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Z Nevo

Publications and source records attributed to Z Nevo.

At least 19 recordsLinked to original sources
PubMed1992

Neuropeptidergic innervation of intramuscular hemangiomas.

Intramuscular hemangiomas are idiopathic lesions which are either tumoral or developmental in origin. A close association of abnormal blood vessels with nerve fibers is found and may suggest that nerves have a primary inciting role in the development of these lesions. In the current study, the number of nerve fibers in different zones around the tumors, as well as the type of neuropeptides present in these fibers, was quantitatively assessed by computer-assisted image analysis of immunohistochemical staining of histological slides. The number of nerve fibers as determined by positive staining by anti-protein S-100 antibodies was found to be elevated in the immediate vicinity of the abnormal blood vessels. The density of the nerve fibers rapidly declined with increasing distance from the hemangiomas, reaching normal values at distances of over 2 mm. Furthermore, hemangiomas contain a significantly higher number of calcitonin gene-related peptide (CGRP), substance P, and Met-enkephalin-positive fibers. The most significant rise in number is that of CGRP-positive fibers. This neuropeptide is a known mitogen, which could be responsible for the growth of the hemangiomatous blood vessels. Substance P is a nociceptive neurotransmitter and its presence can explain the pain which often accompanies even tiny intramuscular hemangiomas.

Adolescent↗
PubMed1992

Hyperosmotic activation of the Na(+)-H+ exchanger in a rat bone cell line: temperature dependence and activation pathways.

1. The hyperosmotic activation of the Na(+)-H+ exchanger was studied in an osteoblast-like rat cell line (RCJ 1.20). The activation was monitored by recording the intracellular pH (pHi) changes employing double excitation of the pH-sensitive fluorescent dye 2'7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM). 2. Exposure of the cells to a hyperosmotic HCO(3-)-free medium at 37 degrees C produced an initial cytosolic acidification of 0.05 pH units followed by a lag period and an alkalinization overshoot of about 0.2 pH units, without a concomitant change of the free cytosolic calcium [Ca2+]i by the use of Fura-2 calcium-sensitive probes. This response was completely inhibited by amiloride (0.33 mM) or by Na+ depletion from the external medium and insensitive to the extracellular Cl- replacement, indicating the involvement of a Na(+)-H+ exchanger in the hyperosmotic response. 3. Hyperosmotic stimuli (200 moSM sucrose) applied in the temperature range of 17-37 degrees C demonstrated a shortening of the lag period preceding alkalinization and an increased rate of proton extrusion upon temperature elevation. The biochemical reaction underlying the lag period and the proton extrusion resulted in apparent activation energies of 19 and 29 kcal mol-1, respectively, as calculated from the appropriate Arrhenius plots. 4. Stimulation of the exchanger under isosmotic conditions by 25 nM 4 beta-phorbol 12-myristate 13-acetate (PMA) and 0.1 mM vanadate resulted in an amiloride-sensitive pHi increase of about 0.08 pH units. The hyperosmotic stress was additive to the stimulatory effects of these agents, suggesting an independent hyperosmotic activation pathway. 5. The hyperosmotic activation of the Na(+)-H+ exchanger was independent of cAMP, cGMP, cytosolic Ca2+ and protein kinase C. Thus, none of the classical transduction mechanisms seem to be involved directly in the hyperosmotic activation of the antiporter. 6. The pHi response induced by the hyperosmotic stress was abolished by two calmodulin inhibitors, W-7 and chlorpromazine (50% inhibition, Ki at 28 and 20 microM, respectively), 20 microM cytochalasin B, but not by 10 microM colchicine. The results suggest the involvement of actin and calmodulin-like structural elements of the cytoskeleton in the transduction process leading to the activation of the Na(+)-H+ exchanger.

Animals↗
PubMed1992

Devascularization of the anterior cruciate ligament by synovial stripping in rabbits. An experimental model.

In rabbits, synovial stripping of the anterior cruciate ligament was performed, and histologic and mechanical changes were followed up to 2 months. The operation did not immediately affect the strength of the ligament or its histological structure. However, a gradual deterioration of mechanical properties, associated with collagen necrosis and an ineffectual reparative response, was evident. Thus, synovial stripping of the ligament with the attendant concomitant devascularization leads to ligamentary insufficiency despite the lack of structural damage to the ligament by the contusion itself.

Animals↗
PubMed1991

Regulation of the Na+/H+ exchanger under conditions of abolished proton gradient: isosmotic and hyperosmotic stimulation.

Activation of the Na+/H+ exchanger following isosmotic and hyperosmotic stimuli was investigated in an osteoblast cell line (RCJ 1.20). The pH dependence of the transporter activity was studied under conditions of abolished proton gradient (pHi = pHo) across the membrane. The isotonic response is Na+o dependent, increases towards higher pH-values, displaying a sigmoidal dependence on pHi = o (Hill coefficient approximately 1.8) and is controlled by pHo. The greater than first order dependence on pH suggests that H+o inhibits the exchange beyond the rate expected from competition with the Na+o alone. This may be due to the existence of an external H+ regulatory site with a negative cooperative effect on the intra- or extracellular transport site. The hyperosmotic activation is Na+o independent, parallels the sigmoidal pH dependence of the isosmotic stimulus (Hill coefficient approximately 2.0) and is mediated through an increase of the Vmax without a change in the intracellular proton sensitivity.

Animals↗
PubMed1990

Decrease in the basal levels of cytosolic free calcium in chondrocytes during aging in culture: possible role as differentiation-signal.

Cell- and matrix-related parameters, which characterize the aging and differentiation process of cartilage in vivo, were measured in cultured chick epiphyseal chondrocytes during maintenance in a suspension culture for 34 days. A gradual decrease in the rates of proliferation and an increase in the size of the cells were observed. Ultrastructural examination revealed increased vacuolization and appearance of glycogen-storing pools. The rate of proteoglycan synthesis gradually increased. Age-related changes in the composition of the proteoglycan consisted of an increase in the ratio of keratan sulfate/chondroitin sulfate. The results indicate that the process of aging in culture resembles maturation and differentiation of cartilage tissue in vivo. The levels of cytosolic free calcium ions ([Ca2+]i) were measured in fura-2-loaded cells during the course of aging in culture. A gradual decrease in [Ca2+]i was observed. In 5-day cultures, a value of 184 nM [Ca2+]i was measured; this value decreased to 61 nM in 34-day cultures. On the basis of the present data and the previous results, which showed that cartilage-derived growth factors caused a decrease in [Ca2+]i, concomitantly with enhancing differentiation, whereas factors which elevated [Ca2+]i caused an increase in proliferation and a decrease in proteoglycan synthesis, we suggest a model for control of chondrocyte differentiation and aging. The model suggests that the rate of differentiation may be paced by changes in steady-state levels of [Ca2+]i.

Animals↗
PubMed1990

Regenerating hyaline cartilage in articular defects of old chickens using implants of embryonal chick chondrocytes embedded in a new natural delivery substance.

Partial and full thickness defects were created mechanically in articular cartilage and subchondral bone of the tibiotarsal joint condyles of 3-year-old chickens. The wounds were then repaired using embryonal chick chondrocytes embedded in a new biocompatible, hyaluronic acid-based delivery substance. Controls were similarly operated on but received either no treatment or implants of the delivery substance only. Animals were killed from 1 week to 6 months postoperatively. Sections from the two groups were examined and compared macroscopically, histologically, and histochemically. Results of 6-month follow-up showed that only the defects of the experimental chickens were completely filled with reparative hyaline cartilage tissue, with no signs of inflammation or immunologic rejection. Initially the entire defect cavity, whether partial thickness or full thickness up to the deep regions in the subchondral bone, was filled with cartilaginous reparative tissue. Relatively rapid maturation occurred under the tidemark; chondrocytes hypertrophied, were invaded with vascular elements and ossified. In the superficial areas, the reparative tissue remained cartilaginous and matured as typical hyaline cartilage tissue. These results indicate that aged chicken cartilage and its accompanying thin and spongy osteoporotic bone offer a favorable host environment for embryonal cell implants.

Animals↗
PubMed1989

Fate of allogeneic embryonal chick chondrocytes implanted orthotopically, as determined by the host's age.

Chondrocytes derived from chick embryos can be successfully implanted in defects of adult chick articular cartilage surfaces. Such implants thrive in their implantation site and create a new articular surface. The chondrocytes mature and hypertrophy in the orthotopic site without invoking an immune response. Eventually a steady state is reached in which mature chondrocytes resurface the defect while in the deeper areas spongy bone replaces the hypertrophic chondrocytes. Time schedules of these repair events have been studied in hosts of different ages. We compared 4-month-old chicks with 3-year-old chickens. The embryonal chondrocytes implanted in the latter group underwent an accelerated aging process. The defects were completely filled-up after 1 month as compared with 2-3 months in the younger age group. Endochondral ossification in the older group was evident as early as 2 months post implantation and was completed after 6 months. This contrasts with the situation in the younger group where the chondrocytes only began to hypertrophy after 6 months. At this stage endochondral ossification was hardly seen at all. A unique response to the cartilaginous implants is seen in the old group only in the vicinity of the reparative tissue, accumulation of hematopoietic centers. This study seem to indicate that the host's environment affects the "biological clock", i.e. rate and degree of aging of the implanted cells, as well as their matrices.

Age Factors↗
PubMed1979

Growth factors.

Explore the source record for details and available documents.

Animals↗
PubMed1979

Fetal bone grafts do not elicit allograft rejection because of protecting anti-Ia alloantibodies. Implications to the immune survival of fetuses in allogeneic mothers.

In a previous study we showed that allografts of BN fetal bone, unlike allografts of adult bone, are not rejected by allogeneic recipients of the Lewis strain in spite of the existence of major histocompatibility complex (MHC) incompatibility between donors and hosts. In the present study, we analyzed the relationships existing between the host and fetal tissue that determine graft survival. We found that (1) the fetal BN graft, unlike adult grafts, induces in Lewis recipients a vigorous humoral response consisting mainly in the production of IgG antibody that seems to be directed against antigens of Ia-like specificities. (2) The BN rats are genetically defective in their capacity to respond to determinants and thus are not capable of producing anti-Ia antibodies; in accordance, Lewis fetal bone grafts are rejected by the BN recipients. (3) Chondrocytes isolated from fetal mouse bones do express Ia antigenic determinants. We suggest that the survival of an allogeneic fetal graft in an immunologically intact recipient depends on an active and selective immune response directed against the Ia components associated with the MHC on the embryonic and fetal cells. On the basis of these notions, we propose that the capacity of Ia determinants expressed on cells of the embryo, to elicit anti-Ia and IgG alloantibodies in the pregnant mother, determines the capacity of the embryo to escape rejection by the histoincompatible mother.

Animals↗
PubMed1978

Hyaluronidase release from guinea pig spermatozoa as affected by reproductive tract secretions and metabolic inhibitors.

Cauda epididymal sperm of mature guinea pigs were incubated (37 degrees, 5% CO2 in air). 10% of the total enzyme activity was released into the medium in 4 hr, 30% in 24 hr. Addition of lysolecithin resulted in rapid release of hyaluronidase. Vitamin C (0.54 mM), sodium fluoride (0.02 M), and cholesterol increased the rate of release whereas citrate (20 mM) diminished it. No effect upon hyaluronidase release was noted upon addition of KCN (10(-2)M), progesterone (250 microgram/ml), testosterone (500 microgram/ml), spermine (1.15 mg/ml), inositol (5.6 mM), or chloroquine phosphate (0.54 mM).

Animals↗