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F Solomon

Publications and source records attributed to F Solomon.

At least 73 records · Page 4Linked to original sources
PubMed1986

A chicken-yeast chimeric beta-tubulin protein is incorporated into mouse microtubules in vivo.

The role of divergent primary sequences in restricting tubulin function was tested in vivo by a gene transfection experiment. A chicken-yeast chimeric beta-tubulin DNA was introduced into 3T3 cells using the transfection vector pSV2. The 5' end of this gene, from chicken, is similar but not identical with that of mouse beta-tubulins; the 3' end, from yeast, contains a carboxyl terminus that is very different from other known beta-tubulin sequences. The chimeric protein is incorporated efficiently into each of the microtubule structures and each of the microtubules in the host cells. The presence of the protein has no apparent effect on either growth rate or cell morphology. The results suggest that the divergent sequences in this chimeric tubulin molecule place no restrictions on its activities in mouse cells.

Amino Acid Sequence↗
PubMed1986

Multiple NADPH-producing pathways control glutathione (GSH) content in retina.

Glutathione (GSH), together with NADPH-producing pathways and glutathione reductase, provides a defense system against oxidants. Oxidation of GSH causes stimulation of the hexose monophosphate shunt and increased production of NADPH. We have asked if hexose monophosphate shunt activity is required for the recovery of GSH following exposure of the isolated rat retina to an oxidant. Hexose monophosphate shunt activity was decreased by depleting the retina of hexose stores, before exposing the tissue to diamide (0.04-1.0mM), an oxidant for GSH, for 30 min. After exposure, retinas were transferred to either glucose-containing or glucose-free recovery medium for an additional 30 min. Control retinas kept in glucose-free, oxygenated medium (no diamide) for 90-120 min maintained GSH at 90% of the value found in retinas incubated with glucose. After exposure of hexose-depleted retinas to 0.4 mM diamide, a nearly 90% decrease in GSH was observed. When the oxidant was removed, the level of GSH returned to more than 80% of the control value in the presence or absence of glucose. In contrast, no recovery of GSH was observed after diamide treatment if the retinas were transferred to ice-cold (1-5 degrees C) media with or without glucose or if the retinas were pre-treated with 2 mM 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) to inhibit glutathione reductase. Measurements of two NADPH-producing cytosolic enzymes, namely NADP+-dependent malic enzyme and NADP+-dependent isocitrate dehydrogenase, revealed high activities. Optimum production of NADPH from malic enzyme was 0.90 nmol NADPH produced min-1 per retina, while with isocitrate dehydrogenase the average rate was 6.9 nmol NADPH produced min-1 per retina. We suggest that these enzymes together with a long-lived endogenous substrate (probably glutamate) are responsible for the recovery of GSH in hexose-depleted retinas. The present results suggest that more than one NADPH-producing system is capable of controlling the GSH concentration in retina. Studies that have focused on the hexose monophosphate shunt pathway as the sole source of NADPH for glutathione reductase in retina and other tissues may require re-evaluation depending on the overall metabolic capacity and substrate utilization of the particular tissue. Thus, the present findings are significant not only with respect to the retina but also for other tissues whose metabolic characteristics are similar to those found in the retina.

Animals↗
PubMed1986

Components of microtubular structures in Saccharomyces cerevisiae.

Most studies of cytoskeletal organelles have concentrated on molecular analyses of abundant and biochemically accessible structures. In many of the classical cases, however, the nature of the system chosen has precluded a concurrent genetic analysis. The mitotic spindle of the yeast Saccharomyces cerevisiae is one example of an organelle that can be studied by both classical and molecular genetics. We show here that this microtubule structure also can be examined biochemically. The spindle can be isolated by selective extractions of yeast cells by using adaptations of methods successfully applied to animal cells. In this way, microtubule-associated proteins of the yeast spindle are identified.

Benzimidazoles↗
PubMed1986

Two functional alpha-tubulin genes of the yeast Saccharomyces cerevisiae encode divergent proteins.

Two alpha-tubulin genes from the budding yeast Saccharomyces cerevisiae were identified and cloned by cross-species DNA homology. Nucleotide sequencing studies revealed that the two genes, named TUB1 and TUB3, encoded gene products of 447 and 445 amino acids, respectively, that are highly homologous to alpha-tubulins from other species. Comparison of the sequences of the two genes revealed a 19% divergence between the nucleotide sequences and a 10% divergence between the amino acid sequences. Each gene had a single intervening sequence, located at an identical position in codon 9. Cell fractionation studies showed that both gene products were present in yeast microtubules. These two genes, along with the TUB2 beta-tubulin gene, probably encode the entire complement of tubulin in budding yeast cells.

Amino Acid Sequence↗
PubMed1986

Genetically essential and nonessential alpha-tubulin genes specify functionally interchangeable proteins.

Microtubules in yeast are essential components of the mitotic and meiotic spindles and are essential for nuclear movement during cell division and mating. The relative importance in these processes of the two divergent alpha-tubulin genes of the budding yeast Saccharomyces cerevisiae, TUB1 and TUB3, was examined through the construction of null mutations and by increasing their copy number on chromosomes and on plasmids. Experiments with null alleles of TUB3 showed that TUB3 was not essential for mitosis, meiosis, or mating. Null alleles of TUB3, however, did cause several phenotypes, including hypersensitivity to the antimicrotubule drug benomyl and poor spore viability. On the other hand, the TUB1 gene was essential for growth of normal haploid cells. Even in diploids heterozygous for a TUB1 null allele, several dominant phenotypes were evident, including slow growth and poor sporulation. This functional difference between the two genes is apparently due to different levels of expression, because extra copies of either gene could suppress the defects caused by a null mutation in the other. We conclude that in spite of the 10% divergence between the products of the two genes, there is no essential qualitative functional difference between them.

Alleles↗
PubMed1985

Smell and other sensory disturbances in migraine.

Osmophobia or hyperosmia featured in 25 of 50 migraineurs during the headache phase of their attacks. Pleasant or unpleasant odours could precipitate migraines in 11 patients in this series. Other sensory disturbances and precipitants were also studied. Neurological precipitation of attacks provides further support for a primary neural rather than a vascular pathogenesis of migraine.

Adolescent↗
PubMed1985

Analyzing the components of microtubules: antibodies against chartins, associated proteins from cultured cells.

In previous work, we have identified cytoplasmic microtubule-associated proteins by isolating the microtubule organelles of several different cultured cells. Among those proteins are the chartins, a family of polypeptides with related sequence but of varying molecular weight and isoelectric point. Biochemical analyses of the distribution of the chartins in the cytoplasm, and among cells with different functions, suggest that they may regulate microtubule structure in vivo. We describe here the preparation and application of antibodies to chartins. These antibodies enable us to demonstrate that the chartins colocalize with assembled tubulin in the cytoplasm, as assessed by immunofluorescence, so that they fulfill a major criterion that has been applied to other putative microtubule components. The results also demonstrate that the tau proteins, which fractionate and copurify with chartins, are in fact clearly distinguishable from them. The implications of these results for evaluating microtubule composition are discussed.

Animals↗
PubMed1984

Kinetics and intermediates of marginal band reformation: evidence for peripheral determinants of microtubule organization.

The microtubules of the mature erythrocyte of the chicken are confined to a band at the periphery. Whole-mount electron microscopy after extraction reveals that the number of microtubules in each cell is almost the same. All the microtubules can be depolymerized by incubation in the cold, and the marginal band can be quantitatively and qualitatively reformed by return to 39 degrees C. These properties allow the reformation of the marginal band to be treated as an in vivo microtubule assembly reaction. The kinetics of this reaction and the intermediates detected during reformation suggest a mechanism of microtubule organization that is distinct from that observed in other cell types. Apparently only one or two growing microtubule ends are available for assembly--assembly is only detected at the cell periphery, even at early times--and there is no evidence of the participation of a microtubule-organizing center.

Animals↗
PubMed1984

Reformation of the marginal band of avian erythrocytes in vitro using calf-brain tubulin: peripheral determinants of microtubule form.

The microtubules of nucleated erythrocytes form an extraordinary structure: they are organized into a marginal band at the periphery of the cell. This unusual organelle, recurring in detail in each cell, provides an excellent opportunity to study the determinants of microtubule form. We have been able to reform the marginal band, using detergent-extracted erythrocytes that have been depleted of microtubules in vivo and phosphocellulose-purified tubulin from calf brain. We find that detergent-extracted cytoskeletons incubated under these conditions again have microtubules, and that the pattern of these microtubules recapitulates several features of the intact marginal band. In particular, most of the microtubules after regrowth are located in a band at the periphery of the cell, and curve to form an ellipse. These results support the hypothesis that the specification of microtubule location and shape in these cells is governed by determinants that reside at the periphery of the cell.

Animals↗
PubMed1984

Direct isolation of neuronal microtubule skeletons.

The microtubule skeletons of cultured neuronal cells have been isolated in their original form utilizing taxol and rigorous extraction conditions. Continuous microtubules are visible throughout the cell body and into the processes. These preparations include the complex set of microtubule-associated proteins of 69,000 and 80,000 daltons previously identified in these cells.

Animals↗