Ezra Rahamim

Protective Effects of Tea Polyphenols against Oxidative Damage to Red Blood Cells

Tea polyphenols (TPP) from black and green teas were evaluated for their antioxidant effects on normal red blood cells (RBC) and beta-thalassemic RBC membranes challenged with exogenous oxidants in vitro. The TPP of both types protected RBC against primaquine-induced lysis; they also protected the whole cells and the membranes against H2O2-induced lipid peroxidation so that about 80% protection was reached at [TPP] = 10 microg/mL. TPP from black tea at the same concentration protected normal RBC from morphological alterations caused by the peroxide treatment. The mechanism of the effects of TPP was investigated using a chemical system generating .OH (iron + ascorbic acid). TPP from both black and green teas inhibited the .OH fluxes in a concentration-dependent manner, indicating the possibility of iron chelation by TPP. Spectrophotometric titration revealed that TPP could stoichiometrically bind ferric iron to form a redox-inactive Fe-TPP complex. Quantitative analysis suggests that one or more major catechins from the TPP preparations are the likely iron-binding compounds accounting for the antioxidant effects of TPP on RBC.

The blood-testis barrier in Aphanius dispar (Teleostei)

SummaryThin sections of normal testes from the cyprinodont Aphanius dispar were studied by electron microscopy after intravascular injection of live specimens with horseradish peroxidase. The intercellular space in the spermatogenic cysts is marked differently by the tracer according to the degree of differentiation of the germ cells. Spermatogonia and gonocytes undergoing meiosis are surrounded by a dark band of the marker. This band gradually disappears during spermiogenesis. In cysts containing ripe spermatozoa, the marker penetrates a short distance between the bases of adjoining Sertoli cells bordering the cysts, but is arrested by tight junctional complexes near the lumina of the cysts. The tight junctions between the Sertoli cells provide a permeability barrier between the vascular spaces of the stroma and the lumina of ripe cysts.

The response of supraalveolar gingival collagen to orthodontic rotation movement in dogs

An orthodontically rotated tooth relapses toward its pretreatment position. Explanations for this phenomenon have been given after light microscopic studies, according to which it had been assumed that stretched supraalveolar gingival fibers pulled back the tooth and brought about relaxation of the stretched fibers. The rotational relapse, however, can be prevented by supraalveolar fiberotomy of the gingiva around the tooth. This investigation was initiated to reevaluate the validity of the hitherto assumed causes for the relapse, by obtaining ultrastructural data on the response of collagen fibers after orthodontic intervention. Lateral maxillary incisors in the dog were rotated with bonded fixed appliances. The teeth were divided into groups according to different orthodontic procedures. Scanning and transmission electron microscopic analyses were performed on gingival samples after proper processing. Analyses of the untreated control samples showed well-organized, parallel, and densely packed thick bundles of collagen fibers, interconnected with thin fibers. After rotation-followed-by-retention, the gingival fibers were torn, ripped, disorganized, and laterally spaced and of increased diameter. Thus it was concluded that all these patterns are incompatible with stretching. Also, an increased number of elastic fibers were seen in proximity to the torn collagen fibers. After gingival fiberotomy, most fibers resumed the appearance of the organized pattern of large fiber bundles similar to those seen in the controls.

The relationship between drug release rate, particle size and swelling of silicone matrices

Abstract Matrices composed of silicone elastomer (polydimethylsiloxane) have been used extensively as implantable controlled release drug delivery systems. This study examined the relationship between drug particle size, release rate and swelling of silastic matrices, by using a model drug (potassium dichromate) and two types of silicone polymer. The drug particles were found to be the driving force for water uptake by the matrix. The release rate was directly proportional to the degree of swelling, which in turn was directly proportional to the drug particle size. The release rate and swelling of matrices composed of silastic 382 increased with decreasing drug particle size, while increasing drug particle size resulted in increased release rate and decreased swelling of silastic Q7 matrices, probably because air is entrapped during fabrication of these matrices. More retarded release and swelling was exhibited by silastic Q7 matrices in comparison to matrices composed of silastic 382, probably due to the different physical properties of these silicones.

Cytofluorometric analysis of thymic interdigitating cells from C57BL/6 mice prior and after leukemogenic X-irradiation

The thymus is populated by various Ia+ cell populations, including epithelial cells, macrophages and dendritic cells. Thymic cell suspensions were stained with an anti-Ia antibody and shown by cytofluorometry to contain a small number of strongly Ia+ cells characterized by a large diameter. The cell population was separated with the aid of the fluorescence-activated cell sorter (FACS) and characterized. They were shown to express high levels of membranal Ia antigens; they demonstrated ATPase activity and displayed the ultrastructural features characteristic of the previously described thymic interdigitating cells. C57BL/6 mice were submitted to various regimens of X-irradiation. Whereas exposure to a single dose of X-irradiation was followed by an increase in the percentage of strongly Ia+ cells, exposure to a leukemogenic regimen of fractionated X-irradiation led to a decrease in the percentage and absolute numbers of these cells in the thymus. Of the C57BL/6 mice that were irradiated with fractionated X-irradiation, 77% developed leukemia. Intravenous injection of syngeneic bone marrow one day following the last irradiation or protection of the femur during irradiation prevented both the appearance of leukemia and the disappearance of interdigitating cells. Therefore an inverse correlation between the presence of thymic dendritic cells and the incidence of leukemia in C57BL/6 mice could be demonstrated. These findings are discussed in relation to the putative role of dendritic cells in the thymus.

Bacilliform inclusions in cells of the proximal pars distalis in the pituitary of four species of Tilapia (Teleostei)

SummaryThin sections and replicas of freeze-etched pituitaries from six species of the teleostean family of Cichlidae were studied by electron microscopy. Four species belonging to the genus Tilapia exhibit rod-like structures, i.e., “bacilliform inclusions” (BI), about 1–2 μm in length in cells of the proximal Pars distalis. The BI are found either isolated or fused in small groups. They are enclosed in an envelope similar to that of secretory granules. Both the BI and the secretory granules give a positive PAS-reaction.