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Biomedical subjects

S Ofer

Publications and source records attributed to S Ofer.

17 recordsLinked to original sources
PubMed2004

The flow rate of whole and submandibular/sublingual gland saliva in patients receiving replacement complete dentures.

Provision of complete dentures to a new denture wearer increases the salivary flow rate is well known. The new dentures act as an additional mechanical stimulus to the salivary reflexes, thus increasing the flow rate. The purpose of this study was to determine whether replacing complete dentures would elicit the same response. Unstimulated and stimulated whole and submandibular/sublingual (SM/SL) saliva were collected before inserting complete replacement dentures and again after 2 days and after 3 weeks of denture wearing. Unstimulated whole salivary flow rate increased significantly 2 days after inserting replacement dentures, decreasing at 3 weeks but remaining significantly above the baseline. Stimulated whole salivary flow rate increased significantly after 2 days but decreased to normal after 3 weeks. Stimulated and unstimulated SM/SL salivary flow rate increased significantly after 2 days, decreasing at 3 weeks while remaining significantly above the values found before denture insertion.

Aged↗
PubMed1987

Effect of extracellular hemin on hemoglobin and ferritin content of erythroleukemia cells.

Mouse (MEL) and human (K-562) erythroleukemia cell lines can be induced to undergo erythroid differentiation, including hemoglobin (Hb) synthesis, by extra cellular hemin. In order to study the effect of extracellular hemin on intracellular ferritin and Hb content, we have used Mossabauer spectroscopy to measure the amount of 57Fe incorporated into ferritin or Hb and a fluorescent enzyme-linked immunosorbent assay (ELISA) to measure the ferritin protein content. When K-562 cells were cultured in the presence of a 57Fe source either as transferrin or citrate, in the absence of a differentiation inducer, all the intracellular 57Fe was detected in ferritin. When the cells were cultured in the presence of 57Fe-hemin, 57Fe was found in both ferritin and Hb. 57Fe in ferritin increased rapidly, and after 2 days it reached a plateau at 5 X 10(-14) g/cell. 57Fe in Hb increased linearly with time and reached the same value after 12 days. Addition of other iron sources such as iron-saturated transferrin, iron citrate, or iron ammonium citrate caused a much lower increase in ferritin protein content as compared to hemin. When K-562 cells were induced by 57Fe-hemin in the presence of 56Fe-transferrin, 57Fe was found to be incorporated in equal amounts into both ferritin and Hb. However, when the cells were induced by 56Fe-hemin in the presence of 57Fe-transferrin, 57Fe was incorporated only into ferritin, but not into Hb, which contained 56Fe iron. These results indicate that in K-562 cells, when hemin is present in the culture medium it is preferentially incorporated into Hb, regardless of the availability of other extra- or intracellular iron sources such as transferrin or ferritin. In MEL cells induced to differentiate by dimethylsulfoxide (DMSO) a different pattern of iron incorporation was observed; 57Fe from both transferrin and hemin was found to incorporate in ferritin as well as in Hb.

Animals↗
PubMed1985

Iron uptake by teeth and bones: a Mossbauer effect study.

Iron uptake (Fe2+ and Fe3+) by bones, teeth, and dental enamel was studied, in vivo and in vitro, by chemical, powder X-ray diffraction and Mossbauer spectroscopy methods. Atomic absorption tests have revealed the permanent uptake of small amounts of iron by dental enamel soaked in vitro in solutions containing Fe2+. Mossbauer spectra show that the iron attached to the dental enamel stays at the same valency it had in the soaking solutions. Mossbauer measurements of in vivo samples show that iron is present in bones and teeth mainly as Fe3+ (10% Fe2+ in teeth), in compound similar to FeOOH. Iron is released or exchanged from teeth at a much lower rate than from bones.

Animals↗
PubMed1984

The malarial pigment in rat infected erythrocytes and its interaction with chloroquine. A Mössbauer effect study.

Mössbauer studies of rat erythrocytes infected by Plasmodium berghei malaria parasites, using 57Fe-enriched rat red blood cells, were carried out in order to determine the physical parameters which characterize the malarial pigment iron and to test the effect of the widely used antimalaria drug, chloroquine, on these parameters. The iron in the malarial pigment which is derived from hemoglobin digestion by the intracellular parasite was found to be trivalent, high spin, with Mössbauer parameters which are significantly different from those of any known iron porphyrin containing compound. No difference was found between the parameters obtained in erythrocytes infected by drug-sensitive and drug-resistant strains of P. berghei, both before and after the treatment with chloroquine. The iron compound consists of microaggregates, about 30 A in diameter. These are somewhat larger in chloroquine-resistant strains and tend to increase in size in chloroquine-sensitive strains upon treatment with the drug. Mössbauer spectra of erythrocytes infected by a chloroquine-resistant strain revealed pigment iron in relative amounts invariable of those found in chloroquine-sensitive strains, demonstrating that drug-resistant parasites indeed digest hemoglobin.

Animals↗
PubMed1984

Magnetosome dynamics in magnetotactic bacteria.

Diffusive motions of the magnetosomes (enveloped Fe3O4 particles) in the magnetotactic bacterium Aquaspirillum magnetotacticum result in a very broad-line Mössbauer spectrum (T approximately 100 mm/s) above freezing temperatures. The line width increases with increasing temperature. The data are analyzed using a bounded diffusion model to yield the rotational and translational motions of the magnetosomes as well as the effective viscosity of the material surrounding the magnetosomes. The results are [theta 2] l/2 less than 1.5 degrees and [x2] 1/2 less than 8.4 A for the rotational and translational motions, respectively, implying that the particles are fixed in whole cells. The effective viscosity is 10 cP at 295 K and increases with decreasing temperature. Additional Fe3+ material in the cell is shown to be associated with the magnetosomes. Fe2+ material in the cell appears to be associated with the cell envelope.

Bacterial Physiological Phenomena↗
PubMed1983

Dynamics of heme iron in crystals of metmyoglobin and deoxymyoglobin.

The 57Fe gamma-ray resonance absorption spectra have been measured in crystals of metmyoglobin and deoxymyoglobin over a wide range of temperatures. Above a critical temperature common to both proteins (220 K), the dynamics of heme iron display a dramatic change, in that two kinds of thermal fluctuations come into play--a fast fluctuation associated with a steep decrease of the total fluctuation of characteristic time 10(-8) sec, associated with bounded diffusive motion. By using both discrete jump and continuous diffusion models, the latter based on the Brownian motion of an overdamped harmonic oscillator, the essential parameters of the iron motion (mean square displacement and jump frequency or diffusion constant) can be derived as a function of temperature. Thus, for deoxy Mb at 288 K, the mean square displacement for the fast fluctuation is about 6 X 10(-2) A2 and for the diffusive motion is 1.6 X 10(-2) A2; the diffusion constant is 4 X 10(-10) cm2/sec. The diffusive process is associated with an activation energy of about 0.75 kcal/mol. Although the same general kinds of phenomena are observed in crystals of MetMb and deoxy Mb, significant differences in behavior are found, which suggest that the main dynamical phenomenon observed reflects internal large-scale motions of the protein.

Animals↗
PubMed1983

Iron storage in ferritin following intracellular hemoglobin denaturation in erythroleukemic cells.

Murine erythroleukemia (MEL) and human K-562 cell lines were cultured in the presence of 57Fe, and the quantities of cellular iron-containing compounds were determined with the aid of Mössbauer spectroscopy. Upon induction of differentiation, both ferritin-iron and hemoglobin (Hb) iron could be detected. Treatment of the cells with 0.01%-0.02% acetylphenylhydrazine (APH) resulted in gradual denaturation of Hb and incorporation of the released Hb-iron into ferritin. Following treatment with APH, the ratio of Hb-57Fe to ferritin-57Fe decreased from 2.6 to 0.2 in MEL cells and from 0.56 to 0.12 in K-562 cells. No change was observed in the total intracellular iron. Using fluorescence ELISA, an increased level of immunologically detectable ferritin was found in hemoglobinized K-562 cells treated with APH, as compared to the amount of ferritin found in untreated cells. Ferritin may thus function not only as an intermediate during Hb synthesis, but also as storage protein for iron released during Hb denaturation.

Animals↗
PubMed1982

Study of storage iron in cultured chick embryo fibroblasts and rat glioma cells, using Mössbauer spectroscopy.

57Fe Mössbauer spectra of normal and Rous sarcoma virus-infected cultured chick embryo fibroblasts and rat glioma cells have been measured between 0.08 and 318 K. Ferritin-like iron and bacterio-ferritin-like iron have been found in these cells, in various relative amounts, indicating a close relationship between the two storage materials. The bacterio-ferritin-like iron was found to be predominantly membrane-bound. Above 260 K very wide lines were observed in the Mössbauer spectra, yielding an effective viscosity of about 1 poise in the normal chick embryo fibroblasts and about 0.5 poise in the virus-infected chick embryo fibroblasts.

Animals↗
PubMed1981

Mössbauer spectroscopy of iron-containing dermal granules from Molpadia intermedia.

Dermal granules containing hydrous ferric oxide cores from Molpadia intermedia were studied by Mössbauer spectroscopy from 1.5 to 300 K and in magnetic fields up to 80 kOersted at 4.2 K. A magnetic phase transition to an antiferromagnetically ordered state is observed at 10 K. The results are compared with the magnetic behavior of micellar cores of ferritin from eukaryotes and iron-storage materials from prokaryotes.

Animals↗
PubMed1981

The composition and the structure of bacterioferritin of Escherichia coli.

Bacterioferritin isolated from Escherichia coli is of two kinds: a protein containing a polynuclear iron compound, the bacterioferritin proper and a protein free of the polynuclear iron compound, the apo-bacterioferritin. Bacterioferritin of both kinds is characterized by absorption maxima at 417,530 and 560 nm, contributed by protohaem IX. Single crystals of bacterioferritin of the space group I432 suggest that the molecule is made up of 24 identical subunits related by a cubic point symmetry. The molecular weight of the protein subunit, as determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, is 15000. In the electron microscope the bacterioferritin molecule appears to be a sphere of 9.5 nm (95 A) diameter composed of a negatively staining outer shell and an inner electron-dense core of 6 nm (60 A) diameter.

Apoproteins↗
PubMed1981

Ferritin concentration in normal and abnormal erythrocytes measured by immunoradiometric assay with antibodies to heart and spleen ferritin and Mössbauer spectroscopy.

Immunoradiometric assays using antibodies to spleen and heart ferritin were combined with Mössbauer studies on normal and pathological erythrocytes. All erythrocytes examined were found to contain greater amounts of heart type than spleen type ferritin. The ferritin concentration in erythrocytes from patients with beta thalassaemia, sickle cell disease and sideroblastic anaemia is much higher than in normal cells. When the concentration of ferritin-like iron in the pathological erythrocytes measured by Mössbauer spectroscopy is compared to the total amount of ferritin assayed by the two antibodies in the same haemolysates the iron/protein ratio ranges between 0.3 and 3.4. The iron/protein ratio in iron-filled ferritin molecules is about 0.56 and values in excess of this suggest that the iron detected in these cells is a mixture of ferritin molecules, partly denatured ferritin polymers and 'haemosiderin'. There is a possibility that erythrocytes contain an immunologically distinct type of ferritin that is not detected by existing assays, but we have no direct evidence for this.

Anemia, Sickle Cell↗
PubMed1981

Iron incorporation into ferritin and hemoglobin during differentiation of murine erythroleukemia cells.

Hemoglobin and ferritin iron content have been followed during differentiation in tissue cultures of murine erythroleukemia cells (MELC) using the techniques of Mössbauer spectroscopy and electron microscopy. In undifferentiated cells grown without DMSO, only iron stored in ferritin was detected. The amount of iron in a cell grown in the presence of iron citrate is approximately 1.2 X 10(-14) g, whereas in a cell grown in the presence of transferrin the amount is approximately 0.28 X 10(-14) g. These quantities do not depend on the iron concentration in the nutrition medium in a range from 0.3 to 2.0 microgram Fe/ml and are the same for growth times between 8 hr and 7 days. Cells grown with DMSO contain, in addition to ferritin, increasing concentrations of hemoglobin. Chase experiments prove that ferritin iron participates in hemoglobin synthesis. The amount of ferritin iron reaches saturation within less than 8 hr in MELC grown with or without DMSO. In differentiating cells grown with iron citrate there is a decrease with time in ferritin iron content concomitant with the increase in hemoglobin. Cells grown with transferrin incorporate additional amounts of iron, which are approximately equal to the amounts used for hemoglobin synthesis maintaining a constant ferritin iron level. In the electron microscope, iron is seen only as ferritin within lysosomes. The density of the ferritin in lysosomes correlates with the ferritin iron concentrations determined by Mössbauer spectroscopy.

Animals↗
PubMed1980

Mössbauer spectroscopy of Escherichia coli and its iron-storage protein.

57Fe Mössbauer spectra of whole frozen Escherichia coli cells and of an iron storage protein isolated from iron-rich cells of E. coli have been measured over a range of temperatures down to 0.08 K. The spectra of E. coli cells with high iron content and of the iron storage protein were found to be very similar. Above 4 K these spectra consist of a quadrupole split doublet characteristic of Fe3+. Below 3.5 K, the spectra display magnetic hyperfine splitting which is temperature dependent, and point to the existence of an ordered magnetic phase associated with a saturation magnetic hyperfine field of 43 tesla in both samples. The results indicate that the bulk of iron in the iron-rich cells is in the form of aggregates similar in nature to the iron cores in the isolated protein, although the latter account for not more than 1% of the total iron in the cells. The Mössbauer spectra of the isolated protein are different from those observed in ferritin, the iron-storage protein of plants and higher animals, showing that the iron cores in these two proteins are different.

Escherichia coli↗
PubMed1980

Iron storage in Mycoplasma capricolum.

Considerable quantities or iron were incorporated into the Mycoplasma capricolum cell membrane. Mossbauer studies showed that the iron is in a form which becomes magnetically ordered at low temperatures. The iron-enriched cells contained membrane-bound electron-dense particles of about 6.0 nm in diameter.

Cell Membrane↗
PubMed1979

Quantitative studies of ferritinlike iron in erythrocytes of thalassemia, sickle-cell anemia, and hemoglobin Hammersmith with Mössbauer spectroscopy.

By using the technique of recoil-free absorption (Mössbauer effect) in iron, we found large amounts of iron, yielding a well-defined spectrum different from that of oxy- or deoxyhemoglobin, in whole erythrocytes of 13 patients with beta-thalassemia major and intermedia, 3 with hemoglobin H disease, 2 with sickle-cell anemia, and 1 with unstable hemoglobin Hammersmith. The Mössbauer spectra at various temperatures of this additional component of iron were found to be identical to spectra obtained from isolated ferritin or hemosiderin. This observation, together with additional arguments, strongly suggests that the compound responsible for the additional subspectrum is an iron storage protein, ferritin or hemosiderin. The amounts of ferritinlike iron were comparable to those of hemoglobin iron and were particularly large in reticulocytes. No ferritinlike iron was detected in patients with severe autoimmune hemolytic anemia and pernicious anemia. The large quantities of ferritinlike iron in hemoglobinopathies are probably due to intracellular hemoglobin denaturation and the consequent release of excess iron.

Anemia↗