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Biomedical subjects

M Belkin

Publications and source records attributed to M Belkin.

At least 55 records · Page 3Linked to original sources
PubMed1997

MK-801 has neuroprotective and antiproliferative effects in retinal laser injury.

PURPOSE: Treatment of the retina by laser photocoagulation often is complicated by an immediate side effect of visual impairment, caused by unavoidable, laser-induced destruction of healthy tissue adjacent to the lesion. A neuroprotective therapy that salvages this healthy tissue might enhance the benefit obtained from the treatment. This study was proposed to determine whether glutamate-receptor blockers can provide adjuvant neuroprotection during laser photocoagulation. The effect of MK-801, an NMDA-receptor antagonist, on laser-induced retinal injury was examined, in a rat model. METHODS: Argon laser lesions were created in the retinas of 36 DA rats, and were followed immediately by intraperitoneal injections of MK-801 (2 mg/kg) or saline. The animals were killed after 3, 20, or 60 days and the retinal lesions were evaluated histologically and morphometrically. RESULTS: Photoreceptor-cell loss was significantly less in MK-801-treated rats than in control animals. The proliferative membrane composed of retinal pigment epithelial cells and neovascular blood vessels, which was seen at the base of the lesion in control group retinas, was smaller in the MK-801-treated retinas. In rats treated with a higher dose of MK-801, the lesions showed almost no proliferative reaction. CONCLUSIONS: A potent noncompetitive NMDA-receptor blocker, MK-801 exhibits neuroprotective and antiproliferative properties in the retina. Glutamate-receptor blockers should be investigated further as potential adjuvant therapy in retinal photocoagulation treatments.

Animals↗
PubMed1996

Infrainguinal arterial reconstruction with nonreversed greater saphenous vein.

PURPOSE: This study was undertaken to examine the effectiveness and the possible advantages of infrainguinal arterial reconstruction with nonreversed greater saphenous vein (NRGSV) grafts. We reviewed the results achieved with 189 consecutive NRGSV bypass procedures from July 1, 1985, to August 31, 1995, and compared them with 568 consecutive in situ greater saphenous vein (INGSV) bypass procedures completed over the same interval. METHODS: NRGSV bypass procedures were performed by selecting the optimum inflow and outflow vessels and then excising the best available appropriate-length segment of greater saphenous vein. The valves were lysed with a Mills valvulotome using gentle antegrade distention with an isotonic electrolyte solution containing heparin (1000 U/500 ml) and papaverine (60 mg/500 ml). The graft was then translocated to the inflow site, where the proximal and distal anastomoses were sequentially completed, followed by a completion arteriography. RESULTS: Demographic and risk factor characteristics did not differ between patients who underwent NRGSV and those who underwent INGSV bypass. Compared with INGSV bypasses, NRGSV bypasses were more commonly secondary procedures (26% vs 8%; p < 0.001) and were more often performed for limb salvage indications (89% vs 68%; p < 0.001). NRGSV bypasses also had more distal inflow vessels (23% superficial femoral artery [SFA] and 28% popliteal artery [POP] vs 10% SFA and 1% POP; p < 0.001) and more distal outflow vessels (52% tibial and 22% pedal artery vs 47% tibial and 3% pedal artery; p < 0.001) than did INGSV bypasses. Despite the higher incidence of secondary bypass procedures and more distal outflow vessels in the NRGSV group, the overall results achieved at 5 years did not differ between the two groups. The 5-year primary patency rates were 65% +/- 5% for NRGSV and 72% +/- 3% for INGSV (p < 0.12), and the 5-year secondary patency rates were 74% +/- 5% and 82% +/- 2% (p < 0.08), respectively. Similarly, the 5-year limb salvage rate among bypass procedures performed for limb salvage indications did not differ for NRGSV (82% +/- 5%) and INGSV (90% +/- 2%; p < 0.06). CONCLUSIONS: The application of the NRGSV bypass graft preserves the INGSV's main advantage of optimal size match between artery and vein at each anastomosis, but facilitaties the tailoring of the procedure to the patients anatomy and the completion of the bypass with the shortest, best-quality conduit available. Our application of the NRGSV in a more challenging series of bypass procedures produced equivalent results to those achieved in a concurrent series of INGSV bypass procedures.

Aged↗
PubMed1996

Improvement in results of repair of type IV thoracoabdominal aortic aneurysms.

PURPOSE: Although management of extensive type I and II thoracoabdominal aortic aneurysms (TAA) remains a formidable challenge, results of repair of TAA originating in the distal thoracic aorta (type IV) appear to have improved significantly. To quantitate this perceived improvement, the following retrospective study was undertaken to examine the results of type IV TAA repair at the Brigham & Women's Hospital over the past 18-year period. METHODS: From July 1977 to September 1994, nonruptured atherosclerotic type IV TAAs were repaired in 58 patients. The mean age was 70 years, and associated risk factors included smoking (91%), hypertension (86%), coronary artery disease (52%), and previous aortic surgery (38%). Mean follow-up was 2.4 years (median 2 years). RESULTS: Overall 30-day mortality was 5.3% (two deaths). Morbidity included stroke (3.5%), paraplegia (1.8%), permanent paraparesis (1.8%), myocardial infarction (7%), pneumonia (8.8%), gastrointestinal bleeding (11%), intestinal ischemia (5.3%), wound infection (7.0%), peripheral ischemia (5.3%), in-hospital dialysis (8.8%), and permanent dialysis (1.9%). Overall 5-year survival was 50%. With univariate analysis, survival was positively correlated with more recent year of operation (p = 0.002), smaller volume of intraoperative blood transfusion (p = 0.02), decreased supraceliac ischemia time (p = 0.04), and the use of the retroperitoneal approach (p = 0.09). Multiple regression analysis revealed that the year of operation was the only independent predictor of survival (p = 0.003). Subgroup analysis of patients who underwent operation between 1977 and 1987 (n = 13) and 1988 and 1994 (n = 45) revealed statistically significant improvements in length of hospital stay (46 +/- 12 vs 21 +/- 4 days, p = 0.02), postoperative dysrhythmia (50% vs 16%, p = 0.03), postoperative maximum serum glutamic oxaloacetic-transaminase (516 +/- 234 vs 319 +/- 139 mg%, p = 0.04), incidence of hemorrhage requiring reexploration (33% vs 0%, p = 0.002), 30-day mortality (23% vs 0%, p = 0.009), and in-hospital mortality (39% vs 2.2%, p = 0.002). CONCLUSIONS: The modern mortality, morbidity, and survival of surgical repair of type IV TAA in our institution approaches that of infrarenal abdominal aortic aneurysm.

Aged↗
PubMed1996

HU-211, a nonpsychotropic cannabinoid, produces short- and long-term neuroprotection after optic nerve axotomy.

HU-211 is a novel synthetic analog of tetrahydrocannabinol that was recently shown in animal models to be nonpsychotropic. In this study we show that HU-211 can potentially be used as a neuroprotective compound in the CNS. Using a calibrated crush injury of adult rat optic nerve, we show that HU-211 can reduce injury-induced metabolic and electrophysiological deficits. Energy metabolism was monitored by measuring the intramitochondrial nicotine-amine adenine dinucleotide redox state hourly for 6 h after injury and treatment. Electrophysiological activity was assessed by compound action potential and visual evoked potential response. Beneficial effects were dose-dependent, being optimal at 7 mg/kg, administered intraperitoneally. The time window during which treatment was effective was found to be from the time of injury for at least 5 h, with treatment most effective at the time of injury. These results strongly suggest that HU-211, given immediately after CNS injury at the optimal dosage, may possess neuroprotective activities.

Action Potentials↗
PubMed1996

Brain edema after carotid surgery.

The postoperative hyperperfusion syndrome describes an abrupt increase in blood flow with loss of autoregulation in surgically reperfused brain. Reports described a spectrum of findings, including severe headache, transient ischemia, seizures, and intracerebral hemorrhage. Hypertension is common after carotid artery surgery and often plays a role in the pathophysiology. We now report five patients with severe white matter edema after carotid surgery, a finding not previously included in the hyperperfusion syndrome. Five to 8 days after carotid surgery and after hospital discharge, each patient developed hypertension, headache, hemiparesis, seizures, and aphasia or neglect due to severe white matter edema ipsilateral to the carotid surgery. One patient had a small hemorrhage within the edematous area. Hypertension was severe in four patients and moderate in one. The carotid artery was patent by ultrasound or angiography in each patient after surgery. Transcranial Doppler showed increased velocities ipsilateral to surgery in two patients and bilaterally in one. Computed tomographic abnormalities and neurologic signs resolved within 3 weeks in four of the five patients treated with antihypertensives and anticonvulsants. The fifth patient died from herniation secondary to massive edema. Brain edema with focal neurologic signs should be included as a serious but potentially reversible component of the postoperative hyperperfusion syndrome.

Aged↗
PubMed1996

Clinical assessment of Holo-Or trifocal diffractive contact lens.

PURPOSE: To evaluate the objective and subjective performance of the Holo-Or multifocal contact lens, a new rigid gas permeable (RGP) trifocal diffractive contact lens. METHODS: Eleven experienced and two non-experienced RGP contact lens wearers participated in the study. Eleven patients were presbyopic (age range: 40-57 years) and two were aphakic (ages: 12 and 14 years). Each patient was evaluated by comparing best spectacle correction to Holo-Or multifocal contact lens correction, using the following tests of visual function: visual acuity at 6 m, 80 cm, and 40 cm; contrast sensitivity at near and distance; and depth of focus. RESULTS: No significant differences were found between best spectacle correction and the Holo-Or contact lenses. When using the contact lenses, there was an improvement in depth of focus and a small reduction in contrast sensitivity compared with best spectacle correction. Overall satisfaction and comfort was good to excellent in ten of thirteen patients. CONCLUSIONS: Holo-Or trifocal diffractive contact lenses are a satisfactory means of optical correction for patients with presbyopia or accommodative problems.

Adult↗
PubMed1996

Potential treatment modalities for glaucomatous neuropathy: neuroprotection and neuroregeneration.

PURPOSE: This article presents the rationale and an experimental strategy for the development of new treatment modalities for glaucomatous neuropathy. Accumulating evidence suggests that regardless of the primary trigger of the retinal and optic nerve damage in glaucoma, the disease will continue to progress even when the cause is removed. The resulting damage can be mimicked by the progression of damage secondary to an acute partial crush injury at the optic nerve head. Such secondary damage includes degeneration of the directly injured optic nerve fibers culminating in death of their cell bodies, as well as degeneration of nerve fibers that escaped acute injury but nevertheless deteriorate as a result of their exposure to injury-induced mediators of secondary degeneration released by the directly affected neurons. CONCLUSION: We therefore propose that substances found to be effective in rescuing fibers from secondary degeneration and in increasing the survival rate or prolonging survival of retinal ganglion cells in the partially lesioned optic nerve may be useful for the treatment of glaucoma. The new approach does not replace hypotensive therapy, but addresses the glaucoma-induced damage by promoting nerve protection and neuroregeneration.

Animals↗
PubMed1995

The impact of gender on the results of arterial bypass with in situ greater saphenous vein.

BACKGROUND: This 10-year review of in situ saphenous vein bypass surgery was undertaken to assess the impact of gender on infrainguinal arterial reconstruction. PATIENTS AND METHODS: From March 1983 to March 1993, the results of 244 in situ saphenous vein bypasses performed in women were compared with 338 performed in men. Women were older than men (70.9 versus 66.8 years; P < 0.001) and had a higher incidence of hypertension but a lower incidence of coronary artery disease, smoking history, and chronic obstructive pulmonary disease. The primary indication for surgery was limb salvage for both genders (women 70.1%, men 68%; P = not significant [NS]). Men had bypasses to more-distal outflow vessels with 52.5% to the tibial level compared with 42.2% of women (P < 0.003). RESULTS: Women had lower perioperative mortality rates than men (0.8% versus 3.3%; P < 0.025) and a similar incidence of major complications (6.6% versus 7.7%; P = NS), but a higher incidence of significant wound complications (13.5% versus 3.3%; P < 0.001). Life-table evaluation at 10 years after surgery showed no significant differences between women and men in primary graft patency rate (67.8% versus 58.2%; P = NS), secondary patency rate (73.5% versus 77.2%; P = NS ), limb salvage rate (87.9% versus 92%; P = NS) or patient survival rate (35.5% versus 24.4%; P = NS). For bypasses to the tibial arteries, graft patency rates were slightly inferior for women (69.8% versus 81.1%, 5-year secondary patency rate; P < 0.008). Similarly, in bypasses performed for limb salvage, women had lower 5-year primary patency rates than men (60.3% versus 70.3%; P < 0.002). Secondary patency rates in this limb salvage group however, did not differ (75.5% versus 82.8%; P = NS). CONCLUSIONS: Despite small gender differences in the results of in situ bypass grafts for limb salvage and those carried to the tibial level, women had the same overall patency, limb salvage, and survival rates as men after infrainguinal bypass surgery. Treatment of infrainguinal occlusive disease should not vary based on inaccurate perceptions concerning differences in surgical results for men and women.

Aged↗
PubMed1995

Contralateral intracerebral hemorrhage after carotid endarterectomy.

Postoperative intracerebral hemorrhage is a rare but devastating complication of carotid endarterectomy. Intracerebral hemorrhage on the side contralateral to the carotid endarterectomy has been reported only twice before in the literature. We present a case of fatal postoperative right intracerebral hemorrhage after left carotid endarterectomy in an 81-year-old patient. A review of the literature and a discussion of the pathophysiology of this condition is presented.

Aged↗
PubMed1995

Femorotibial bypass for claudication: do results justify an aggressive approach?

PURPOSE: The role of infrainguinal arterial reconstructive surgery for claudication is controversial. We reviewed the results of femorotibial bypass procedures performed in a select group of patients with disabling claudication in an attempt to define a role for this aggressive approach. METHODS: Data were retrieved from the vascular registry, and hospital records were obtained for all patients undergoing femorotibial reconstruction for disabling claudication during the past 16 years at Brigham and Women's Hospital. Follow-up interviews were obtained to assess overall health, walking impairment, functional status, and patient satisfaction. RESULTS: During a 16-year period a total of 57 tibial reconstructions were performed in 53 patients for claudication (5% of all infrainguinal vein reconstructions). Autogenous vein conduit was used in all cases, most of which (70%) involved the greater saphenous vein in situ. Distal anastamoses were to the tibioperoneal trunk (12%), anterior tibial (18%), posterior tibial (47%), and peroneal (23%) arteries. Major complications occurred in 9%, and no perioperative deaths occurred. Overall 5-year survival was 54% +/- 15%, and no major amputations were performed. Cumulative primary and secondary graft patency at 5 years were 81% +/- 6% and 86% +/- 5%, respectively. Patency rates were significantly better than those achieved in a concurrent series of tibial bypasses for limb salvage and were equivalent to those achieved with femoropopliteal bypass for claudication. Interviewed patients reported improved walking distance, reduced claudication, and a high degree of overall satisfaction with their operation. CONCLUSION: Results obtained with femorotibial bypass performed for claudication were superior to those obtained for limb salvage and were equivalent to those obtained with femoropopliteal bypass for claudication. The results obtained in this highly selected cohort suggest that patients at low risk with significant functional impairment from claudication, available autogenous vein, and suitable tibial outflow to the ischemic muscular bed can be offered revascularization with the expectation of durable long-term results.

Adult↗
PubMed1995

Safety and efficacy of transaortic renal endarterectomy as an adjunct to aortic surgery.

PURPOSE: A study was undertaken to assess the safety and efficacy of transaortic endarterectomy for orificial atherosclerotic renovascular disease (ASRD), particularly in conjunction with surgery for concomitant aortic disease. METHODS: Forty-three consecutive patients with ASRD treated with transaortic orificial eversion endarterectomy were studied retrospectively to identify surgical indications, technical features, operative morbidity and mortality rates, and efficacy. RESULTS: A total of 76 renal arteries underwent transaortic endarterectomy for hypertension (88% of patients) or serum creatinine of 1.5 mg/dl or greater (65% of patients), including two patients undergoing dialysis. Concomitant aortic surgery was performed in 39 patients for aneurysmal (n = 30) or occlusive (n = 9) disease. Two (2.6%) of 76 renal endarterectomies required intraoperative conversion to bypass because of poor flow, and three arteries (3.9%) were reimplanted or bypassed because of fragility of the renal orifice after endarterectomy. Thirty-day operative death occurred in two patients (4.7%), and major morbidity occurred in six (14.0%). Hypertension was cured or improved in 83% of patients with hypertension. Among patients with preoperative renal insufficiency, function was improved in 19%, with dialysis discontinued in one of two patients receiving dialysis, and function was worse in 23%, with one patient dependent on dialysis. CONCLUSION: Transaortic renal endarterectomy is an acceptably safe and effective adjunctive technique in selected patients with combined aortic disease and ASRD.

Aged↗
PubMed1995

Preferred strategies for secondary infrainguinal bypass: lessons learned from 300 consecutive reoperations.

PURPOSE: To determine the optimal surgical strategies in reoperative infrainguinal bypass, we reviewed our results in 300 consecutive secondary bypasses in 251 patients operated on between Jan. 1, 1975, and Nov. 1, 1993. METHODS: There were 168 men (67%) and 83 women (33%), with a mean age of 64.8 years and a typical distribution of risk factors including smoking (76.4%), diabetes (33.7%), and coronary artery disease (47.1%). The indications for surgery were limb-threatening ischemia in 83.5% and severe claudication in 16.5% of patients. The majority of conduits (n = 213) were autogenous vein and were composed of a single segment of greater saphenous vein in 121 bypasses (57%) and various alternative veins including composite, arm, and lesser saphenous vein in 92 bypasses (43%). Prosthetic conduits included 69 polytetrafluoroethylene, 16 umbilical vein, and two Dacron grafts. RESULTS: There was one perioperative death (0.3%) and a 25% total morbidity rate including a 1.7% myocardial infarction rate. There was a 28.6% early (< 30 days) graft failure and 10.7% early amputation rate for prosthetic bypass grafts compared with 13.6% early graft failure and 5.6% early amputation rates for vein grafts. Autogenous vein bypasses had higher 5-year secondary patency rates than had prosthetic grafts (51.5% +/- 4.6% vs 27.4% +/- 6.1%, p < 0.001). Results with autogenous vein bypass improved significantly from the 1975 to 1984 to the 1985 to 1993 interval with 5-year secondary patency rates increasing from 38.3% +/- 6.9% to 59.1% +/- 5.8% (p = 0.017) and 5-year limb-salvage rates increasing from 40.4% +/- 7.6% to 72.4% +/- 6.6% (p < 0.001). Vein grafts to the popliteal and tibial outflow levels had equivalent long-term results. Vein grafts completed for claudication demonstrated results superior to those for limb salvage, with a 5-year secondary patency rate of 75.8% +/- 8.1% versus 52.3% +/- 7.9% (p = 0.048). Secondary autogenous vein bypass grafting performed after early primary graft failure (< 3 months) did particularly poorly, with only a 27.2% +/- 7.7% 4-year secondary patency rate. Greater saphenous veins tended to perform better than alternative vein bypasses, with a 5-year secondary patency rate of 68.5% +/- 6.0% compared with 48.3% +/- 10.5% (p = 0.09) and a 5-year limb-salvage rate of 77.8% +/- 7.4% versus 54.2% +/- 11.8% (p = 0.046). CONCLUSIONS: When patients suffer a recurrence of limb-threatening ischemia at the time of infrainguinal graft failure, aggressive attempts at secondary revascularization with autogenous vein are warranted based on the low surgical morbidity and mortality rates and the improved patency and limb salvage rates that are currently attainable.

Amputation, Surgical↗
PubMed1995

The Israeli ocular injuries study: incidence of legal blindness from ocular trauma.

A 3 year nationwide study of the incidence of hospitalized civilian ocular injuries was conducted in Israel between October 1981 and September 1984. Of the 2,276 hospitalized cases (2,416 eyes), 457 resulted in unilateral, and 6 in bilateral legal blindness. These figures represent an average annual incidence rate of legal blindness of 3.8/100,000 persons, which was highest among 6-17 year olds (4.9/100,000). Injuries sustained in road accidents were the most highly morbid, resulting in blindness in 34% of road accident victims. Sports injuries accounted for 5% of all injured eyes and led to blindness in 10% of the cases so injured. Blindness resulting from injury occurs among people of all ages, often leads to a lifelong disfiguring disability, and increases the risk of bilateral blindness. It is widely maintained that with proper education and adoption of proper safety standards, such injuries can be largely prevented.

Accidents, Traffic↗
PubMed1994

Recovery of visual response of injured adult rat optic nerves treated with transglutaminase.

Failure of axons of the central nervous system in adult mammals to regenerate spontaneously after injury is attributed in part to inhibitory molecules associated with oligodendrocytes. Regeneration of central nervous system axons in fish is correlated with the presence of a transglutaminase. This enzyme dimerizes interleukin-2, and the product is cytotoxic to oligodendrocytes in vitro. Application of this nerve-derived transglutaminase to rat optic nerves, in which the injury had caused the loss of visual evoked potential response to light, promoted the recovery of that response within 6 weeks after injury. Transmission electron microscopy analysis revealed the concomitant appearance of axons in the distal stump of the optic nerve.

Animals↗