mechanisms to prevent the formation of stable interactions between surface receptors and their zona pellucida ligands during penetration.

A family of concanavalin A-binding peptides from a hexapeptide epitope library

The lectin concanavalin A (Con A) binds methyl alpha-D-mannopyranoside (Me alpha Man) as well as alpha-D-mannosyl groups at the nonreducing terminus of oligosaccharides. Ligand peptides that mimic the binding of Me alpha Man to Con A were identified from screening an epitope library composed of filamentous phage displaying random hexapeptides. A consensus sequence was identified among affinity-purified phage; Con A binds phage bearing this sequence and is inhibited from doing so by Me alpha Man. When tested for binding against a panel of lectins, phage bearing this sequence bind only weakly to a closely related D-mannose-binding lectin, indicating that binding to Con A is highly selective. A synthetic peptide bearing the consensus sequence blocks the precipitation of Con A by dextran with an inhibition strength equivalent to that of methyl alpha-D-glucopyranoside. These results demonstrate that the specificity of Con A is not limited to carbohydrates and that highly selective sugar-mimics for lectins of plant, animal, or bacterial origin may be identified from epitope libraries.

[Dynamics of endothelial cells of the peripheral area of cornea]

Clinical corneal buttons of 150 cases were stained with try-pan blue and alizalin red S, so as to compare the relative density of endothelial cells and to analyse the forms of the cell nuclei. The result showed that cell densities of fetal corneal endothelium of 25 cases with fetal period from 19 to 34 weeks, had no significant difference (P > 0.05) between the central and peripheral areas of cornea. However, the cell densities of corneal endothelium of 19 cases, aged from newborn to 53 years, showed a significant difference (p < 0.01). The cell nuclei of the fetal corneal endothelium have elliptic forms mainly, which are similar between central and peripheral area of corneal endothelium. However, the forms show an unstable nucleus morphological structure. From newborn to adult cornea, the nucleus forms of corneal endothelial cells tend to be stable and circular, but there are unstable forms of endothelial cell nuclei dispersed in corneal periphery. This emphasize that the endothelial cells in corneal periphery still keep its cell differential function of development in some degree.

[Survey of fungi and bacterinum of the conjunctival sac in Guangzhou area]

This paper presents the results of fungal culture from healthy conjunctival sac in 178 eyes. The rate of positive culture of the fungi was 25% in farmers, 11.1% in cleaners, and 8.8% in city residents respectively. Culture for aerobic was carried out in the samples from conjunctival sacs of 137 eyes. The rate of positive culture was 71.9% in farmers, 80.6% in cleaners, and 23.2% in city residents respectively. On the other hand, the rate of fungal positive culture was 9.7% and that of aerobic was 30% in the patients managed with steroid eyedrops for more than one month. The aspergillus and penicillium were the most commonly seen species among the isolated fungal strain, whereas the staphylococci and streptococcus pneumonia were the most common among the isolated aerobic. The results run parallel to the fact that the main pathogens of ocular infection seen clinically are fungi and aerobics. The authors emphasize that the conjunctival sac should be disinfected to prevent infections caused by opportunistic pathogens.

Penetrating keratoplasty combined with cataract extraction

The authors report the results of penetrating keratoplasty combined with cataract extraction in 50 cases. The rate of transparent grafts was 62% after an average follow-up of 19 months. 60% of the patients restored their vision to 0.1 and better. The rate of transparent grafts and visual improvement did not correlate with the mode of cataract extraction; however, the extracapsular procedure had less vitreous during operation than the intracapsular modality did. The authors recommend that the combined operation be adopted for patients with corneal opacity and cataract, and preferably using the extracapsular mode.