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Biomedical subjects

F Solomon

Publications and source records attributed to F Solomon.

At least 109 records · Page 6Linked to original sources
PubMed1979

Identification with cellular microtubules of one of the co-assemlbing microtubule-associated proteins.

In this paper we describe a procedure for detecting proteins associated with cytoplasmic microtubules in vivo. Detergent-extracted cytoskeletons of NIL8 hamster cells are prepared under conditions which preserve the microtubules. The cytoskeletons are then extracted in the presence of calcium, which depolymerizes the microtubules and quantitatively extracted cytoskeletons are prepared from cells that have been incubated with colchicine. The cytoskeletons from these cells contain no microtubules or tubulin. Electrophoretic analysis of the calcium extracts of the colchicine-treated and untreated cells reveals several radioactively labeled polypeptides. There is, however, no apparent quantitative or qualitative difference between the two extracts other than the tubulin polypeptides. Each of the extracts is mixed with an excess of unlabeled calf brain microtubule protein and carried through cycles of temperature-dependent microtubule assembly. Distinct species from each extract co-assemble at a constant ratio, but only one polypeptide is uniquely derived from cells containing intact microtubules. The molecular weight of this polypeptide is similar to that proposed for the tau species detected in brain microtubule preparations.

Animals↗
PubMed1979

Detailed neurite morphologies of sister neurolbastoma cells are related.

Neuroblastoma cells exhibit a wide variety of patterns of neurite morphology. However, when these cells are induced to extend neurites under conditions in which mitotic sister cells are readily identifiable, 60% of these sister pairs display analogous morphologies. These cells are related either as identical twins or as mirror images of each other. The relatedness is expressed in considerable detail of neurite morphology. These relationshiops can persist through at least two cell divisions. The results suggest that animal cells can inherit specific determinants of shape.

Animals↗
PubMed1979

The outer boundary of the cytoskeleton: a lamina derived from plasma membrane proteins.

We prepared the cytoskeletal framework by gently extracting cells with Triton X-100. Lipids and soluble proteins were removed, leaving a complex meshlike structure which contains the cell nucleus and is composed of the major cell filament networks as well as the microtrabeculae with attached polyribosomes. The surface sheet or lamina covering this structure contains most of the cell surface proteins by the following criteria. Intact cells are labeled externally with radioiodine and then extracted with detergent. The iodinated poteins remain almost entirely with skeletal framework. A new major integral protein, the coat protein of Sindbis virus, is inserted into the plasma membrane of infected cells. This new protein is heavily iodinated and remains almost completely associated with the framework after extraction. Lectin binding and poliovirus binding sites are also retained after detergent extraction. Our results indicate that plasma membrane proteins form a sheet or lamina upon removal of lipids. This lamina reproduces even complex surface convolutions and appears to be supported by and intimately connected to the underlying skeleton. In this case, the surface lamina, and hence the plasma membrane of the original intact cell, might be viewed as a component of the cytoskeletal framework.

Animals↗
PubMed1979

Crawling movements of lymphocytes on and beneath fibroblasts in culture.

Some lymphocytes become highly motile upon immunological stimulation in vivo or in vitro. When introduced into a culture of 3T3 or L cells and followed by live-cell microscopy, some of these lymphocytes were observed to crawl on top of, along the edges of, and preferentially beneath the attached fibroblasts. The crawling could be as rapid as 20 mum/min, easily detectable without a time-lapse device. The striking ability of crawling lymphocytes to penetrate beneath attached 3T3 cells provided a quantitative means to compare the crawling activity of different lymphocyte populations under various conditions. Crawling was diminished by inhibitors of energy metabolism, by agents that disrupt the cytoskeleton, and by absence of Mg(2+) and Ca(2+), but not of Ca(2+) alone. Crawling lymphocytes were virtually absent in normal thymus and spleen cells. They increased greatly in 5-day mixed lymphocyte cultures and in peritoneal exudate lymphocytes taken after mice had been immunized with allogeneic tumor cells. T cells accounted for most of the crawlers. Of two T-cell leukemias tested, R1(+) cells were crawlers whereas EL-4 cells were not. The H-2 haplotype of the 3T3 fibroblasts (i.e., whether syngeneic or allogeneic) had no apparent effect on lymphocyte crawling activity. The crawling may relate to the exploration of cell surface antigens by lymphocytes (immune surveillance), to the mode of action of cytotoxic T cells, to the migration of lymphocytes across blood vessel walls, or to the penetration of lymphocytes into "solid" masses of normal tissue or tumor cells.

Animals↗
PubMed1978

A case of listeriosis in pregnancy with fetal survival.

Listeriosis during pregnancy is generally considered to result in an intrauterine infection which affects the fetus before birth or in the perinatal period. A case of listeriosis in a 38-yr-old diabetic woman with an influenza-like disease in her 32nd wk of pregnancy is presented. Two successive blood cultures were positive for Listeria monocytogenes type 4b and her serum showed a rising titer for agglutinins to this organism. After antibiotic treatment of the patient she gave birth to a healthy child.

Adult↗
PubMed1977

Binding sites for calcium on tubulin.

Calcium ions can inhibit the in vitro assembly of microtubules and, therefore, may play a role in the regulation of microtubule formation in vivo. In order to test the validity of this hypothesis; the interaction between calcium and pruified brain microtubular protein has been investigated by standard binding assays. We have detected and characterized two classes of binding sites for calcium on tubulin, the major component of cytoplasmic microtubules. There is a single high-affinity site per tubulin molecule, characterized by a dissociation constant of 3.2 X 10(-6) M. That site is inhibited by magnesium (k1 = 5 X 10(-5) M) and potassium chloride. There are approximately 16 low-affinity sites which have a dissociation constant of 2.8 X 10(-4) M, and which are also inhibited by potassium chloride. Binding at the low-affinity sites is slightly enhanced by low magnesium concentrations. Both classes of sites are distinguishable from the colchicine binding site, and are apparently also distinct from the vinblastine and guanine nucleotide sites. The characteristics of the calcium binding activity of tubulin are similar to those found for the calcium-binding proteins of sarcoplasmic reticulum. The results are consistent with a physiological role for calcium in the regulation of microtubule assembly.

Animals↗
PubMed1976

Utilization of the inactivation rate of coenzyme A transferase by thiol reagents to determine properties of the enzyme-CoA intermediate.

The rate of inactivation of succinyl-CoA:3-ketoacid coenzyme A transferase by thiol reagents is increased 3 to 100 times by very low concentrations of acyl-CoA substrates. The same maximum inactivation rate is found with acetoacetyl-CoA and succinyl-CoA. The enhanced rate of inactivation is caused by the stoichiometric formation of the enzyme-CoA intermediate and an accompanying conformation change of the enzyme. The inactivation rate provides a simple assay for the amount of enzyme present as the enzyme-CoA intermediate, using only catalytic concentrations of enzyme. This technique has been utilized to measure (a) a rate constant for hydrolysis of the enzyme-CoA intermediate of 0.10 min-1 at pH 8.1; (b) a stoichiometry of two active sites per enzyme molecule; and (c) the equilibrium constants for formation of the enzyme-CoA intermediate from dilute solutions of substrates (and hence for the overall reaction) by determining the ratio of [enzyme-CoA]/[enzyme] in the presence of a series of substrate "buffers" at different ratios of [RCOO-]/[RCOSCoA]. As the total concentration of acyl-CoA and carbosylate substrates is increased, the inactivation rate is decreased. This indicates that the Michaelis complexes are protected against inactivation.

Binding Sites↗
PubMed1976

Intermolecular tritium transfer in the transcarboxylase reaction.

Transfer of tritium from [3-3H]pyruvate into propionyl-CoA is found during the reaction of transcarboxylase: Methylmalonyl-CoA + pyruvate leads to oxalacetate + propionyl-CoA. About 5% of the tritium counts that are labilized in the reaction are found in a position of the propionate that exchanges rapidly with water in the presence of transcarboxylase. Transfer from [2-3H]propionate of propionyl-CoA to pyruvate is real but only about one-tenth as great. The tritium transfers between reactants on two subunits are difficult to explain by a "carbanion" mechanism of --C--H bond cleavage and support the cyclic mechanism in which carboxybiotin itself is the base and the enol form of biotin is the proton-transferring agent.

Carboxyl and Carbamoyl Transferases↗
PubMed1976

Isolation of Mycoplasma from the placenta after cesarean section.

Placentas obtained at cesarean section were cultured for Mycoplasma and other microorganisms in 123 randomly selected patients in order to evaluate the incidence of Mycoplasma, to identify factors which may contribute to their presence, and to correlate their presence with the occurrence of postpartum infection. Twenty-eight placentas (22.8%) yielded Mycoplasma positive cultures. The incidence of Mycoplasma in the placenta was significantly higher in patients with ruptured membranes. The incidence of postpartum fever was significantly higher (P less than 0.01) in cases positive for Mycoplasma as compared to cases in which the placenta was negative for Mycoplasma. Findings were similar for both groups with regard to the incidence of unexplained postpartum fever. The results of this study suggest that Mycoplasma may be considered a relatively frequent pathogen and should be considered a possible cause of postpartum fever.

Cesarean Section↗
PubMed1975

Infections with mycoplasma and bacteria in induced midtrimester abortion and fetal loss.

Placentas and fetuses from cases of induced midtrimester abortion and fetal loss (13 weeks of pregnancy or more) were examined microbiologically. In the series of midtrimester fetal loss, bacteria were isolated in 14 per cent and genital Mycoplasma in 37 per cent of the placentas. In induced abortion, 18 per cent of the placentas grew bacteria and in only one case out of 27 was a Mycoplasma strain isolated. Fetal organs yielded cultures positive for bacteria in 16 per cent and for genital Mycoplasma in 23 per cent of the spontaneous fetal loss material, whereas pyogenic cocci were isolated from fetal organs in 18 per cent and Mycoplasma in no case of induced abortion. In the positive cases, the fetal lungs were most often infected (in 34 out of 37 positive cases of spontaneous and 4 out of 5 positive cases of induced abortion). On the other hand, microorganisms could be isolated from the brain in only 5 out of 28 cases of spontaneous and none of induced abortion. In the series of fetal loss, positive microbiologic findings from the fetal organs seemed correlated to prolonged bleeding before abortion or labor and to premature rupture of membranes.

Abortion, Induced↗