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Biomedical subjects

Y Levy

Publications and source records attributed to Y Levy.

At least 37 records · Page 2Linked to original sources
PubMed2003

[The use of autogenous block graft for augmentation of the atrophic alveolar ridge].

The use of osseointegrated implants has become a standard treatment option in modern dental rehabilitation. Adequate bone quantity and quality is a prerequisite for good esthetic and biomechanical result. Alveolar ridge defects can be the result of trauma, periodontal diseases or other pathologic conditions. In these cases, alveolar ridge augmentation is needed if endosseous implants are to be used. While xenografts, alloplastic bone grafts and allografts have been proposed for alveolar ridge augmentation, the use of autogenous bone grafts represents the "gold standard" for bone augmentation procedures. Either intraoral or extraoral sites may be considered for donor sites. Although the iliac crest is the most common donor site in maxillofacial reconstruction, the mandibular symphysis or ramus offer important advantages like avoidance of general anesthesia, convenience due to the proximity between the donor site and the augmentation site and avoidance of cutaneous scar. Bone harvested from intraoral donor site is less associated with resorption when compared with iliac bone because membranous grafts revascularize more quickly than endocondral bone grafts. The main disadvantage of the intraoral donor sites is the limited amount of available bone. Alveolar ridge augmentation using autologous bone block, can be done during implant placement or staged with implant placement, after bone graft healing. In the staged technique, a better implant positioning and the use of wide diameter implants are possible. The overall implant success is higher in the staged technique. Alveolar ridge augmentation using autogenous block graft is a predictable way of treatment, for the atrophic alveolar ridge before implant placement.

Alveolar Bone Loss↗
PubMed2002

Successful pregnancy outcome in a patient with Gaucher's disease and antiphospholipid syndrome.

Gaucher's disease is characterized by increased incidence of several autoantibodies, but autoimmune phenomena are rare in Gaucher patients. We report the first occurrence of Gaucher's disease and antiphospholipid syndrome in the same patient. A 27-year-old woman with hepatosplenomegaly and thrombocytopenia who was diagnosed as having Gaucher's disease with the genotype 1226G/1226G developed Coombs'-positive hemolytic anemia, recurrent abortions, and a high titer of IgG and IgM anticardiolipin antibodies constituting the diagnosis of antiphospholipid syndrome. A successful pregnancy outcome was achieved by combined therapy with aspirin, low-molecular-weight heparin, prednisone, and enzyme replacement therapy with imiglucerase. The possible pathogenicity of antiphospholipid antibodies found in the sera of many asymptomatic Gaucher patients should be further clarified.

Adult↗
PubMed2002

Transverse myelitis in patients with antiphospholipid antibodies--the importance of early diagnosis and treatment.

Transverse myelitis (TM) is a rare manifestation of systemic lupus erythematosus (SLE) and the antiphospholipid syndrome (APS). No uniform therapeutic protocol exists for its treatment, and the prognosis is usually poor. Here we describe four patients having TM associated with antiphospholipid antibodies. Treatment measures and delay in diagnosis between symptom onset and the initiation of treatment varied between patients, but the earlier the diagnosis and the more aggressive the treatment the better was the patient's outcome. Based on these cases and on a literature review we suggest that early aggressive treatment (usually with pulses of methylprednisolone and cyclophosphamide) might improve the prognosis of patients with TM associated with antiphospholipid antibodies.

Adult↗
PubMed2002

Red and/or blonde hair association with pigmentary glaucoma in Israel.

PURPOSE: To assess the prevalence of red and/or blonde hair in a defined pigmentary glaucoma (PG) population and to compare their clinical findings with those of PG patients with black or brown hair. METHODS: Hair color was studied in 35 consecutive PG patients and 35 consecutive primary open angle glaucoma (POAG) patients who served as controls. Patients were classified into red and/or blonde hair group or into black or brown hair group. Clinical characteristics were contrasted between PG patients of red and/or blonde hair with PG patients of black or brown hair. RESULTS: Of the 35 PG patients, 19 (54.3%) had red and/or blonde hair and 16 (45.7%) had black or brown hair. Of the 35 POAG patients, two (5.8%) had red and/or blonde hair and 33 (94.2%) had black or brown hair. This difference in prevalence of hair color is highly significant (P < 0.001; chi2). Clinical characteristics of the PG patients (age at initial diagnosis, gender, positive family history for glaucoma, initial IOP, refraction, severity of optic nerve damage and prevalence of retinal detachment) were similar in the red and/or blonde hair and the black or brown hair groups. CONCLUSIONS: A very high prevalence of red and/or blonde hair was found among PG patients in Israel. Should supportive evidence for this association accumulate subsequent to this report, screening of people with these hair colors for PG may be justified.

Adolescent↗
PubMed2001

Helix-coil transition of PrP106-126: molecular dynamic study.

A set of 34 molecular dynamic (MD) simulations totaling 305 ns of simulation time of the prion protein-derived peptide PrP106-126 was performed with both explicit and implicit solvent models. The objective of these simulations is to investigate the relative stability of the alpha-helical conformation of the peptide and the mechanism for conversion from the helix to a random-coil structure. At neutral pH, the wild-type peptide was found to lose its initial helical structure very fast, within a few nanoseconds (ns) from the beginning of the simulations. The helix breaks up in the middle and then unwinds to the termini. The spontaneous transition into the random coil structure is governed by the hydrophobic interaction between His(111) and Val(122). The A117V mutation, which is linked to GSS disease, was found to destabilize the helix conformation of the peptide significantly, leading to a complete loss of helicity approximately 1 ns faster than in the wild-type. Furthermore, the A117V mutant exhibits a different mechanism for helix-coil conversion, wherein the helix begins to break up at the C-terminus and then gradually to unwind towards the N-terminus. In most simulations, the mutation was found to speed up the conversion through an additional hydrophobic interaction between Met(112) and the mutated residue Val(117), an interaction that did not exist in the wild-type peptide. Finally, the beta-sheet conformation of the wild-type peptide was found to be less stable at acidic pH due to a destabilization of the His(111)-Val(122), since at acidic pH this histidine is protonated and is unlikely to participate in hydrophobic interaction.

Amino Acid Substitution↗
PubMed2001

Mutations of CD40 gene cause an autosomal recessive form of immunodeficiency with hyper IgM.

CD40 is a member of the tumor necrosis factor receptor superfamily, expressed on a wide range of cell types including B cells, macrophages, and dendritic cells. CD40 is the receptor for CD40 ligand (CD40L), a molecule predominantly expressed by activated CD4(+) T cells. CD40/CD40L interaction induces the formation of memory B lymphocytes and promotes Ig isotype switching, as demonstrated in mice knocked-out for either CD40L or CD40 gene, and in patients with X-linked hyper IgM syndrome, a disease caused by CD40L/TNFSF5 gene mutations. In the present study, we have identified three patients with an autosomal recessive form of hyper IgM who fail to express CD40 on the cell surface. Sequence analysis of CD40 genomic DNA showed that one patient carried a homozygous silent mutation at the fifth base pair position of exon 5, involving an exonic splicing enhancer and leading to exon skipping and premature termination; the other two patients showed a homozygous point mutation in exon 3, resulting in a cysteine to arginine substitution. These findings show that mutations of the CD40 gene cause an autosomal recessive form of hyper IgM, which is immunologically and clinically undistinguishable from the X-linked form.

CD40 Antigens↗
PubMed2001

Deregulation of the expression of the fractalkine/fractalkine receptor complex in HIV-1-infected patients.

Fractalkine is the only member of the CX3C chemokine family. Polymorphism of the fractalkine receptor gene may influence the prognosis of human immunodeficiency virus (HIV) infection, but the nature of the cells expressing fractalkine or its receptor in HIV-infected patients remains unknown. We show that, in contrast to HIV-uninfected individuals, a large number of cells expressed fractalkine in T-cell zones of lymph nodes from HIV-infected patients. CD83(+) mature and CD123(+) plasmacytoid dendritic cells as well as plasma cells are involved in this increased expression of fractalkine. Increased numbers of plasmacytoid dendritic cells and plasma cells were present in T-cell zones of HIV-infected patients. CD83(+) dendritic cells were present in similar number in HIV-infected patients and controls, but an increased fraction of these cells produced fractalkine in HIV-infected patients. Many plasma cells in the gut-associated lymphoid tissue from HIV-infected patients also produced fractalkine, whereas few cells produced fractalkine in the gut of controls. The fraction of CD45RO(+) and CD45RO(-) T helper (Th) cells expressing the fractalkine receptor CX3CR1 was higher in HIV-infected patients than in healthy individuals, and these cells were abnormally sensitive to fractalkine stimulation. This increased response correlated with HIV viremia, and it returned to normal levels in patients successfully treated with antiretroviral drugs. The increased expression of the fractalkine/fractalkine receptor complex associated with HIV infection may affect adhesion and migration of Th lymphocytes and their interaction with dendritic cells. Thus, it may influence the equilibrium between depletion and renewal of the Th lymphocyte compartment.

Antigens, CD↗
PubMed2001

Immunological and virological effects of long term IL-2 therapy in HIV-1-infected patients.

We report the long-term outcome of 27 HIV-infected patients treated for over 3 years with IL-2 and binucleoside analogues. These patients experienced a sustained increase in CD4 cells and a decrease of proviral DNA with infrequent IL-2 cycles. In three cases, virus could not be isolated from activated peripheral cells. A high frequency of HIV-1-specific memory CD4 T cells was found in the patients studied. IL-2 maintains specific effector cells and reduces the pool of infected cells in patients, albeit treated only with binucleosides.

Anti-HIV Agents↗
PubMed2001

Galectin-8 functions as a matricellular modulator of cell adhesion.

The interaction of cells with the extracellular matrix regulates cell adhesion and motility. Here we demonstrate that different cell types adhere and spread when cultured in serum-free medium on immobilized galectin-8, a mammalian beta-galactoside-binding protein. At maximal doses, galectin-8 is equipotent to fibronectin in promoting cell adhesion and spreading. Cell adhesion to immobilized galectin-8 is mediated by sugar-protein interactions with integrins, and galectin-8 triggers integrin-mediated signaling cascades including Tyr phosphorylation of focal adhesion kinase and paxillin. Cell adhesion is potentiated in the presence of Mn(2+), whereas it is interrupted in the presence of soluble galectin-8, integrin beta(1) inhibitory antibodies, EDTA, or thiodigalactoside but not by RGD peptides. Furthermore, cells readily adhere onto immobilized monoclonal galectin-8 antibodies, which are equipotent to integrin antibodies in promoting cell adhesion. Cell adhesion to immobilized galectin-8 is partially inhibited by serum proteins, suggesting that complex formation between immobilized galectin-8 and serum components generates a matrix that is less supportive of cell adhesion. Accordingly, cell motility on immobilized galectin-8 readily takes place in the presence of serum. Truncation of the C-terminal half of galectin-8, including one of its two carbohydrate recognition domains, largely abolishes its ability to modulate cell adhesion, indicating that both carbohydrate recognition domains are required to maintain a functional form of galectin-8. Collectively, our findings implicate galectin-8 as a physiological modulator of cell adhesion. When immobilized, it functions as a matrix protein equipotent to fibronectin in promoting cell adhesion by ligation and clustering of cell surface integrin receptors. In contrast, when present in excess as a soluble ligand, galectin-8 (like fibronectin) forms a complex with integrins that negatively regulates cell adhesion. Because of its dual effects on the adhesive properties of the cells and its association with fibronectin, galectin-8 might be considered a novel type of matricellular protein.

Animals↗
PubMed2001

Solvent effects on the energy landscapes and folding kinetics of polyalanine.

The effect of a solvation on the thermodynamics and kinetics of polyalanine (Ala(12)) is explored on the basis of its energy landscapes in vacuum and in an aqueous solution. Both energy landscapes are characterized by two basins, one associated with alpha-helical structures and the other with coil and beta-structures of the peptide. In both environments, the basin that corresponds to the alpha-helical structure is considerably narrower than the basin corresponding to the beta-state, reflecting their different contributions to the entropy of the peptide. In vacuum, the alpha-helical state of Ala(12) constitutes the native state, in agreement with common helical propensity scales, whereas in the aqueous medium, the alpha-helical state is destabilized, and the beta-state becomes the native state. Thus solvation has a dramatic effect on the energy landscape of this peptide, resulting in an inverted stability of the two states. Different folding and unfolding time scales for Ala(12) in hydrophilic and hydrophobic chemical environments are caused by the higher entropy of the native state in water relative to vacuum. The concept of a helical propensity has to be extended to incorporate environmental solvent effects.

Kinetics↗
PubMed2001

Leptin induces angiopoietin-2 expression in adipose tissues.

Adipose tissues consisting of adipocytes, microvasculature, and stroma are completely ablated upon over-expression of leptin in rats. This tissue regression is mediated by enhanced lipid beta-oxidation, adipocyte dedifferentiation, and apoptosis. To further characterize this phenomenon, we studied the possible effect of leptin on the adipose microvasculature. Tissue microvasculature is maintained by the interplay between positive and negative signals mediated by factors including vascular endothelial growth factor (VEGF), basic fibroblast growth factor, angiopoietin-1 (Ang-1), and Ang-2. Expression of the negative signal Ang-2 was reported in fetal tissues and in the adult ovary, which undergoes vascular remodeling or regression. We demonstrate that leptin induces the expression of Ang-2 in adipose tissue without a concomitant increase in VEGF. Induction of Ang-2 occurred in an autocrine manner, as demonstrated in cultured adipocytes but not in several other cell types. This tissue-specific induction of Ang-2 coincided with initiation of apoptosis in adipose endothelial cells. We propose that induction of Ang-2 by leptin in adipose cells is one of the events leading to adipose tissue regression.

3T3 Cells↗
PubMed2001

Congenital insensitivity to pain with anhidrosis (CIPA): the spectrum of radiological findings.

BACKGROUND: Congenital insensitivity to pain with anhidrosis (CIPA) is an exceedingly rare, hereditary, sensory autonomic neuropathy (HSAN). AIM: To evaluate the various skeletal manifestations and cranial CT features in children affected by CIPA. MATERIALS AND METHODS: In the semidesert area of the Negev, the Bedouin tribes constitute a closed society where consanguineous marriages are the custom. This has resulted in a group of 20 children being affected by this rare autosomal recessive HSAN. The skeletal surveys and CT scans of these 20 Bedouin patients, 12 girls and 8 boys, ages ranging between 1 month and 8 years, were retrospectively analysed. Cranial CT scans were performed in ten children because of neonatal hypotonia and psychomotor retardation. The skeletal findings were classified as follows: fractures, joint deformities, joint dislocations, osteomyelitis, avascular necrosis and acro-osteolysis. RESULTS: All 20 patients had fractures of the extremities and acro-osteolysis of the fingers. Six had joint deformities. Three children had recurrent hip joint dislocations and another three had avascular necrosis. Ten patients presented with osteomyelitis of the limbs, acetabulum and scapula. The cranial CT scans disclosed mild brain volume loss with some ventriculomegaly. CONCLUSIONS: CIPA is a severe autosomal recessive condition that leads to self-mutilation early in life and to fractures, osteomyelitis and limb amputation in older children. Mental retardation is common. Death from hyperpyrexia occurs in almost 20 % of patients in the first 3 years of life.

Arabs↗
PubMed2001

Optimization of solutions for the one plant protection problem.

Plant protection problems are simulated by a system of ordinary differential equations with given initial conditions. The sensitivity and resistance of pathogen subpopulations to fungicide mixtures, fungicide weathering, plant growth, etc. are taken into consideration. The system of equations is solved numerically for each set of initial conditions and parameters of the disease and fungicide applications. Optimization algorithms were investigated and a computer program was developed for optimization of these solutions. 14 typical cases of the disease were simulated and optimized in order to determine optimal fungicide treatments. The optimized strategy for fungicide application differs considerably from the commonly used method and seems to be an important new principle in plant protection. The approach developed in this study may be useful for a wide spectrum of purposes in the simulation of leaf diseases. It may also help the biologist to decrease or pinpoint experimental work and analyze its results and is perspective for plant disease control.

Algorithms↗