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Biomedical subjects

E Dahan

Publications and source records attributed to E Dahan.

At least 19 recordsLinked to original sources
PubMed2006

[What should be done when surgery fails? Congenital Glaucoma: IOP rises years after surgery].

The treatment for congenital glaucoma is based on surgery, initially nonpenetrating and then penetrating. To start with, a simple trabeculectomy can be augmented by a deep sclerectomy, concentrated Mitomycin C application and iridencleisis. This surgical alternative starts with an "L" shaped conjunctival flap, followed by a superficial scleral flap, then by a deep scleral flap in which bed, Mitomycin C is applied. A trabeculectomy is then performed in the deep sclerectomy. The iris is prolapsed followed by a horseshoe iridotomy in order to suture it in the deep sclerectomy. The scleral flap is tightly sutured and the anterior chamber is filled with viscelastic material. The postoperative treatment consists of topical steroids until the IOP reaches 14mmHg; by then NSAIDs are used for several weeks. If needed, a beta-blocker or acetazolamide can be used during the hypertensive period.

Glaucoma↗
PubMed2001

Developmental regulation of heat shock protein 83 in Leishmania. 3' processing and mRNA stability control transcript abundance, and translation id directed by a determinant in the 3'-untranslated region.

Developmental gene regulation in trypanosomatids proceeds exclusively by post-transcriptional mechanisms. Stability and abundance of heat shock protein (HSP)70 and HSP83 transcripts in Leishmania increase at mammalian-like temperatures, and their translation is enhanced. Here we report that the 3'-untranslated region (UTR) of HSP83 (886 nucleotides) confers the temperature-dependent pattern of regulation on a chloramphenicol acetyltransferase (CAT) reporter transcript. We also show that the majority of the 3'-UTR sequences are required for increasing mRNA stability during heat shock. Processing of the HSP70 and HSP83 primary transcripts to poly(A)(+) mRNA was more efficient during heat shock; therefore, even when stability at 33 degrees C was reduced by deletions in the 3'-UTR, transcripts still accumulated to comparable and even higher levels. Translation of heat shock transcripts in Leishmania increases dramatically upon temperature elevation. Unlike in other eukaryotes in which the 5'-UTR confers preferential translation on heat shock transcripts, we show that translational control of HSP83 in Leishmania originates from its 3'-UTR. The 5'-UTR alone cannot induce translation during heat shock, but it has a minor contribution when combined with the HSP83 3'-UTR. We identified an element located between positions 201 and 472 of the 3'-UTR which is essential for increasing translation of the CAT-HSP83 reporter RNA at 33-37 degrees C. This region confers preferential translation during heat shock even in transcripts that were less stable. Thus, investigating the traditionally conserved heat shock response reveals that Leishmania parasites use unique pathways for translational control.

3' Untranslated Regions↗
PubMed2001

Post transcriptional control of gene expression in Leishmania.

Leishmania parasites are ancient eukaryotes, characterized by unusual molecular mechanisms. We have used the gene encoding for Hsp83 as a model system for studying regulatory mechanisms that control developmental gene regulation. We previously showed that protein coding genes are regulated exclusively by post-transcriptional mechanisms, while no transcriptional activation could be observed even for the conserved Hsp83 gene. We now show that processing and maturation of the Hsp83 polycistronic primary transcripts is more efficient at elevated temperatures. The mature transcripts are more stable during heat shock, with regulation conferred by 3' UTRs. Poly(A) tails of Hsp83 are approximately 30 nucleotides long, as common for other low eukaryotes. The mechanism that signals differential degradation is still unclear, since it was not possible to detect differences in deadenylation of Hsp83 transcripts at varying temperatures. Heat shock transcripts are preferentially translated at 33-37 degrees C, but unlike Drosophila, translational regulation is controlled by a region within the 3' UTR. Using this traditionally conserved system emphasizes that regulatory mechanisms in Leishmania differ from those prevailing in other eukaryotes.

3' Untranslated Regions↗
PubMed2001

Respiratory impedance response to continuous negative airway pressure in awake controls and OSAS.

The aim of the study was to determine whether the response of respiratory impedance (Zrs) to decreasing levels of continuous negative airway pressure (CNAP) during wakefulness, differs in controls and subjects with obstructive sleep apnoea syndrome (OSAS). Zrs was measured by the forced oscillation technique (4-32 Hz) in 15 controls and 21 patients with OSAS (apnoea/hypopnoea index >20 per sleep hour) with normal lung function, in the basal state and with application of decreasing CNAP of -5, -10, and -15 hPa. Respiratory resistance was extrapolated to 0 Hz (R0) and estimated at 16 Hz (R16) by linear regression analysis of respiratory resistive impedance versus frequency. Respiratory elastance (Ers) and inertance (Irs) were estimated by multilinear regression analysis of respiratory reactance versus frequency, and resonance frequency (RF) was determined as RF=(1/2pi)(Ers/Irs)0.5. In both groups, R0, R16, Ers and RF significantly increased as the CNAP level decreased (p <0.0001 for all). R0, Ers, and RF increased significantly more in OSAS than in controls (p < 0.01, 0.001, and 0.0001, respectively), independently of the severity of obesity. Receiver operator characteristic curves showed that the parameter which best detected OSAS was RF, with a sensitivity of 81% and 93% specificity for the 13.6 Hz cut-off point. The results of the present study suggest that the response of respiratory impedance to decreasing continuous negative airway pressure levels, might allow detection of obstructive sleep apnoea syndrome in subjects with normal lung function.

Adult↗
PubMed2001

Combined effects of a nasal dilator and nasal prongs on nasal airflow resistance.

STUDY OBJECTIVES: Nasal prongs (NPs), when used to assess nasal flow, can result in dramatic increases in nasal airflow resistance (NR). The aim of this study was to investigate whether the NP-induced increases in NR could be corrected by the simultaneous use of an internal nasal dilator (ND). DESIGN: NR was estimated by posterior rhinomanometry, in the basal state (NRb), and while breathing with NP (NRp), with ND (NRd), and with both ND and NP (NRd + p). PARTICIPANTS: The study was performed in 15 healthy subjects. MEASUREMENTS AND RESULTS: NR (mean NRb [+/- SEM], 2.5 +/- 0.4 cm H(2)O/L/s) significantly decreased with ND (NRd = 1.4 +/- 0.2 cm H(2)O/L/s; p < 0.001) and significantly increased with NP (NRp = 3.8 +/- 0.8 cm H(2)O/L/s; p < 0.001). A significant logarithmic relationship was found between NRd and NRb (r(2) = 0.95; p < 0.0001), and a significant exponential relationship was found between NRp and NRb (r(2) = 0.99; p < 0.0001). While breathing with both ND and NP, NRd + p was significantly lower than NRb (1.9 +/- 1.4 cm H(2)O/L/s; p < 0.02). CONCLUSIONS: Our results demonstrate that the ND tends to slightly overcorrect the NP-induced increase in NR and suggest that, in view of the possible effects of NPs on upper airway resistance, the combination of both devices might be used for nasal airflow monitoring during nocturnal polysomnography in patients presenting with highly resistive nares.

Adult↗
PubMed2000

NADP(+)-isocitrate dehydrogenase gene expression and isozyme activity during citrus fruit development.

The accumulation of citric acid and its decline toward fruit maturation is typical of citrus fruit. We studied NADP(+)-isocitrate dehydrogenase (NADP-IDH), an enzyme involved in citrate metabolism. A cDNA encoding the enzyme was cloned from lemon (Citrus limon) juice sac cells, and is the first-reported NADP-IDH from fruits. Sequence comparisons and phylogenetic analysis indicate that it most probably belongs to a monophyletic clade of plant cytosolic enzymes. The mRNA level in the juice sac cells was induced during lemon fruit growth, and increased by about 15-fold to a peak as the fruit neared maturation. Spectrophotometric assay of the NADP-IDH activity in the pulp during fruit development showed that in young fruit, most of the activity was associated with the mitochondrial preparation and that, as the fruit grew, the activity shifted to the soluble fraction. The two activities could also be distinguished by isozyme gel electrophoresis: while one isozyme was detected in the mitochondrial preparation of young fruit and declined later, the other was induced in the soluble fraction of older fruit and increased as the fruit grew. The increasing activity of NADP-IDH in the soluble fraction throughout fruit development correlated well with the increase in gene expression, which suggests that the soluble activity is regulated by the expression of the cytosolic NADP-IDH gene. The possible role of this form of the enzyme in citric acid catabolism in the pulp is discussed.

Journal Article↗
PubMed2000

A comparison of the rate of refractive growth in pediatric aphakic and pseudophakic eyes.

OBJECTIVE: To compare the rate of refractive growth in pseudophakic children's eyes to that of aphakic eyes. DESIGN: Multicenter, retrospective observational case series. PARTICIPANTS: 83 patients with pseudophakic eyes (100 eyes) and 74 patients with aphakic eyes (106 eyes), with an age of surgery between 3 months and 10 years and a minimum follow-up time of 3 years or more, depending on the age at surgery. METHODS: A logarithmic model was used to analyze the rate of refractive growth for each eye. MAIN OUTCOME MEASURES: Age at surgery, intraocular lens power, intraocular lens A-constant, initial postoperative refraction, final refraction, and final age. RESULTS: Overall, pseudophakic eyes showed a lesser rate of refractive growth than aphakic eyes (-4.6 diopter vs. -5.7 diopter, P = 0.03). This trend was also present but less significant when the eyes were grouped into those less than 6 months of age at surgery (-3.3 diopter vs. -4.6 diopter, P = 0.09) and older patients (-5.0 diopter vs. -6.1 diopter, P = 0.07). However, the mean quantity of myopic shift was greater in pseudophakic eyes than in aphakic eyes (-5.26 diopter vs. -4.54 diopter), despite shorter follow-up times in the pseudophakic eyes. This is due to the optical effects of a constant intraocular lens power in a growing eye. CONCLUSIONS: Pediatric pseudophakic eyes have a slightly lesser rate of refractive growth than aphakic eyes. The new rate values should be used for predicting future refractions in these eyes.

Aphakia, Postcataract↗
PubMed2000

Nonpenetrating filtration surgery for glaucoma: control by surgery only.

PURPOSE: To report on intraocular pressure (IOP) control by nonpenetrating filtration surgery without medical treatment in eyes with primary open-angle glaucoma (POAG). SETTING: Oxford Eye Center and St. John Eye Hospital, Johannesburg, South Africa. METHODS: This retrospective study evaluated IOP control by nonpenetrating filtration surgery in 46 patients (86 eyes) with POAG who had surgery between February 1992 and February 1998 (mean follow-up 46 months); 48 eyes were previously treated, and 38 were newly diagnosed, untreated eyes. Under a trapezoidal scleral flap, a deep sclerectomy and a fenestration in Schlemm's canal were created without penetrating the anterior chamber. Postoperatively, when IOP rose above 20 mm Hg, instead of adding medical treatment, the filtration site was revised to re-establish filtration. RESULTS: The mean drop in IOP was 50%, from a mean of 30.4 mm Hg preoperatively to a mean of 15.35 mm Hg postoperatively. After a mean period of successful filtration of 29.9 months, the filtration site was revised in 48 eyes (56%) to maintain the IOP below 21 mm Hg without medication. The reoperation rate was 4.7 times higher in previously treated patients than in untreated patients. CONCLUSIONS: Nonpenetrating filtration surgery in eyes with POAG was more rewarding in untreated patients than in medically treated patients. To control IOP without medication, revision of the filtration site is feasible and needed in the medium and long term.

Adult↗
PubMed2000

Opposite clear corneal incisions to correct pre-existing astigmatism in cataract surgery.

In cataract surgery, the clear corneal incision (CCI) has a small flattening effect on corneal curvature, which can be used to reduce pre-existing astigmatism (PEA). Adding an identical, penetrating CCI opposite the first one can enhance the flattening effect. The paired opposite CCIs (OCCIs) are placed on the steepest meridian axis to flatten it. One CCI is used to perform cataract surgery, and the opposite CCI is made to enhance the flattening effect on the cornea to modulate PEA. During the past 12 months, we have used 2.8 to 3.5 mm OCCIs in 33 eyes with PEA greater than 2.00 diopters (D) having cataract surgery. The mean astigmatism correction achieved with this technique was 2.06 D. This technique is simple and effective and yields stable results that rival those of arcuate keratotomy. The OCCI technique has a potential application for the correction of astigmatism in general refractive surgery. Opposite clear corneal incision nomograms with variables such as width, length, and distance from the limbus will be needed for future applications.

Astigmatism↗
PubMed2000

Does primary intraocular lens implantation prevent "aphakic" glaucoma in children?

PURPOSE: Open-angle glaucoma may develop after surgery for congenital or developmental cataract with an incidence ranging from 3% to 41%. The pathogenesis of "aphakic" (open-angle) glaucoma remains unknown. Despite numerous reported clinical series (>1000 eyes), we are unaware of any reported case of open-angle glaucoma after primary intraocular lens (IOL) implantation for congenital or developmental cataract. We decided to test the hypothesis that primary posterior chamber IOL implantation might decrease the incidence of open-angle glaucoma in children. METHODS: Pseudophakic eyes were collected from surgeons who contributed data to a refractive study and who monitored intraocular pressure on a regular basis. IOL implantation was commonly performed in eyes with a corneal diameter >10 mm. Comparable primary data on aphakic eyes were included from 2 published studies on aphakic glaucoma, which included corneal diameters and the patient's age at surgery. Glaucoma-free survival estimates for each cohort were estimated. RESULTS: Only 1 case of glaucoma was found among 377 eyes with primary pseudophakia (mean age of patient, 5.1 +/- 4.7 years; mean follow-up, 3.9 +/- 2.7 years). There were 14 eyes (11.3%) with glaucoma among 124 aphakic eyes (mean age of patient, 2.7 +/- 2.6 years; mean follow-up time, 7.2 +/- 3.9 years). CONCLUSIONS: We report a decreased incidence of open-angle glaucoma among eyes rendered primarily pseudophakic compared with those that remained aphakic after cataract surgery. We propose 2 theories on the possible mechanism of reduction in the incidence of glaucoma in pseudophakic eyes.

Adolescent↗
PubMed2000

Intraocular lens implantation in children.

Over the past 15 years, lens implant surgery in children has disseminated so much that it is no longer a controversial issue. It has become rather a specialized topic in the widespread field of lens implantation in the general population. To match the excellent results seen in adults, issues such as the surgical technique, the choice of the lens, and dioptric power of that lens, are constantly being refined and adapted to children's growing eyes. Scleral tunnels and small, self-sealing corneal incisions are being replicated in children to benefit from their advantages. Polymethyl methacrylate material remains unrivalled from the point of view of safety and longevity in the human eye. Intraocular lenses (IOLs) with an overall diameter of 12 mm can safely be used in nonmicrophthalmic eyes of children more than 3 years of age. Several investigators now recognize the need for smaller pediatric IOLs for neonates, toddlers, and microphthalmic eyes. Fortunately, modern IOLs are smaller today than they were 15 years ago. The accumulating evidence on the myopic shift that occurs in pseudophakic children have led to an almost unanimous agreement that the IOL power should aim for a certain amount of hypermetropia at time of surgery. The residual refractive error can be corrected with spectacle glasses that are adjusted throughout childhood. The goal is to start with hypermetropia in childhood that will convert into emmetropia or mild myopia in adulthood.

Child↗
PubMed2000

Effects of nasal prongs on nasal airflow resistance.

STUDY OBJECTIVES: The aim of this study was to investigate whether nasal prongs, which have been proposed to assess nasal flow during sleep, affect nasal airflow resistance (NR). DESIGN: NR was estimated by posterior rhinomanometry at a 0.5 L/s flow, under eight conditions: in the basal state, and with seven different nasal prongs. PARTICIPANTS: The study was performed in 17 healthy supine subjects, 8 of whom had basal NR values within the normal range (< or = 2 cm H(2)O.L(-1).s, group 1), and 9 had increased basal NR values (> 2.5 cm H(2)O.L(-1).s, group 2), because of nare narrowness and/or deviated nasal septum. MEASUREMENTS AND RESULTS: NR increased significantly while breathing with nasal prongs (p < 0.0001 in both groups). The changes in NR (DeltaNR) induced by the different nasal prongs were characterized by large intersubject and intrasubject variability, with a maximum DeltaNR of 24.2 cm H(2)O.L(-1).s. Significant differences were found between the DeltaNR induced by the different nasal prongs (p < 0.001 in group 1, and p < 0.0003 in group 2), and for six of them, DeltaNR was significantly higher in group 1 than in group 2 (p < 0.02). CONCLUSIONS: This study demonstrates that nasal prongs can markedly increase NR in subjects presenting with nare narrowness and/or deviated nasal septum. Further investigations that would include nocturnal polysomnography are still required to evaluate the possible influence of nasal prongs on the diagnosis of obstructive sleep apnea syndrome and its severity.

Adult↗
PubMed1999

Effect of acidic pH on heat shock gene expression in Leishmania.

Temperature and pH shifts trigger differential gene expression and stage transformation in Leishmania. The parasites encounter dramatic fluctuations in the extra-cellular pH between the mid-gut of the sand fly (pH>8) and the phagolysosomal vacuole of mammalian macrophages (pH<6). The authors examined the effect of pH shifts on heat shock gene expression in Leishmania amazonensis and Leishmania donovani promastigotes. Acidic pH resulted in preferential stability of the hsp83 transcripts at 26 degrees C, but hsp transcripts were not preferentially translated as observed during heat shock. Pre-conditioning of promastigotes to acidic pH did not alter the temperature threshold for hsp synthesis but lead to an increase in hsp synthesis mainly in L. donovani at 37 degrees C, and to a slight decrease in the arrest of tubulin synthesis in L. amazonensis. The stage specific morphological alterations that take place in vitro correlated with the arrest in tubulin synthesis and occurred at different temperatures in L. donovani and L. amazonensis.

Animals↗
PubMed1999

Effect of age at time of cataract surgery on subsequent axial length growth in infant eyes.

PURPOSE: To determine whether removal of the crystalline lens and placement of an intraocular lens (IOL) in human infant eyes retard the growth of the pseudophakic eye. METHODS: A unilateral lensectomy with placement of a posterior chamber IOL in the sulcus was performed in 11 infants between 2 and 4 months of age. Axial length measurements of both eyes were obtained preoperatively and postoperatively. RESULTS: Patients were followed for a mean of 5.6 years. In 7 patients, the mean axial growth was 0.46 mm less in the pseudophakic eye than in the fellow eye (range 0.15 to 0.70 mm). In 1 patient, there was no interocular axial length difference and in 3, the pseudophakic eye was longer. When measurements from the only patient with microphthalmia were excluded, the interocular difference in axial growth was highly significant (signed rank test, P = .006). Median visual acuity of the pseudophakic eyes at the last follow-up was 20/60 (range 20/30 to 20/200). The final visual acuity in the pseudophakic eyes did not correlate with the degree of interocular axial length difference (P > .05). CONCLUSIONS: Our study suggests there may be a reduction in axial growth in infantile eyes following cataract extraction and IOL implantation. This effect probably reduces the magnitude of the myopic shift in these eyes.

Aging↗
PubMed1999

Effects of continuous negative airway pressure on lung volume and respiratory resistance.

This study was designed to determine the responses of lung volume and respiratory resistance (Rrs) to decreasing levels of continuous negative airway pressure (CNAP). Twenty normal subjects were studied in the basal state and under CNAP levels of -5, -10, and -15 hPa. Rrs was measured by the forced oscillation technique (4-32 Hz). End-expiratory lung volume (EELV) and tidal volume (VT) were measured by whole body plethysmography. Rrs was extrapolated to 0 Hz (R(0)) and estimated at 16 Hz (R(16)) by linear regression analysis of Rrs vs. frequency. Specific Rrs, SR(0) and SR(16), were then calculated as R(0) (EELV + VT/2) and R(16) (EELV + VT/2), respectively. EELV significantly decreased, whereas R(0), R(16), SR(0), and SR(16) significantly increased, as the CNAP level decreased (P < 0.0001 for all). At the lowest CNAP level, R(0) and R(16) reached 198 +/- 13 and 175 +/- 9% of their respective basal values. The CNAP-induced increase in R(0) was significantly higher than that in R(16) (P < 0.004). Our results demonstrate that the CNAP-induced increase in Rrs does not result from a direct lung volume effect only and strongly suggest the involvement of other factors affecting both intrathoracic and extrathoracic airway caliber.

Adult↗
PubMed1999

Protruding the tongue improves posterior rhinomanometry in obstructive sleep apnoea syndrome.

In posterior rhinomanometry (PRM), oropharyngeal pressure is measured using a tube placed between the tongue and the hard palate. For valid results the patient must position the tongue and soft palate so that both the oropharynx and nasopharynx remain open. A high rate of failure of conventional PRM has been reported in normal individuals. In patients with obstructive sleep apnoea syndrome (OSAS), upper airway abnormalities may further increase the failure rate. This study proposes a modification of the technique in which protrusion of the tongue enhances pressure transmission between the nasopharynx and the mouth. In eight normal subjects, resistance was similar when measured by both methods. Of 24 OSAS patients, conventional PRM was unsuccessful in 11. In the remaining 13 patients, a significant correlation between the two methods was found, but resistance was lower by "tongue-out" than by conventional PRM, consistent with a decrease, during tongue protrusion, in retropalatal resistance, which is a component of the "nasal" resistance measured by PRM. In 26 OSAS patients, unilateral nasal resistance values measured by "tongue-out" PRM were similar to those measured by anterior rhinomanometry. When the "tongue-out" method was used routinely in 541 snorers, failure rates were 1.1% in the 272 non-OSAS patients and 3.7% in the 269 OSAS patients. These results indicate that posterior rhinomanometry with tongue protrusion is a highly effective tool for measuring nasal resistance in snorers.

Adolescent↗
PubMed1999

Combined effects of a mechanical nasal dilator and a topical decongestant on nasal airflow resistance.

The goal of this study was to compare the isolated and combined effects of two treatments being used to reduce nasal airflow resistance (NR): an internal nasal mechanical dilator (Nozovent; Prevancure; Sté Pouret, Paris, France) and a topical decongestant, fenoxazoline hydrochloride (Aturgyl; Synthelabo; Le Plessis-Robinson, France). The study was performed in 17 healthy subjects. NR was estimated by active posterior rhinometry at a 0.5 L/s flow under four conditions: in the basal state, with the internal nasal mechanical dilator, after treatment with fenoxazoline hydrochloride, and with both fenoxazoline hydrochloride and the mechanical dilator. The mean NR (+/- SD) decreased from 1.65+/-0.54 cm H2O/L/s in the basal state to 1.02+/-0.27 cm H2O/L/s with the mechanical dilator (p < 0.001), 1.03+/-0.47 cm H2O/L/s with fenoxazoline hydrochloride (p < 0.001), and 0.48+/-0.15 cm H2O/L/s with both the mechanical dilator and fenoxazoline hydrochloride (p < 0.001). The decreases in NR observed after using either the mechanical dilator (deltaNR(N)) or fenoxazoline hydrochloride (deltaNR(A)) were not significantly different. The decrease in NR observed with both (deltaNR(N + A)) was not significantly different from the sum deltaNR(N) + deltaNR(A): 1.16+/-0.53 cm H2O/L/s vs 1.25+/-0.63 cm H2O/L/s, respectively (p > 0.05). deltaNR(N + A) strongly correlated with deltaNR(N) + deltaNR(A): deltaNR(N + A) = 0.80 (deltaNR(N) + deltaNR(A)) + 0.15 (r = 0.96; p < 0.0001). However, the slope of the regression line of deltaNR(N + A) vs deltaNR(N) + deltaNR(A) was significantly lower than unity (p < 0.003). These results demonstrate that, although not totally additive, the effects of using the mechanical dilator and fenoxazoline hydrochloride are cumulative. Further studies that include patients with nasal obstruction would allow us to better evaluate the benefit of a therapy combining both treatments.

Administration, Topical↗