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Biomedical subjects

S G Cohen

Publications and source records attributed to S G Cohen.

At least 55 records · Page 3Linked to original sources
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

Rhinomaxillary mucormycosis in a kidney transplant patient.

Rhinomaxillary mucormycosis is an uncommon but important pathologic entity with a rapidly fatal course if treatment is delayed. This is of particular interest to dentists, since many of the earliest clinical signs appear in the oral and perioral regions. Successful therapy demands early diagnosis by biopsy, institution of amphotericin B therapy, and surgical débridement. A case of nonfatal rhinomaxillary mucormycosis is presented, and all other reported cases in transplant patients are reviewed.

Adult↗
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↗
PubMed1976

Carboxamidomethyl esters as reactive substrates for alpha-chymotrypsin. Orientational effects of hydrogen-bonding interactions.

Effects of hydrogen-bonding interactions of amide groups on reactivity of esters to alpha-chymotrypsin were studied. Of the methyl esters studied, only that from acetyl-L-phenylalanine has k3 rate-limiting. In methyl beta-phenylpropionates an alpha-acetamido substituent increased k2 greater than 550 times, k3 approximately 5 times; an alpha-acetylclycyloxy substituent increased k2 approximately 2 times, k3 approximately 6 times, both in comparison with the alpha-acetoxy esters. Essentially all carboxamidomethyl esters studied have k3 rate-limiting; reactivity to hydroxide is only 4 times that of methyl esters. In alpha-substituted beta-phenylpropionates, carboxamido-methyl esters show k2 values greater than 110 times greater than 280 times, greater than 26 times, and 7 times the k2 values of the methyl esters for the alpha substituents, acetoxy, acetylglycyloxy, hydroxy, and hydrogen, respectively. In esters of alpha-acetamido acids, carboxamidomethyl esters show k2 values 44 times, greater than 110 times, greater than 12 times, and approximately 33 times the k2 values of the methyl esters of glycine, alanine, leucine, and phenylalanine, respectively. Cyanomethyl esters also had k3 rate-limiting. Hydrogen-bonding to the enzyme of either an alpha-acetamido group or a carboxamidomethyl group combined with bonding of the beta-aryl group, orients the hydrolyzing groups properly, increasing k2. Hydrogen-bonding of both alpha-acetamido and carboxamido-methyl groups is effective to a lesser degree. The amide group appears to have small effects on Ks as hydrogen bonding is balanced by desolvation. It is proposed that desolvation during bonding increases k2 and Ks.

Amides↗