Sensitivity of aerosol bolus behavior to methacholine-induced bronchoconstriction

Thanatin is the first inducible insect peptide that has been found to have, at physiological concentrations, a broad range of activity against bacteria and fungi. Thanatin contains 21 amino acids including two cysteine residues that form a disulfide bridge. Two-dimensional (2D) 1H-NMR spectroscopy and molecular modelling have been used to determine its three-dimensional (3D) structure in water. Thanatin adopts a well-defined anti-parallel beta-sheet structure from residue 8 to the C-terminus, including the disulfide bridge. In spite of the presence of two proline residues, there is a large degree of structural variability in the N-terminal segment. The structure of thanatin is quite different from the known structures of other insect defence peptides, such as antibacterial defensin and antifungal drosomycin. It has more similarities with the structures of various peptides from different origins, such as brevinins, protegrins and tachyplesins, which have a two-stranded beta-sheet stabilized by one or two disulfide bridges. Combined with activity test experiments on several truncated isoforms of thanatin, carried out by Fehlbaum et al. [Fehlbaum, P., Bulet, P., Chernysh, S., Briand, J. P., Roussel, J. P., Letellier, L., Hétru, C. & Hoffmann, J. (1996) Proc. Natl Acad. Sci. USA 93, 1221-1225], our structural study evidences the importance of the beta-sheet structure and also suggests that anti-Gram-negative activity involves a site formed by the Arg20 side-chain embedded in a hydrophobic cluster.     

Genetics of ethanol-induced locomotor activation: detection of QTLs in a C57BL/6J x DBA/2J F2 intercross

Moderate doses of ethanol (1-2 g/kg) markedly increase locomotor activity in some inbred mouse strains, for example, the DBA/2J (D2), but have relatively little effect in other strains, for example, the C57BL/6J (B6). In the present study, we conducted a genome-wide search in a B6D2 F2 intercross (N = 925) for quantitative trait loci (QTLs) associated with the locomotor response. A QTL with a LOD score of 8.4 was detected on Chromosome (Chr) 2; this QTL accounted for 11.4% of the phenotypic variance and approximately 30% of the genetic variance. The QTL on Chr 2 is in the same general region as QTLs previously described for ethanol preference/consumption (Rodriguez et al. Alcohol Clin Exp Res 19, 367, 1995; Melo et al. Nat Genet 13, 147, 1996; Phillips et al. Mamm Genome, in press), acute ethanol withdrawal (Buck et al. J. Neurosci 17, 3946, 1997) and nitrous oxide withdrawal severity (Belknap et al. Behav Genet 23, 213, 1993). A logical candidate gene in the region of interest is the enzyme which synthesizes GABA, glutamic acid decarboxylase 1 (GadI).     

The Forbidden Rotational Q-Branch of CH3CF3: Torsional Properties and (A1 - A2) Splittings

The pure rotational spectrum driven by the small distortion dipole moment perpendicular to the symmetry axis has been investigated between 8 and 18 GHz for CH3CF3 in the ground vibrational state using a pulsed Fourier transform waveguide spectrometer. This molecule has been selected as a prototype for the case of a symmetric top with small ( approximately 500 kHz) torsional energy splittings in the ground torsional state (nu6 = 0). In this state, six (k +/- 3 <-- k) Q-branch series have been measured for lower state K = |k| between 3 and 8 with 27 相似文献   

Positive thought disorder in a hypothetically psychosis-prone population.

Proverb interpretations of subjects who scored high on the Perceptual Aberration-Magical Ideation Scale (Per-Mags) (Chapman & Chapman, 1985) were compared with those of low-scoring controls. Responses to 10 familiar and 3 unfamiliar proverbs were scored for Bizarre-idiosyncratic thinking (J. Marengo et al; see record 1987-30079-001) and literalness (C. A. Hertler et al; see record 1979-12346-001). A Group by Type of Proverb (familiar versus unfamiliar) interaction was found for bizarre-idiosyncratic scores; Per-Mags scored higher than controls on unfamiliar, but not familiar proverbs. The Group?×?Familiarity interaction for bizarre-idiosyncratic scores indicates that the Per-Mag group displayed a subclinical, positive-thought disorder that is affected by the familiarity of the proverbs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A molecular theory of cartilage viscoelasticity

Recent work on the subject of cartilage mechanics has begun to focus on the relationship between the microscopic structure of cartilage and its macroscopic mechanical properties (Bader et al., Biochem. Biophys. Acta, 1116 (1992) 147-154; Buschmann, PhD Thesis, Massachusetts Institute of Technology, 1992; Kovach, Biophys. Chem., 53 (1995) 181-187; Lai et al., J. Biochem. Eng., 113 (1991) 245-248; Armstrong and Mow, J. Bone Jt. Surg., 64A (1982) 88; Jackson and James, Biorheology, 19 (1982) 317-330). This paper reviews recent theoretical developments and presents a comprehensive explanation of the viscoelastic properties of cartilage in terms of molecular structure. In doing this, a closed form hybrid solution to the non-linear, cylindrical Poisson-Boltzmann equation is developed to describe the charge-dependent component of the equilibrium elasticity arising from polysaccharide charge (Benham, J. Chem. Phys., 79 (4) (1983) 1969-1973; Einevoll and Hemmer, J. Phys. Chem., 89 (1) (1988) 474-484; Fixman, J. Chem. Phys., 70 (11) (1979) 4995-5001; Ramanathan and Woodburg, J. Chem. Phys., 82 (3) (1985) 1482-1491; Wennerstrom et al., J. Chem. Phys., 76 (9) (1982) 4665-4670). This solution agrees with numerical solutions found in the literature (Buschmann, PhD Thesis, Massachusetts Institute of Technology, 1992). The charge-independent, entropic contribution to the equilibrium elasticity is explained in a manner similar to that recently presented for concentrated proteoglycan solution (Kovach, Biophys. Chem., 53 (1995) 181-187). This approach exploits a lattice model of the solution, subject to a Bragg-Williams type approximation to derive the volume dependence of polysaccharide configuration entropy (Flory, Principles of Polymer Chemistry, Cornell University Press, Ithaca, NY, 1953; Huggins, Some properties of Solutions of Long-chain Compounds, 1941, pp. 151-157; Stanley, Introduction to Phase Transitions and Critical Phenomena, Oxford University Press, Oxford, 1971). Together, these two contributions accurately reproduce the experimentally determined osmotic pressure of cartilage as previously determined by Maroudas (Maroudas and Bannon, Biorheology, 18 (1981) 619-632). The time-dependent, or creep, phenomena which cartilage exhibits when subject to mechanical load is explained in terms of frictional drag on the polysaccharide chain monomers in terms of a Kirkwood-Riseman type model (Kirkwood and Riseman, J. Chem. Phys., 16 (6) (1948) 573-579). This approach is shown to accurately predict the hydraulic permeability of cartilage as previously determined by Maroudas (Madouras, Ann. Rheum. Dis., 34 (suppl. 3) (1975) 77). By use of a quasi-static approximation (neglecting inertial effects) the time-dependent response to a uniform compressive force is determined and also found to be in good agreement with experimental values from the literature.     

Differential stimulation of c-fos expression in hypothalamic nuclei of the rat brain during short-term heat acclimation and mild dehydration

Evidence that multiple, probably non-endocytic mechanisms are involved in the uptake into mammalian cells of the alpha-helical amphipathic model peptide FLUOS-KLALKLALKALKAALKLA-NH2 (I) is presented. Extensive cellular uptake of N-terminally GC-elongated derivatives of I, conjugated by disufide bridges to differently charged peptides, indicated that I-like model peptides might serve as vectors for intracellular delivery of polar bioactive compounds. The mode of the cellular internalization of I comprising energy-, temperature-, pH- and ion-dependent as well as -independent processes suggests analogy to that displayed by small unstructured peptides reported previously (Oehlke et al., Biochim. Biophys. Acta 1330 (1997) 50-60). The uptake behavior of I also showed analogy to that of several protein-derived helical peptide sequences, recently found to be capable of efficiently carrying tagged oligonucleotides and peptides directly into the cytosol of mammalian cells (Derossi et al., J. Biol. Chem. 269 (1994) 10444-10450; Lin et al., J. Biol. Chem. 270 (1995) 14255-14258; Fawell et al., Proc. Natl. Acad. Sci. USA 91 (1994) 664-668; Chaloin et al., Biochemistry 36 (1997) 11179-11187; Vives et al., J. Biol. Chem., 272 (1997) 16010-16017).     

"University productivity rankings: A psychologist by any other name": Reply.

Responds to the report by J. Levin et al (1978) of inconsistencies between data reported by W. M. Cox and V. Catt (see record 1978-21651-001) and that of J. Levin et al regarding productivity ratings of graduate psychology programs based on publication in American Psychological Association journals. A reexamination of Cox and Catt's tabulations suggests that the inconsistencies are in fact errors of J. Levin et al. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

FGF and EGF are mitogens for immortalized neural progenitors

Individual neural progenitors, derived from the external germinal layer of neonatal murine cerebellum, were previously immortalized by the retrovirus-mediated transduction of avian myc (v-myc). C17-2 is one of those clonal multipotent progenitor cell lines (Snyder et al., 1992, Cell 68: 33-51; Ryder et al., 1990, J. Neurobiol. 21:356-375). When transplanted into newborn mouse cerebellum (CB), the cells participate in normal CB development; they engraft in a cytoarchitecturally appropriate, nontumorigenic manner and differentiate into multiple CB cell types (neuronal and glial) similar to endogenous progenitors (Snyder et al., 1992, as above). They also appear to engraft and participate in the development of multiple other structures along the neural axis and at multiple other stages (Snyder et al., 1993, Soc. Neurosci. Abstr. 19). Thus conclusions regarding these immortalized progenitors may be applicable to endogenous neural progenitors in vivo. To help identify and analyze factors that promote differentiation of endogenous progenitors, we first investigated the ability to maintain C17-2 cells in a defined, serum-free medium (N2). The cells survive in vitro in N2 but undergo mitosis at a very low rate. Addition of epidermal growth factor (EGF), however, either from mouse submaxillary gland or the human recombinant protein, appreciably stimulates thymidine incorporation and cell division approximately threefold. Basic fibroblast growth factor (bFGF) is an even more potent mitogen, promoting thymidine incorporation, cell division, and a net increase in cell number equal to that in serum. Both EGF and bFGF are active at very low nanomolar concentrations, suggesting that they interact with their respective receptors rather than a homologous receptor system. The findings demonstrate that C17-2 cells can be maintained and propagated in a fully defined medium, providing the basis for analysis of other growth and differentiation factors. That EGF and particularly bFGF are mitogenic for these cells is in accord with recent observations on primary neural tissue (Reynolds and Weiss, 1992, Science 255:1707-1710; Kilpatrick and Bartlett, 1993, Neuron 10:255-265; Ray et al., 1993, Proc. Natl. Acad. Sci. USA 90:3602-3606) suggesting that bFGF and EGF responsiveness may be fundamental properties of neural progenitors.     

Lymphocyte subset redistribution during acute laboratory stress in young adults: Mediating effects of hemoconcentration.

Acute psychological stress is known to alter the distribution of circulating lymphocyte subsets and also to cause a reduction of plasma volume. Data were reanalyzed from 4 previously reported studies (E. A. Bachen et al., 1995; T. B. Herbert et al., 1994; A. L. Marsland, S. B. Manuck, T. V. Fazzari, C. J. Stewart, & B. S. Rabin, 1995; A. L. Marsland, S. B. Manuck, P. Wood, et al., 1995) to determine the extent to which changes in the concentration of lymphocyte subsets are attributable to such hemoconcentration. Meta-analytic procedures showed circulating concentrations of T-suppressor/cytotoxic (CD8) and natural killer (NK) cells to increase following acute laboratory challenge, whereas T-helper (CD4) and B- (CD19) cell populations did not change. Adjustments for concomitant hemoconcentration reduced the magnitude of stress-related increases in CD8 and NK cells significantly and revealed a decrease in CD4 and CD19 cell concentrations from baseline to stress measurements. These data provide evidence (a) that increases in circulating numbers of CD8 and NK cells following acute stress are partially attributable to hemoconcentration and (b) that CD4 and CD19 cell concentrations decrease during acute stress when hemoconcentration is taken into account. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessing method variance in multitrait-multimethod matrices: The case of self-reported affect and perceptions at work.

P. Spector (see record 1987-33304-001) concluded that there was little evidence of method variance in multitrait–multimethod data from 10 studies of self-reported affect and perceptions at work, but L. J. Williams et al (see record 1989-31744-001) concluded that method variance was prevalent. These studies were extended by examining several important but often neglected issues in assessing method variance. A direct-product model is described that can represent multiplicative method effects and propose that model assumptions, individual parameters, and diagnostic indicators, as well as overall model fits, be carefully examined. Reanalyses indicate that method variance in these studies is more prevalent than Spector concluded but less prevalent than Williams et al asserted. The methods can have multiplicative effects, supporting the claim made by D. T. Campbell and E. J. O'Connell (1967, 1982). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rigor, rigor mortis, and conspiratorial views of depression research.

The authors reassert the need for methodological changes in depression research appearing in the Journal of Personality and Social Psychology and other personality and social psychology journals. In this rejoinder the authors update their earlier literature review (H. Tennen, J. Hall, & G. Affleck; see record 1995-31710-001) and respond to the commentaries by P C. Kendall and E. C. Flannery-Schroeder (see record 1995-31700-001) and G. Weary, J. A. Edwards, and J. A. Jacobson (see record 1995-31713-001). The authors notice that G. Weary et al.'s own findings demonstrate the need to change how depression is measured and participants are assigned to experimental groups. The authors also challenge G. Weary et al.'s contention that structured interviews are limited because they require interviewer judgments, and they urge personality and social psychologists to learn more about these interviews. Finally, G. Weary et al.'s suspicion that depression research guidelines reflect professional parochialism is disputed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Understanding why heterosexual adults do not practice safer sex: a comparison of two samples

This study evaluated the relationship between benzene exposure and low white blood cell (WBC) and red blood cell (RBC) counts. Hematologic screening data collected over a 35 year period at a rubber hydrochloride manufacturing plant were analyzed; an increased risk of leukemia had been demonstrated previously among workers at the plant [Infante et al. (1977).' Lancet 2:76-78; Rinsky et al. (1981): Am J Ind Med 2:217-45 (1987): NEJM 316:1044-1050/. Hematologic screening data were available for 657 of 1,037 (63.3%) individuals employed at the plant from 1939 through 1976. There was a total of 21. 710 blood test records (range per individual 1-354). The study utilized a case-control design and estimated benzene exposures using the job exposure matrix developed by Rinsky et al. (1987): NEJM 316:1044-1050]. The effects of benzene exposure in the 30, 90, and 180 days before the blood test date, as well as cumulative exposure up until the blood test date, were examined using conditional logistic regression. For WBCs there was a strong exposure response and all of the exposure metrics selected showed a significant relationship with low blood count. For RBCs there was a weak positive exposure-response, which was significant (p = 0.03) for one of the dose metrics. The finding of an exposure-response relationship in the range of exposures represented in this study, where the maximum daily benzene exposure estimate was 34 ppm, is consistent with findings of several animal studies demonstrating a decrease in peripheral lymphocyte counts at benzene exposures as low as 10 ppm, and a stronger effect of benzene exposure on lymphocytes (as reflected in total WBC count) than on red cells. There was no evidence for a threshold for the hematologic effects of benzene exposure, suggesting that even exposure to relatively low levels of benzene (e.g., <5 ppm) may result in hematologic suppression.     

Elevated 8-hydroxy-2'-deoxyguanosine levels in lung DNA of A/J mice and F344 rats treated with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and inhibition by dietary 1,4-phenylenebis(methylene)selenocyanate

1,4-Phenylenebis(methylene)selenocyanate (p-XSC) is an effective chemopreventive agent against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung adenoma in female A/J mice. While p-XSC can effectively inhibit NNK-induced DNA methylation in female A/J mice and in male F344 rats, its effect on NNK-induced oxidative DNA damage had not been determined. Thus, the effect of p-XSC on the levels of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in lung DNA from A/J mice and F344 rats treated with NNK was examined. Mice were given NNK by gavage (0.5 mg/mouse in 0.2 ml corn oil, three times per week for 3 weeks) or by a single i.p. injection (2 mg/mouse in 0.1 ml saline) while maintained on a control diet (AIN-76A) or control diet containing p-XSC at 10 or 15 p.p.m. (as Se) starting 1 week before NNK administration and continuing until termination. Mice were killed 2 h after the last NNK gavage in the multiple administration protocol or 2 h after the single i.p. injection. Treatment with NNK by gavage significantly elevated the levels of 8-OH-dG in lung DNA of A/J mice from 0.7 +/- 0.1 to 1.6 +/- 0.2 adducts/10(5) 2'-deoxyguanosine (dG) (P < 0.001), while dietary p-XSC (at 10 p.p.m. Se) prevented significant elevation of the levels of this lesion caused by NNK, keeping them at 0.9 +/- 0.1 adducts/10(5) dG (P < 0.003). Injection of NNK in saline also significantly increased the levels of 8-OH-dG in lung DNA of A/J mice from 1.2 +/- 0.6 to 3.6 +/- 0.8/10(5) dG adducts (P < 0.01), while dietary p-XSC (at 15 p.p.m. Se) kept these levels at 1.9 +/- 0.5 adducts/10(5) dG (P < 0.03). Rats were given a single i.p. injection of NNK (100 mg/kg body wt) in saline while being maintained on control diet (AIN-76A) or control diet containing p-XSC (15 p.p.m. as Se) starting 1 week before NNK administration and continuing until termination. The rats were killed 2 h after injection. Treatment with NNK using this protocol significantly elevated the levels of 8-OH-dG in lung DNA of F344 rats from 2.6 +/- 0.5 to 3.5 +/- 0.5 adducts/10(5) dG (P < 0.03), while dietary p-XSC (at 15 p.p.m. Se) kept the levels of this lesion at 2.2 +/- 0.6 adducts/10(5) dG (P < 0.01). Our findings suggest that the chemopreventive efficacy of p-XSC against NNK-induced lung tumorigenesis in A/J mice and F344 rats may be due in part to inhibition of oxidative DNA damage.     

The use of decision making analysis for evaluating hepatitis B inoculation strategy

We used a recently described anion-exchange chromatographic method (Vedie et al. J Lipid Res 1991;32:1359) to study the protective effect of potential inhibitors of low-density lipoprotein (LDL) oxidation mediated by cupric ion. By way of an example, we studied eight flavonoids (flavone, 3-hydroxyflavone, chrysin, galangin, fisetin, morin, quercetin, and myricetin) as well as three non-flavonoid antioxidants, butylated hydroxytoluene (BHT), probucol, and vitamin C, as reference compounds. Each compound was tested at various concentrations (1-100 microM). For flavonoid concentrations of 10 microM, an index was calculated as the (LDL control-flavonoid)/(LDL control-probucol) ratio, in which each term is expressed as the percentage of the most electronegative LDL fraction (fraction E). If the index is positive, the flavonoid inhibits LDL oxidation. A value > 1 (3-hydroxyflavone and galangin) means greater activity than probucol, whereas a value < 1 means lower activity (fisetin). If the index is around 0 (flavone and chrysin), the flavonoid is inactive. Finally, a negative value reflects possible prooxidant activity (morin, quercetin, and myricetin). Our results show that this chromatographic method can be applied to screening new pharmacological agents for activity against LDL oxidation.     

Occurrence versus moderation of the automatic attitude activation effect: Reply to Fazio.

In this reply to R. H. Fazio's (see record 1993-32136-001) commentary on the article by J. A. Bargh et al (see record 1992-33847-001), the main purposes and findings of that research are reviewed. This reply presents new data that replicates the original findings of J. A. Bargh et al regarding the conditions under which reliable moderation of automatic attitude activation by speed is more versus less likely. It also responds to the renditions of them by H. Fazio's and J. A. Bargh et al. This reply argues that automatic attitude activation is a pervasive phenomenon and that moderation by attitude speed may be a more limited tendency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cytotoxic T-lymphocyte-defined human minor histocompatibility antigens with a restricted tissue distribution

Cytotoxic T lymphocytes (CTL) specific for human minor histocompatibility (H) antigens can be isolated from the blood of major histocompatibility complex (MHC)-matched allogeneic bone marrow transplant (BMT) recipients and may play a prominent role in the graft-versus-host (GVH) and graft-versus-leukemia (GVL) reactions (Tsoi et al, J Immunol 125:2258, 1980; Tsoi et al, Transplant Proc 15:1484, 1983; Goulmy et al, Nature 302:159, 1983; Irle et al, Transplantation 40:329, 1985; and Niederwieser et al, Blood 81:2200, 1993). The identification of minor H antigens that are expressed in hematopoietic cells, including leukemic cells, but not in fibroblasts and other tissue types has suggested that such tissue-restricted antigens could potentially serve as targets for T-cell immunotherapy to enhance GVL activity without inducing GVH disease (de Bueger et al, J Immunol 149:1788, 1992; van der Harst et al, Blood 83:1060, 1994; and Dolstra et al, J Immunol 158:560, 1997). To explore the feasibility of this strategy, donor CD3+CD8+ CTL clones specific for recipient minor H antigens were isolated and characterized from allogeneic BMT recipients. CTL clones were obtained from the majority of donor/recipient pairs. Seventeen distinct minor H antigens distinguishable by their MHC-restricting allele, population frequency, and/or distribution of tissue expression were defined by 56 CD3+CD8+ CTL clones isolated from these patients. The MHC-restricting alleles for these CTL clones included HLA-A2 and HLA-B7, which had previously been shown to present minor H antigens to CTL, as well as HLA-A3, -A11, -B8, -B53, and -Cw7, which had not previously been described to present minor H antigens to CTL. Estimated phenotype frequencies for these 17 distinct minor H antigens range from 0.17 to 0.92. In vitro cytotoxicity assays using hematopoietic cells and fibroblasts as target cells showed that 5 of the 17 minor H antigens were expressed in both hematopoietic cells and fibroblasts. However, 12 were presented for CTL recognition only by hematopoietic cells and not by dermal fibroblasts derived from the same donors. These results significantly extend the spectrum of CTL-defined human minor H antigens that could potentially serve as target antigens for cellular immunotherapy to promote GVL activity after allogeneic BMT.     

Comparison of age-extended norms for the Wechsler Adult Intelligence Scale—Revised in patients with Alzheimer's disease.

Recent studies by R. J. Ivnik et al (see record 1993-04116-001), J. F. Malec et al (see record 1993-04120-001), and J. J. Ryan et al (see record 1991-08835-001) have provided age-extended norms for the Wechsler Adult Intelligence Scale—Revised (WAIS—R). The current study compared IQ scores based on these newer age-extended norms in 216 elderly Alzheimer's disease (AD) patients. Results showed that when the norms from Ryan et al were used, IQ scores were consistently the same as or higher than when WAIS—R manual norms were used. When the norms provided by Ivnik et al and Malec et al were used, IQ scores tended to be lower than WAIS—R manual norms for younger patients with more intellectual impairment. Results illustrate the importance of reporting the normative sample upon which IQ test scores for older adults are based and provide guidelines for selecting which set of age-extended WAIS—R norms to use with cognitively impaired elderly Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Avoiding bias in the search for artifact: A reply to Carlopio, Adair, Lindsay, and Spinner.

J. Carlopio et al (see record 1983-31564-001) criticized several aspects of the present authors' (see record 1982-12761-001) procedures and conclusions in a study of S roles and contended that the entire "subject role" approach is misguided. In this reply, the merits of the arguments and follow-up study of Carlopio et al are considered along with the "alternative" conception of S behavior they proposed. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The reconstitution of microtubules from purified calf brain tubulin

The in vitro reconstitution of calf brain tubulin, purified by the method of Weisenberg et al. [(1968), Biochemistry 7, 4466-4479; (1970), Biochemistry 9, 4110-4116] as modified by Lee et al. [(1973), J. Biol. Chem. 248, 7253-7262], was successful in a medium consisting of 10(-2) M sodium phosphate, 10(-4) M GTP, and concentrations of magnesium ions ranging from 0.5 to 16 X 10(-3) M at 37 degrees. Filaments resembling native microtubules were formed. The filaments are in equilibrium with the associating species of tubulin and the equilibrium can be shifted to depolymerization by lowering the temperature to 20 degrees. Filament formation is inhibited by calcium ions which also cause disassembly of the formed filaments. The effects of calcium ion can be reversed by the addition of [ethylenebis-oxyethylenenitrilo)]tetraacetic acid. The formation of filaments is favored by the presence of 3.4 M glycerol; only twisted abnormal filaments are observed in the presence of 1 M sucrose. The high molecular weight components observed in the sodium dodecyl sulfate polyacrylamide gel electrophoresis patterns of many tubulin preparations were shown not to be essential for the formation of the filaments.