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Biomedical subjects

M Belkin

Publications and source records attributed to M Belkin.

At least 109 records · Page 6Linked to original sources
PubMed1991

Prostaglandin E2 changes in the retina and optic nerve of an eye with injured optic nerve.

Changes in arachidonic acid metabolism were studied in the optic nerve, the chorioretina, and in the vitreous following crush injury to the optic nerve of rats. Crush injury led to: (i) a 3.9-fold increase in optic nerve prostaglandin type E2 in vitro production which peaked on day 5 and was followed by a gradual decline, but was still significantly higher than baseline levels by day 12; (ii) a two-fold increase in the chorioretina prostaglandin type E2 in vitro production which peaked on day 1, and resumed baseline levels by day 3; (iii) a 3.5-fold increase in vitreous prostaglandin type E2 levels on day 1 which remained at 1.5-2 times higher than baseline levels for the rest of the study period (12 days). The findings indicate that the pattern of changes in prostaglandin type E2 production by the optic nerve (consisting mostly of white matter) is different from that described for injured brain tissues. The prolonged accumulation of vitreal prostaglandin type E2 in eyes with damaged optic nerve may lead to undesirable effects on the retina beyond those directly manifested in the retina by altered axonal flow in the injured optic nerve.

Animals↗
PubMed1991

Long-term follow-up of patients operated on for recurrent carotid stenosis.

We reviewed our experience with 29 operations for recurrent carotid stenosis in 27 patients who underwent both their primary carotid endarterectomy and their reoperations at our institution. These 27 patients represent 4% of the 667 patients who underwent primary carotid endarterectomies at our institution and who are included in our carotid follow-up registry. Reoperation was prompted by recurrent symptoms in 19/29 (65.5%) cases. Comparison of long-term stroke prevention in those patients who did (84% at 5 years, 78.6% at 10 years) and did not (90.3% at 5 years, 83.6% at 10 years) develop recurrent stenosis requiring reoperation revealed no statistically significant difference (p = 0.48) when measured from the time of primary operation. The perioperative stroke and death rates for reoperation (3.4% and 0%) were acceptable. We conclude that with our acceptably low perioperative stroke morbidity (3.4%), surgery for recurrent carotid stenosis in symptomatic patients or in asymptomatic patients with high-grade (greater than or equal to 75%) stenosis maintains the durable stroke prevention offered by primary carotid endarterectomy.

Carotid Arteries↗
PubMed1991

Evaluation of accommotrac biofeedback training for myopia control.

A new treatment for myopia, biofeedback training for control of accommodation, has been proposed and developed over the past decade. Various reports in the literature show marked inconsistencies in the results of such treatment. A double-masked study with experimental and control groups of 15 subjects each was designed to obtain a definitive answer concerning the efficacy of this method. The parameters evaluated were visual acuity, cycloplegic and noncycloplegic retinoscopy, subjective refraction, amplitude of accommodation, and flexibility of accommodation. In all categories no significant difference was found between the control and experimental subjects. The consequences of these findings are discussed as to the benefit of treatments using this method and avenues to explore in future studies.

Accommodation, Ocular↗
PubMed1991

New surgical approach to overcome the inability of injured mammalian axons to grow within their environment.

We present a new method for creating conditions conductive to axonal growth in injured optic nerves of adult rabbits. The surgical approach consists of making a cavity in the adult rabbit optic nerve, into which a piece of nitrocellulose soaked with conditioned medium originating from regenerating fish optic nerves is implanted. In addition, daily irradiation (10 days, 5 min, 35 mW) with low energy He-Ne laser is carried out. Such a combined treatment may open a door to neurobiologists and clinicians, hoping to unravel the enigma of mammalian CNS regeneration.

Animals↗
PubMed1991

Modification of the thrombogenicity of a self-expanding vascular stent.

When placed in the iliac arteries of normal healthy animals, the Wall-stent self-expanding endovascular prosthesis exhibits minimal thrombogenicity, measured by 111In-labeled platelet uptake. Preliminary clinical reports suggest a greater thrombogenicity in diseased human arteries. When evaluated in an ex vivo shunt, these stents exhibit significant thrombogenicity. The ex vivo shunt may therefore provide a model to evaluate strategies to reduce thrombogenicity in the clinical setting. Stents were released into shunts and the uptake of In111-labeled platelets was measured by gamma imaging for 2 h at a flow rate of 100 mL/min. The effect of systemic heparin, 100 U/kg, oral aspirin, 325 mg, and local application of heparin-benzalkonium chloride complex were evaluated. At the end of each study the stents were fixed in situ and evaluated with scanning electron microscopy (SEM). Control stents exhibited a rapid, significant uptake of platelet associated 111In activity, which reached a maximum in approximately 1 h. Twenty-two percent of control stents occluded before 2 h. Aspirin reduced maximum platelet uptake by 46%. Systemic heparin, with a clotting time greater than five times control, reduced maximum platelet uptake by 86%. The benzalkonium-heparin complex coating, with no increase in clotting time, reduced maximum platelet uptake by 84%. No occlusions were observed with the anti-thrombotic regimes. SEM evaluation of the stents supports the results of the isotope uptake studies.

Animals↗
PubMed1991

A nation-wide study of myopia prevalence in Israel. Findings in a population of 312,149 young adults.

We conducted a nation-wide survey of the Prevalences of Myopia and other refractive errors in Israel, from data of medical examinations of an unselected population of 312,149 subjects ages 17 to 19 years. 80.47% of the population were emmetropic in both eyes. Myopia in both eyes was found in 16.27% of the population. The prevalence of monocular myopia was 1.69%. Manifest hyperopia in both eyes was found in 0.93% and astigmatism at least in one eye was found in 7.13%. The various errors of refraction (myopia, hyperopia and astigmatism) were more common among females.

Adolescent↗
PubMed1990

Growth of injured rabbit optic axons within their degenerating optic nerve.

Spontaneous growth of axons after injury is extremely limited in the mammalian central nervous system (CNS). It is now clear, however, that injured CNS axons can be induced to elongate when provided with a suitable environment. Thus injured CNS axons can elongate, but they do not do so unless their environment is altered. We now show apparent regenerative growth of injured optic axons. This growth is achieved in the adult rabbit optic nerve by the use of a combined treatment consisting of: (1) supplying soluble substances originating from growing axons to be injured rabbit optic nerves (Schwartz et al., Science, 228:600-603, 1985), and (2) application of low energy He-Ne laser irradiation, which appears to delay degenerative changes in the injured axons (Schwartz et al., Lasers Surg. Med., 7:51-55, 1985; Assia et al., Brain Res., 476:205-212, 1988). Two to 8 weeks after this treatment, unmyelinated and thinly myelinated axons are found at the lesion site and distal to it. Morphological and immunocytochemical evidence indicate that these thinly myelinated and unmyelinated axons are growing in close association with glial cells. Only these axons are identified as being growing axons. These newly growing axons transverse the site of injury and extend into the distal stump of the nerve, which contains degenerating axons. Axons of this type could be detected distal to the lesion only in nerves subjected to the combined treatment. No unmyelinated or thinly myelinated axons in association with glial cells were seen at 6 or 8 weeks postoperatively in nerves that were not treated, or in nerves in which the two stumps were completely disconnected. Two millimeters distal to the site of injury, the growing axons are confined to a compartment comprising 5%-30% of the cross section of the nerve. A temporal analysis indicates that axons have grown as far as 6 mm distal to the site of injury, by 8 weeks postoperatively. Anterograde labeling with horseradish peroxidase, injected intraocularly, indicates that some of these newly growing axons arise from retinal ganglion cells.

Animals↗
PubMed1990

[Ocular injuries from seashore racketball].

A 3-year prospective study revealed 39 hospitalized cases of ocular injuries from seashore racketball sports. Most were children and young adults and most had internal injuries of the globe. Over a third had retinal edema, 2 eyes were blinded, and at least 4 are subject to serious future complications.

Adult↗
PubMed1990

Eye injuries in children in Israel. A nationwide collaborative study.

A nationwide prospective collaborative study on ocular trauma was performed in Israel during a period of 3 years (1981 through 1983). Almost half of the traumas (1127 [47%] of 2416 eyes) were sustained by children younger than age 17 years, and mainly between the ages of 6 and 12 years. Most of the injuries happened at home (38.1%) or in the street (26.8%) and during play and sport (65.1%). The male-to-female ratio among the children was 4:1. Blunt injuries accounted for 59.2%; 30.5% were perforating injuries and the rest were chemical and radiation injuries. The visual acuity at the time of hospital discharge was better than 6/30 in the majority of the eyes but 122 patients (11%) had a visual acuity of less than 6/60, and no light perception was the result in 40 eyes (3%). The reasons for the severe outcome were as follows: 23 eyes (2%) owing to phthisis, 22 eyes (1.9%) were enucleated, and 16 eyes (1.4%) suffered from endophthalmitis.

Adolescent↗
PubMed1990

Low-energy laser irradiation--a new measure for suppression of arachidonic acid metabolism in the optic nerve.

Helium-neon low-energy laser (LEL) irradiation, known for its therapeutic effects in arthritis, wound healing, and muscular strain, was applied to eyes of rats that had sustained an optic nerve crush injury. Crush injury to the optic nerve resulted in a long-lasting in vitro elevation of prostaglandin E2 (PGE2) production (1.8-3.9-fold above control values during the 12 day study period). LEL irradiation per se had no effect in vitro on PGE2 production by the optic nerve; however, LEL irradiation of eyes with crushed optic nerve inhibited the enhanced production of PGE2 and leukotriene B4 in vitro by 55% and 75% during the late and immediate phase after trauma, respectively. Our findings of the suppressive effect of LEL irradiation on arachidonic acid metabolism are reminiscent of the actions of steroidal and nonsteroidal anti-inflammatory drugs, and might indicate, for the first time, the possible biochemical mechanisms associated with the clinical anti-inflammatory effects of LEL irradiation.

Animals↗
PubMed1990

Combined transluminal angioplasty and infrainguinal reconstruction in multilevel atherosclerotic disease.

Patients with multilevel atherosclerotic disease represent a difficult surgical challenge. This report is a retrospective review of 46 patients who were treated using a combination of iliac transluminal angioplasty and infrainguinal reconstruction. There were 42 male and 4 female patients with an average age of 62 years (range: 40 to 74 years). Follow-up ranged from 1 month to 10 years (mean: 27.3 months). These patients had multiple health problems typical of patients with peripheral vascular disease, including coronary artery disease (67%), hypertension (61%), and diabetes mellitus (42%); 80% of the patients were smokers. Forty-one patients were treated for rest pain and/or tissue loss, while five were treated for incapacitating claudication. Forty-three patients had a combination of angioplasty and distal bypass, while 3 patients had a form of femoral endarterectomy. Iliac artery pressure gradients were reduced from 35.4 +/- 4 mm Hg preangioplasty to 0.6 +/- 0.3 mm Hg postangioplasty. The procedures were well tolerated with no mortality and four serious complications. Vascular laboratory studies showed an improvement in the mean ankle-brachial index from 0.35 +/- 0.03 preoperatively to 0.71 +/- 0.04 postoperatively (p less than 0.05). Life-table analysis revealed a 72% 5-year primary patency rate, with a 93% 5-year limb salvage. Eight patients required a secondary procedure to maintain limb salvage. Five patients underwent amputation, three due to early graft thrombosis and two due to late graft failure. We conclude that combined iliac angioplasty and infrainguinal reconstruction is a safe and effective method for managing the patient with severe multilevel atherosclerotic disease.

Adult↗
PubMed1990

Iloprost infusion decreases skeletal muscle ischemia-reperfusion injury.

Iloprost (a long-acting prostacyclin analog) has been demonstrated to decrease cardiac muscle infarct size after ischemia-reperfusion injury. We investigated the ability of iloprost to decrease skeletal muscle injury and platelet sequestration after ischemia-reperfusion injury in a canine bilateral isolated gracilis muscle model. Anesthesized animals (n = 13) were subjected to 6 hours of gracilis muscle ischemia and 1 hour of reperfusion. Fifteen minutes before muscle reperfusion, the animals were infused with radium 111-labeled autogenous platelets. Experimental animals (n = 7) received a continuous preischemic intravenous infusion of iloprost (0.45 microgram/kg/hr) and two 0.45 microgram/kg intravenous injections of iloprost (10 minutes before the ischemic interval and 10 minutes before reperfusion). Muscle injury was measured with triphenyltetrazolium chloride histochemical staining. Platelet sequestration within ischemic muscle specimens was determined by measuring indium 111 activity in a gamma counter. Iloprost infusion decreased muscle infarct size from 57.0% +/- 12.6% in control animals to 15.8% +/- 4.4% in experimental animals (p less than 0.05). Platelet uptake in experimental and control muscle was 1.2 +/- 0.21 x 10(7) and 2.17 +/- 0.48 x 10(7) platelets/gm ischemic muscle, respectively (p = 0.1). Although platelet sequestration was not altered significantly in this experiment, a reduction in skeletal muscle injury was confirmed. Further investigation on the mechanisms of action of iloprost in chronic and acute skeletal muscle ischemia is warranted.

Animals↗
PubMed1990

Observations on the use of thrombolytic agents for thrombotic occlusion of infrainguinal vein grafts.

Vein graft failure remains a major challenge for the vascular surgeon. Thrombolysis of occluded vein grafts has shown promising short-term results in restoring vein graft patency, however, the long-term results are not established. This study examines the long-term patency and limb salvage after successful thrombolysis and revision of 22 thrombosed vein grafts in 21 patients. There were 17 men and four women with an average age of 60 years (38 to 77 years). Failed vein grafts had an average primary patency of 19 months (1 to 84 months) and included eight in situ grafts and 14 non-in situ grafts. Twelve grafts were to the popliteal level, whereas 10 were infrapopliteal. Thrombolytic agents used included urokinase (15), tissue plasminogen activator (5), and streptokinase (2). After successful thrombolysis, 19 grafts underwent 26 additional procedures including percutaneous transluminal angioplasty (9), vein patch angioplasty (4), vein interposition or jump extension graft (9), or other procedures (4). Three patients had no additional procedure, but one was placed on sodium warfarin (Coumadin). After successful initial vein graft salvage, life-table analysis revealed a 36.6% +/- 11.9% patency at 1 year and a 22.9% +/- 11.6% patency at 3 years. After secondary failure six patients had further interventions contributing to an improved limb salvage of 66.9% +/- 11.6% at 1 year and 60.3% +/- 19.0% at 3 years. The results suggest that thrombosed vein grafts initially salvaged with thrombolysis and revision do not have a favorable long-term patency, and that a premium must be placed on the detection of the failing vein graft before thrombosis.

Adult↗
PubMed1990

Screening for hypercoagulable states in vascular surgical practice: a preliminary study.

The prevalence and importance of hypercoagulable states in the general vascular surgical population is unknown. Antithrombin III, protein C, protein S, plasminogen, lupus-like anticoagulant, and heparin-induced platelet activation were determined prospectively in 158 patients with aneurysmal (27), renovascular (1), cerebrovascular (28), aortoiliac (31), or infrainguinal (71) disease. Sixteen abnormal test results were obtained in 15 patients (9.5%) as follows: deficiencies of antithrombin III (2), protein C (4), and protein S (1) and presence of lupus-like anticoagulant activity (5) and heparin-induced platelet activation (4). Reconstructive surgery was performed in 137 of the study patients. Five reconstructions, all infrainguinal bypass grafts, suffered thrombosis within 30 days. Early graft thrombosis occurred in three (27%) of 14 patients with abnormal preoperative test results compared to two (1.6%) of 123 patients with normal testing (p less than 0.01). Of the three patients with abnormal test results and graft thrombosis, lupus-like anticoagulant was detected in two and heparin-induced platelet activation in one. This preliminary study supports routine preoperative screening for lupus-like anticoagulant and heparin-induced platelet activation in patients undergoing infrainguinal reconstruction. Hypercoagulable states appear to be sufficiently common and important in the general vascular surgical population to warrant further investigation.

Adult↗
PubMed1990

Prostanoids in the vitreous of diabetic and nondiabetic human eyes with retinal detachment.

We measured prostaglandin E2 (PGE2) and prostacyclin levels in the vitreous bodies of 5 eyes of patients with diabetic retinopathy complicated by rhegmatogenous retinal detachment (RRD) and compared them with the corresponding levels in 9 nondiabetic eyes with the same condition as well as with 10 control eyes of deceased patients with no known ocular pathology. We also studied the effect of surgical retinal reattachment on vitreal PGE2 and prostacyclin levels in 4 eyes. Vitreal samples from both nondiabetic and diabetic eyes with RRD were obtained during vitrectomy, while samples from deceased subjects (controls) were obtained 2-6 h after death. Vitreal PGE2 and prostacyclin levels in the control eyes approximated plasma levels (79.9 +/- 20.5 and 124.5 +/- 38.5 pg/ml, means +/- SD, respectively), while RRD in the nondiabetic eyes was associated with increased levels of both PGE2 and prostacyclin (3,170 +/- 3,024 and 467 +/- 283 pg/ml, respectively). In the diabetic eyes with diabetic retinopathy complicated by RRD, all of which underwent retinal photocoagulation, PGE2 and prostacyclin levels were 2-4 times lower than those of the nondiabetic eyes with detached retina. Following surgical retinal reattachment, vitreal levels of both components in diabetics and nondiabetics showed a reduction suggesting that the surgical procedure for obtaining vitreal samples was not the cause for elevated prostaglandin levels in the eyes with detached retina. We showed that RRD is associated with an excessive accumulation of PGE2 and prostacyclin in the vitreous, which is higher in nondiabetic than in diabetic eyes, indicating that diabetic retinopathy in laser-treated eyes might lead to reduced vitreal levels of these metabolites.

Adult↗
PubMed1989

Temporal parameters of low energy laser irradiation for optimal delay of post-traumatic degeneration of rat optic nerve.

Compression injury of a central nerve results in its degeneration with irreversible loss of function due to the inability of the mammalian central nervous system (CNS) to regenerate. In contrast, the CNS of lower vertebrates has a high capacity to regenerate. Recently, low energy laser irradiation was shown to attenuate degeneration in injured CNS nerves. The optic nerves of rats were subjected to moderate crush, calibrated so that some electrophysiological activity was preserved. The nerves were then subjected to low energy laser irradiation (10.5 mW, 2 min daily) for various periods. The electrical activity of the nerves, distal to the site of injury, was determined by measuring the compound action potential at the termination of the experiment. Two weeks of irradiation begun immediately after injury and continued daily thereafter, resulted in a compound action potential which was significantly higher (mean +/- S.E.M. 1856 +/- 535 microV) than that of non-irradiated injured nerves (351 +/- 120 microV). The effect was temporary and subsided within a week. This two-week irradiation was slightly more effective than a treatment lasting one week (1406 +/- 225 microV) and was significantly more effective than 4 days of irradiation (960 +/- 133 microV). The number of treatments is therefore important. The time at which the treatment commences relative to the injury is also critical. Irradiation initiated two hours after the crush was about half as effective as immediate irradiation (810 +/- 42 microV). No apparent effect was evident when the laser was applied for the first time 5 h, or longer, after the crush.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗