Distribution of the HLA-DQA1 and polymarker alleles in the Basque population of Spain

HLA-DQA1 and polymarker (LDLR, GYPA, HBGG, D7S8, and GC) genotypic and allelic frequencies are determined for a population sample of 102 unrelated Basque individuals using PCR-based methodology. All six loci met Hardy-Weinberg expectations in at least two of the three analyses performed (HLA-DQA1 failed to meet Hardy-Weinberg requirements in the heterozygote deficiency test). Three linkage analysis programs (GDA, GENEPOP and LINKDOS) detected possible linkage disequilibrium between LDLR and HBGG and results from one (GDA) indicated a possible non-random association between HBGG and HLA-DQA1 as well. Allelic data for the six loci are compared to that previously established for other populations (18 for polymarker alone, 16 for polymarker plus HLA-DQA1) to determine homogeneity between the Basque sample and these groups. According to the results of G-tests based on these loci, the Tadjik, a nomadic Caucasian group from western Asia, and the Basque residents are the only sample populations surveyed that are homogenous with the Basque sample. Phylogenetic analysis places the Basque sample correctly within the Caucasian cluster.

The putative tumor suppressors EXT1 and EXT2 form a stable complex that accumulates in the Golgi apparatus and catalyzes the synthesis of heparan sulfate

Hereditary multiple exostoses, a dominantly inherited genetic disorder characterized by multiple cartilaginous tumors, is caused by mutations in members of the EXT gene family, EXT1 or EXT2. The proteins encoded by these genes, EXT1 and EXT2, are endoplasmic reticulum-localized type II transmembrane glycoproteins that possess or are tightly associated with glycosyltransferase activities involved in the polymerization of heparan sulfate. Here, by testing a cell line with a specific defect in EXT1 in in vivo and in vitro assays, we show that EXT2 does not harbor significant glycosyltransferase activity in the absence of EXT1. Instead, it appears that EXT1 and EXT2 form a hetero-oligomeric complex in vivo that leads to the accumulation of both proteins in the Golgi apparatus. Remarkably, the Golgi-localized EXT1/EXT2 complex possesses substantially higher glycosyltransferase activity than EXT1 or EXT2 alone, which suggests that the complex represents the biologically relevant form of the enzyme(s). These findings provide a rationale to explain how inherited mutations in either of the two EXT genes can cause loss of activity, resulting in hereditary multiple exostoses.

T-cell co-stimulation through B7RP-1 and ICOS

T-cell activation requires co-stimulation through receptors such as CD28 and antigen-specific signalling through the T-cell antigen receptor. Here we describe a new murine costimulatory receptor-ligand pair. The receptor, which is related to CD28 and is the homologue of the human protein ICOS, is expressed on activated T cells and resting memory T cells. The ligand, which has homology to B7 molecules and is called B7-related protein-1 (B7RP-1), is expressed on B cells and macrophages. ICOS and B7RP-I do not interact with proteins in the CD28-B7 pathway, and B7RP-1 co-stimulates T cells in vitro independently of CD28. Transgenic mice expressing a B7RP-1-Fc fusion protein show lymphoid hyperplasia in the spleen, lymph nodes and Peyer's patches. Presensitized mice treated with B7RP-1-Fc during antigen challenge show enhanced hypersensitivity. Therefore, B7RP-1 exhibits co-stimulatory activities in vitro and in vivo. ICOS and B7RP-1 define a new and distinct receptor-ligand pair that is structurally related to CD28-B7 and is involved in the adaptive immune response.

New perspectives on the molecular basis of hereditary bone tumours

Bone development is a highly regulated process sensitive to a wide variety of hormones, inflammatory mediators and growth factors. One of the most common hereditary skeletal dysplasias, hereditary multiple exostoses (HME), is an autosomal dominant disorder characterized by skeletal malformations that manifest as bony, benign tumours near the end of long bones. HME is usually caused by defects in either one of two genes, EXT1 and EXT2, which encode enzymes that catalyse the biosynthesis of heparan sulphate, an important component of the extracellular matrix. Thus, HME-linked bone tumours, like many other skeletal dysplasias, probably result from disruptions in cell surface architecture. However, despite the recent success in unravelling functions for several members of the EXT gene family, significant challenges remain before this knowledge can be used to develop new approaches for the diagnosis and treatment of disease.

Calcium cell signalling and cataract: role of the endoplasmic reticulum

The lens possesses an impressive array of G-protein receptors that are coupled to the release of intracellular calcium. They include members of the muscarinic, adrenergic and purinergic families and activation of the former has been implicated in cataract for some time. There are several possible mechanisms whereby activation of such receptors could give rise to cataract. A prolonged increase in intracellular calcium would be expected to activate proteases such as calpain and so could induce unscheduled and irreversible breakdown of important structural proteins. It has recently been shown that activation of G-protein receptors also modulates lens cell growth, and any interference with the highly controlled pattern of cell growth and development within the lens is also likely to have catastrophic consequences. If the calcium store is totally inactivated in lens cells, for example by exposure to thapsigargin, then growth ceases. This finding provides a means of inhibiting the lens cell growth which leads to posterior capsular opacification (PCO). For example, it has been shown that thapsigargin-coated intraocular lenses totally inhibit lens cell growth within cultured capsular bags, and if this technology could be transferred to the clinic then it could provide a simple and relatively inexpensive means of preventing PCO.

Ultraviolet irradiation (UVB) interrupts calcium cell signaling in lens epithelial cells

A preliminary study was undertaken to establish whether low-dose UV irradiation (UVB) affects calcium cell signaling in rabbit lens epithelia. In a suspension of lens epithelial cells (line NN1003A), changes in intracellular Ca2+ were measured by Fura-2 fluorescence in response to exogenously added ATP. The cellular response to ATP, referred to as the calcium signal, is characterized by a brief increase and subsequent decrease in cytosolic Ca2+ levels. Ultraviolet B irradiation (1.8-9 mJ/cm2) was found to reduce the magnitude of the Ca2+ signal in a dose-dependent manner. A 5 min UVB exposure (9 mJ/cm2) completely altered the biphasic nature of the calcium signal, causing only an immediate and steady rise in cytosol Ca2+ levels. Lower fluences of UVB irradiation (2 min exposure times or 3.6 mJ/cm2) induced a 50% reduction in the calcium signal. When irradiated cells were returned to culture for 3 h after irradiation, calcium signals induced by ATP were normal. In view of the photooxidative nature of UVB irradiation, the oxidative state of cells was assessed by measuring glutathione (GSH) levels. Ultraviolet B irradiation caused a rapid 20% decline in GSH levels that returned to near-control values after a 3 h postirradiation incubation. The results of this study indicate that fluences lower than previously found to be cataractogenic can perturb calcium cell signaling in cultured lens epithelial cells.

Thapsigargin inhibits a potassium conductance and stimulates calcium influx in the intact rat lens

1. An increase in lens cell calcium has long been associated with cortical cataract. Recently, it has been shown that thapsigargin induces a rise in lens cell calcium by release from endoplasmic reticulum stores. The effects of this rise on the optical and membrane characteristics of the lens were studied in the isolated rat lens. 2. The electrical characteristics of the isolated, perifused rat lens were measured using a two-internal microelectrode technique that permits measurement of plasma membrane conductance (Gm), membrane potential (Vm) and junctional conductance in the intact lens. 3. Thapsigargin (1 microM) induced a rapid overall depolarization of Vm that was accompanied by first a decrease and then an increase in Gm. 4. Replacing external Na+ with tetraethylammonium (TEA) abolished the decrease in Gm. However, a transient increase phase was still observed. 5. The changes in conductance were further characterized by measuring 22Na+ and 45Ca2+ influxes into the isolated lens. Thapsigargin (1 microM) induced a transient increase in 45Ca2+, but did not affect Na+ influx. 6. The Ca2+ channel blocker La3+ (10 microM) totally inhibited the thapsigargin-induced Ca2+ influx. It also blocked the increase in Gm observed in control and in Na+-free-TEA medium. In the absence of external calcium, thapsigargin induced a small depolarization in Vm. 7. These data indicate that thapsigargin induces both a decrease in K+ conductance and an increase in Ca2+ conductance. These probably result from release of stored Ca2+ and subsequent activation of store-operated Ca2+ channels (capacitative Ca2+ entry). 8. Thapsigargin application over the time course of these experiments (24 h) had no effect on junctional conductance or on the transparency of the lens.

Salmonella pullorum in the common pheasant (Phasianus colchicus)

In 1996, pullorum disease due to Salmonella enterica serovar Gallinarum biovar pullorum (Salmonella pullorum) was diagnosed in pheasants on a gamebird rearing enterprise in south-west Scotland. The gross pathology and bacteriological findings are described, as are the results of screening for S pullorum on the site in 1997. The causal organism was readily isolated from the lung, liver, yolk sac and heart blood on direct culture, but less readily from the digestive tract or by the use of selective media. The bacteria recovered from the pheasants were identified as S pullorum phage type 7, a phage type previously associated with pheasants rather than domestic fowl, and the organisms were most probably introduced to the site by the movement of carrier pheasants.

Molecular mechanisms of poliovirus persistence: key role of capsid determinants during the establishment phase

As viral persistence is of major medical importance, well-characterized, simple models are needed to improve our understanding of persistent infections. We have chosen to study the molecular mechanisms of viral persistence with the poliovirus (PV), because this picornavirus is one of the best characterized animal viruses, it infects the central nervous system which is a target organ for viral persistence, and it belongs to the Picornaviridae family of viruses, which includes several naturally persisting viruses. We have developed models of PV persistence in neuronal and epidermoid cells, and the present review will focus on the latter one because both lytic and persistent PV strains can be used to study the PV-HEp-2 cell interactions. The viral determinants of persistence have been investigated with this model, and PV determinants have proven to be of crucial importance for the establishment of persistence in HEp-2 cells. Precise determinants of PV persistence have been identified for PV serotypes 1 and 3, in capsid proteins VP1 and VP2. These determinants modify the early steps of the PV cycle, and in particular, the conformational modifications of the capsid following virus adsorption onto its receptor. These results permit us to propose several hypotheses concerning PV persistence and the early steps of the PV cycle.

Serotonergic basis of antipsychotic drug effects in schizophrenia

Recent attention has been focused on the involvement of serotonin (5-HT) in the pathophysiology of schizophrenia and its role in mediating antipsychotic drug effects. There are two reasons for the new emphasis: the tremendous success of the so-called "atypical" antipsychotic drugs (a common feature of which is their high affinity for specific 5-HT receptor subtypes); and the elucidation of a complex family of 5-HT receptors whose function and pharmacology is only beginning to be understood. This paper will review the evidence that pertains to the role of 5-HT in mediating antipsychotic drug effects. The interaction of dopamine and 5-HT systems will be reviewed, and the mechanisms of action of atypical antipsychotic drugs will be evaluated in this context. The impact of serotonin on neurodevelopment, and the involvement of serotonin in the psychotomimetic and psychotogenic properties of hallucinogens, will be discussed. Together, these facts will be placed into the context of changes in serotonergic function in schizophrenia.

Five new species of Lachenalia (Hyacinthaceae) from arid areas of Namibia and South Africa

Five new species of  Lachenalia are described:  L. nutans G.D.Duncan from southwestern Namibia,  L. attenuata W.F.Barker ex G.D Duncan from the Roggeveld Plateau. Little Karoo and southern Cape; L doleritica G.D.Duncan from the Bokkeveld Plateau;  L lactosa G.D.Duncan from the Lowland Fvnbos of the Hermanus District, and  L leipoldtii G D Duncan from the Olifants River Valley and Little Karoo

An approach to understanding the mechanisms of poliovirus persistence in infected cells of neural or non-neural origin

BACKGROUND

Poliovirus (PV) is the etiologic agent of paralytic poliomyelitis, which is sometimes followed, after decades of clinical stability, by new symptoms, including progressive muscular atrophy, collectively known as the post-polio syndrome. This raises the question of possible PV persistence in post polio patients.

OBJECTIVE

To test the capacity of PV to establish persistent infections in human cells, three models were developed.

STUDY DESIGN

This review focuses on the viral and cellular parameters involved in persistent PV infection.

RESULTS

Many PV strains, which are generally lytic in primate cell lines, are able to establish persistent infections in human neuroblastoma cells. During persistent infection, PV mutants (PVpi) are consistently selected, and several of their capsid substitutions occur at positions known to be involved in PV-PV receptor interactions. PVpi have a particular property: they can establish persistent infections in non-neural HEp-2 cells. PV can also persistently infect primary cultures of human fetal brain cells and the majority of cells which survive infection belong to the neuronal lineage.

CONCLUSIONS

The results obtained with the three models of persistent PV infection in human cells suggest that several mechanisms are used by PV to establish and maintain persistent infections in neural and non-neural cells. The interactions of the virus with its receptor seem to be a key-step in all cases. In the future, the elucidation of the etiology of the post-polio syndrome will require the characterization of PV sequences having persisted for decades in post-polio patients.

One amino acid change on the capsid surface of poliovirus sabin 1 allows the establishment of persistent infections in HEp-2c cell cultures

Poliovirus mutants (PVpi) selected during the persistent infection of human neuroblastoma cells can establish secondary persistent infections in nonneural HEp-2c cells (I. Pelletier, T. Couderc, S. Borzakian, E. Wyckoff, R. Crainic, E. Ehrenfeld, and F. Colbère-Garapin, 1991, Virology, 180, 729-737). Previous results from our laboratory have also shown that, in the genome of PVpi S11 derived from the Sabin 1 strain, the genomic region involved in this phenotype contains 11 missense mutations which map exclusively to the genes encoding the capsid proteins VP1 and VP2. We report here the identification of precise viral determinants able to confer the capacity to establish persistent infections in HEp-2c cell cultures to the lytic Sabin 1 strain. We used a strategy based on the observation that PVpi, after a few months of persistent infection in HEp-2c cells, tend to regain a more lytic phenotype in uninfected HEp-2c cell cultures. We constructed mutant viruses carrying only a few mutations potentially involved in the phenotype of persistence. Two mutations were identified, one corresponding to the substitution His>Tyr of amino acid 142 of VP2 and another corresponding to the substitution Val>Ile of amino acid 160 of VP1. Mutants carrying one or the other of the two determinants established persistent infections in HEp-2c cell cultures in about 20% of the infections. Higher frequencies were obtained with the mutant carrying both determinants (30%), and with PVpi S11 (63%), indicating that the effects of several determinants can be cumulative. The two determinants are localized on the capsid surface in a region known to be involved in the interactions between poliovirus and its cell receptor and in fact, we demonstrate here that in the case of the two persistent mutants, these interactions are modified.

Molecular aspects of poliovirus biology with a special focus on the interactions with nerve cells

Poliovirus (PV), the pathogenic agent of paralytic poliomyelitis, is the prototype of the picornavirus family. Although paralytic poliomyelitis has been nearly totally eradicated in most industrialized countries, PV continues to be an important public health problem in many developing countries. Moreover, in industrialized countries, two current concerns are the occurrence, albeit at a very low frequency, of vaccine-associated paralytic poliomyelitis, due to the genetic instability of the attenuated oral PV strains in vaccines, and the emergence of a neuro-muscular pathology in many survivors of the acute disease, called the post-polio syndrome. PV has been targeted by the World Health Organization for world-wide eradication in the coming decade and continues to be the subject of intensive research. The advances made in the molecular biology of PV, taken together with the development of new animal and cell models, have permitted a new look at a key step in the pathogenesis of poliomyelitis, i.e. the interactions between PV and nerve cells. These aspects of PV biology are developed in this review according to three themes: (i) the PV host range; (ii) the molecular determinants of PV neurovirulence and attenuation; and (iii) the persistence of PV in nerve cells, which has proven to be an interesting new domain in the field of PV research.

Two amino acid substitutions in the type 3 poliovirus capsid contribute to the establishment of persistent infection in HEp-2c cells by modifying virus-receptor interactions

After 2.5 months of persistent infection in human neuroblastoma cells by the type 3 poliovirus (PV3) wild-type Leon strain, a mutant (PVpi), L2-2, capable of establishing a persistent infection in nonneural HEp-2c cells was isolated. Sequence analysis of the viral capsid protein genes revealed the presence of seven missense mutations, three of which were also present in a second PVpi, suggesting that they could be important determinants of the persistent phenotype. When the three mutations were introduced into the lytic Leon strain separately, in pairs or all together, all but one of the viruses was capable of establishing a persistent infection. However, aside from the triple mutant, only one mutant virus, bearing a Leu at position VP213 in the capsid interior and an Asn at position VP1290 on the capsid surface, was capable of establishing persistent infections in more than 30% of the cultures. When present together, these two determinants affect the early steps of the virus cycle including cell binding and the receptor-mediated conformational changes believed to be necessary for viral penetration and uncoating. In fact, this persistent double mutant appears to undergo a novel capsid transition when in contact with the human PV receptor, altering from the native virion which sediments at 160S to a form which sediments at about 147S. We propose that this modification could be the mechanism by which PV3 is able to establish persistent infections in HEp-2c cell cultures.

Transferrin in after-cataract and as a survival factor for lens epithelium

The Fe-transport protein, transferrin (Tf), is synthesized and secreted by whole lenses and cultured lens epithelial cells. Because of Tf's central role in cell growth and proliferation, its participation in lens cell proliferation following cataract extraction was explored using a rabbit model of after-cataract. Varying amounts of the central anterior lens capsule were removed (0, 35, or 80%) following extraction of the lens. The Tf content of and secretion by after-cataract lens capsular sacs containing regenerated lens tissue was determined ex vivo at 0, 3, 5, 7 and 9 weeks post-surgery. In all cases Tf content of and secretion by the lens sacs was higher than that of their contralateral controls (whole lenses). Tf secretion was up to 5-fold higher and metabolic labeling studies indicated secretion of newly synthesized Tf. The sacs contained up to 10 times the concentration of Tf as the control lenses. Human lens after-cataract capsular bags also secreted Tf. The function of Tf as a survival factor was tested on cultured lens epithelial cells. Cells cultured in serum-free medium had a survival rate of only 20-34% if the medium was changed each day. If the medium was never changed during this period, the survival rate was 43-52%, suggesting secretion of essential growth factors by these cells. Addition of 200 microg ml-1 Tf to the medium during each daily change increased survival to levels attained when the medium was not changed. Addition of Tf antibodies to the culture medium during each daily change decreased cell survival to 14%. Apparently Tf acts as a survival factor for lens epithelia and its synthesis is up-regulated in after-cataract lens sacs. These factors suggest that Tf may play an important role in the pathogenesis of lens epithelial cell proliferation and after-cataract formation following cataract surgery.

Watchful waiting or watchful progression?: Prostate specific antigen doubling times and clinical behavior in patients with early untreated prostate carcinoma

BACKGROUND

Prostate specific antigen doubling time (PSAdt) is a dynamic model of prostate tumor biology. It predicts aggressive disease and subsequent clinical recurrence after radical treatment. However, as yet there is only limited evidence for its validity in the watchful waiting population.

METHODS

One hundred and thirteen previously untreated patients with adenocarcinoma of the prostate who were referred to the British Columbia Cancer Agency for a management opinion subsequently were placed into a prospective watchful waiting program. The reasons for watchful waiting, previous medical history, serial PSA, and histopathologic data were recorded.

RESULTS

The median age of patients was 75 years (range, 49-85 years). The median follow-up from the time of the first appointment was 14 months (range, 0-58 months). The reasons for watchful waiting were correlated highly with T classification (P = 0.003) and past medical history (P = 0.002). Approximately 40% of T1 patients and 51% of T2 patients had clinical progression by 2 years, increasing to 60% at 3 years. On multivariate analysis PSAdt strongly correlated with clinical progression (P < 0.0001), stage progression (P = 0.01), and time to treatment (P = 0.0001); tumor grade and initial stage were not found to be predictive for any of the endpoints studied. Initial PSA only was significant in predicting for time to treatment (P = 0.03). Approximately 50% of patients with a PSAdt of <18 months progressed within 6 months. At last follow-up, no deaths from prostate carcinoma had been recorded. Overall survival at 2 and 5 years was 92% and 68%, respectively.

CONCLUSIONS

Using digital rectal examination, the findings of this study demonstrated high rates of clinical tumor progression within the watchful waiting population. PSAdt rather than standard histopathologic criteria was found to be the most powerful indicator of disease activity.

Acetylcholine-induced membrane potential oscillations in the intact lens

PURPOSE

Factors that interfere with the acetylcholine signaling system have long been implicated in cataract. The authors sought to investigate the nature of the electrical response of the intact rabbit lens to acetylcholine.

METHODS

Membrane potential (Vm) and electrical conductance (Gm) were monitored in the isolated, perifused lens by a technique utilizing two internal microelectrodes.

RESULTS

Acetylcholine (100 nM to 1 mM) induced a decrease in membrane conductance and a depolarization of membrane potential in the intact lens. The responses were reversed by application of the muscarinic antagonist, atropine (1 microM to 100 microM). In the presence of 1 microM thapsigargin and 30 microM cyclopiazonic acid, acetylcholine still induced an electrical response. Long exposures to acetylcholine induced sustained oscillations of Vm in 10 of 29 lenses (34%). Oscillations were blocked by atropine and the L-type Ca2+ channel blocker nifedipine (10 microM) but were potentiated by thapsigargin.

CONCLUSIONS

The rabbit lens expressed muscarinic receptors that when activated modulate ionic conductances and cause membrane potential oscillations throughout the tissue. Ca2+ influx rather than primary release from intracellular stores appeared to play a major role in the oscillatory response to acetylcholine.

Phacoemulsification versus extracapsular cataract extraction: a comparative study of cell survival and growth on the human capsular bag in vitro

AIMS/BACKGROUND

Phacoemulsification is rapidly replacing conventional extracapsular cataract extraction (ECCE) as the method of choice for cataract surgery in the Western world. However, posterior capsule opacification (PCO) still remains the major postoperative complication, affecting 20-50% of patients, and results from persistent cell growth of epithelial cells remaining after surgery. This study aimed to compare cell survival and growth on capsular bags following ECCE and phacoemulsification surgery using an established human capsular bag culture system.

METHODS

Sham ECCE and phacoemulsification cataract operations were performed on pairs of human donor eyes. Capsular bags were dissected free, pinned flat on a petri dish, and incubated with Eagle's minimum essential medium (EMEM) alone or EMEM supplemented with 10% fetal calf serum (FCS). Ongoing observations were made using phase contrast microscopy.

RESULTS

Cell growth was observed across the posterior capsule of all preparations studied. It was found that there was no significant difference in the rate of cell growth on the posterior capsule with the two extraction methods, such that 50% confluency was achieved in 7.0 (SD 1.8) (n = 7) days for ECCE and 7.43 (2.1) (n = 7) days for phacoemulsification surgery. The physical changes to the capsule as a result of cell growth, such as wrinkling and capsular tensioning, were also seen in both groups.

CONCLUSIONS

Cell survival and growth is dependent on the donor, rather than the surgical technique performed. There is no significant difference between phacoemulsification and ECCE surgery on the rate and nature of cell growth on the posterior capsule in vitro.

Thapsigargin-coated intraocular lenses inhibit human lens cell growth

Cataract is responsible for rendering several million people blind throughout the world and is also by far the most common cause of low visual acuity. Although cataract surgery is common, routine and effective, posterior capsule opacification (PCO) occurs in 30-50% of patients following modern cataract surgery. This condition arises from stimulated cell growth within the capsular bag after surgery. The resulting decline in visual acuity requires expensive laser treatment, and PCO therefore prevents modern cataract surgery from being carried out routinely in underdeveloped countries. The present study, using a human lens capsular bag culture system, has confirmed that cells from a wide age range of donors proliferate in the absence of added serum protein and explains why PCO is such a common problem even in aged patients. This study also provides one possible solution for PCO by using polymethylmethacrylate (PMMA) implanted intraocular lenses as a drug delivery system. PMMA lenses coated with thapsigargin, a hydrophobic inhibitor of endoplasmic reticulum (ER) (Ca2+)-ATPase, greatly reduced cell growth in the capsular bag at relatively low coating concentrations (200 nM) but, more significantly, induced total cell death of the residual anterior epithelial cells at higher concentrations (>2 microM).

Human lens epithelial cell proliferation in a protein-free medium

PURPOSE

The ocular humors are relatively low in protein, yet cell growth in the human capsular bag still occurs after extracapsular cataract extraction (ECCE) surgery. This resilient growth gives rise to posterior capsule opacification (PCO) in a significant proportion (30%) of patients. This study compared the ability of human lens cells to proliferate in serum-supplemented and protein-free medium.

METHODS

Sham cataract operations were performed on human donor eyes. The capsular bag was dissected free, pinned flat on a petri dish, and incubated in Eagle's minimal essential medium (EMEM) alone or in EMEM supplemented with 10% fetal calf serum. Observations were made by phase-contrast microscopy. At the endpoint, capsules were studied by fluorescence or electron microscopy. Mitotic activity was identified using Bromo-2-deoxyuridine labeling and detection techniques. When required, an intraocular lens was implanted when surgery was performed.

RESULTS

It was found that human lens cells from a wide age spectrum of donors proliferate and migrate on the lens capsule in the absence of added protein. The rate of growth was age-dependent, such that the posterior capsule was completely confluent after 8.0 +/- 0 days (n = 3) and 24.4 +/- 5.3 days (n = 3) for donor lenses aged < 40 years and > 60 years, respectively. The outgrowth of epithelial cells gave rise to capsular contraction, wrinkling, and increased light scatter. Growth on the anterior surface of the intraocular lens was less prolific than on the posterior capsule.

CONCLUSION

The protein-free model replicates many features of clinically-observed PCO. The resilient cell growth on the natural collagen capsule explains the high prevalence of PCO, especially in younger patients, and suggests that inflammation and external growth factors are not necessary for PCO. Furthermore, the protein-free capsular bag system can be used to explore fundamental questions concerning the autocrine control of lens epithelial cell survival and growth.