Posterior synechia formation after phacovitrectomy - Predicting factors and the role of short-acting mydriatics

PURPOSE

To evaluate the influence of topical short-acting mydriatics on the formation of posterior synechia after phacovitrectomy surgery of pars plana vitrectomy and phacoemulsification with intraocular lens implantation.

METHODS

A prospective randomised controlled trial. Fifty-seven adult (>18 years old) patients (57 eyes) who underwent phacovitrectomy surgery at a single tertiary hospital, were randomly divided into two groups. The control group (29 eyes) received standard postoperative treatment (topical antibiotics and steroids). The study group (28 eyes) received short-acting mydriatics together with standard therapy. Patients were followed until 24 months after surgery. The primary outcome measure was the formation of posterior synechia during the follow-up period.

RESULTS

A total of 7 patients developed posterior synechia during the follow-up period (12%), 3 in the study group (11%) and 4 in the control group (14%). There was no statistical difference between the groups. Significant associations for the development of posterior synechia were surgery for retinal detachment, longer surgery duration (>93 min) and the use of tamponade, in particular silicone oil.

CONCLUSIONS

The use of topical short-acting mydriatic drops after phacovitrectomy surgery, in addition to standard post-operative treatment, did not reduce the formation of posterior synechia. However, we identified several factors that may influence or act as predictors for the development of posterior synechia: surgery for retinal detachment, using silicone oil tamponade and a longer surgery duration. Our findings may aid in the standardisation of post-phacovitrectomy surgery treatment and define potential at-risk patients who should be monitored more closely.

Prognostic factors for visual acuity improvement after treatment of submacular hemorrhage secondary to exudative age-related macular degeneration

PURPOSE

To recognize prognostic factors for better final visual acuity (VA) in patients presenting with submacular hemorrhage (SMH) secondary to exudative age-related macular degeneration.

METHODS

This retrospective study included patients who presented to a tertiary ophthalmology department between 2012 and 2019 with SMH and were treated by pars plana vitrectomy (PPV) or injection of tissue plasminogen activator (tPA) with pneumatic displacement. Baseline characteristics included demographic data, VA and optical coherence tomography (OCT) characteristics of the SMH. Patients were divided into groups by improvement of at least 2 lines in BCVA (best corrected visual acuity), and by having a final BCVA better than 20/200.

RESULTS

Forty-three eyes of 43 patients were included. Mean age was 86.72 ± 7.18. Prognostic factors for final VA better than 20/200 included better VA at presentation (1.25 vs 1.90 logMAR, p < 0.001), smaller area of SMH in the infra-red image (19.47 mm2 vs 38.45 mm2, p = 0.024), and lower height of SMH as measured by OCT (713.5 µm vs 962.5 µm, p = 0.03). Third of the patients improved in ≥2 lines from presentation, all in the group of the pneumatic and TPA displacement.

CONCLUSION

Smaller SMHs with good VA at presentation have a better chance for improvement and result in a better final VA. These patients may benefit the most from pneumatic displacement of the SMH with intravitreal tPA and gas.

Optical coherence tomography angiography patterns of type 1 macular neovascularization in age-related macular degeneration patients

PURPOSE

To compare morphologic characteristics of type 1 macular neovascularization (MNV) flow pattern in treatment-naïve and previously treated patients with age-related macular degeneration (AMD) as assessed by optical coherence tomography angiography (OCTA).

STUDY DESIGN

Cross-sectional study.

MATERIALS AND METHODS

Macular OCT angiography images were acquired using RTVue XR Avanti with AngioVue. Distinct morphologic biomarkers and quantifiable features of the neovascular membranes were studied on en-face projection images comparing treatment-naïve and previously treated patients.

RESULTS

The study included 68 eyes of 58 patients. Among them, 24 eyes were treatment-naïve, and the remaining eyes had received a mean of 19.6 injections. Immature lesions were more associated with treatment-naïve eyes and hyper-mature lesions were associated with previously treated eyes (p = 0.005). Tangle pattern was associated with treatment-naïve eyes (p = 0.013), whereas mature core vessels and sea fan pattern were associated more with previously treated eyes (p = 0.001 and p = 0.044, respectively). Vascular density of the neovascular membrane was higher in the treatment-naïve group (p = 0.036) and the average MNV area was similar between the 2 groups (p = 0.683).

CONCLUSIONS

Based on OCTA, morphologic biomarkers of type 1 MNV might be an indication of previous treatment. The MNV pattern can improve our understanding of its maturation under anti-VEGF treatment and might be valuable to better guide therapeutic decisions and provide more personalized care to patients with AMD.

Visual acuity outcome in patients with subretinal hemorrhage - office procedure vs. surgical treatment

PURPOSE

To evaluate the effects of intravitreal injection of tissue plasminogen activator (tPA) and gas vs. pars plana vitrectomy (PPV) surgery as first-line treatment for subretinal hemorrhage.

METHODS

Retrospective study of 107 adults treated for subretinal hemorrhage at a tertiary hospital during 2008-2019; 51 received injection of tPA and gas and 56 underwent PPV.

RESULTS

No between-group differences were found in age and sex, medical history, use of anticoagulants or antiplatelets, history of ocular surgeries, and previous use of intravitreal anti-VEGF. Overall follow-up time was longer in the PPV group (median 4.9 vs 3.28 years, p = 0.005). The hemorrhage was displaced in a similar percentage of patients in the tPA-and-gas group (n = 40, 78.4%) and the PPV group (n = 45, 80.4%) (p = 0.816). Approximately 80% of patients in the tPA-and-gas group were able to forgo PPV surgery. Visual acuity (in LogMAR) was similar in the two groups prior to the diagnosis of subretinal hemorrhage but better in the tPA-and-gas group at the end of follow-up (p < 0.001).

CONCLUSION

Injection of gas and tPA can be done immediately following diagnosis of subretinal hemorrhage as an office procedure. Visual acuity outcome is good, with a high rate of blood displacement. About 20% of patients might require additional PPV as secondary intervention.

Postoperative complications of combined phacoemulsification and pars plana vitrectomy in diabetic retinopathy patients

Purpose

To compare intra- and postoperative complications in combined phacoemulsification and pars plana vitrectomy surgeries performed in patients with non-proliferative diabetic retinopathy (NPDR) vs. proliferative diabetic retinopathy (PDR).

Methods

Retrospective, case series of patients with diabetic retinopathy who underwent combined phacovitrectomy surgery between 2008 and 2017. We compared intraoperative complications including posterior capsular rupture and retinal tear, and postoperative complications including corneal edema, macular edema (ME), epiretinal membrane (ERM), neovascular glaucoma and persistent inflammation.

Results

A total of 104 eyes of 104 patients were included in this study. Twenty-four eyes (23.1%) were categorized as NPDR and 80 eyes (76.9%) as PDR. The most common indications for surgery in the NPDR group were ERM (67%) and rhegmatogenous retinal detachment (12.5%), while in the PDR group, indications were vitreous hemorrhage (56%) and tractional retinal detachment (19%). The most common intraoperative complication was retinal tear (8% in NPDR and 19% in PDR, p = 0.195) and postoperative complication was ME (29% in NPDR and 26% in PDR, p = 0.778). There were no statistically significant differences in intra- and postoperative complication rates between the NPDR and PDR groups, even after adjusting for confounders; patient age at surgery and indication for surgery.

Conclusion

After combined phacovitrectomy in NPDR and PDR patients, new-onset ME was found in about a quarter of eyes in both groups. Intraoperative anti-VEGF or steroid administration, and intense postoperative anti-inflammatory medication and follow-up should be regarded after phacovitrectomy regardless of the DR level.

Intravitreal Tissue Plasminogen Activator Injection for the Treatment of Proliferative Vitreoretinopathy in a Rabbit Model

INTRODUCTION

The purpose of this study was to evaluate the effect of intravitreal injection of tissue plasminogen activator (tPA) on proliferative vitreoretinopathy (PVR).

METHODS

PVR was induced in a rabbit model by intraocular injection of dispase (0.05 U/0.1 mL). Progression of PVR was followed by indirect ophthalmic examination. Following 6 weeks, 5 animals received intravitreal injection of 25 µg/0.1 mL tPA and four were injected with balanced salt solution (BSS). Animals were euthanized at 48 h following tPA/BSS injection, and eyes were enucleated for histological evaluation and staining with α-smooth muscle actin (αSMA) and Sirius Red.

RESULTS

Following tPA injection, one eye had a reduction in PVR from grade 2 to 1 and three eyes remained stable. Following BSS, PVR grade was unchanged in three eyes. In one eye in each group, the severity of PVR could not be assessed due to limited view. Staining with αSMA showed reduced presence of fibroblasts in eyes injected with tPA compared with those injected with BSS. Collagen type I and III, demonstrated by Sirius Red staining, was reduced in the tPA group in comparison with controls.

CONCLUSION

Our results suggest that intravitreally injected tPA may show an inhibitory effect on PVR progression. Further exploration in clinical trials is desired.

Outcomes of Combined Scleral Buckling Plus Pneumatic Retinopexy Vs. Scleral Buckling for Primary Rhegmatogenous Retinal Detachment

PURPOSE

To evaluate the outcomes and complications of scleral buckle surgery alone or combined with pneumatic retinopexy (pneumatic buckle) for the treatment of primary rhegmatogenous retinal detachment.

DESIGN

Retrospective chart review.

PARTICIPANTS

Two hundred thirteen patients with rhegmatogenous retinal detachment of whom 101 underwent primary scleral buckle surgery at Rabin Medical Center in 2005-2015 (SB group) and 112 underwent pneumatic buckle surgery at Royal Alexandra Hospital in 2013-2015 (PB group).

METHODS

All patients were followed for ≥12 months. Data on clinical and surgical parameters, outcome, and complications were collected from the medical files.

MAIN OUTCOME MEASURES

Best corrected visual acuity and anatomical outcomes.

RESULTS

At 12 months, average best corrected visual acuity was 0.3 logMar in the SB group and 0.42 logMar in the PB group (P < 0.05). Rates of anatomical reattachment were high and similar in the two groups (99% and 97%, respectively, P = 0.623). The SB group had a higher percentage of patients requiring additional laser applications (21% vs. 7%; P < 0.01) and buckle readjustment surgery (6% vs. 0; P = 0.01), and the PB group had a higher percentage of patients who required postoperative pars plana vitrectomy (30% vs. 17%; P = 0.03).

CONCLUSION

Scleral buckle surgery alone is efficient for the treatment of rhegmatogenous retinal detachment. Its combination with pneumatic retinopexy usually has no significant added value in terms of anatomical reattachment rate. Outcomes of Pneumatic buckling vs Scleral Buckling for RRD.

Aflibercept clearance through the drainage system in a rat model

Background

As intravitreal anti-VEGF injections became the mainstay of treatment for many retinal diseases, the cause of a secondary sustained elevated intraocular pressure is still unclear. The aim of our study was to study the clearance of Aflibercept from the anterior chamber angle, in a rat model, to test if an aggregation exists.

Methods

Choroidal neovascular lesions (CNV) were induced in the right eye of 12 brown Norway rats, using indirect laser ophthalmoscope. Intravitreal Aflibercept injection (0.12 mg/3 µl) was performed 3 days after CNV induction. Rats were euthanized at predetermine time intervals of 3, 6, 24 and 48 h post injection, with immediate enucleation for histological analysis with H&E and immunofluorescence staining. Aflibercept molecules were stained with red fluorescence thanks to the formation of the immune complex Aflibercept-Rabbit anti human IgG-Anti rabbit antibodies-Cy3.

Results

Immediately after the injection, a strong fluorescence signal was detected, indicating the presence of Aflibercept in the iridocorneal angle. At 3- and 6-h interval a strong signal of Aflibercept was still seen. Six hours post injection, the signal was highly concentrated in Schlemm’s canal. In the 2 eyes harvested 24 h post Aflibercept injection, red fluorescence signal intensity was decreased in one eye, occupying mainly intra scleral venous plexuses, and absent in the other eye. At 48 h there was no fluorescence signal, confirming complete clearance of Aflibercept.

Conclusions

In our rat model, a complete clearance of Aflibercept from the anterior chamber angle, was seen 48 h after the injection. This finding refutes the theory of possible connection between IOP elevation and mechanical obstruction. Evacuation time of Aflibercept through the angle is of the same magnitude as that of Bevacizumab in the same rat model.

Effect of Penetration Angle and Velocity During Intravitreal Injection on Pain

Purpose: To evaluate the effect of velocity and angle of the intravitreal injection of anti-vascular endothelial growth factors on pain sensation.Methods: Patients were randomly assigned to one of four injection methods: straight and fast, straight and slow, tunneled and fast, and tunneled and slow. Later, they graded their pain sensation on a Visual Analog Scale (range 0-10).Results: The cohort included 180 patients. Mean pain score was 2.81 ± 2.34. There was no statistically significant difference in mean pain score among the four groups (p = .858); between the slow-injection (straight and tunneled) and fast-injection groups (p = .514); and between the straight-injection (fast and slow) and tunneled-injection groups (p = .992), nor other background variables.Conclusion: Velocity and angle of intravitreal injections are unrelated to the pain sensation. Therefore, the method may be left to the clinician's discretion. This implies that the sensation is mostly subjective.

Success Rates for Retinal Detachment Repair in Alberta: A Physician Learning Program Initiative

OBJECTIVE

To identify primary surgical success rates for retinal detachment repair in Alberta and compare functional outcomes of methods of repair.

METHODS

Data was retrospectively extracted from the Alberta Health Services Discharge Abstract Database and the National Ambulatory Care Reporting System for all patients diagnosed with retinal detachment and vitreoretinal procedures during the 2008/09 to 2012/13 fiscal years.

RESULTS

Of the 5,433 surgeries for retinal detachment identified, 279 were excluded due to invalid provincial health numbers, unidentified procedure location, and/or treating physician other than an Alberta retina surgeon. The final analysis included 4,336 detachments in 4,020 patients. The average primary retinal detachment success rate was 84.9% (3,680/4,336). Primary success rates varied between vitrectomy only (84.9%, 2,149/2,532), vitrectomy and scleral buckle (85.5%, 818/957), and scleral buckle (84.4%, 702/832).

CONCLUSIONS

Alberta retina surgeons have an average primary success rate of 84.9% (3,680/4,336) for repair of retinal detachments. This result is in keeping with other published retinal detachment success rate studies.

Retinal Penetration of Intravitreally Injected Tissue Plasminogen Activator: A Rat Model Study

PURPOSE

To determine whether intravitreal unconjugated tissue plasminogen activator (tPA) (alteplase) can penetrate the intact neural retina and reach the subretinal space in an experimental model.

METHODS

This study was performed in 24 Sprague-Dawley rats aged 12 weeks. Under general anesthesia, the right eye was injected with either 0.75 μg of 3 μL tPA (14 rats; study group) or saline (10 rats, control group) into the vitreous. Animals were euthanized at 3, 24, and 48 h. The eyes were enucleated, and cryosections were prepared for immunofluorescence staining. Goat anti-tPA antibody was used to detect tPA.

RESULTS

In the study group, staining for tPA was detected in the deep retinal layers in all eyes. The staining was deeper and more intense at 3 and 24 h than at 48 h. There was no tPA staining in the retina of eyes injected with saline.

CONCLUSIONS

This experimental study shows that unconjugated tPA administered into the vitreous is capable of penetrating the deep retinal layers and the subretinal space. These findings suggest that further clinical research is warranted on the benefits of intravitreal tPA in the treatment of submacular hemorrhage.

Thermomechanical Mechanisms of Reducing Ice Adhesion on Superhydrophobic Surfaces

Superhydrophobic (SH) coatings have been shown to reduce freezing and ice nucleation rates, by means of low surface energy chemistry tailored with nano/micro roughness. Durability enhancement of SH surfaces is a crucial issue. Consequently, the present research on reducing ice adhesion is based on radiation-induced radical reaction for covalently bonding SiO2 nanoparticles to polymer coatings to obtain durable roughness. Results indicated that the proposed approach resulted in SH surfaces having high contact angles (>155°) and low sliding angles (<5°) with improved durability and transparency. In a subsequent stage, the synthesized SH coating was investigated for its icephobic characteristics using a variety of substrates. Results indicated that supercooled water drops bounced back when impinging on SH polycarbonate substrate and froze on SH copper substrate held at -10 to -30 °C and were easily peeled off when coated by ice formed during exposure to air/supercooled water drops at -20 °C. The ice shear adhesion investigation (at -20 °C) demonstrated reduction of shear adhesion to a variety of SH treated substrates having low thermal expansion coefficient (copper and aluminum) and high thermal expansion coefficient (polycarbonate and poly(methyl methacrylate)). It was concluded that the thermal mismatch between the adhering ice and the various substrates and its resultant interfacial thermal stresses affect the adhesion strength of the ice to the respective substrate.

Scleral Cross-linking Using Riboflavin and Ultraviolet-A Radiation for Prevention of Axial Myopia in a Rabbit Model

Myopic individuals, especially those with severe myopia, are at higher-than-normal risk of cataract, glaucoma, retinal detachment and chorioretinal abnormalities. In addition, pathological myopia is a common irreversible cause of visual impairment and blindness. Our study demonstrates the effect of scleral crosslinking using riboflavin and ultraviolet-A radiation on the development of axial myopia in a rabbit model. The axial length of the eyeball was measured by A-scan ultrasound in New Zealand white rabbits aged 13 days (male and female). The eye then underwent 360° conjunctival peritomy with scleral crosslinking, followed by tarsorrhaphy. Axial elongation was induced in 13 day-old New Zealand rabbits by suturing their right eye eyelids (tarsorrhaphy). The eyes were divided into quadrants, and every quadrant had two scleral irradiation zones, each with an area of 0.2 cm² and a radius of 4 mm. Crosslinking was performed by dropping 0.1% dextran-free riboflavin-5-phosphate onto the irradiation zones 20 sec before ultraviolet-A irradiation and every 20 sec during the 200 sec irradiation time. UVA radiation (370 nm) was applied perpendicular to the sclera at 57 mW/cm² (total UVA light dose, 57 J/cm²). Tarsorrhaphies were removed on day 55, followed by repeated axial length measurements. This study demonstrates that scleral crosslinking with riboflavin and ultraviolet-A radiation effectively prevents occlusion-induced axial elongation in a rabbit model.

Bevacizumab clearance through the iridocorneal angle following intravitreal injection in a rat model

Antivascular endothelial growth factor (Anti-VEGF) agents have been widely used for a variety of ocular disorders. The etiology of sustained ocular hypertension following intravitreal administration of anti-VEGF agents is yet to be unraveled. Our study investigates and characterizes the presence of intravitreally injected bevacizumab in the aqueous outflow channels of a rat model. Choroidal neovascularization (CNV) was induced by diode laser photocoagulation to the right eye of twelve Brown Norway rats. Bevacizumab (25 mg/ml) was injected intravitreally after 3 days. Immediately after bevacizumab injection, and 3, 6, 24 and 48 h later, animals were euthanized for immunofluorescence staining. Donkey anti-human IgG labeled with Alexa Fluor(®) 488 was used for bevacizumab immunoreactivity detection. Anti-CD31 antibody was used as a marker for Schlemm's canal endothelial cells. Untreated eyes were used as negative controls. The intensity of the immunostaining was analyzed qualitatively. Bevacizumab immunoreactivity was found in the aqueous outflow channels including the trabecular meshwork and Schlemm's canal immediately after injection, and declined incrementally within the following hours. Forty-eight hours after the injection, no bevacizumab staining was detected in the aqueous outflow channel structures. Our manuscript demonstrates the presence of bevacizumab in the trabecular meshwork and Schlemm's canal structures after intravitreal injection in a CNV induced rat model. Bevacizumab molecules passed through the aqueous outflow channels within 48 h after intravitreal bevacizumab injection.

Scleral cross-linking using riboflavin and ultraviolet-a radiation for prevention of progressive myopia in a rabbit model

Our study demonstrates the effect of scleral cross-linking using riboflavin and ultraviolet-A radiation on the development of axial myopia in a rabbit model. Axial length of the eyeball was measured by A-scan ultrasound in 22 New Zealand white rabbits aged 13 days. The right eyes then underwent 360-degree conjunctival peritomy with (experimental group, n = 11) or without (control group, n = 11) scleral cross-linking, followed by tarsorrhaphy. The left eyes served as a control eye. In the experimental group, the right eyeballs were divided into quadrants, and every quadrant had either 2 (n = 8) or 6 (n = 3) scleral irradiation zones, each with an area of 0.2 cm² and radius of 4 mm. Cross-linking was performed by dropping 0.1% dextran-free riboflavin-5-phosphate onto the irradiation zones at 20 s before ultraviolet-A irradiation and every 20 s during the 200-s irradiation time. UVA radiation (370 nm) was applied perpendicular to the sclera at 57 mW/cm² (total UVA light dose, 57 J/cm²). Tarsorrhaphies were removed on day 55, followed by repeated axial-length measurement. In the control group, mean axial length in the right eyes increased from 10.50 ± 0.67 mm at baseline to 15.69 ± 0.39 mm 55 days later, for a mean change of 5.19 ± 0.85 mm. In the experimental group, corresponding values were 10.68 ± 0.74 mm and 14.29 ± 0.3 mm, for a mean change of 3.61 ± 0.76 mm. The between-group difference in the change in mean axial length was statistically significant (p < 0.001, Mann-Whitney nonparametric test). The present manuscript demonstrates that scleral cross-linking with riboflavin and ultraviolet-A radiation effectively prevents occlusion-induced axial elongation in a rabbit model.

Contralateral lateral rectus muscle recession in patients with Duane retraction syndrome type 3

AIMS

The aim of this study was to evaluate the motor, sensory, functional, and head posture results of recession of the lateral rectus muscle contralateral to the involved eye in patients with exotropic Duane retraction syndrome (DRS) type 3.

METHODS

This was a retrospective, longitudinal, observational study of a consecutive clinical case series. Of the 11 patients with DRS type 3 operated on at a tertiary medical center from 1977 to 2012, 8 underwent recession of the lateral rectus muscle contralateral to the involved eye (with combined Y-splitting of ipsilateral lateral rectus muscle in 3 of them). Full ophthalmic, orthoptic, and neurological examination was performed before and after surgery. Main outcome measures included intragroup changes in motor misalignment, abnormal head turn, ocular upshoot, and stereopsis.

RESULTS

Mean patient age was 8.75±3.1 years at surgery. Mean exodeviation for distance was -17.3±3.5 prism diopters (PD) preoperatively and -4.0±6.1 PD postoperatively; corresponding values for near were -23.1±7.2 PD and -5.9±8.7 PD. Motor deviation improved by 77% for distance (P=0.017) and 74.5% for near (P=0.01). In 7/8 patients, the postoperative residual exodeviation (distance and near) was <8.0 PD. There was an 80% improvement in head turn, from 15.3±4° before surgery to 3.1±5.0° after (P=0.01). Stereopsis improved significantly in 6/8 patients. Findings remained stable during follow-up (mean duration 35.9±50.8 months, range 5-132 months).

CONCLUSIONS

Contralateral lateral rectus muscle recession appears to be a promising technique for the treatment of moderate unilateral DRS type 3, with patients showing significant motor and functional improvement and a decrease in head turn.

Gender-dependent differences in biological rhythms of mice

The advantage of a variable's rhythm resides in its optimal time-phasing. This implies that, for a given function, members of a species will strive to exhibit identical time-phasing namely, their inter-individual genetic differences will be masked. To examine the generality of this assumption we explored if inbred mice exhibit gender dependent differences in rhythm parameters of biochemical variables. Male and female mice, entrained by exposure to 12:12 light:dark illumination were sacrificed, every 3 hours over a 27 hours period. Activities of creatine-phosphokinase (CK) and alkaline- phosphatase (AP), white blood cell (WBC) counts and urea nitrogen (UN) concentration were determined at each time point. For each significant rhythm four parameters were computed: period, acrophase, mesor and amplitude. In addition two derived parameters were also calculated: relative-amplitude (RA) and the rate of change in RA (CRA) which provide information about the slope and width of the peak. Patterns of most variables exhibited a compound rhythm containing two significant periodicities. Gender dependent differences were documented in the parameters of most rhythms indicating that the genetic and physiological differences limit to a certain extent the phasing ability of the entraining signals and point to an independent control of each of the rhythm parameters.

Asynchronous replication of homologous alpha-satellite DNA loci in man is associated with nondisjunction

We tested the hypothesis that loss of replication control of DNA loci associated with human centromeres affects the main centromere function, namely, ensuring proper sister chromatid separation and accurate chromosomal segregation during cell division. Applying one-color fluorescence in situ hybridization (FISH) to interphase nuclei, we studied the replication patterns of homologous DNA loci associated with human centromeres (alpha-satellite sequences) of chromosome pairs 10, 11, 17, and X in PHA-stimulated lymphocytes of female cancer patients with a familial predisposition to malignancy and normal, healthy women. Concomitantly, we measured the rates of aneuploidy for these chromosomes in the same cells. To elucidate the replication patterns of the various centromeric loci, we analyzed the replication-dependent configuration signals obtained following FISH with four chromosome-specific alpha-satellite probes. Our data showed an association between replication timing of alpha-satellite sequences and centromeric function. Chromosome pairs whose homologous alpha-satellite loci replicated highly synchronously revealed low rates of aneuploidy, whereas chromosome pairs with a slightly asynchronous replication pattern (i.e., short intervals between early- and late-replicating loci) revealed intermediate rates of aneuploidy, and chromosome pairs exhibiting asynchrony with long-time intervals between early- and late-replicating loci showed the highest rate of aneuploidy.

Modification in the inherent mode of allelic replication in lymphocytes of patients suffering from renal cell carcinoma: a novel genetic alteration associated with malignancy

Using fluorescence in situ hybridization (FISH) to interphase nuclei, we examined the replication timing of 1 allele relative to its counterpart in PHA-stimulated peripheral blood lymphocytes of normal subjects and patients suffering from a solid tumor (renal cell carcinoma). In the FISH assay, an unreplicated DNA sequence is identified by a single dot-like hybridization signal, whereas a replicated region gives rise to a duplicated, bipartite signal. Accordingly, lymphocytes of normal individuals show 2 patterns of allelic replication: (i) synchronized replication of allelic counterparts, as exemplified by the biallelically expressed loci TP53 and D21S55; and (ii) non-synchronized replication of allelic partners, as exemplified by the early and late replicating alleles of GABRB3, an imprinted locus subjected to monoallelic expression. However, when present in lymphocytes of the cancer patients, all 3 loci change their replication mode: alleles of TP53 and D21S55 become asynchronous, whereas the early replicating allele of GABRB3 delays replication, leading to relaxation in the imprinted mode of replication. Based on the tight relationship between temporal order of allelic replication and allelic mode of expression, the modified order of allelic replication observed in nonmalignant cells of individuals diagnosed with cancer represents a novel genetic alteration associated with malignancy. This alteration detected by simple cytogenetic means, applied to peripheral blood lymphocytes, offers a potential test for cancer identification. Genes Chromosomes Cancer 27:270-277, 2000.

Time dependency of hematopoietic growth factor coupled to chronotoxicity of carboplatin

A growing body of data suggests that cancer therapy may be improved and toxicity reduced by administration of antineoplastic agents and cytokines at carefully selected times of the day. The time-dependent effects of each of the drugs have been documented, but not their mutual time dependencies. In the present studies we sought to determine the best time for granulocyte colony-stimulating factor (G-CSF) administration after carboplatin treatment. Carboplatin was injected in different groups of ICR mice at four different circadian stages for 5 consecutive days. Mice were synchronized with an alternation of 12 h of light (from 6:00 a.m. to 6:00 p.m.) and 12 h of darkness. After the last injection, peripheral WBCs of three mice from each group were counted every 4 h over a 24-h period. Bone marrow toxicity was estimated with the mean 24-h WBC count. The most severe leukopenia occurred in the group injected at 3:00 p.m. - 9 h after light onset. The second set of experiments evaluated the time-dependent effect of G-CSF when singly injected or given after carboplatin injections for 5 days only at 3:00 p.m. G-CSF was injected into various groups on days 8 and 9 at the same four different circadian stages. On the 10th day after the first injection, peripheral WBCs of three mice from each group were counted every 4 h over a 24-h period. Time-dependent effects were observed when G-CSF was injected as a single agent. When G-CSF was given at various times to the group with the most severe carboplatin-induced leukopenia, peripheral WBC count recovery was monitored at all injection times; it reached its highest level (exceeding even that of the control) when G-CSF was injected at 3:00 a.m. Dosing times of both chemotherapy and growth factor are relevant for optimization of carboplatin's hematologic tolerability.

Daily rhythms in male mice meiosis

Various processes associated with mammalian reproduction exhibit circadian rhythms, yet no information is available concerning the presence of rhythmicity in meiosis-the crucial process of the production of sex cells. Following meiosis in cells derived from male mice exposed in vivo to daily light-dark cycles (LD), we were able to demonstrate the existence of a clear 24h rhythmic pattern in the overall meiotic process, as well as in the production of spermatids, the immediate products of male meiosis and the precursors of male sex cells. On the other hand, cells of free-running male mice exposed to constant external conditions (light-light, LL) revealed a 12h rhythmic pattern in the overall meiotic process, indicating the endogenous nature of this rhythm. The existence of a 24h rhythm component in a long-lasting (approximately 12 days) process like meiosis suggests a time-dependent gating mechanism that controls the dynamics of miocyte arrest and release. The 12h rhythms observed in LL may indicate the presence of either a 12h rhythm component or of two 24h endogenous components, phased 12h from each other, that are coupled in daily LD cycles and split up in the free-running condition (LL). The rhythmic pattern observed in the course of male meiosis might have significant implications for male reproduction.

The Environmental Health Profile (EHP) for the Acre Valley (Israel): xenobiotics in animals and physiological evidence of stress

The scope of this study was to analyse the levels of various xenobiotics in animals, wild and domestic, of the Acre Valley in the north of Israel, the most polluted and dense urbanised part of the country. The focus was placed upon the bioaccumulation of heavy metals, such as Pb, Hg, Cu, Zn, Al, Fe, as well as other elements and PCBs. Analysis was also performed on levels of cholinesterase and acetylcholinesterase in birds and man influenced by insecticides in the same region. For this study we used X-ray scanning electron microscopic (S.E.M.) electron probe, atomic absorption spectrophotometry, gas chromatography for PCBs and biochemical methods specific for enzymes. We studied four species of littoral molluscs, four species of birds and five species of mammals including dogs and cats. The results showed very high levels of metals and PCBs and enzyme deviations in birds and man around the sprayed cotton fields, as compared to man from the close to towns. All the collected data will serve as an Environmental Health Profile for immediate and future consideration.

Long ultradian rhythms in red blood cells and ghost suspensions: possible involvement of cell membrane

Oscillations in glyceraldehyde-3-phosphate dehydrogenase (GAPD) and glucose-6-phosphate dehydrogenase (G6PD) activities were recorded in suspensions of intact human red blood cells (RBCs) exposed to various light regimens. The periods of these oscillations, defined as "long ultradian," ranged between 13 and 18 h regardless of light regimen. The patterns of enzymatic activities were the same when assayed at each time point, in full hypotonic hemolysates, and membrane-free hemolysates. However, if hemolysates were prepared by sonication the activity pattern did not exhibit significant oscillations and the activity was higher than that recorded in hypotonic hemolysates. The observed rhythms may reflect a time-dependent attachment and detachment of enzyme molecules from cell membrane, suggesting that at the bound state the enzyme molecules are (temporarily) inactive. Oscillations with similar long ultradian periods were also observed in Ca++ concentration of suspended RBCs and in the binding of Ca++45 to human RBC ghosts. Treatment of the RBCs with A2C or Diamide before the preparation of the ghosts changed or distorted the rhythmic pattern of Ca++45 binding. These results point to the role of the membrane in processing the long ultradian oscillations. The relation between this type of oscillations to circadian rhythm is discussed.

Increased spindle resistance to antimicrotubule agents in cells prone to chromosomal nondisjunction

The cytological behavior of the spindle apparatus was studied in cells prone to nondisjunction (ND), i.e., PHA-stimulated lymphocytes derived from children suffering from different types of neoplasia. These cells, which exhibited a high frequency of nonspecific aneuploidy, revealed an increased resistance of the spindle fibers to colchicine, podophyllotoxin, and cold, which was several times that of lymphocytes derived from healthy children. The results are in accord with previous findings showing a high resistance of spindle microtubules to the antimicrotubular agents colchicine, podophyllotoxin, vinblastine, and cold in PHA-stimulated lymphocytes derived from individuals prone to meiotic ND. It is therefore assumed that high resistance of the spindle apparatus to antimicrotubule agents characterizes cells at high risk for aneuploidy, and possibly, the overstabilized spindle fibers are responsible for failure of chromosomal disjunction.

Increased spindle resistance to antimicrotubule agents in women of high risk for meiotic nondisjunction

Spindle sensitivity of phytohemagglutinin (PHA)-stimulated lymphocytes to three antimicrotubule drugs was compared in two groups of women who differ in their predisposition to meiotic aneuploidy: young women of low-risk age (ranging from 22 to 34 years) and middle-aged women of high-risk age (ranging from 40 to 52 years). Numerical sensitivity values for the antimicrotubule drugs, colchicine, podophyllotoxin, and vinblastine were obtained for each woman by recording the percentage of fully arrested metaphases out of the total metaphase cell population, i.e., cells exhibiting short, thick, and condensed chromosomes with sister chromatids clearly separated at their distal parts. Sensitivity increased linearly with increasing drug concentrations and was highly correlated with youth: its rate was significantly higher for women of the low-risk group. In addition, dividing lymphocytes of young mothers (26-33 years old) of Down syndrome children revealed significantly lower sensitivity to colchicine and podophyllotoxin than those of all young women of the low-risk group and similar sensitivity to that of the middle-aged women, i.e., the high-risk age group. The data are consistent with the theory that factors involved in meiotic nondisjunction may be concurrently operating in somatic cells. These factors presumably shift the equilibrium between tubulin and microtubules towards microtubules stabilization and thereby affect some of their functions.

Circadian rhythms of enzymes' activity in mice tissues during exposure to continuous illumination

Activity rhythms of enzymes were determined in various tissues of C57BL/6J male mice. The determinations were carried out on mice which were kept in 14 hr light: 10 hr dark regimen, and on day 2, day 5 and day 21 during exposure to continuous illumination. Locomotor activity rhythms were followed in light: dark and up to the seventh day in constant light. All the activities exhibited a significant circadian rhythm in the light: dark regimen. During the exposure to continuous illumination, the locomotor activity exhibit a free running circadian rhythm with a consistent 24 hr and 40 min, major period component. At the same time recording the rhythms of enzyme activity; enzymes exhibited various formats of response which differed from those of the locomotor activity. The results suggest that rhythms of enzyme activity, as well as the desynchronization of the rhythms, are not enzyme specific.