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M Benchimol

Publications and source records attributed to M Benchimol.

At least 73 records · Page 4Linked to original sources
PubMed1984

Tritrichomonas foetus: localization of filipin-sterol complexes in cell membranes.

The polyene antibiotic, filipin, was used as a probe for the detection of sterols in the freeze-fractured plasma membrane and the flagellar membranes of the pathogenic protozoa, Tritrichomonas foetus. A homogeneous distribution of filipin-sterol complexes was seen throughout the plasma membrane, and the membrane of the three anterior and the one recurrent flagella. No or very few filipin-sterol complexes were observed in some specialized regions such as the base of the flagella (necklace), the portion of the recurrent flagellum, and that part of the cell body to which the flagellum was attached. The density of filipin-sterol complexes varied from one cell to the other. In some cells, about 205 complexes/micron 2 were seen. A larger number of filipin-sterol complexes were observed on both faces of the membrane of cytoplasmic structures, probably corresponding to vacuoles. No complexes were seen in the nuclear membrane and in the membrane of the endoplasmic reticulum. Very few or no complexes were observed in the membrane of the hydrogenosomes. Treatment of living cells with filipin induced aggregation of filipin-sterol complexes at some points of the plasma membrane.

Animals↗
PubMed1984

High voltage electron microscopy of critical point dried trypanosomatids.

This paper describes the use of high voltage electron microscope for the observation of whole trypanosomatids. The protozoa were adhered, through the use of polylysine, to formvar-coated grids which were treated or not with different concentrations of Triton X-100, fixed with glutaraldehyde, dehydrated and dried by the critical point drying method. The results obtained indicate that it is possible to observe the entire mitochondrion of the whole trypanosomatid and the spatial array of the sub-pellicular microtubules.

Animals↗
PubMed1983

Fine structure and cytochemistry of the hydrogenosome of Tritrichomonas foetus.

Fine structural studies of the hydrogenosomes of Tritrichomonas foetus using an improved fixative reveal that they are enclosed by two closely apposed 6 nm membranes, which separate at some regions forming a large intramembranous vacuole where Ca++-binding sites are located. Fixation of the cells in a glutaraldehyde solution containing 5 mM CaCl2 and postfixation in an osmium tetroxide-potassium ferrocyanide solution led to the appearance of a reaction product associated with certain regions of the membrane of the hydrogenosomes and in the cisternae of the endoplasmic reticulum, in the recurrent flagellum, and in the plasma membrane. Treatment of ultrathin sections with EGTA removed the reaction product. These results, in association with others previously described, indicate the existence of several similarities between the hydrogenosomes and the mitochondria.

Animals↗
PubMed1982

Tritrichomonas foetus: fine structure of freeze-fractured membranes.

Freeze-fracture techniques reveal differences in fine structure between the anterior three flagella of Tritrichomonas foetus and its recurrent flagellum. The anterior flagella have rosettes of 9-12 intramembranous particles on both the P and E faces. The recurrent flagellum lacks rosettes but has ribbon-like arrays of particles along the length of the flagellum, which may be involved in the flagellum's attachment to the cell body. This flagellum is attached to the membrane of the cell body along a distinct groove that contains few discernible particles. Some large intramembranous particles are visible on the P face of the cell body membrane at the point where the flagellum emerges from the cell body. The randomly distributed particles on the P and E faces of the plasma membrane have a particle density of 919/micron2 and 468/micron2 respectively, and there are areas on both faces that are devoid of particles. Freeze-fracture techniques also reveal numerous fenestrations in the membrane of the Golgi complex and about 24 pores per micron2 in the nuclear membrane.

Animals↗
PubMed1981

Leishmania mexicana amazonensis: attachment to the membrane of the phagocytic vacuole of macrophages in vivo.

Intracellular forms of Leishmania mexicana amazonensis divide inside the phagocytic vacuole of macrophages. Some parasites attach to the membrane of the phagocytic vacuole while others remain free in the vacuole. Examination of thin sections of the attachment region by electron microscopy revealed a space of 2 nm between the membrane of the phagocytic vacuole and the plasma membrane of the parasite. Freeze-fracture replicas showed an array of intramembranous particles in some areas of the parasite's plasma membrane resembling a gap junction which, in other cells, is involved in the process of intracellular communication.

Adhesiveness↗
PubMed1981

Cell surface carbohydrates in Tritrichomonas foetus.

The cell surface of Tritrichomonas foetus was characterized by using 18 highly purified lectins with specificities for N-acetyl glucosamine, N-acetyl galactosamine, galactose, mannose, and sialic acid. The specificity of the lectin-induced cell agglutination was verified by inhibition of the agglutination with the specific sugars. By using cytochemical techniques associated with electron microscopy, carbohydrates were detected on the cell surface of T. foetus. The following techniques were used: periodic acid--thiosemicarbazide--silver proteinate, concanavalin A--horseradish peroxidase, and ruthenium red. Anionic sites were detected on the cell surface of the protozoan at pH's 1.8 and 7.2 with the use of colloidal iron hydroxide and cationized ferritin particles, respectively. The binding of colloidal iron particles, as well as the agglutination induced by the lectin from Limulus polyphemus, indicated the presence of sialic acid on the cell surface of T. foetus.

Acetylgalactosamine↗
PubMed1981

Specializations in the flagellar membrane to Tritrichomonas foetus.

Tritrichomonas foetus has three anterior flagella and one recurrent flagellum. The latter originate at the anterior portion of the protozoa and extends towards the posterior region of the cell adhering to the cell body. Freeze-fracturing studies showed in the flagellar membranes of the three anterior flagella, groups of nine to 12 intramembrane particles forming rosettes which could be observed on both the P- and the E-faces of the flagellar membrane. The rosettes are numerous and found along the length of the flagella. No such structure was seen in the membrane of the recurrent flagellum. The rosettes coexist with other particles in apparently random distribution.

Animals↗
PubMed1980

Observations on the innervated face of the electrocyte of the main organ of the electric eel (Electrophorus electricus L.).

The innervated face of electrocytes in the main electric organ of Electrophorus electricus L. was examined by light microscopy, both conventional and with Nomarski contrast, and by transmission and scanning electron microscopy. Acetylcholinesterase cytochemistry was used in the demonstration of the greater density of synapses over the caudal papillae. The various techniques contributed to a better understanding of the distribution and form of papillae and synapses at the posterior face of the electrocyte. Caudal papillae are longer and thinner than those at the rostral face, but it was not possible to recognize a different type sometimes referred to in the literature as small papillae. The contact of nerve endings with the electrocyte seems to be made predominantly on the terminal half of caudal papillae, however a smaller number occur elsewhere on the posterior face. Synaptic terminals frequently appear as round profiles, but may be also elongated, with or without bulges, usually occupying a depression, and separated from the post-synaptic membrane by a space of 60-100 nm, where an expansion may be found.

Acetylcholinesterase↗
PubMed1980

Freeze-fracture study of the plasma membrane of Leishmania mexican amazonensis.

The fine structure of the plasma membrane of promastigotes of Leishmania mexicana amazonensis was studied by freeze-fracture techniques. Measurement of the number of intramembranous particles per square micrometer of membrane area revealed a particle density of 2,040 +/- 213/micron2 on the P-face and 890 +/- 186/micron2 on the E-face. The particle density of the flagellar membrane was 448 +/- 53/micron2. Clusters of intramembranous particles were seen on the flagellar membrane at the region of adhesion between the flagellum and the cell body. Aggregation of particles was observed in both P- and E-faces of the plasma membrane of some cells.

Animals↗
PubMed1979

Cytochemistry and freeze-fracture of membranes isolated from the electrocyte of Electrophorus electricus (L.).

Membranes were isolated from the main electric organ of Electrophorus electricus and studied by means of cytochemistry and freeze-fracture. The membrane fractions consisted of vesicles inside-in as determined by localization of anionic sites using colloidal iron and cationized ferritin particles. The anionic sites were not homogeneously distributed on the surface of the vesicle. Freeze-fracture showed the presence of intramembranous particles associated with either protoplasmic (P) or extracellular (E) faces of the membrane. Regions of the membrane without particles were observed. The results are discussed in relation to the existence of association between intramembranous particles and membrane receptors.

Animals↗
PubMed1979

Distribution of anionic groups at the cell surface of different Sporothrix schenckii cell types.

The distribution of anionic groups at the cell surface of yeastlike forms, hyphae, and conidia of Sporothrix schenckii was studied by staining with colloidal iron hydroxide and cationized ferritin. By using colloidal iron hydroxide it was shown that the external cell wall layer of one strain (strain 1099.18) could be resolved into two reactive sublayers and that these layers were present in many but not all cells of the same population. In contrast, most cells of another strain (strain 1099.12) were stained by colloidal iron hydroxide, but only one reactive layer was seen. Acidic layers of the yeastlike forms of the two strains were much thicker than those of conidia and hyphae. By the cationized ferritin staining procedure it was observed that the acidic layers of yeast forms sloughed off of cells, probably due to cell-cell or cell-medium attrition in shaken submerged cultures or to a process by which the outer layers detach from cells as they are replaced by newly synthesized ones. The colloidal iron hydroxide- and cationized ferritin-reactive cell surface layers of S. schenckii correspond to the previously described (L. R. Travassos et al., Exp. Mycol. 1:293-305, 1977) concanavalin A-reactive peptidorhamnomannan complexes, and their reactivity is probably due to the presence of acidic amino acids of low pK values rather than to glucuronic acid units.

Anions↗
PubMed1977

An electron microscopic investigation of the surface coat of the electrocyte of electrophorus electricus.

The surface coat of the electrocyte of the main electric organ of Electrophorus electricus was studied using cytochemical methods (periodic acid-silver methanamine, periodic acid-chromic acid-silver methenamine, periodic acid-thiosemicarbazide-silver proteinate, Concanavalin A - horseradish peroxidase, ruthenium red, Alcian-blue lanthanum nitrate, colloidal iron hydroxide and cationized ferritin). The surface of the electrocyte presents perpendicularly oriented tubular invaginations of the cell membrane. The fibrous coat 50-100 nm thick, penetrates into the lumen of the invaginations. It is also observed in the synaptic clefts existent in the posterior face of the electrolyte. The coating of the surface membrane gives a positive reaction with all techniques used. Binding of colloidal iron hydroxide particles was observed only in the outer layer of the coat. With the Alcian-blue lanthanum nitrate technique , microtubules were observed in the cytoplasm of the electrocyte. The results indicate that the surface coat of the electrocyte contains mucopolysaccharides, glycoproteins, acid mucopolysaccharides and anionic sites detected at low (colloidal iron hydroxyde) and neutral (cationized ferritin) pH.

Animals↗
PubMedDate not supplied

Trichomonas vaginalis: evaluating capsid proteins of dsRNA viruses and the dsRNA virus within patients attending a sexually transmitted disease clinic.

Some isolates of Trichomonas vaginalis, the number one, non-viral sexually transmitted disease agent, are infected with one or several distinct double stranded (ds)-RNA virus. Immune rabbit anti-capsid serum (IRS) reacted with the capsid protein of purified dsRNA virus of a subset of the virus-infected T. vaginalis isolates. A monoclonal antibody (mAb) that recognized the capsid protein reactive with the IRS was generated. Analysis of the virus capsid protein of virus-infected isolates by probing nitrocellulose blots with mAb revealed diversity among immunoreactivity and in the size of the reactive capsid protein. Despite difficulties in visualizing virus within parasites by cross-section electron microscopy, gold-conjugated mAb readily labeled the cytoplasm of virus-positive trichomonads. Finally and importantly, isolates infecting patients attending an STD clinic, 75% of which were virus-positive isolates, had capsid protein of the same size detected by mAb present in all dsRNA viruses.

Animals↗