PubMed Health⌕ Search

Biomedical subjects

M Sebag

Publications and source records attributed to M Sebag.

At least 19 recordsLinked to original sources
PubMed2000

Successful goniosynechialysis for angle-closure glaucoma after vitreoretinal surgery.

PURPOSE: To describe 2 cases of long-term successful clinical outcome after goniosynechialysis for secondary angle-closure glaucoma after vitreoretinal surgery. METHODS: Case reports. Goniosynechialysis was performed bilaterally in 1 patient and unilaterally in another for uncontrolled angle-closure glaucoma after vitreoretinal surgery. RESULTS: Angle reopening was performed 2 to 4 months after initial closure. After follow-up of between 3 and 5 years, intraocular pressure has remained below 21 mm Hg without medication in all three eyes. CONCLUSION: Goniosynechialysis should be considered a viable therapeutic alternative to filtration surgery in selected patients with a recent history of angle-closure glaucoma after vitreoretinal surgery.

Aged↗
PubMed1998

Disruption of vitamin D receptor-retinoid X receptor heterodimer formation following ras transformation of human keratinocytes.

A partial resistance to the growth inhibitory influence of 1, 25-dihydroxyvitamin D3 is apparent when immortalized keratinocytes are transformed by the ras oncogene. The vitamin D receptor (VDR) was isolated, analyzed, and found to be identical in normal, immortalized, and ras-transformed keratinocytes. Subsequently, nuclear extracts from immortalized and ras-transformed keratinocytes were analyzed in gel mobility shift assays utilizing labeled vitamin D response elements or thyroid hormone response elements. A specific protein.DNA complex that was shown to contain VDR using an anti-VDR antibody was identified in both types of extracts; however, the addition of an anti-retinoid X receptor (RXR) antibody identified RXR in the complex of both normal and immortalized keratinocyte cell extracts, but not in ras-transformed keratinocytes. Furthermore, transfection of ras-transformed keratinocytes with wild-type human RXRalpha rescued VDR.RXR and thyroid hormone receptor.RXR complexes as demonstrated by a supershift in the presence of the anti-RXR antibody. Both cell lines were found to express RXRalpha message in equal amounts. Western blot analysis revealed that RXRalpha protein from ras-transformed keratinocytes was indistinguishable from that from immortalized keratinocytes and from control cells. These results suggest a causal relationship between resistance to the growth inhibitory influences of 1,25-dihydroxyvitamin D3 and disruption of the VDR.RXR complex in malignant keratinocytes.

Base Sequence↗
PubMed1997

Expression of parathyroid hormone-related peptide (PTHrP) and PTH/PTHrP receptor in newborn human calvaria osteoblastic cells.

We examined the expression of parathyroid hormone-related peptide (PTHrP) and its receptor in normal newborn human calvaria osteoblastic (NHCO) cells. Northern blot analysis showed that NHCO cells express a single 1.6 kb transcript of PTHrP, which was increased within 1 h (2x) and peaked at 6 h (7x) after serum treatment. In the culture media, the release of PTHrP peptide was maximally increased (4x) 24 h after the addition of serum, as determined by immunoradiometric assay. NHCO cells exhibited a cytoplasmic immunostaining for PTHrP in the presence of serum, and most PTHrP-positive cells were alkaline phosphatase-negative, suggesting that PTHrP was expressed in undifferentiated cells. Furthermore, RT-PCR analysis showed that both PTHrP and PTH/PTHrP receptor were expressed in NHCO cells in basal conditions or after stimulation with serum. The maximal PTHrP expression induced by serum suppressed PTH/PTHrP receptor expression, suggesting that PTHrP down-regulated its receptor in NHCO cells. Treatment with 10 nM human PTH(1-34) which binds to PTH/PTHrP receptors, increased intracellular cAMP levels and alkaline phosphatase activity, and decreased cell growth, indicating that ligand binding to PTH/PTHrP receptors regulates NHCO cell proliferation and differentiation. The expression and synthesis of PTHrP and the presence of functional PTH/PTHrP receptors suggest a possible paracrine mechanism of action of PTHrP in normal human calvaria osteoblastic cells.

Cells, Cultured↗
PubMed1996

Identification and characterization of 1,25-dihydroxyvitamin D3-responsive repressor sequences in the rat parathyroid hormone-related peptide gene.

Parathyroid hormone-related peptide (PTHRP) gene transcription is suppressed by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the active metabolite of vitamin D3. In the present report, we examined 1, 25(OH)2D3-mediated repression of PTHRP expression by transfection of PTHRP promoter/reporter constructs in normal human keratinocytes and by DNA binding. We localized an element conferring 1, 25(OH)2D3-mediated repression in vivo to a 47-base pair (bp) region located -1121 to -1075 from the transcriptional start site. Mobility shift analysis revealed that this vitamin D response element (VDRE) forms DNA-protein complexes. The addition of a monoclonal antibody that recognizes the DNA binding region of the vitamin D receptor (VDR) attenuated binding of the receptor to the 47-bp sequence, whereas the addition of monoclonal antibody raised against the retinoid X receptor (RXR) further retarded the mobility of the protein-DNA complex. Consequently, the PTHRP promoter element binds a VDR.RXR heterodimer. Examination of this VDRE revealed complete sequence homology with a half-site of the human and rat osteocalcin VDRE (GGGTGA). Furthermore, mutation analysis suggests that a 16-bp domain consisting of an almost perfect repeat separated by a 3-base pair "spacer" GGGTGGAGAGGGGTGA is responsible for the DNA-protein interaction within this 47-bp sequence. Our results therefore indicate the existence of an inhibitory VDRE within the PTHRP promoter that is similar in sequence composition and cellular factor requirement to classical up-regulatory VDREs.

Animals↗
PubMed1994

Effect of 1,25 dihydroxyvitamin D3 and calcium on growth and differentiation and on c-fos and p53 gene expression in normal human keratinocytes.

Calcium enhances keratinocyte differentiation, and 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) is both antiproliferative and prodifferentiative in many cell types, including normal human keratinocytes. In the present study, we examined the combined effects of calcium and 1,25(OH)2D3 on parameters of growth and differentiation and on c-fos and p53 gene expression in normal human keratinocytes. Exposure of normal human keratinocytes to 1,25(OH)2D3 markedly reduced [3H] thymidine incorporation and cell number at low and high medium Ca++ concentrations. Simultaneously, cells in the G0/G1 phase of the cell cycle increased significantly and those in the S phase fell precipitously. 1,25(OH)2D3 and calcium also induced keratinocyte differentiation independently, as assessed by immunocytochemistry and by induction of involucrin mRNA. Both Ca++ and 1,25(OH)2D3 were shown, by nuclear run-on assays, to increase involucrin gene transcription. A rapid, transient elevation in c-fos protooncogene expression preceded these effects when epidermal growth factor was present alone. When 1,25(OH)2D3 was added to quiescent keratinocytes, there was a marked augmentation of c-fos mRNA accumulation at low and high medium Ca++ concentrations. Varying medium Ca++ concentrations had no effect on c-fos mRNA levels. Increasing medium Ca++ concentrations from 0.15 to 2.0 mM produced marked elevations of p53 mRNA accumulation and of the rate of p53 gene transcription, whereas 1,25(OH)2D3 had no effect. These results, therefore, suggest that 1,25(OH)2D3 and calcium act in concert to modulate the expression of two important cell-cycle-associated genes, which may be important components in the initial programming of growth and differentiation of normal human keratinocytes.

Calcitriol↗
PubMed1994

Regulation of parathyroid hormone-related peptide production in normal human mammary epithelial cells in vitro.

We have examined the expression and production of parathyroid hormone-related peptide (PTHRP) in primary cultures of normal human mammary epithelial cells (HMEC) derived from nonlactating breast tissue. In response to growth factors such as insulin, insulin-like growth factor I (IGF-I), and epidermal growth factor (EGF), immunoreactive PTHRP was released into conditioned medium, and PTHRP mRNA rapidly increased. In contrast, hydrocortisone and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] inhibited these effects in a dose-dependent manner. Addition of prolactin (PRL) in the presence or absence of insulin, IGF-I, or EGF did not influence PTHRP production during the time course studied. To investigate whether these factors were acting at the transcriptional level, we performed nuclear run-on assays and demonstrated that IGF-I increased PTHRP gene transcription whereas hydrocortisone and 1,25(OH)2D3 inhibited this effect. These studies therefore demonstrate that IGF-I, EGF, 1,25(OH)2D3, and hydrocortisone modulate PTHRP expression in HMEC and that these effects occur in part at the level of gene transcription. Additionally, PRL, a known stimulator of PTHRP expression in vivo, has no effect in this in vitro model.

Breast↗
PubMed1994

Antisense-mediated inhibition of parathyroid hormone-related peptide production in a keratinocyte cell line impedes differentiation.

We have used antisense RNA technology to inhibit endogenous PTH-related peptide (PTHRP) production in an established human keratinocyte cell line, HPK1A, to assess the role of PTHRP as a modulator of cell differentiation. Initially to determine the specificity of any alterations in cell function that might be observed, HPK1A cells and Rat-2 fibroblasts (which do not synthesize PTHRP) were both infected with the same retrovirus (pYN) containing antisense PTHRP. In contrast to antisense-infected HPK1A cells (HPK1A-AS), which show accelerated growth indices when endogenous PTHRP production is blocked, antisense-infected Rat-2 cells (Rat-2-AS) displayed no increase in cell proliferation. Consequently, this alteration in HPK1A cell function appeared to be specific to the inhibition of PTHRP production. In HPK1A-AS cells, no PTHRP transcript was observed in cytoplasmic RNA, and none was sequestered in a nuclear RNA preparation. Therefore, hybridization with the antisense strand appears to destabilize PTHRP mRNA, leading to rapid disappearance of the sense-antisense heteroduplex. We then examined the effect of PTHRP inhibition on keratinocyte differentiation using three indices. PTHRP inhibition in HPK1A-AS cells resulted in reduced high mol wt keratin production, as assessed by immunocytochemistry. Expression of mRNA encoding transglutaminase and involucrin was decreased in HPK1A-AS cells compared to that in control cells under conditions of high ambient calcium. Involucrin protein levels were also diminished in HPK1A-AS cells in parallel with the reduced levels of involucrin gene expression. These data, therefore, show that interference with PTHRP production inhibits expression of maturation-specific keratinocyte indices and indicate that endogenous PTHRP acts to enhance differentiation in this keratinocyte model.

Animals↗
PubMed1994

Effect of timolol vs. acetazolamide on sodium hyaluronate-induced rise in intraocular pressure after cataract surgery.

This prospective study was done to compare the efficacy of timolol and acetazolamide in lowering the intraocular pressure (IOP) secondary to the use of sodium hyaluronate (Healon) in cataract surgery. Fifty patients undergoing extracapsular cataract extraction and implantation of a posterior chamber lens were randomly assigned to one of four treatment groups: no viscoelastic (10 patients), Healon with 0.5% timolol drops postoperatively (12 patients), Healon with acetazolamide postoperatively (16 patients), or Healon only (12 patients). The IOP was measured during the first 24 hours after surgery. Sodium hyaluronate caused a marked increase in IOP in the early (6 to 12 hours) postoperative period. Timolol proved to be more effective than acetazolamide in controlling this pressure increase.

Acetazolamide↗
PubMed1993

The penetration of oral ciprofloxacin into the aqueous humor, vitreous, and subretinal fluid of humans.

We examined ciprofloxacin levels in the aqueous humor, vitreous, or subretinal fluid in 40 patients undergoing cataract extraction, vitrectomy, or scleral buckling. Ciprofloxacin, 750 mg, was administered orally an average of 17 1/2 and 5 1/2 hours preoperatively. We obtained mean ciprofloxacin levels of 0.53 microgram/ml in aqueous humor, 0.51 microgram/ml in vitreous, and 0.71 microgram/ml in subretinal fluid. These vitreous levels exceed the minimum inhibitory concentration (MIC)90 of Staphylococcus epidermidis, Propionibacterium species, Pseudomonas aeruginosa, Proteus mirabilis, and Haemophilus influenzae, as well as the MIC70 of S. aureus and Bacillus cereus. Therefore, ciprofloxacin may have a role in the management and prevention of endophthalmitis.

Administration, Oral↗
PubMed1992

Relative resistance to 1,25-dihydroxyvitamin D3 in a keratinocyte model of tumor progression.

We have examined the effect of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on mitogen-stimulated growth and on c-myc proto-oncogene expression in a keratinocyte model of tumor progression. A dose-dependent inhibition of cell growth by 1,25-(OH)2D3 was demonstrated in both established (HPK1A) and malignant (HPK1A-ras) cells. However, this inhibition was observed with the addition of 1,25-(OH)2D3 at a higher concentration in HPK1A-ras cells than in HPK1A cells. Cell cycle analysis revealed a blockage of the normal progression of the cell cycle from G0 to S phase in the presence of 1,25-(OH)2D3. A higher concentration of 1,25-(OH)2D3 was required in HPK1A-ras cells to overcome the mitogen-stimulated progression into S phase, when compared with HPK1A cells. Analysis of c-myc messenger RNA revealed a strong inhibition of its expression at early time points with higher concentrations of 1,25-(OH)2D3 being required to obtain an inhibition in HPK1A-ras cells similar to that obtained in HPK1A cells. 1,25-(OH)2D3 receptor characterization by sucrose gradient analysis and equilibrium binding demonstrated the presence of a single 3.7 S protein with similar receptor numbers and affinity in both cell lines. These observations therefore demonstrate that an alteration of the growth inhibitory response to 1,25-(OH)2D3 occurs when keratinocytes acquire the malignant phenotype and suggest that the alteration lies beyond the interaction of the ligand with its receptor. In addition, relative resistance to 1,25-(OH)2D3 was also observed in the expression of the cell-cycle associated oncogene c-myc. These studies may therefore have important implications in vivo in the development and growth of epithelial cell cancers.

Animals↗
PubMed1991

Dysregulation of parathyroid hormone-like peptide expression and secretion in a keratinocyte model of tumor progression.

Using a human keratinocyte model of tumor progression, we have examined the regulation of gene expression and secretion of a parathyroid hormone-like peptide (PLP) that has been implicated in the pathogenesis of hypercalcemia in cancer. A rapid and transient induction of PLP mRNA in response to serum stimulation was demonstrated in both established (HPK1A) and malignant (HPK1A-ras) cells; however the dose dependent increases were greater in HPK1A than in HPK1A-ras. Significant inhibition of this induction was noted with the addition of 1,25-dihydroxyvitamin D3 at a lower concentration in HPK1A than in HPK1A-ras. Amino-terminal PLP immunoreactivity and bioactivity correlated well (r = 0.98) when measured in conditioned medium. In the absence of mitogenic stimuli, malignant keratinocytes (HPK1A-ras) secreted significantly more PLP than established (HPK1A) keratinocytes. However, in response to increasing concentrations of epidermal growth factor and fetal bovine serum, PLP release was far greater from HPK1A (maximum 13 x basal) than from HPK1A-ras (maximum 3 x basal) cells. In addition, 1,25-dihydroxyvitamin D3 was more effective in inhibiting both basal and stimulated PLP secretion in HPK1A than in HPK1A-ras cultures. Reduction of extracellular Ca2+ from 2.0 mM to 0.5 mM appeared to be more effective at an early time point in reducing PLP secretion from the established cells compared with the malignant cells. These studies therefore demonstrate a progressive dysregulation of PLP expression and secretion in human keratinocytes in the transformation from established to malignant phenotype and may have important implications for understanding the pathogenetic mechanisms involved in vivo in the development of hypercalcemia in cancer.

Blotting, Northern↗
PubMed1991

Choroidal blood flow in diabetic retinopathy.

The ocular hemodynamics in diabetic patients with increasingly severe retinopathy have been evaluated using a non-invasive computerized methodology. In a group of 19 healthy volunteers the mean ophthalmic arterial pressure and the ocular pulsatile blood flow were 83 +/- 2.4 mmHg and 648 +/- 42 microliters min-1 respectively. Nine diabetics with no apparent retinopathy had ophthalmic pressures and pulsatile blood flows similar to those in the control subjects. In 11 diabetic patients with background retinopathy the mean pulsatile blood flow was 471 +/- 70 microliters min-1. Thirteen diabetics with proliferative retinopathy had a pulsatile blood flow of 210 +/- 37 microliters min-1 and abnormally low ophthalmic arterial pressures. The results provide evidence that the choroidal blood flow decreases with the severity of the retinopathy in diabetes due to increased vascular resistance and a decreased ocular perfusion pressure.

Adult↗
PubMed1991

Image analysis of changes in drusen area.

Computerized image processing was used to analyze color fundus photographs of 11 patients (22 eyes) with macular drusen who were followed for more than 2 years (mean follow-up, 4.7 years). Significant changes over time (more than +/- 20% of baseline area) were measured in the surface area of macular drusen in 18 of 22 (82%) eyes. An increase in the drusen area was associated significantly with eyes with mostly hard drusen and an initially smaller drusen area; but a decrease was associated with eyes with mostly soft drusen and an initially larger drusen area (P less than 0.01). The mean absolute rate of change in the drusen area was more than twice as great in eyes with mostly soft drusen compared with those with mostly hard drusen (P less than 0.05). All eye pairs studied showed a concomitant increase or decrease in the drusen area.

Aged↗
PubMed1989

Proliferative vitreoretinopathy membranes. An immunohistochemical study.

Proliferative vitreoretinopathy (PVR) is the leading cause of failure after retinal detachment surgery. Therefore, both the extracellular matrix and cellular components of preretinal membranes from 23 eyes with PVR were characterized immunohistochemically. The membrane stroma was composed primarily of types I, II, and III collagen. Laminin and both heparan sulfate proteoglycans and collagens types IV and V were co-distributed in discrete regions within the stroma. Glial and retinal pigment epithelial (RPE) cell populations were identified in these membranes using specific immunohistochemical markers as was a small but significant macrophage population. Double-labeling experiments indicated that RPE cells in these membranes expressed the class II histocompatibility antigen HLA-DR, although neither the RPE monolayer in situ nor cultured RPE cells was HLA-DR positive unless induced by gamma interferon. Only rare isolated vascular endothelial cells were detected in 5 of the 23 membranes.

Collagen↗
PubMed1988

Paraneoplastic optic neuritis and encephalomyelitis. Report of a case.

A 63-year-old man developed bilateral paresis of horizontal and upward eye movements. He was found to have a small oat cell carcinoma of the lung. Four months later he experienced acute visual blurring on the right side. Examination of the right eye at that time revealed a visual acuity of 3/200 and a central scotoma. There was swelling of the right optic disc. Three weeks after the onset of the visual loss, the acuity of the right eye spontaneously improved to 20/60, the field deficit lessened, and there was a decrease in the swelling of the optic disc. Subsequently, his neuro-ophthalmologic condition remained unchanged but his general health deteriorated, and he died nine months after the onset of the disease. Neuropathologic examination showed mild perivascular lymphocytic infiltration and fibrosis of the meninges throughout the central nervous system, loss of neurons and gliosis in the third and fourth cranial nerve nuclei, perivascular inflammation and gliosis of the optic nerves, and chiasm and central demyelination of the right optic nerve. No tumor cells were seen. These findings were consistent with a diagnosis of paraneoplastic optic neuritis and paraneoplastic encephalomyelitis. The present case confirms the existence of paraneoplastic optic neuritis and illustrates the clinical course of the disease.

Encephalomyelitis↗
PubMed1987

[Course of retinopathy in premature infants treated by cryopexy].

Beneficial effect of cryopexy on 180 degrees to 360 degrees of avascular retina was demonstrated in 7 prematurely born infants (14 eyes) affected with advanced retinopathy of prematurity. Intravitreous new vessels were present in all eyes before treatment. The treatment of one eye was supplemented with scleral indentation. Only one of the treated eyes went on unfavourably with retrolental fibroplasia and consecutive loss of visual acuity. We believe that cryopexy, when administered promptly, when limited to the avascular zone, and when supplemented with scleral indentation in cases with important vitreous traction, is a valuable treatment with fewer risks than unchecked evolution for advanced cases of retinopathy of prematurity.

Cryosurgery↗
PubMed1986

Biochemical changes in progressive muscular dystrophy. XII. Cyclic nucleotides in lymphoid and nonlymphoid organs of dystrophic mice.

Concentrations of cAMP and cGMP were measured (per milligram DNA) in the lymphoid (thymus, spleen) and nonlymphoid organs (liver, brain, kidney, lungs, heart, pancreas, skeletal muscle, lens) of normal (+/+) and dystrophic (dy/dy) 129 ReJ mice aged 30, 60, and 90 days. The cAMP concentrations in the thymus did not reveal any significant differences at 30 and 60 days of dystrophy, but were considerably higher (2-fold) at 90 days. cGMP concentrations were decreased in the thymus at 30 days (0.20-fold) and markedly elevated at 60 (2-fold) and 90 days (3-fold) of the disease. The [cAMP]/[cGMP] ratio was increased (1.30-fold) at 30 days of dystrophy, and this was followed by a sharp decline at 60 days (2-fold), with a lesser decrease at 90 days (0.34-fold). In the spleen, the cAMP concentrations were augmented significantly in all stages of dystrophy (1.5- to 2.6-fold). cGMP (per milligram DNA) did not show any significant variation at 30 and 60 days of the disease but was increased (3-fold) at 90 days. The [cAMP]/[cGMP] ratio, which was enhanced in the spleen at 30 (2-fold) and 60 days (1.5-fold), demonstrated no change at 90 days of dystrophy. These results indicated significant differences in the concentration of cyclic nucleotides and their ratios in the thymus and spleen of 129 ReJ dy/dy mice. The modifications were not limited to lymphoid organs alone, having been noted in the nonlymphoid organs as well. These changes could, in turn, influence immune responsiveness and could cause immunodepression in dystrophic mice.

Aging↗