Pupil size in Jewish theological seminary students

PURPOSE

To investigate the authors' clinical impression that pupil size among myopic Jewish theological seminary students is different from pupil size of similar secular subjects.

METHODS

This cross-sectional study was conducted on 28 male Jewish theological seminary students and 28 secular students or workers who were matched for age and refraction. All participants were consecutively enrolled. Scotopic and photopic pupil size was measured by means of a Colvard pupillometer. Comparisons of various parameters between the groups were performed using the two-sample t-test, Fisher exact test, a paired-sample t-test, a two-way analysis of variance, and Pearson correlation coefficients as appropriate.

RESULTS

The two groups were statistically matched for age, refraction, and visual acuity. The seminary students were undercorrected by an average of 2.35 diopters (D), while the secular subjects were undercorrected by only 0.65 D (p<0.01). The average pupil size was larger in the religious group under both scotopic and photopic luminance. This difference was maintained when the two groups were compared according to iris color under both conditions, reaching a level of statistical significance (p<0.0001). There was a significant difference in photopic pupil size between dark and light irises (p=0.049), but this difference was not maintained under scotopic conditions.

CONCLUSIONS

The average pupil size of young ultraorthodox seminary students was significantly larger than that of matched secular subjects. Whether this is the result of intensive close-up work or of apparently characteristic undercorrection of the myopia is undetermined.

[Phacogenic uveitis with luxation of of Soemmering's ring formation in the vitreous body 63 years after cataract surgery]

BACKGROUND

After extracapsular cataract extraction, the remaining epithelial cells near to the equator may lead to the formation of a Soemmerings ring. Only 4 cases of dislocation of the ring in the vitreous are reported in the literature. A spontaneous dislocation associated with a phacolytic uveitis has not been described before.

HISTORY AND SIGNS

In 1999 a 68-year-old man attended our clinic with a vision loss from 0.3 to hand movements in his left eye. For some years his right eye had been blind after unsuccessful retinal detachment surgery. In his left eye conjunctival inflammation, anterior chamber flare and complete occlusion of the pupil were found. Intraocular pressure was normal under hypotensive medication. Ophthalmoscopy was not possible and ultrasound revealed a ring-like dense structure in the vitreous cavity.

THERAPY AND OUTCOME

Pars plana vitrectomy showed a Soemmerings ring, which was successfully removed by pars plana fragmentation. Forty-eight months postoperatively the patient had a visual acuity of 0.2 in a healthy and normotensive eye.

CONCLUSIONS

Even years after cataract extraction a spontaneous dislocation of Soemmerings ring is possible.

An open-label trial of the PPAR-gamma ligand rosiglitazone for active ulcerative colitis

OBJECTIVES

Previous research has demonstrated that ligands for the gamma subtype of peroxisome proliferator-activated receptors (PPARs) reduce inflammation in two different murine models of colitis. This study was designed to examine the potential efficacy of rosiglitazone, a ligand for the gamma subtype of PPARs, as a therapy for active ulcerative colitis.

METHODS

Fifteen patients with mild to moderately active ulcerative colitis despite therapy with 5-aminosalicylic acid compounds were enrolled in an open-label study of rosiglitazone (4 mg b.i.d. p.o.) for 12 wk. Thirteen of 15 patients were receiving concomitant therapy with corticosteroids and/or immunomodulator medications. Disease activity was measured with the Disease Activity Index.

RESULTS

After 12 wk of therapy, four patients (27%) had achieved clinical remission, of whom three (20%) also had an endoscopic remission. Four additional patients (27%) had a clinical response without achieving remission. Two patients were hospitalized with worsened disease activity, and one patient was withdrawn for nephrotic syndrome.

CONCLUSIONS

These data suggest that ligands for the gamma subtype of PPARs may represent a novel therapy for ulcerative colitis. A double blind, placebo-controlled, randomized trial is warranted.

Histone deacetylase is a direct target of valproic acid, a potent anticonvulsant, mood stabilizer, and teratogen

Valproic acid is widely used to treat epilepsy and bipolar disorder and is also a potent teratogen, but its mechanisms of action in any of these settings are unknown. We report that valproic acid activates Wntdependent gene expression, similar to lithium, the mainstay of therapy for bipolar disorder. Valproic acid, however, acts through a distinct pathway that involves direct inhibition of histone deacetylase (IC(50) for HDAC1 = 0.4 mm). At therapeutic levels, valproic acid mimics the histone deacetylase inhibitor trichostatin A, causing hyperacetylation of histones in cultured cells. Valproic acid, like trichostatin A, also activates transcription from diverse exogenous and endogenous promoters. Furthermore, valproic acid and trichostatin A have remarkably similar teratogenic effects in vertebrate embryos, while non-teratogenic analogues of valproic acid do not inhibit histone deacetylase and do not activate transcription. Based on these observations, we propose that inhibition of histone deacetylase provides a mechanism for valproic acid-induced birth defects and could also explain the efficacy of valproic acid in the treatment of bipolar disorder.

The SMRT and N-CoR corepressors are activating cofactors for histone deacetylase 3

Repression of gene transcription is linked to regulation of chromatin structure through deacetylation of core histone amino-terminal tails. This action is mediated by histone deacetylases (HDACs) that function within active multiprotein complexes directed to the promoters of repressed genes. In vivo, HDAC3 forms a stable complex with the SMRT corepressor. The SMRT-HDAC3 complex exhibits histone deacetylase activity, whereas recombinant HDAC3 is an inactive enzyme. Here we report that SMRT functions as an activating cofactor of HDAC3. In contrast, SMRT does not activate the class II HDAC4, with which it also interacts. Activation of HDAC3 is mediated by a deacetylase activating domain (DAD) that includes one of two SANT motifs present in SMRT. A cognate DAD is present in the related corepressor N-CoR, which can also activate HDAC3. Mutations in the DAD that abolish HDAC3 interaction also eliminate reconstitution of HDAC activity. Using purified components, the SMRT DAD is shown to be necessary and sufficient for activation of HDAC3. Moreover, the DAD is required both for HDAC3 to function enzymatically and for the major repression function of SMRT. Thus, SMRT and N-CoR do not serve merely as platforms for HDAC recruitment but function as an integral component of an active cellular HDAC3 enzyme.

Effect of sub-Tenon's and peribulbar anesthesia on intraocular pressure and ocular pulse amplitude

PURPOSE

To compare the effect of peribulbar and sub-Tenon's anesthesia on intraocular pressure (IOP) and ocular pulse amplitude (OPA) in the injected eye and the fellow noninjected (control) eye.

SETTING

Tel Aviv Medical Center, Tel Aviv, Israel.

METHODS

This prospective study measured IOP and OPA at baseline and 1 and 10 minutes after administration of lidocaine anesthesia in 40 consecutive adult patients having elective cataract surgery.

RESULTS

The IOP remained stable throughout the study with both modes of anesthesia. One minute after injection of the anesthetic agent, the OPA was significantly decreased in the injected eyes in both the sub-Tenon's (24%; P < .05) and peribulbar (25%; P < .05) groups. The decrease in the OPA in the sub-Tenon's group (14%; P < .05) was detectable after 10 minutes in the control eyes. In the peribulbar anesthesia group, the OPA in the control eyes increased significantly (9%; P < .05) 1 minute after injection of the anesthetic agent, returning to preinjection levels 10 minutes after the injection.

CONCLUSIONS

The OPA in the eyes in which lidocaine was injected decreased significantly in both the sub-Tenon's and peribulbar groups. These findings have implications for the management of patients whose ocular circulation may be compromised.

Dimerization of resistin and resistin-like molecules is determined by a single cysteine

Resistin is a peptide hormone secreted by adipocytes. Cysteine residues comprise 11 of 94 (12%) amino acids in resistin. The arrangement of these cysteines is unique to resistin and its recently discovered family of tissue-specific secreted proteins, which have been independently termed resistin-like molecules (RELMs) and the FIZZ (found in inflammatory zone) family. Here we show that resistin is a disulfide-linked homodimer that can be converted to a monomer by reducing conditions. The intestine-specific RELM beta has similar characteristics. Remarkably, however, the adipose-enriched RELM alpha is a monomer under non-reducing conditions. We note that RELM alpha lacks a cysteine residue, closest to the cleaved N terminus, that is present in resistin and RELM beta in multiple species. Conversion of this cysteine to alanine abolishes dimerization of resistin. Thus, a single disulfide bond is necessary to connect two resistin subunits in a homodimer. The additional 10 cysteines most likely participate in intramolecular disulfide bonds that define the conserved structure of the family members. The monomeric nature of RELM alpha suggests structural and potentially functional divergence between resistin and this close family member.

Inhibition of cellular proliferation through IkappaB kinase-independent and peroxisome proliferator-activated receptor gamma-dependent repression of cyclin D1

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-regulated nuclear receptor superfamily member. Liganded PPARgamma exerts diverse biological effects, promoting adipocyte differentiation, inhibiting tumor cellular proliferation, and regulating monocyte/macrophage and anti-inflammatory activities in vitro. In vivo studies with PPARgamma ligands showed enhancement of tumor growth, raising the possibility that reduced immune function and tumor surveillance may outweigh the direct inhibitory effects of PPARgamma ligands on cellular proliferation. Recent findings that PPARgamma ligands convey PPARgamma-independent activities through IkappaB kinase (IKK) raises important questions about the specific mechanisms through which PPARgamma ligands inhibit cellular proliferation. We investigated the mechanisms regulating the antiproliferative effect of PPARgamma. Herein PPARgamma, liganded by either natural (15d-PGJ(2) and PGD(2)) or synthetic ligands (BRL49653 and troglitazone), selectively inhibited expression of the cyclin D1 gene. The inhibition of S-phase entry and activity of the cyclin D1-dependent serine-threonine kinase (Cdk) by 15d-PGJ(2) was not observed in PPARgamma-deficient cells. Cyclin D1 overexpression reversed the S-phase inhibition by 15d-PGJ(2). Cyclin D1 repression was independent of IKK, as prostaglandins (PGs) which bound PPARgamma but lacked the IKK interactive cyclopentone ring carbonyl group repressed cyclin D1. Cyclin D1 repression by PPARgamma involved competition for limiting abundance of p300, directed through a c-Fos binding site of the cyclin D1 promoter. 15d-PGJ(2) enhanced recruitment of p300 to PPARgamma but reduced binding to c-Fos. The identification of distinct pathways through which eicosanoids regulate anti-inflammatory and antiproliferative effects may improve the utility of COX2 inhibitors.

Analysis of partial volume effects in diffusion-tensor MRI

The diffusion tensor is currently the accepted model of diffusion in biological tissues. The measured diffusion behavior may be more complex when two or more distinct tissues with different diffusion tensors occupy the same voxel. In this study, a partial volume model of MRI signal behavior for two diffusion-tensor compartments is presented. Simulations using this model demonstrate that the conventional single diffusion tensor model could lead to highly variable and inaccurate measurements of diffusion behavior. The differences between the single and two-tensor models depend on the orientations, fractions, and exchange between the two diffusion tensor compartments, as well as the diffusion-tensor encoding technique and diffusion-weighting that is used in the measurements. The current single compartment model's inaccuracies could cause diffusion-based characterization of cerebral ischemia and white matter connectivity to be incorrect. A diffusion-tensor MRI imaging experiment on a normal human brain revealed significant partial volume effects between oblique white matter regions when using very large voxels and large diffusion-weighting (b approximately 2.69 x 10(3) sec/mm(2)). However, the apparent partial volume effects in white matter decreased significantly when smaller voxel dimensions were used. For diffusion tensor studies obtained using typical diffusion-weighting values (b approximately 1 x 10(3) sec/mm(2)) partial volume effects are much more difficult to detect and resolve. More accurate measurements of multiple diffusion compartments may lead to improved confidence in diffusion measurements for clinical applications.

Retinal toxicity of gentamicin after subconjunctival injection performed adjacent to thinned sclera

OBJECTIVE

To investigate the potential toxicity to the retina of gentamicin injected near surgically thinned scleral areas in a rabbit model.

DESIGN

Experimental study.

METHODS

Scleral scraping to half thickness was performed in the superotemporal scleral area in both eyes of adult rabbits (n = 10). Gentamicin sulfate was injected subconjunctivally to the right eye and saline to the left eye, which always served as a control eye. Four weeks after the procedure, electroretinography (ERG) was performed to assess retinal function. Then, the eyes were enucleated and prepared for histologic evaluation of structural damage. In four eyes of two additional rabbits, vitreous gentamicin concentrations were measured using a fluorescence polarization assay.

MAIN OUTCOME MEASURES

Dark- and light-adapted ERG responses and histopathologic damage.

RESULTS

Dark- and light-adapted ERG responses in all rabbits were similar in the experimental and control eyes. Gentamicin levels were more than 10 microg/ml after subconjunctival injection of gentamicin with scraping and 0.29 microg/ml after subconjunctival injection of gentamicin with no scraping. Histopathologic examination revealed significant local damage to the photoreceptors adjacent to the area of scraping and subconjunctival injection. A significantly lesser degree of damage was seen if gentamicin was injected in pigmented rabbits or in albino rabbits, but only 4 weeks after scleral scraping.

CONCLUSIONS

Increased penetration of gentamicin through thinned sclera may lead to toxic levels of the drug in a localized area adjacent to the site of injection. These toxic effects are also influenced by the degree of pigmentation and acute inflammation.

Determinants of CoRNR-dependent repression complex assembly on nuclear hormone receptors

Ligand-dependent exchange of coactivators and corepressors is the fundamental regulator of nuclear hormone receptor (NHR) function. The interaction surfaces of coactivators and corepressors are similar but distinct enough to allow the ligand to function as a switch. Multiple NHRs share features that allow corepressor binding, and each of two distinct corepressors (N-CoR and SMRT) contains two similar CoRNR motifs that interact with NHRs. Here we report that the specificity of corepressor-NHR interaction is determined by the individual NHR interacting with specific CoRNR boxes within a preferred corepressor. First, receptors have distinct preferences for CoRNR1 versus CoRNR2. For example, the retinoic acid receptor binds CoRNR1, while RXR interacts almost exclusively with CoRNR2. Second, the NHR preference for N-CoR or SMRT is due to differences in CoRNR1 but not CoRNR2. Moreover, within a single corepressor, affinity for different NHRs is determined by distinct regions flanking CoRNR1. The highly specific determinants of NHR-corepressor interaction and preference suggest that repression is regulated by the permissibility of selected receptor-CoRNR-corepressor combinations. Interestingly, different NHR surfaces contribute to binding of CoRNR1 and CoRNR2, suggesting a model to explain corepressor binding to NHR heterodimers.

Transcriptional control of adipogenesis

The major transcriptional factors involved in the adipogenic process include proteins belonging to the CCAAT/enhancer binding protein family, peroxisome proliferator-activated receptor gamma, and adipocyte determination and differentiation dependent factor 1, also known as sterol regulatory element-binding protein 1. This process has been characterized with the aid of cell lines that represent various stages in the path of adipocyte commitment, ranging from pluripotent mesodermal fibroblasts to preadipocytes. Molecular analyses have led to a cascade model for adipogenesis based on timed expression of CCAAT/enhancer-binding proteins and peroxisome proliferator-activated receptor gamma. Gene targeting and transgenic-mouse technologies, which allow the manipulation of endogenous genes for these transcription factors, have also contributed to the understanding of adipogenesis. This review aims to integrate this information to gain an understanding of the transcriptional regulation of fat cell formation.

Characteristics and outcomes of paediatric rhegmatogenous retinal detachment treated by segmental scleral buckling plus an encircling element

PURPOSE

To evaluate the outcome of paediatric rhegmatogenous retinal detachment treated by segmental scleral buckling plus an encircling element.

METHODS

A retrospective review was carried out of 15 consecutive paediatric patients (16 eyes).

RESULTS

Thirteen of the 15 patients were male (87%), 2 (13%) were female. Their average age was 10.9 years (range 6-18 years; median 10 years). Retinal detachment was caused by trauma in 9 of 16 eyes (56%), high myopia in 5 of 16 eyes (31%) and had an unknown cause in 2 of 16 eyes (13%). Diagnosis was delayed by more than 1 month in 10 of 16 eyes (63%). The visual acuity was 6/60 or worse and the macula was detached on presentation in 13 of 16 eyes (81%). Two of 16 eyes (13%) had mild proliferative vitreoretinopathy. Final reattachment was achieved in all cases. Of 11 eyes with a follow-up of 6 months or more, there was improvement in visual acuity in 7 (63%), and a best-corrected visual acuity of 6/20 or better in 5 (46%).

CONCLUSION

Paediatric rhegmatogenous retinal detachment is characterised by a delay in diagnosis and a high degree of macular involvement on presentation. Anatomical reattachment with segmental scleral buckling plus an encircling element was successful in all eyes, and improvement of visual acuity was achieved in one-half of the eyes which had a follow-up of 6 months or more.

Laser in situ keratomileusis to correct hyperopic shift after radial keratotomy

PURPOSE

To assess the safety and efficacy of excimer laser in situ keratomileusis (LASIK) to correct hyperopic shift following radial keratotomy (RK).

SETTING

Ophthalmic Health Center, Tel Aviv, Israel.

METHODS

The study comprised 15 eyes of 12 patients who had uneventful RK and subsequently developed a hyperopic shift. Laser in situ keratomileusis was performed using the Chiron Automated Corneal Shaper and the Nidek EC-5000 excimer laser with 5.5 mm central and 7.5 mm peripheral ablation zones. The corneal flap was 160 microm in thickness and 8.5 mm in diameter. The refractive correction corresponded to the patients' refractive errors.

RESULTS

The mean time after RK was 10.46 years +/- 2.21 (SD) and the mean follow-up after LASIK, 7.3 months (range 1 to 42 months). The mean spherical equivalent refraction was corrected from +3.08 +/- 1.02 diopters (D) to -0.16 +/- 0.73 D after LASIK. At the last examination, 12 eyes (80%) had a refractive error within +/-1.00 D of emmetropia and an uncorrected visual acuity of 20/40 or better. No wound dehiscence, epithelial ingrowth, or other significant complication developed in any eye.

CONCLUSIONS

Early postoperative results of the correction by LASIK of a hyperopic shift after RK are encouraging, but long-term studies of a larger population group are required to evaluate the method's clinical value.

The hormone resistin links obesity to diabetes

Diabetes mellitus is a chronic disease that leads to complications including heart disease, stroke, kidney failure, blindness and nerve damage. Type 2 diabetes, characterized by target-tissue resistance to insulin, is epidemic in industrialized societies and is strongly associated with obesity; however, the mechanism by which increased adiposity causes insulin resistance is unclear. Here we show that adipocytes secrete a unique signalling molecule, which we have named resistin (for resistance to insulin). Circulating resistin levels are decreased by the anti-diabetic drug rosiglitazone, and increased in diet-induced and genetic forms of obesity. Administration of anti-resistin antibody improves blood sugar and insulin action in mice with diet-induced obesity. Moreover, treatment of normal mice with recombinant resistin impairs glucose tolerance and insulin action. Insulin-stimulated glucose uptake by adipocytes is enhanced by neutralization of resistin and is reduced by resistin treatment. Resistin is thus a hormone that potentially links obesity to diabetes.

A family of tissue-specific resistin-like molecules

We have identified a family of resistin-like molecules (RELMs) in rodents and humans. Resistin is a hormone produced by fat cells. RELMalpha is a secreted protein that has a restricted tissue distribution with highest levels in adipose tissue. Another family member, RELMbeta, is a secreted protein expressed only in the gastrointestinal tract, particularly the colon, in both mouse and human. RELMbeta gene expression is highest in proliferative epithelial cells and is markedly increased in tumors, suggesting a role in intestinal proliferation. Resistin and the RELMs share a cysteine composition and other signature features. Thus, the RELMs together with resistin comprise a class of tissue-specific signaling molecules.

Oligomerization of ETO is obligatory for corepressor interaction

Nearly 40% of cases of acute myelogenous leukemia (AML) of the M2 subtype are due to a chromosomal translocation that combines a sequence-specific DNA binding protein, AML1, with a potent transcriptional repressor, ETO. ETO interacts with nuclear receptor corepressors SMRT and N-CoR, which recruit histone deacetylase to the AML1-ETO oncoprotein. SMRT-N-CoR interaction requires each of two zinc fingers contained in C-terminal Nervy homology region 4 (NHR4) of ETO. However, here we show that polypeptides containing NHR4 are insufficient for interaction with SMRT. NHR2 is also required for SMRT interaction and repression by ETO, as well as for inhibition of hematopoietic differentiation by AML1-ETO. NHR2 mediates oligomerization of ETO as well as AML1-ETO. Fusion of NHR4 polypeptide to a heterologous dimerization domain allows strong interaction with SMRT in vitro. These data support a model in which NHR2 and NHR4 have complementary functions in repression by ETO. NHR2 functions as an oligomerization domain bringing together NHR4 polypeptides that together form the surface required for high-affinity interaction with corepressors. As nuclear receptors also interact with corepressors as dimers, oligomerization may be a common mechanism regulating corepressor interactions.

Progress in cardiovascular biology: PPAR for the course

Studies on mice lacking the peroxisome proliferator-activated receptor (PPAR) suggest that PPAR ligands reduce lipid accumulation in foamy macrophages, and may target other receptors. These findings warrant an in-depth investigation into the gene regulatory mechanisms of PPAR ligands, which are currently being developed as drugs to treat atherosclerosis and diabetes.

Cofactor dynamics and sufficiency in estrogen receptor-regulated transcription

Many cofactors bind the hormone-activated estrogen receptor (ER), yet the specific regulators of endogenous ER-mediated gene transcription are unknown. Using chromatin immunoprecipitation (ChIP), we find that ER and a number of coactivators rapidly associate with estrogen responsive promoters following estrogen treatment in a cyclic fashion that is not predicted by current models of hormone activation. Cycles of ER complex assembly are followed by transcription. In contrast, the anti-estrogen tamoxifen (TAM) recruits corepressors but not coactivators. Using a genetic approach, we show that recruitment of the p160 class of coactivators is sufficient for gene activation and for the growth stimulatory actions of estrogen in breast cancer supporting a model in which ER cofactors play unique roles in estrogen signaling.

The mechanism of action of thyroid hormones

Thyroid hormone is essential for normal development, differentiation, and metabolic balance. Thyroid hormone action is mediated by multiple thyroid hormone receptor isoforms derived from two distinct genes. The thyroid hormone receptors belong to a nuclear receptor superfamily that also includes receptors for other small lipophilic hormones. Thyroid hormone receptors function by binding to specific thyroid hormone-responsive sequences in promoters of target genes and by regulating transcription. Thyroid hormone receptors often form heterodimers with retinoid X receptors. Heterodimerization is regulated through distinct mechanisms that together determine the specificity and flexibility of the sequence recognition. Amino-terminal regions appear to modulate thyroid hormone receptor function in an isoform-dependent manner. Unliganded thyroid hormone receptor represses transcription through recruitment of a corepressor complex, which also includes Sin3A and histone deacetylase. Ligand binding alters the conformation of the thyroid hormone receptor in such a way as to release the corepressor complex and recruit a coactivator complex that includes multiple histone acetyltransferases, including a steroid receptor family coactivator, p300/CREB-binding protein-associated factor (PCAF), and CREB binding protein (CBP). The existence of histone-modifying activities in the transcriptional regulatory complexes indicates an important role of chromatin structure. Stoichiometric, structural, and sequence-specific rules for coregulator interaction are beginning to be understood, as are aspects of the tissue specificity of hormone action. Moreover, knockout studies suggest that the products of two thyroid hormone receptor genes mediate distinct functions in vivo. The increased understanding of the structure and function of thyroid hormone receptors and their interacting proteins has markedly clarified the molecular mechanisms of thyroid hormone action.

A core SMRT corepressor complex containing HDAC3 and TBL1, a WD40-repeat protein linked to deafness

The corepressor SMRT mediates repression by thyroid hormone receptor (TR) as well as other nuclear hormone receptors and transcription factors. Here we report the isolation of a novel SMRT-containing complex from HeLa cells. This complex contains transducin beta-like protein 1 (TBL1), whose gene is mutated in human sensorineural deafness. It also contains HDAC3, a histone deacetylase not previously thought to interact with SMRT. TBL1 displays structural and functional similarities to Tup1 and Groucho corepressors, sharing their ability to interact with histone H3. In vivo, TBL1 is bridged to HDAC3 through SMRT and can potentiate repression by TR. Intriguingly, loss-of-function TRbeta mutations cause deafness in mice and humans. These results define a new TR corepressor complex with a physical link to histone structure and a potential biological link to deafness.

Oligomerization of RAR and AML1 transcription factors as a novel mechanism of oncogenic activation

RAR and AML1 transcription factors are found in leukemias as fusion proteins with PML and ETO, respectively. Association of PML-RAR and AML1-ETO with the nuclear corepressor (N-CoR)/histone deacetylase (HDAC) complex is required to block hematopoietic differentiation. We show that PML-RAR and AML1-ETO exist in vivo within high molecular weight (HMW) nuclear complexes, reflecting their oligomeric state. Oligomerization requires PML or ETO coiled-coil regions and is responsible for abnormal recruitment of N-CoR, transcriptional repression, and impaired differentiation of primary hematopoietic precursors. Fusion of RAR to a heterologous oligomerization domain recapitulated the properties of PML-RAR, indicating that oligomerization per se is sufficient to achieve transforming potential. These results show that oligomerization of a transcription factor, imposing an altered interaction with transcriptional coregulators, represents a novel mechanism of oncogenic activation.

Post-transcriptional regulation of thyroid hormone receptor expression by cis-acting sequences and a naturally occurring antisense RNA

Thyroid hormone (T(3)) coordinates growth, differentiation, and metabolism by binding to nuclear thyroid hormone receptors (TRs). The TRalpha gene encodes T(3)-activated TRalpha1 (NR1A1a) as well as an antagonistic, non-T(3)-binding alternatively spliced product, TRalpha2 (NR1A1b). Thus, the TRalpha1/TRalpha2 ratio is a critical determinant of T(3) action. However, the mechanisms underlying this post-transcriptional regulation are unknown. We have identified a non-consensus, TRalpha2-specific 5' splice site and conserved intronic sequences as key determinants of TRalpha mRNA processing. In addition to these cis-acting elements, a novel regulatory feature is the orphan receptor RevErbAalpha (NR1D1) gene, which is transcribed from the opposite direction at the same locus and overlaps the TRalpha2 coding region. RevErbAalpha gene expression correlates with a high TRalpha1/TRalpha2 ratio in a number of tissues. Here we demonstrate that coexpression of RevErbAalpha and TRalpha regulates the TRalpha1/TRalpha2 ratio in intact cells. Thus, both cis- and trans-regulatory mechanisms contribute to cell-specific post-transcriptional regulation of TR gene expression and T(3) action.

The DRIP complex and SRC-1/p160 coactivators share similar nuclear receptor binding determinants but constitute functionally distinct complexes

Transcriptional activation requires both access to DNA assembled as chromatin and functional contact with components of the basal transcription machinery. Using the hormone-bound vitamin D(3) receptor (VDR) ligand binding domain (LBD) as an affinity matrix, we previously identified a novel multisubunit coactivator complex, DRIP (VDR-interacting proteins), required for transcriptional activation by nuclear receptors and several other transcription factors. In this report, we characterize the nuclear receptor binding features of DRIP205, a key subunit of the DRIP complex, that interacts directly with VDR and thyroid hormone receptor in response to ligand and anchors the other DRIP subunits to the nuclear receptor LBD. In common with other nuclear receptor coactivators, DRIP205 interaction occurs through one of two LXXLL motifs and requires the receptor's AF-2 subdomain. Although the second motif of DRIP205 is required only for VDR binding in vitro, both motifs are used in the context of an retinoid X receptor-VDR heterodimer on DNA and in transactivation in vivo. We demonstrate that both endogenous p160 coactivators and DRIP complexes bind to the VDR LBD from nuclear extracts through similar sequence requirements, but they do so as distinct complexes. Moreover, in contrast to the p160 family of coactivators, the DRIP complex is devoid of any histone acetyltransferase activity. The results demonstrate that different coactivator complexes with distinct functions bind to the same transactivation region of nuclear receptors, suggesting that they are both required for transcription activation by nuclear receptors.

Nonadrenergic, noncholinergic relaxation of bovine iris sphincter: role of endogenous nitric oxide

PURPOSE

To investigate the role of endogenously generated nitric oxide (NO) in the relaxation of bovine iris sphincter.

METHODS

Isolated bovine sphincters were mounted on an isometric tension apparatus. Contraction-relaxation response was elicited by electrical field stimulation (ES; 12 Hz, 50-msec duration, 70-80 V). Relaxation was arbitrarily defined as maximal decrease of tension below prestimulation baseline after cessation of ES. We also determined the tissue levels of cyclic guanosine monophosphate (cGMP) by radioimmunoassay.

RESULTS

ES produced a biphasic response: contraction followed by relaxation. After cessation of ES, the muscle relaxed to below the initial baseline tension. Tetrodotoxin (TTX) abolished most of the contraction and all the relaxation response. Atropine blocked most of the contraction component, leaving the relaxation component unchanged. Prazosin and bupranolol (alpha1-adrenergic and beta-adrenergic antagonists, respectively) also did not affect the relaxation component of the response. Neither substance P nor its antagonist (N-acetyl-L-tryptophane 3,5-bis (trifluoromethyl)-benzyl ester; ATTB) inhibited or mimicked the response. The nitric oxide synthase (NOS) inhibitors Nomega-nitro-L-arginine methyl ester (L-NAME), Nomega-nitro-L-arginine (L-NNA), and aminoguanidine dose-dependently inhibited the relaxation response by 50% to 70%. The free radical scavenger 2-(4-carboxyphenyl) 4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (carboxy-PTIO) and the guanylyl cyclase inhibitor methylene blue also abrogated 70% and 45% of the relaxation response, respectively. ES caused an increase in muscle cGMP from 2.3+/-0.3 to 3.9+/-0.5 picomoles per muscle. L-NNA or L-NAME significantly decreased the tissue cGMP content (to 1.2+/-0.1 picomoles per muscle) and prevented the increase caused by ES.

CONCLUSIONS

The relaxation component of the iris sphincter response to ES is a distinct nonadrenergic, noncholinergic, ES-induced event. Most of the relaxation is mediated by the endogenously generated NO-guanylyl cyclase-cGMP cascade.

Intraocular penetration of vancomycin eye drops after application to the medial canthus with closed lids

AIMS

To investigate the intraocular penetration of vancomycin eye drops and to compare the conventional method of drop instillation to the lower cul de sac with applying drops to the medial canthus with closed lids.

METHODS

This prospective randomised trial evaluated 53 eyes of 53 patients who had undergone extracapsular cataract extraction (ECCE) with intraocular lens implantation. Vancomycin (50 mg/ml) eye drops were applied to either the lower cul de sac with open lids (conventional method), or to the medial canthus with the patient in a supine position and with closed lids. After paracentesis performed during ECCE, an aqueous humour sample was taken and vancomycin concentration was measured using the TDX vancomycin assay (fluorescence polarisation immunoassay).

RESULTS

Vancomycin concentration in the anterior chamber were above the minimal inhibitory concentration for Gram positive bacteria in the two methods of drop instillation examined (2.04 (SD 1.9) microg/ml and 1.49 (1.1) microg/ml in the open and closed methods, respectively (p =0.202)).

CONCLUSIONS

Vancomycin (50 mg/ml) reaches therapeutic concentration in the anterior chamber after topical drop application. Comparable concentrations were reached when drops were applied in either the lower cul de sac or to the medial canthus with closed lids. The latter method is proposed as likely to improve patient compliance.

A dominant-negative peroxisome proliferator-activated receptor gamma (PPARgamma) mutant is a constitutive repressor and inhibits PPARgamma-mediated adipogenesis

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) promotes adipocyte differentiation, exerts atherogenic and anti-inflammatory effects in monocyte/macrophages, and is believed to mediate the insulin-sensitizing action of antidiabetic thiazolidinedione ligands. As no complete PPARgamma antagonists have been described hitherto, we have constructed a dominant-negative mutant receptor to inhibit wild-type PPARgamma action. Highly conserved hydrophobic and charged residues (Leu(468) and Glu(471)) in helix 12 of the ligand-binding domain were mutated to alanine. This compound PPARgamma mutant retains ligand and DNA binding, but exhibits markedly reduced transactivation due to impaired coactivator (cAMP-response element-binding protein-binding protein and steroid receptor coactivator-1) recruitment. Unexpectedly, the mutant receptor silences basal gene transcription, recruits corepressors (the silencing mediator of retinoid and thyroid receptors and the nuclear corepressor) more avidly than wild-type PPARgamma, and exhibits delayed ligand-dependent corepressor release. It is a powerful dominant-negative inhibitor of cotransfected wild-type receptor action. Furthermore, when expressed in primary human preadipocytes using a recombinant adenovirus, this PPARgamma mutant blocks thiazolidinedione-induced differentiation, providing direct evidence that PPARgamma mediates adipogenesis. Our observations suggest that, as in other mutant nuclear receptor contexts (acute promyelocytic leukemia, resistance to thyroid hormone), dominant-negative inhibition by PPARgamma is linked to aberrant corepressor interaction. Adenoviral expression of this mutant receptor is a valuable means to antagonize PPARgamma signaling.

Clonidine provides an allergy-free alternative in glaucoma patients with proven allergy to apraclonidine

PURPOSE

The aim of this study was to determine allergic responses to clonidine hydrochloride 0.25% in glaucoma patients with proven allergic reaction to apraclonidine 0.5%.

METHODS

Fifteen consecutive glaucoma patients with allergic reaction to apraclonidine were prospectively challenged with clonidine hydrochloride 0.25% and evaluated for recurrence of allergic reactions and efficacy of treatment. Intraocular pressure (IOP), conjunctival hyperemia, blood pressure and resting pulse rate were determined at baseline and after 1, 3, 6 and 12 months.

RESULTS

None of the patients developed ocular allergic reaction during 12 months on clonidine therapy. Blood pressure and pulse rate did not change significantly with clonidine treatment. Clonidine caused a significant reduction of IOP from baseline. In one patient, topical clonidine caused fatigue, dizziness and dry mouth.

CONCLUSION

Clonidine did not cause allergic reaction in patients with proven allergy to apraclonidine, indicating that there is no cross-reactivity with apraclonidine. Due to the small series, however, we cannot assume that allergy will not occur with clonidine 0.25% given time and a larger number of patients.

Transcriptional repression by nuclear hormone receptors

Repression by nuclear receptors plays important roles in acute promyelocytic leukemia and other diseases. Nuclear receptor corepressor (N-CoR) and SMRT (silencing mediator of retinoic acid and thyroid hormone receptor) are corepressor proteins whose modular structure facilitates receptor interaction as well as transduction of repression signals involving histone deacetylation, alterations in chromatin structure and direct interactions with the basal transcription machinery. Interactions between nuclear receptors and corepressor complexes have multiple determinants. This allows regulation, and potentially therapeutic manipulation, of receptor, corepressor, cell-type and target-gene specificity.

Nuclear receptor corepressors partner with class II histone deacetylases in a Sin3-independent repression pathway

Transcriptional repression mediated by corepressors N-CoR and SMRT is a critical function of nuclear hormone receptors, and is dysregulated in human myeloid leukemias. At the present time, these corepressors are thought to act exclusively through an mSin3/HDAC1 complex. Surprisingly, however, numerous biochemical studies have not detected N-CoR or SMRT in mSin3- and HDAC1-containing complexes. Each corepressor contains multiple repression domains (RDs), the significance of which is unknown. Here we show that these RDs are nonredundant, and that one RD, which is conserved in N-CoR and SMRT, represses transcription by interacting directly with class II HDAC4 and HDAC5. Endogenous N-CoR and SMRT each associate with HDAC4 in a complex that does not contain mSin3A or HDAC1. This is the first example of a single corepressor utilizing distinct domains to engage multiple HDAC complexes. The alternative HDAC complexes may mediate specific repression pathways in normal as well as leukemic cells.

Cilioretinal artery occlusion during coronary catheterization

PURPOSE

To report on a patient with cilioretinal artery occlusion during cardiac catheterization.

METHODS

A 51-year-old man complained of blurred vision in the left eye immediately following cardiac catheterization. Visual acuity was 6/12 and the eye had a dense central scotoma.

RESULTS

Mild retinal whitening of the posterior pole and segmented filling of the cilio-retinal artery established the diagnosis of cilioretinal artery occlusion. Immediate paracentesis was performed. Two weeks later, a tiny central scotoma could be observed and visual acuity was 6/6.

CONCLUSIONS

Cardiac catheterization may result in retinal infarction. Awareness to any visual symptoms, immediate diagnosis and prompt intervention may prevent permanent visual impairment.

Effectiveness of sub-Tenon's versus peribulbar anesthesia in extracapsular cataract surgery

PURPOSE

To compare the effectiveness of sub-Tenon's versus peribulbar anesthesia in extracapsular cataract surgery.

SETTING

Department of Ophthalmology and the Maccabi Eye Institute, Tel Aviv, Israel.

METHODS

Sixty-four consecutive patients who had extracapsular cataract surgery were randomized to have sub-Tenon's or peribulbar anesthesia. Intraocular pressure (IOP) was measured before and 1 and 10 minutes after injection. The motility of the rectus muscles was evaluated before and 20 minutes after the injection, and the patient's anxiety level was recorded immediately after the injection. Pain was assessed intraoperatively and 1 and 24 hours postoperatively by patient self-grading.

RESULTS

One minute after the injection, IOP increased significantly in the peribulbar group (mean 7.97 mm Hg +/- 8.80 [SD]) (P < .05). There was no significant increase in the sub-Tenon's injection group (mean 0.12 +/- 3.09 mm Hg). In both groups, IOP returned to preinjection levels by 10 minutes postoperatively. Patients with peribulbar anesthesia reported a significantly higher level of anxiety than those who had sub-Tenon's anesthesia (P < .05). Although the intraoperative pain levels were the same, the sub-Tenon's group reported significantly higher levels of pain 1 and 24 hours postoperatively; 16% in the sub-Tenon's group and none in the peribulbar group reported moderate pain 24 hours after anesthesia. Ocular motility was the same except for the inferior rectus muscle, which was less motile on average in the peribulbar group.

CONCLUSION

Sub-Tenon's anesthesia led to less IOP elevation than peribulbar anesthesia and provided similarly good globe immobilization and approximately the same pain levels intraoperatively.

The CoRNR motif controls the recruitment of corepressors by nuclear hormone receptors

N-CoR and SMRT are transcriptional corepressors that associate with nuclear hormone receptors (NRs) in the absence of ligand. This interaction is the molecular target of differentiation therapy for acute promyelocytic leukaemia, wherein retinoic acid dissociates corepressor from leukaemogenic receptor fusion proteins. Binding of ligand to NRs induces a conformation that attracts coactivator proteins containing an Leu-x-x-Leu-Leu motif (the 'NR box'). Here we show that N-CoR and SMRT contain sequences that are similar to the NR box and are repeated in each of two NR interaction domains. We show that this CoRNR ('corner') box is required for NR interaction, and that CoRNR box peptides specifically block corepressor interaction in vitro and repression in vivo. Sequences flanking the CoRNR box determine NR specificity. Thus, the key feature of hormone action, differential recognition of unliganded and liganded NRs by coactivators and corepressors, is due to very subtle differences between CoRNR and NR boxes. The molecular mechanisms of repression and activation by NRs are thus linked in an unexpected manner.

Macular ring in a patient with Terson's syndrome

PURPOSE

To report on a pigmented finding in the macula that is unique to Terson's syndrome, and was previously described only once.

METHOD

A 49-year-old man underwent vitrectomy for vitreous hemorrhage due to Terson's syndrome. During surgery the retina was exposed, and a pigmentation was noticed around the macula. Follow-up of the macular finding is presented.

RESULTS

At surgery a pigmented "ring" encircling the macula was revealed. Two and six months later, the pigmented line was still noticed, and an epiretinal membrane appeared in the temporal macula.

CONCLUSION

Terson's syndrome may be associated with a pigmented "ring" encircling the macula, a finding that may be a result of a detachment of the internal limiting membrane (ILM). The epiretinal membrane that was later noticed, might also be related to the damage to the ILM.

Amplification and overexpression of peroxisome proliferator-activated receptor binding protein (PBP/PPARBP) gene in breast cancer

Peroxisome proliferator-activated receptor binding protein (PBP), a nuclear receptor coactivator, interacts with estrogen receptor alpha (ERalpha) in the absence of estrogen. This interaction was enhanced in the presence of estrogen but was reduced in the presence of antiestrogen, tamoxifen. Transfection of PBP in CV-1 cells resulted in enhancement of estrogen-dependent transcription, indicating that PBP serves as a coactivator in ER signaling. To examine whether overexpression of PBP plays a role in breast cancer because of its coactivator function in ER signaling, we determined the levels of PBP expression in breast tumors. High levels of PBP expression were detected in approximately 50% of primary breast cancers and breast cancer cell lines by ribonuclease protection analysis, in situ hybridization, and immunoperoxidase staining. Fluorescence in situ hybridization of human chromosomes revealed that the PBP gene is located on chromosome 17q12, a region that is amplified in some breast cancers. We found PBP gene amplification in approximately 24% (6/25) of breast tumors and approximately 30% (2/6) of breast cancer cell lines, implying that PBP gene overexpression can occur independent of gene amplification. This gene comprises 17 exons that, together, span >37 kilobases. The 5'-flanking region of 2.5 kilobase pairs inserted into a luciferase reporter vector revealed that the promoter activity in CV-1 cells increased by deletion of nucleotides from -2,500 to -273. The -273 to +1 region, which exhibited high promoter activity, contains a typical CCAT box and multiple cis-elements such as C/EBPbeta, YY1, c-Ets-1, AP1, AP2, and NFkappaB binding sites. These observations, in particular PBP gene amplification, suggest that PBP, by its ability to function as ERalpha coactivator, might play a role in mammary epithelial differentiation and in breast carcinogenesis.

Retinal vein occlusion associated with methylenetetrahydrofolate reductase mutation

OBJECTIVE

To report on the occurrence of methylenetetrahydrofolate reductase (MTHFR) deficiency in patients with retinal vein occlusion (RVO).

DESIGN

Prospective case series

PARTICIPANTS

Fifty-nine consecutive patients with newly diagnosed RVO seen at the Retina Unit in the Tel Aviv Medical Center during 1997. METHODS/TESTING: Interviews and multiple blood analyses were done. Data were compared to the reported incidence of MTHFR deficiency in the Israeli population at large.

RESULTS

Twenty-six patients (44.1%) were heterozygotes and 11 (18.6%) were homozygotes for 677C-T mutation in MTHFR. The MTHFR 677C-T homozygosity was documented as being present in 10.4% of healthy individuals in the Israeli population. The difference in homozygosity was found to be statistically significant (P = 0.038).

CONCLUSIONS

Retinal vein occlusion may be associated with a mutation in MTHFR.

Coactivators for the orphan nuclear receptor RORalpha

A mutation in the nuclear orphan receptor RORalpha results in a severe impairment of cerebellar development by unknown mechanisms. We have shown previously that RORalpha contains a strong constitutive activation domain in its C terminus. We therefore searched for mammalian RORalpha coactivators using the minimal activation domain as bait in a two-hybrid screen. Several known and putative coactivators were isolated, including glucocorticoid receptor-interacting protein-1 (GRIP-1) and peroxisome proliferator-activated receptor (PPAR)-binding protein (PBP/TRAP220/DRIP205). These interactions were confirmed in vitro and require the intact activation domain of RORalpha although different requirements for interaction with GRIP-1 and PBP were detected. Even in the absence of exogenous ligand, RORalpha interacts with a complex or complexes of endogenous proteins, similar to those that bind to ligand-occupied thyroid hormone and vitamin D receptors. Both PBP and GRIP-1 were shown to be present in these complexes. Thus we have identified several potential RORalpha coactivators that, in contrast to the interactions with hormone receptors, interact with RORalpha in yeast, in bacterial extracts, and in mammalian cells in vivo and in vitro in the absence of exogenous ligand. GRIP-1 functioned as a coactivator for the RORalpha both in yeast and in mammalian cells. Thus, GRIP-1 is the first proven coactivator for RORalpha.

A novel role for helix 12 of retinoid X receptor in regulating repression

Nutrients, drugs, and hormones influence transcription during differentiation and metabolism by binding to high-affinity nuclear receptors. In the absence of ligand, some but not all nuclear receptors repress transcription as a heterodimer with retinoid X receptor (RXR). Here we define a novel role for helix 12 (H12) in sterically masking the corepressor (CoR) binding site in apo-RXR. Removing H12 converts RXR to a potent transcriptional repressor. The length but not the specific sequence of H12 is critical for masking RXR's intrinsic repression function. This contrasts with the amphipathic character required for mediating ligand-dependent activation and coactivator recruitment. Physiologically, we show that heterodimerization of RXR with apo-thyroid hormone receptor (TR) unmasks the CoR binding site in RXR and allows the TR-RXR heterodimer to repress. A molecular mechanism that involves sequence-specific interaction between RXR H12 and the coactivator-binding surface of the nuclear receptor is proposed for this heterodimerization-mediated unmasking. Peroxisome proliferator-activated receptor gamma does not interact as well with RXR H12, thus explaining its inability to repress transcription as an RXR heterodimer. The requirement to unmask RXR's latent repression function explains why only certain RXR partners repress transcription.

A novel therapy for colitis utilizing PPAR-gamma ligands to inhibit the epithelial inflammatory response

Peroxisome proliferator-activated receptor gamma (PPAR-gamma), a member of the nuclear hormone receptor superfamily originally shown to play a critical role in adipocyte differentiation and glucose homeostasis, has recently been implicated as a regulator of cellular proliferation and inflammatory responses. Colonic epithelial cells, which express high levels of PPAR-gamma protein, have the ability to produce inflammatory cytokines that may play a role in inflammatory bowel disease (IBD). We report here that PPAR-gamma ligands dramatically attenuate cytokine gene expression in colon cancer cell lines by inhibiting the activation of nuclear factor-kappaB via an IkappaB-alpha-dependent mechanism. Moreover, thiazolidinedione ligands for PPAR-gamma markedly reduce colonic inflammation in a mouse model of IBD. These results suggest that colonic PPAR-gamma may be a therapeutic target in humans suffering from IBD.