Identification of previously unrecognized common elements in eukaryotic promoters. A ribosomal RNA gene initiator element for RNA polymerase I

A new ribosomal RNA promoter element with a functional role similar to the RNA polymerase II initiator (Inr) was identified. This sequence, which we dub the ribosomal Inr (rInr) is unusually conserved, even in normally divergent RNA polymerase I promoters. It functions in the recruitment of the fundamental, TATA-binding protein (TBP)-containing transcription factor, TIF-IB. All upstream elements of the exceptionally strong Acanthamoeba castellanii ribosomal RNA core promoter, to within 6 base pairs of the transcription initiation site (tis), can be deleted without loss of specific transcription initiation. Thus, the A. castellanii promoter can function in a manner similar to RNA polymerase II TATA-less promoters. Sequence-specific photo-cross-linking localizes a 96-kDa subunit of TIF-IB and the second largest RNA polymerase I subunit (A133) to the rInr sequence. A185 also photo-cross-links when polymerase is stalled at +7.

Age-related decline in ubiquitin conjugation in response to oxidative stress in the lens

Accumulation of damaged proteins is a major age-related change in lenses of virtually all species and is associated with lens opacification. Proteolytic removal of the damaged proteins may play an important role in maintaining the transparency of the lens. In many tissues, selective removal of abnormal or damaged proteins occurs via a ubiquitin-dependent proteolytic pathway. Ubiquitin, an 8.5 kDa polypeptide, selectively binds to proteins to form ubiquitin-protein conjugates. This ubiquitin-protein conjugate is, in most cases, a signal for protein degradation. In this work, age-related changes in rat lens in the following aspects were detected: (a) levels of the ubiquitin-protein conjugates, (b) some of the enzymes involved in ubiquitin conjugation in rat lenses, and (c) ability to respond to oxidative damage. Endogenous ubiquitin-protein conjugates were detected in epithelium, cortex and nucleus of lenses from young and old rats. The levels of endogenous high molecular weight (HMW) ubiquitin-protein conjugates in each developmental zone of the lenses from young rats were higher than that in the counterparts of lenses from old animals. Peroxide-treatment generally resulted in elevated levels of endogenous HMW ubiquitin-protein conjugates although masses of bulk proteins remain unchanged. The increases in ubiquitin-protein conjugates in the epithelial sections of young and old lenses upon oxidative stress were comparable. In the cortex of young lenses, there was a significant oxidation-related increase in ubiquitin-protein conjugates. There was a similar trend but diminished response in the cortex of old lenses. Nuclear fibers from young lenses also showed an oxidation-induced increase in the level of ubiquitin-protein conjugates. This response was not observed in nuclear fibers of old lenses. The ability to form HMW-ubiquitin conjugates with exogenous 125I-labeled ubiquitin in the lens also increased upon oxidative stress. The extent of the increase in the de-novo ubiquitin conjugating activity upon exposure to oxidation in old lens was much smaller than in young lens. Ubiquitin-activating enzyme (E1), and ubiquitin conjugating enzymes (E2(17k), E2(20k) and E2(25k) were detected by thiol ester assays or Western blot analysis. No significant age-related changes in the levels of E1, E2(17k), E2(20k) and E2(25k) were detected. The activity of E1 and E2(17k) increased upon exposure to H2O2. These data indicate that lens has the ability to increase ubiquitin conjugation activity in response to oxidative stress and this ability is attenuated upon aging. The age-related decrease in the ability to mount a ubiquitin-dependent response upon oxidation may contribute to the accumulation of damaged proteins in the old lenses.

Effects of calorie restriction and aging on the expression of antioxidant enzymes and ubiquitin in the liver of Emory mice

We studied the effect of age and calorie restriction on the expression of genes involved in antioxidant defenses in livers of young (4.5-6 months) and old (22 months) Emory mice fed a control (C) or restricted (R) diet. Specifically examined were catalase (CAT), glutathione peroxidase (Gpx), Cu/Zn and Mn superoxide dismutase (Cu/ZnSOD and MnSOD). As an indicator of oxidative damage to the tissues we measured lipid peroxidation. As indicators of oxidative stress we determined ubiquitin mRNA levels and endogenous high molecular weight (HMW) ubiquitin conjugates. Lower mRNA levels of ubiquitin (P < 0.05), CAT (P < 0.01) and Gpx (P < 0.01) were observed in tissues from young R versus C animals. The old C group had a lower CAT mRNA level (P < 0.0001) compared with young C. In the R group, age did not affect the CAT mRNA levels or Gpx mRNA levels; however, ubiquitin mRNA levels were higher (P < 0.05). No significant changes in Cu/Zn or MnSOD mRNA were observed with age or diet. Cu/ZnSOD protein levels were lower in the young R at 4.5 months (P < 0.05) than young C, and higher in the old R group versus old C (P < 0.05). CAT protein levels were higher in the old C versus old R (P < 0.05). Changes of HMW ubiquitin conjugates with age r diet were not significant. Of the four groups, the old R group showed the highest levels of lipid peroxidation.

A library of organic landscapes on filamentous phage

A billion-clone library of filamentous phage with different surface structures ("landscapes') was generated by fusing random octapeptides to the N-terminus of all 4000 copies of the major coat protein. Such a "landscape library' might include clones exhibiting emergent properties that inhere in the entire surface architecture, not in the peptides by themselves. Because the diverse surface landscapes are displayed on viable phage, they can be surveyed for exceedingly rare functions using microbiological selection methods. Clones with several emergent properties of the sort envisioned were successfully selected, suggesting that landscape libraries have promise as a novel source of nanomaterials with exploitable surface properties.

[Effect of combining EGF with KGF on proliferation of human corneal epithelial cells]

OBJECTIVE

To select effective drugs for enhancing corneal epithelial wound healing and treating persistent corneal epithelial defect.

METHODS

Epidermal growth factor (EGF) and keratinocyte growth factor (KGF) were added to cultures of human corneal epithelial cells and DNA synthesis in corneal epithelial cells were measured with [3H]-thymidine incorporation and liquid scintillation techniques. The cells were counted in a hemocytometer to determine the doubling time.

RESULTS

10 ng/ml EGF, 10 ng/ml KGF enhanced cellular proliferation effectively (P < 0.01). EGF in combination with KGF, the enhancement was more effective (P < 0.05) and reduced the doubling time.

CONCLUSIONS

Our results suggest that exogenous EGF with KGF can stimulate proliferation of human corneal epithelial cells and it may be of potential use clinically for treatment of persistent corneal epithelial

Probing the basis of antibody reactivity with a panel of constrained peptide libraries displayed by filamentous phage

The structural requirements for peptide binding to an antibody may be elucidated by probing it with a variety of peptides having different constraints. To this end, we have constructed and screened a panel of peptide libraries displayed by filamentous bacteriophage. The peptides in most of the libraries have the potential for constraint by fixed Cys residues, which have been placed at different sites within a randomized amino acid sequence of varying length. When taken together, the binding data obtained from screening the panel with a given antibody allow one to determine the types of constraints that promote binding, as well as the residues that are critical for binding. We describe the construction of 11, pVIII-displayed, peptide libraries, whose sizes range from 150 million to 10 billion clones. The libraries were screened with a number of polyclonal and monoclonal antibodies against peptides, proteins and carbohydrates. Cross-reactivity with peptides was always found for antibodies produced against peptides, linear epitopes on folded proteins and, surprisingly, carbohydrates, whereas antibodies against discontinuous epitopes on proteins were found less frequently. The implications of these results are discussed in terms of the structural basis for cross-reactivity with peptides.

Acoustic nonlinearity parameter tomography for biological specimens via measurements of the second harmonics

The acoustic nonlinearity parameter B/A is a new parameter in ultrasound tissue characterization. In this paper, on the basis of a theoretical analysis of finite amplitude ultrasonic wave propagation in fluidlike media, an experimental system for nonlinearity parameter tomography is developed. Using this system, the amplitude of the second harmonic wave cumulated in the propagation path of the primary wave is measured and the finite amplitude insert-substitution method is used in the conventional computer tomography (CT) technique. The filtered convolution algorithm is implemented using the amplitude of the second harmonic as the projection data, then the B/A tomography can be reconstructed. The B/A images for several biological samples are obtained. Besides, the image of porcine pathological liver tissue is studied and is compared with that of porcine normal liver tissue. These results show the potential applications of the nonlinearity parameter B/A in medical diagnosis.

Red-band holographic storage in azo dye sensitized by noncoherent light

Biphoton holographic storage recorded with 633-nm He-Ne beams has been investigated in Methyl Yellowdoped polystyrene film sensitized by weak noncoherent light from a low-pressure Hg lamp. It is demonstrated that the holography in the sample is erasable without fading. The dynamic behavior of the hologram is dependent on the cis-trans isomerization by noncoherent light and 633-nm beams and photoinduced heat.

[Experimental study of Colles' fracture combined with dorsal radio-carpal subluxation]

By cutting different ligaments and the distal end of radius of 20 fresh specimens with radiophotographic records, the author explored the mechanism of formation and traumatic anatomy of Colles' fracture with dorsal radio-carpal subluxation (DRSA). The results of experimental studies indicate that under normal condition, the change of radiolunate angle has some influence on the displacement of central point of lunate (CPL) but does not lead to DRS. The first is the rupture of the dorsal and palmar ligaments of radiocarpal joint and the second is the fracture of distal end of radius with a reversed palmar tilting angle of articular surface of distal radius. To treat the patients of Colles' fracture with DRS the previous palmar tilting angle should be restored to the full, as well as the anatomic reduction. The fixatiion in neutral or light dorsal extension position should be recommended.

Activation of a G protein complex by aggregation of beta-1,4-galactosyltransferase on the surface of sperm

Fertilization is initiated by the species-specific binding of sperm to the extracellular coat of the egg. One sperm receptor for the mouse egg is beta-1,4-galactosyltransferase (GalTase), which binds O-linked oligosaccharides on the egg coat glycoprotein ZP3. ZP3 binding induces acrosomal exocytosis through the activation of a pertussis toxin-sensitive heterotrimeric guanine nucleotide-binding protein (G protein). The cytoplasmic domain of sperm surface GalTase bound to and activated a heterotrimeric G protein complex that contained the Gi alpha subunit. Aggregation of GalTase by multivalent ligands elicited G protein activation. Sperm from transgenic mice that overexpressed GalTase had higher rates of G protein activation than did wild-type sperm, which rendered transgenic sperm hypersensitive to their ZP3 ligand. Thus, the cytoplasmic domain of cell surface GalTase appears to enable it to function as a signal-transducing receptor for extracellular oligosaccharide ligands.

Site-directed photo-cross-linking of rRNA transcription initiation complexes

Site-specific photo-cross-linking of the rRNA committed transcription complex was carried out by using 5-[N-(p-azidobenzoyl)-3-aminoallyl]-dUMP-derivatized promoter DNA. Putative TAFIs of 145, 99, 96, and 91 kDa, as well as TATA-binding protein (TBP), were found to specifically photo-cross-link to different positions along the promoter. These had been identified as potential subunits of the fundamental transcription initiation factor TIF-IB (also known as SL1, factor D, and TFID) from Acanthamoeba castellanii by purification to apparent homogeneity. No other polypeptides attributable to the rRNA architectural transcription factor UBF were identified, suggesting that this protein is not part of the committed complex. Scanning transmission electron microscopy of the complexes was used to estimate the mass of the complex and the contour length of the DNA in the complex. This showed that a single molecule of TIF-IB is in each committed complex and that the DNA is not looped around the protein, as would be expected if UBF were in the complex. A circular permutation analysis of DNA bending resulting from TIF-IB binding revealed a 45 +/- 3.1 degrees (n = 14) bend centered 23 bp upstream of the transcription initiation site. This degree of bending and the position of the bend relative to the site of TBP photo-cross-linking are consistent with earlier data showing that the TBP TATA box-binding domain is not utilized in the assembly of the rRNA committed complex (C. A. Radebaugh, J. L. Mathews, G. K. Geiss, F. Liu, J. Wong, E. Bateman, S. Camier, A. Sentenac, and M. R. Paule, Mol. Cell. Biol. 14:597-605, 1994).

[Cardial myxoma: analysis of cardiopulmonary bypass perfusion in 95 cases]

From 1980 to 1993, 95 patients with cardial myxoma (male 32 and female 63) were treated surgically. The myxoma located on left-atrium in 88 patients, right-atrium in 5, left-ventricle in 1, and pulmonary in 1. All the operations were carried out under cardiopulmonary bypass. After operations, 12 patients had dyspnea and 8 died of pulmonary infection and heart or respiratory failure. The hemoglobin level was 118.02 +/- 16.7 g/L, 72.33 +/- 8.82 g/L, and 105.75 +/- 5.91 g/L respectively for pre-dilution, post-dilution, and post-operation. The patients with cardial myxoma often complicated with anemia (56), hepatic enlargement (36), and history of heart failure (64), and embolism (12). Combined with clinical characteristics mentioned above, the preparation of prime solution and the management of perfusion were discussed.

[The effects of glucocorticoid on rabbit polymorphonuclears during inflammation]

The CD18 expression on rabbit polymorphonuclears (PMNs) and adhesion rate of rabbit PMNs to ICAM-1 coated magnetic beads were determined, and the correlationship was analysed between CD18 expression and adhesion rate. The results showed that glucocorticoid inhibited the rise of CD18 expression on rabbit PMNs caused by tumor necrosis factor (TNF) and that the inhibitory effect reversed when glucocorticoid receptor (GR) was blocked by RU 38486. There was a positive correlationship (r = 0.966) after PMNs were cultured with a range concentration of dexamethasone (Dex). The data indicate that GC inhibits the rise of CD18 expression on rabbit PMNs caused by TNF which is mediated by GR, and plays an important role in inhibition of PMNs adhesion.

[Effects of glucocorticoid on PMN adhesion induced by TNF]

TNF was used as a stimulating factor to study the effects of glucocorticoid (GC) on polymorphonuclear leucocyte (PMN) adhesion. The results showed that tumor necrosis factor (TNF) could increase the PMN adhesion markedly, and Dex could not inhibit the PMN adhesion induced by TNF, but it had a certain effect of prevention. PMN adhesion was increased prominently when Dex and RU 38486 were given after TNF pretreatment.

[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.