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Biomedical subjects

M Belkin

Publications and source records attributed to M Belkin.

At least 127 records · Page 7Linked to original sources
PubMed1989

Cell division in the healing of the corneal endothelium of cats.

The pattern of cell division of the corneal endothelium of cats was studied during the first week following scraping of 35.2% to 38.3% of the endothelial cells. A small number of mitoses were found 2 days after scraping (mean +/- SD, 8.2 +/- 6.1 per cornea); the number peaked during the third and the fourth days (148.5 +/- 74.5 and 206.8 +/- 40.1, respectively), sharply decreased on the fifth day to a level of 17.0 +/- 9.5, and further decreased on the sixth and seventh days to 4.2 +/- 1.8 and 3.3 +/- 1.5 mitoses per cornea, respectively. Due essentially to amitotic cell division, a multinuclear cell population, mainly binuclear, appeared and increased to a number of 3999 +/- 746 and 3,129 +/- 877 on the sixth and seventh days, respectively, after scraping. Thus, mitotic and amitotic cell division is an integral part of the posttraumatic regeneration process of the corneal endothelium of cats.

Animals↗
PubMed1989

Postischemic hypothermia diminishes skeletal muscle reperfusion edema.

The mechanisms of ischemia-reperfusion injury in skeletal muscle remain controversial. We investigated the ability of postischemic hypothermia to diminish reperfusion edema and improve skeletal muscle pH in a bilateral, in vivo isolated canine gracilis muscle model. In five anesthetized animals, both gracilis muscles were subjected to 6 hr of ischemia followed by 1 hr of reperfusion. After 5 hr of warm ischemia, one gracilis muscle was cooled to 21 degrees C (cold reperfusion, CR) while the contralateral gracilis muscle was maintained at ambient temperature (warm reperfusion, WR). Reperfusion muscle edema was quantitated by measurement of gracilis muscle weight gain. Interstitial muscle pH was monitored by glass microelectrodes. Vascular permeability was measured by analysis of albumin (125I-Alb) leak. Results are presented as the means +/- SEM. (table; see text) Postischemic hypothermia significantly increased the interstitial muscle pH and significantly reduced postreperfusion muscle edema, without changing the vascular permeability to albumin. These data suggest that hypothermia may provide a clinical method for salvaging ischemic skeletal muscle from the postreperfusion edema that can lead to compartment syndromes, reperfusion injury, and subsequent limb loss.

Animals↗
PubMed1989

The role of leukocytes in the pathophysiology of skeletal muscle ischemic injury.

Neutrophilic leukocytes have been implicated as important mediators of ischemic myocardial injury. We investigated the role of neutrophils in skeletal muscle ischemia/reperfusion injury by using the rat hindlimb ischemia model. We rendered Wistar rats neutropenic by administering 750 rad of whole-body radiation (mean white blood cell count, 300 +/- 50/mm3; 3 days after radiation). In anesthetized rats (10 neutropenic and 10 control), 3 hours of ischemia were induced in one hindlimb by application of a tourniquet to the proximal thigh; the contralateral limb served as an internal, nonischemic control. After 1 hour of reperfusion the gastrocnemius and soleus muscles were excised bilaterally and evaluated for ischemic injury by means of a quantitative spectrophotometric assay of triphenyltetrazolium chloride (TTC) reduction. In control rats the reduction of TTC by ischemic muscle averaged 27.0% +/- 7.3% of that by nonischemic muscle; whereas in neutropenic rats the value for ischemic muscle was 65.4 +/- 11.6% (p less than 0.05). To determine if the contribution of the neutrophils to ischemic injury is due to oxygen-derived free radical formation, an additional 10 animals were infused with 5000 units of super-oxide dismutase and 10,000 units of catalase at the time reperfusion was restored. After treatment with free radical scavengers, TTC reduction by ischemic limbs was 25.5% +/- 7.0% of that by nonischemic limbs and did not differ from that in control animals (p greater than 0.05). The results show a protective effect of neutropenia and suggest a significant role of the white cell in the pathophysiology of ischemic skeletal muscle injury.

Animals↗
PubMed1989

Dichotomy of the glial cell response to axonal injury and regeneration.

Neurons in the mammalian central nervous system (CNS) have a poor capacity for regenerating their axons after injury. In contrast, neurons in the CNS of lower vertebrates and in the peripheral nervous system (PNS) of mammals are endowed with a high posttraumatic capacity to regenerate. The differences in regenerative capacity have been attributed to the different compositions of the respective cellular environments and to different responses to injury the nonneuronal cells display, which range from supportive and permissive to nonsupportive and hostile for regeneration. The same cell type may support or inhibit regeneration, depending on its state of maturity or differentiation. Astrocytes and oligodendrocytes are examples of cells in which such a dichotomy is manifested. In developing and in spontaneously regenerating nerves, these cells support (astrocytes) and permit (oligodendrocytes) growth. However, in nonregenerating adult mammalian nerves, astrocytes form the nonsupportive scar tissue; and the mature oligodendrocytes inhibit axonal growth. Maturation of these cells may be regulated differently during development than after injury. Among the putative regulators are factors derived from astrocytes, resident microglia; or cytokines produced by macrophages. During development, regulation leads to a temporal separation between axonal growth and maturation of the cellular environment, which might not occur spontaneously after injury in a nonregenerating CNS without intervention at the appropriate time. Data suggest that temporal intervention aimed at the glial cells might enhance the poor regenerative capacity of the mammalian CNS. Possible regulation of the nonneuronal cell response to injury via involvement of protooncogenes is proposed.

Animals↗
PubMed1989

New biological phenomena associated with laser radiation.

Low-energy laser irradiation produces significant bioeffects. These effects are manifested in biochemical, physiological and proliferative phenomena in various enzymes, cells, tissues, organs and organisms. Examples are given of the effect of He-Ne laser irradiation in preventing the post-traumatic degeneration of peripheral nerves and the postponement of degeneration of the central nervous system. The damage produced by similar radiant exposures to the corneal epithelium and endothelium is also described. It is suggested that the mechanism of laser/tissue interaction at these low levels of radiant exposure is photochemical in nature, explaining most of the characteristics of these effects. These low-energy laser bioeffects are of importance on a basic scientific level, from a laser safety aspect and as a medical therapeutic modality.

Animals↗
PubMed1989

Laser angioplasty for limb salvage: observations on early results.

During a 27-month period laser thermal angioplasty (LTA) was attempted in 15 patients who had totally occluded segments of their superficial femoral--popliteal arteries (SFA) with limb-threatening ischemia (rest pain or tissue necrosis). In five patients (33%) laser perforation of the SFA precluded successful angioplasty, and those five patients have been excluded from further analysis. In the remaining 10 patients the prelaser angiogram demonstrated an average SVS/ISCVS runoff score of 7.7 (best possible score, 1; worst possible score, 10). Seven patients (70%) had occlusions of all infrapopliteal arteries. All 10 patients were available for clinical follow-up, and follow-up angiograms were available for eight patients (80%). Clinical failure was defined as recurrence of the clinical signs or symptoms for which the LTA was performed. After 6 months of follow-up clinical failures occurred in nine patients (90%). Four patients had no clinical improvement. Five patients had transient clinical improvement after LTA, and all subsequently had early recurrence of symptoms. The average time from LTA to recurrence of symptoms was 1.7 months. Seven patients had subsequent bypasses or amputations an average of 2.2 months after laser angioplasty. The SFA patency rate by life-table analysis was 25% at 6 months. The single patient with clinical success (at 12 months) had no tibial vessel disease evident on his prelaser angiogram, and he underwent a concomitant inflow procedure at the time of his LTA. We believe that the disappointing results in this small series of patients can be attributed to tibial vessel disease that was not addressed by this technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Intraarterial urokinase increases skeletal muscle viability after acute ischemia.

Administration of intraarterial fibrinolytic agents has been recommended after balloon catheter thrombectomy to reduce retained thrombus and to improve the patency of collateral vasculature. However, the potential for improvement in the viability of skeletal muscle after ischemia as a result of this therapy has not been evaluated. We investigated the effect of intraarterial urokinase (UK) on the salvage of ischemic skeletal muscle in a bilateral, in vivo, isolated gracilis muscle model. In six anesthetized dogs each gracilis muscle was subjected to 5 hours of ischemia by temporary occlusion of the gracilis artery. Before reperfusion, the experimental muscle received an intraarterial infusion of UK (30,000 units) whereas the control muscle received saline solution. Each muscle was then reperfused for 90 minutes. Triphenyltetrazolium chloride staining demonstrated infarction of 20.2% +/- 8.1% in control muscles compared with 8.6% +/- 6.2% in UK-infused muscles (p less than 0.01). Control muscles gained significantly more weight from edema (33.6 +/- 5.9 gm) than UK-infused muscles (18.2 +/- 4.1 gm; p less than 0.05). Coagulation studies confirmed that an isolated fibrinolytic effect occurred on the experimental side. These studies suggest that intraarterial UK may be a useful adjunctive therapy after revascularization of the acutely ischemic limb and that further clinical trials are recommended.

Acute Disease↗
PubMed1988

The Israeli Ocular Injuries Study. A nationwide collaborative study.

A nationwide study of patients hospitalized for ocular injuries was conducted in Israel during the years 1981 through 1983, with the participation of 17 ophthalmic departments. The study comprised 2276 patients (2416 eyes), 47% of whom were children. The male-female ratio was 4.3:1. Bilateral injuries occurred in 140 patients, with children sustaining the most severe injuries. Ocular injuries occurred most frequently at home, and children at play were most vulnerable. Most patients retained good vision, 3.7% lost vision totally, and 2% of the eyes had to be enucleated.

Adolescent↗
PubMed1988

Parathyroid gland exploration with local anesthesia in elderly and high-risk patients.

The management of symptomatic hyperparathyroidism in elderly and medically compromised patients, who are at risk under general anesthesia, may be safely and effectively accomplished using local anesthesia. Positive localization with ultrasound, thallium 201-technetium Tc 99m subtraction, and computed tomography permit surgical exploration with local anesthesia in one or two stages, or bilaterally in one stage, in selected cases, by employing the surgical lateral approach to parathyroid surgery. Our study of 29 patients selected for this technique affirms the value and the safety of this method, especially as surgical experience has grown and localization studies have improved. During the latter 24 months of our study, 11 (30%) of 36 operations were performed using local anesthesia by one of us. A success rate in ten of 11 cases was achieved, with one patient requiring a second exploration for adenomatous hyperplasia while under local anesthesia.

Aged↗
PubMed1988

A new quantitative spectrophotometric assay of ischemia-reperfusion injury in skeletal muscle.

Characterization of ischemia-reperfusion injury of skeletal muscle remains poorly defined. A new quantitative assay to measure ischemic skeletal muscle injury is described and validated in a rat hindlimb model. This biochemical spectrophotometric technique measures triphenyltetrazolium chloride reduction in ischemic muscle. The reduction assay demonstrated significant injury after 3 hours of ischemia (25.4 +/- 9.7 percent of control activity; p less than 0.05). More severe injury occurred after 4 or more hours (less than 3 percent of control activity; p less than 0.05). This assay is an objective and quantitative method for characterizing ischemia-reperfusion injury.

Animals↗
PubMed1988

Preoperative percutaneous intraluminal balloon catheter control of major arterial hemorrhage.

Preoperative percutaneous balloon catheter control of major arterial hemorrhage is a useful technique when the damaged vessel is difficult or dangerous to expose. We report two cases, one with a gunshot wound to the internal carotid artery and one with a ruptured splenic artery aneurysm, in whom this approach was successfully employed to stop hemorrhage, control shock, and allow a precise, controlled vascular exposure and repair.

Adult↗
PubMed1988

Optic nerve regeneration--new aspects.

Injury to the optic nerve and its environment provokes a process of degeneration that leads to a degenerative process resulting in an irreversible loss of visual function. We succeeded in stimulating regeneration in injured optic nerves of adult rabbits. The stimulus to regeneration was achieved by implanting in injured optic nerves of adult rabbits substances originating from growing (regenerating) optic nerves of fish or developing optic nerves of neonatal rabbits, and by delaying the degenerative process by irradiating the injured optic nerve with a low energy laser. The effect was manifested by abundant growth of new fibers across the injury site and by other manifestation of regeneration characteristics.

Animals↗
PubMed1988

Prophylactic scleral buckling in perforating ocular injuries involving the posterior segment.

Twenty patients suffering from perforating injury involving the posterior segment of the eye without retinal tear or detachment underwent posterior vitrectomy. In 12 of these where traction of the retina was suspected, prophylactic scleral buckling was performed as well. Only two of these patients developed delayed retinal detachment. Six of the eight patients who did not undergo scleral buckling at the time of the vitrectomy developed this complication. This finding was statistically significant (P = .015) and supports the use of prophylactic scleral buckling in the treatment of eyes with perforating injuries involving the posterior segment to prevent delayed retinal detachment.

Adolescent↗
PubMed1988

Benefit of external carotid endarterectomy in patients with advanced cerebrovascular disease.

The external carotid artery and its branches may serve as critical collateral pathways to the cerebral hemisphere when the internal carotid artery is occluded. In this setting, a stenotic lesion of the external carotid artery can result in hypoperfusion as well as lead to embolic phenomena via enlarged collaterals. This is a report of an experience with six external carotid endarterectomies in five patients from April 1983 to March 1986. All five of the patients had an internal carotid artery occlusion ipsilateral to a significant external carotid artery stenosis. Each patient had symptomatic cerebrovascular insufficiency with four of the five patients demonstrating clear cut symptoms, which lateralized to the side with external carotid stenosis and internal carotid occlusion. These symptoms included amaurosis fugax in four patients and transient extremity weakness in two patients. Four out of five patients were completely relieved of their symptoms after external carotid endarterectomy with follow up periods ranging from 6 months to 2 and one half years. There were no perioperative neurological deficits or complications. The duplex scan was useful in identifying possible candidates for this operation. Important technical details include use of an arterial shunt and closure of the internal carotid artery stump, which may be a source of further emboli. It is concluded that with appropriate patient selection, external carotid endarterectomy can be safely employed with gratifying results in patients with advanced cerebrovascular disease.

Aged↗
PubMed1988

Relationship between morphology and functional ability of regenerated corneal endothelium.

Cat corneal endothelium was damaged by a methylmethacrylate segment introduced into the anterior chamber. Within 3 to 6 months after each such operation the endothelial cell density (ECD) diminished, ranging from 1933 to as low as 450 (78% to 16%, respectively, of its preoperative value [PV]). Decrease in the ECD to between 1050 and 1150 (40%-45% of PV) made no impact on the corneal thickness (group 1: "non-swollen" corneas); further decrease was followed by an increase of the corneal thickness to a level of 11.5%-73.5% more than its preoperative value (group 2: "swollen" corneas). The coefficient of variation of ECD increased in both groups. The number of hexagonal endothelial cells diminished, while cells with three or nine or more facets appeared. All these changes were much more pronounced and verifiable in the group 2 corneas, which were distinguished by the appearance of giant endothelial cells, 2957-4095 micron2, ie, 7.5-13.5 times larger than the cells of undamaged endothelium. These data appear to indicate that the decrease of ECD to 1050 to 1150 (40% to 45% of its PV) does not provoke decompensation of the dehydrative function of the endothelium, whereas further decrease does provoke such decompensation, the giant endothelial cells probably being the main factor in this phenomenon.

Animals↗
PubMed1987

Morphological response of injured adult rabbit optic nerve to implants containing media conditioned by growing optic nerves.

Adult rabbit retina can express regeneration-associated characteristics after optic nerve injury, provided it is supplied with appropriate diffusible substances originating from media conditioned by regenerating fish optic nerves or by optic nerves of a newborn rabbit [Hadani et al., Proc. Natl. Acad. Sci. U.S.A., 81 (1984) 7965; Schwartz et al., Science, 228 (1985) 600]. This was shown by applying the active substances to the injured axons in the form of 'wrap-around' implants, consisting of collagen-coated silicone tubes which had been soaked in the conditioned media (CM). The regeneration-associated response was manifested biochemically and by sprouting of nerve fibers in culture. The present work provides morphological evidence that the implantation prolongs survival of ganglion cells and optic nerve fibers and induces new growth. Light microscopic analysis (using horseradish peroxidase (HRP) for labeling the fibers) revealed, 1 week following optic nerve injury, labeled fibers and ganglion cells in both the implanted and control (injured only or injured and implanted with collagen-coated silicone tubes free of CM) nerves. However, from the second week after the injury, distinct differences in the appearance of viable ganglion cells and labeled fibers, were seen between experimental and control preparations. In sections taken through the optic nerve, at the region distal to the site of injury, HRP-labeled fibers were seen in the experimental nerves 1 week, 2 weeks and to a significantly lesser extent 1 month after injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗