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  • Cell & Developmental Biology  (1,170)
  • General Chemistry  (1,091)
  • Organic Chemistry  (822)
  • 1990-1994  (3,083)
  • 1970-1974
  • 1910-1914
  • 1991  (3,083)
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  • 1990-1994  (3,083)
  • 1970-1974
  • 1910-1914
Year
  • 1
    Electronic Resource
    Electronic Resource
    Interaction of propafenone enantiomers with human α1-acid glycoprotein (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 30-34 
    Details
    ISSN: 0899-0042
    Keywords: propafenone ; enantiomers ; α1-acid glycoprotein ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of propafenone enantiomers with human α1-acid glycoprotein was studied using high-performance liquid chromatography. Each of the two optical antipodes interacted with one class of high-affinity binding sites characterized by Ka(R) = (6.18 ± 0.93) × 105 M-1, n(R) = 1.34 ± 0.09 for the (R)-isomer and Ka(S) = (8.93 ± 1.82) × 105 M-1, n(S) = 0.99 ± 0.08 for the (S)-isomer. Nonspecific binding to secondary low-affinity high-capacity binding site(s) was only slightly greater in the case of the (S)-enantiomer (n′k′(S) = (1.06 ± 0.09) × 104 M-1) compared to the (R)-enantiomer (n′k′(R) = (6.87 ± 0.72) × 103 M-1). It was concluded that both enantiomers interact with common single class of high-affinity binding sites on AAG (along with nonspecific binding) exhibiting only slight stereoselectivity for propafenone.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030107
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  • 2
    Electronic Resource
    Electronic Resource
    A molecular dynamics investigation of chiral discrimination complexes as chiral stationary-phase models: Methyl N-(2-naphthyl)alaninate with N-(3,5-dinitrobenzoyl)leucine n-propylamide (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 56-66 
    Details
    ISSN: 0899-0042
    Keywords: molecular recognition ; chiral recognition ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular dynamics simulations were performed on complexes of (S)-methyl N-(2-naphthyl)alaninate (NAP) with the enantiomers of N-(3,5-dinitrobenzoyl)leucine n-propylamide (DNB), which are used as models for chiral stationary-phase systems developed by Pirkle and co-workers. These studies were undertaken to qualitatively examine (pictorially) the role of entropic effects in these systems. The results of the dynamics calculations were used to refine the search for low-energy conformers. The structures were refined by the use of BioDesign's molecular mechanics method implemented in Biograf. The results of the structural refinements support our previous observation that the SR complex can achieve the same three primary interactions which are observed in the SS structure (i.e., two intermolecular hydrogen bonds and pi stacking) without a significant increase in energy. In addition, these primary interactions are conserved during molecular dynamics simulations with the occurrence of conformations which differ only in the rotational states of the alkyl side chains and ester group (which bears two potential hydrogen bond acceptors utilized in both the homo- and heterochiral complexes). The major difference in the two complexes is the relative position of the sec-butyl group and hydrogen atom on DNB's chiral center, both of which are outside the primary interaction region. All other local minima which have different relative pi orientations (“front-back,” “back-back,” and “back-front” as defined herein) are not sufficiently populated to make more than a negligible contribution to the statistical (time- or energy-averaged) analysis of the (SS)- and (SR)-NAP-DNB complexes. Thus the entropic effects observed in this study (e.g., alkyl side chain or ester group rotations) do not show evidence of qualitative differential effects on the maintenance of the same three primary interactions by both the homo- and heterochiral complexes. The reliability of the present study, which provides pictorial representations of the entropic effects, is not sufficient to determine whether the entropic effects observed herein are sufficient to achieve enantiomeric discrimination alone or in conjunction with other factors (e.g., conformational strain energy). Thus, all of the computational studies we have performed to date (i.e., our previous studies, which include strain energy and through-space field effects, and the present study, which includes entropic effects) show no evidence of any qualitative difference in the homo- and heterochiral complexes in terms of maintaining the same three “contact points”.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030110
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  • 3
    Electronic Resource
    Electronic Resource
    A highly enantioselective rhodium catalyst for the hydrogenation of aliphatic α-keto esters (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 370-375 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective catalysis ; (2S)-ethyl-2-hydroxy-4-phenylbutyrate ; (S)-ethyl lactate ; α-hydroxy esters ; (2S,3S)-NORPHOS ; rhodium diphosphine catalyst ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantioselective hydrogenation of several α-keto acid derivatives with rhodium diphosphine catalysts has been investigated using a random screening approach. The neutral rhodium catalyst prepared in situ from bis(2,5-norbornadiene rhodium chloride) and NORPHOS has been found to be an excellent catalyst for preparing aliphatic α-hydroxy esters in high optical purities. The reaction parameters for the hydrogenation of ethyl 2-oxo-4-phenyl-butyrate, an intermediate for the ACE inhibitor Benazepril, were optimized and the best optical yields obtained were 96%.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030423
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  • 4
    Electronic Resource
    Electronic Resource
    N,N-dimethylcarbamyl derivatives of oxazepam (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 212-219 
    Details
    ISSN: 0899-0042
    Keywords: oxazepam ; demoxepam ; 3-O-acyl-1-(N,N-dimethylcarbamyl)oxazepam ; 1-(N,N-dimethylcarbamyl)oxazepam ; 3-O-(N,N-dimethylcarbamyl)oxazepam ; camazepam ; norcamazepam ; 1,3-O-bis(N,N-dimethylcarbamyl)oxazepam ; kinetics of racemization ; enantioselectivity of esterases ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three N,N-dimethylcarbamyl derivatives of oxazepam {1-(N,N-dimethylcarbamyl)oxazepam, 3-O-(N,N-dimethylcarbamyl)oxazepam, and 1,3-O-bis(N,N-dimethylcarbamyl)oxazepam} and a 3-O-acyl-1-(N,N-dimethylcarbamyl)-oxazepam were synthesized from either oxazepam or demoxepam. Enantiomeric pairs of these derivatives and of camazepam were resolved by high-performance liquid chromatography on at least two of three commercially available chiral stationary phase columns employed. Absolute configurations of resolved enantiomers were established by comparing their circular dichroism spectra to those of enantiomeric oxazepams with known absolute stereochemistry. Similar to those of oxazepam, enantiomers of 1-(N,N-dimethylcarbamyl)oxazepam undergo rapid racemization (t½ 1.9 min at 23°C and 0.9 min at 37°C) in an aqueous solution at pH 7.5. The (R)-enantiomer of rac-3-O-acyl-1-(N,N-dimethylcarbamyl)oxazepam was hydrolyzed ∼4.6-fold faster than the (S)-enantiomer by esterases in rat liver microsomes, whereas the (S)-enantiomer was hydrolyzed ∼43-fold faster than the (R)-enantiomer by esterases in rat brain S9 fraction.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030313
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  • 5
    Electronic Resource
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    Prebiotic sources of biomolecular handedness (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 223-226 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; diastereomers ; chirality ; circularly polarized radiation ; circular dichroism ; parity violation ; electroweak interaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fischer demonstrated (1890-1919) that functional biomolecules are composed specifically of the D-sugars and the L-amino acids, and that in the laboratory synthetic reactions of such molecules propagate with chiral stereoselectivity. Given a primordial enantiomer, biomolecular homochirality followed without the intervention of the chiral natural force conjectured by Pasteur (1860), except prebiotically. Polarized solar radiation and other classical chiral forces were proposed as agencies generating a prebiotic enantiomeric excess, but the forces then known were found to be evenhanded on a time and space average, exemplifying parity conservation (1927). The weak nuclear force, shown to violate parity (1956), was unified with electromagnetism in the electroweak force (1970). Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers. The small energy difference between these enantiomer pairs, with Darwinian reaction kinetics in a flow reactor, account for the choice of biomolecular handedness made when life began.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030403
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  • 6
    Electronic Resource
    Electronic Resource
    Chiral aspects of drug action at ion channels: A commentary on the stereoselectivity of drug actions at voltage-gated ion channels with particular reference to verapamil actions at the Ca2+ channel (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 393-404 
    Details
    ISSN: 0899-0042
    Keywords: verapamil ; ion channels ; calcium channels ; 1,4-dihydropyridines ; state-dependent interactions ; channel activators ; channel antagonists ; local anesthetics ; sodium channels ; potassium channels ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ion channels may be considered as pharmacological receptors possessing specific drug binding sites with defined structure-activity relationships. Accordingly drug binding to ion channels is stereoselective. Interpretation of this stereoselectivity may be complex because of the existence of differences in affinity and access to different channel states. Such state-dependent interactions may give rise to quantitative and qualitative differences in stereoselectivity. The implications of such differences are reviewed for drug action at Na+, K+ and Ca2+ channels. Detailed attention is paid to the actions of verapamil enantiomers in the cardiovascular system where activities differ in vascular and cardiac tissues because of state-dependent interactions and stereoselective first-oass metabolism.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030504
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  • 7
    Electronic Resource
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    Interaction of pirprofen enantiomers with human serum albumin (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 412-417 
    Details
    ISSN: 0899-0042
    Keywords: pirprofen enantiomers ; human serum albumin ; binding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of pirprofen enantiomers with human serum albumin (HSA) was investigated by means of high-performance liquid chromatography (HPLC), circular dichroism (CD), and 1H NMR spectroscopy. HPLC experiments indicated that both pirprofen enantiomers were bound to one class of high-affinity binding sites (n(+) = 1.91 ± 0.13, K(+) = (4.09 ± 0.64) × 105 M-1, n(-) = 2.07 ± 0.13, K(-) = (6.56 ± 1.35) × 105 M-1) together with nonspecific binding (n′K′(+) = (1.51 ± 0.21) × 104 M-1, n′K′(-) = (0.88 ± 0.13) × 104 M-1). Slight stereoselectivity in specific binding was demonstrated by the difference in product n(+)K(+) = (0.77 ± 0.08) × 106 M-1 vs. n(-)K(-) = (1.30 ± 0.21) × 106 M-1, i.e., the ratio n(-)K(-)/n(+)K(+) = 1.7. CD measurements showed changes in the binding sites located on the aromatic amino acid side chains (a small positive band at 315 nm and a pronounced negative extrinsic Cotton effect in the region 250-280 nm). The protein remains, however, in its predominantly alpha-helical conformation. The 1H NMR difference spectra confirmed that both pirprofen enantiomers interacted with HSA specifically, most probably with site II on the albumin molecule.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030506
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  • 8
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    In vitro assessment of stereoselective hepatic metabolism of disopyramide in humans: Comparison with in vivo data (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 405-411 
    Details
    ISSN: 0899-0042
    Keywords: disopyramide ; enantiomers ; metabolism ; human hepatocyte cultures ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metabolism of disopyramide (DP) enantiomers has been investigated in primary cultures of adult human hepatocytes. Results were compared with in vivo data obtained from a previous pharmacokinetic study (Le Corre et al. Drug Metab. Dispos. 16:858-864 1988). Metabolism of DP enantiomers as a function of incubation time showed constant velocity over time. The intracellular/extracellular distribution of both DP and mono-N-desisopropyldisopyramide did not appear to be stereoselective. Metabolism of DP enantiomers as a function of substrate concentration followed a first order kinetics. The average fractions of (-)-(R)-DP and (+)-(S)-DP metabolized in vitro (4.7 ± 2.7 and 7.1 ± 4.2%, respectively, n = 4) were about 5-fold lower than the fractions metabolized in vivo (26.0 ± 6.0 and 40.2 ± 8.8%, respectively, n = 6). The stereoselective index [(+)-(S)/(-)-(R)] of the N-dealkylation pathway obtained in vitro (1.51 ± 0.11, n = 4) was very close to the one obtained in vivo (1.55 ± 0.10, n = 6). These results highlight the interest of hepatocyte cultures in the evaluation of drug metabolism and especially in the assessment of stereoselectivity.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530030505
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  • 9
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    Chiral separation of N-aminoalkylsuccinimides on an α1 - acid glycoprotein column: A quantitative structure - enantioselectivity relationship study (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 422-426 
    Details
    ISSN: 0899-0042
    Keywords: CHIRAL-AGP ; HPLC ; PLS ; principal components ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two quantitative structure-enantioselectivity models have been developed for a series of N-aminoalkylsuccinimides using the statistical method PLS. The models permit the prediction of enantioselectivity on an α1-acid glycoprotein column. The models are based on a physiocochemical description of the structures.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530030508
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  • 10
    Electronic Resource
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    An evaluation of ibuprofen bioinversion by simulation (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 418-421 
    Details
    ISSN: 0899-0042
    Keywords: chiral bioinversion ; pharmacokinetics ; (+)-(S)-ibuprofen ; (-)-(R)-ibuprofen ; rac-ibuprofen ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a pharmacokinetic model recently proposed to explain ibuprofen disposition in man,1 plasma concentrations of pure ibuprofen enantiomers were simulated following oral administration of (-)-(R)-ibuprofen, (+)-(S)-ibuprofen, or rac-ibuprofen. Simulated and literature values for AUC's were used to compare S/R ratios for different cases of the model and for different methods of calculating the fraction of R bioinverted to S. Numerical simulation using STELLA confirmed previous results for different cases of bioinversion. Simulated S/R AUC ratios, for administration of the racemate, ranged from 4.0 (presystemic bioinversion) to 1.66 (systemic bioinversion). Literature values for S/R AUC ratios averaged 1.53±0.2 for administration of the racemate; therefore, systemic bioinversion was concluded to be representative of ibuprofen disposition. Additional simulations of S/R AUC ratios, for administration of (-)-(R)-ibuprofen only, ranged from 1.5 (presystemic bioinversion) to 0.66 (systemic bioinversion). Literature values for S/R AUC ratios averaged 0.50±0.9 for administration of (-)-(R)-ibuprofen only, which again supported conclusions of systemic bioinversion. Using different equations for estimation of fraction of R inverted to S (FR→S), results based on simulated data were identical; however, FR→S values based on literature data were different. Therefore, assumptions made for different FR→S equations do not appear to be rigorous. Calculations of FR→S, based on literature data, averaged 0.52 overall, indicating bioavailability of (+)-(S)-ibuprofen may be similar for a 150 mg dose of (+)-(S)-ibuprofen compared to a 200 mg dose of racemate.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530030507
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  • 11
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    The absolute configuration of the enantiomers of 6-chloro-9-(4′-diethylamino-1′-methylbutyl)-amino-2-methoxyacridine (quinacrine) (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 436-437 
    Details
    ISSN: 0899-0042
    Keywords: stereochemistry ; quinacrine ; enantiomers ; enantioselectivity ; circular dichroism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute configurations have been assigned to the enantiomers of the antimalarial drug quinacrine dihydrochloride. Condensation of (-)-(R)-4-amino-1-diethylaminopentane (from L-glutamic acid) with 6,9-dichloro-2-methoxyacridine gave (-)-(R)-6-chloro-9-(4′-diethylamino-1′-methylbutyl) amino-2-methoxyacridine [(-)-(R)-quinacrine] while (+)-(S)-quinacrine was obtained from the enantiomeric diamine.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530030510
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  • 12
    Electronic Resource
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    Steric hindrance influence on the enantiorecognition ability of tyrosine-derived chiral stationary phases (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 427-435 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric separations ; chiral stationary phases ; tyrosine chiral selector ; HPLC ; reversal of elution order ; chiral recognition mechanisms ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four chiral stationary phases (CSPs) derived from N-(3,5-dinitrobenzoyl)tyrosine have been synthesized. They differ by the substituent nature (methyl, ethyl, isopropyl, tert-butyl) of the aliphatic amide function. The enantiorecognition ability of these CSPs was evaluated with 10 racemates. For the majority of them, the stereoselectivity increases with the steric hindrance of the substituent. The chiral selector enantiomeric separation on the resulting CSPs has evidenced a reversal of elution order only for CS 4 on CSP 4 (tert-butyl substituent), suggesting a change in its conformation.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530030509
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  • 13
    Electronic Resource
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030601
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  • 14
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    Editorial: Notes from the editor-in-chief (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 439-439 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030602
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  • 15
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    Letter to the editors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 440-440 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030603
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  • 16
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    Letter to the editors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 441-441 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030604
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  • 17
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    Letter to the editors: Should the terminology used in chirality be more precise? (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 442-442 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030605
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  • 18
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    Steric aspects of agonism and antagonism at β-adrenoceptors: Synthesis of and pharmacological experiments with the enantiomers of formoterol and their diastereomers (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 443-450 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; enantiomeric purity ; tracheal smooth muscle ; skeletal muscle ; cardiac muscle ; guinea pig ; in vitro ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomers of formoterol (R;R and S;S) and their diastereomers (R;S and S;R) were synthesized and purified using a new procedure which required the preparation of the (R;R)- and (S;S)-forms of N-(1-phenylethyl)-N-(1-(ρ-methoxyphenyl)-2-propyl)-amine as important intermediates. The enantiomeric purity obtained was greater than 99.3%, usually 〉 99.7%. The four stereoisomers were examined with respect to their ability to interact in vitro with β-adrenoceptors in tissues isolated from guinea pig. The effects measured were (1) relaxation of the tracheal smooth muscle (mostly β2), (2) depression of subtetanic contractions of the soleus muscle (β2), and (3) increase in the force of the papillary muscle of the left ventricle of the heart (β1). All enantiomers caused a concentration-dependent and complete relaxation of the tracheal smooth muscle which was inhibited by propranolol. The order of potency was (R;R) 〉 〉 (R;S) = (S;R) 〉 (S;S). There was a 1,000-fold difference in potency between the most and the least potent isomer. The presence of the (S;S)-isomer did not affect the activity of the (R;R)-isomer on the tracheal smooth muscle. Also on the skeletal and cardiac muscles (R;R)-formoterol was more potent than its (R;S)-isomer. The selectivity for β2-adrenoceptors appeared to be slightly higher for the (R;R)-isomer than for the (R;S)-isomer. The potency of the (S;R)- and (S;S)-isomers on the papillary muscle was too low to be determined accurately. The present study shows that determination of enantiomeric ratios and conclusions regarding structure-effect relationships are critically dependent on a very high degree of stereochemical purity.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530030606
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  • 19
    Electronic Resource
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    Stereoselective accumulation of the β-receptor blocking drug atenolol by human platelets (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 451-453 
    Details
    ISSN: 0899-0042
    Keywords: enantioselective ; stereoisomers ; β-blockers ; adrenergic β-receptor blockaders ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied the stereochemistry of accumulation of the hydrophilic β-adrenoceptor antagonist rac-atenolol by human platelets in vitro. The accumulation was slow, not reaching equilibrium until 90 min at 37°C. The uptake was temperature dependent with the accumulation at 37°C being 3-4 times greater than at 4°C. The accumulation was also stereoselective at 37°C, favoring the active (-)-enantiomer over the (+)-enantiomer by 2.3-fold. Reserpine, but not desipramine, inhibited the platelet accumulation of rac-atenolol enantiospecifically. This uptake profile is different from the platelet uptake of lipophilic β-blockers, which is characterized by nonspecific membrane binding, but similar to the carrier-mediated accumulation of the neurotransmitter norepinephrine by storage granules within the platelet.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chir.530030607
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  • 20
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    Stereoselective inhibition of diphenylhydantoin metabolism by p-hydroxyphenyl-phenylhydantoin enantiomers in rats (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 454-459 
    Details
    ISSN: 0899-0042
    Keywords: phenytoin ; product inhibition ; p-HPPH ; rat liver microsomes ; ligand-exchange chromatography ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different doses of rac-p-HPPH (0.4 and 4 mg/h) were given repeatedly to rats infused with [14C]phenytoin. The serum levels of 14C-labeled and unlabeled p-HPPH, and [14C]phenytoin were measured by an HPLC method and radiometric analysis. The clearance of phenytoin and p-HPPH was determined by rate of dosing divided by the steady-state concentration. The phenytoin clearance was significantly lower in the high dose p-HPPH injection group than in the low dose group (87 versus 262 ml/h), whereas p-HPPH clearance showed no difference. The formation clearance of [14C]p-HPPH was also significantly lower in rats injected with high dose of p-HPPH (35 versus 169 ml/h). The clearance of other elimination pathways was also lower in rats with high dose of p-HPPH (53 versus 89 ml/h). The serum protein binding of phenytoin was lower in rats injected with high dose of p-HPPH. The result indicated that injections of rac-p-HPPH mainly inhibited on the formation of p-HPPH itself. The formation of (R)-p-HPPH and (S)-p-HPPH in microsomal preparation was measured by a ligand-exchange chromatographic method. The formation of (S)-p-HPPH or (R)-p-HPPH was not only inhibited by the enantiomer itself, but also cross-inhibited by the other enantiomer. To the formation of either (S)-p-HPPH or (R)-p-HPPH, (S)-p-HPPH showed a higher inhibitory activity. The use of rac-p-HPPH to inhibit phenytoin metabolism in vivo involved several mechanisms. In addition to binding displacement on the serum proteins, one is the product inhibition by the respective p-HPPH metabolite, the other is the competitive inhibition by the other p-HPPH enantiomer.
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    Stereoselectivity of (R)- and (S)-hexahydro-difenidol binding to neuroblastoma M1, cardiac M2, pancreatic M3, and striatum M4 muscarinic receptors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 118-123 
    Details
    ISSN: 0899-0042
    Keywords: hexahydro-difenidol enantiomers ; muscarinic receptor subtypes M1, M2, M3 and M4 ; stereoselective interaction ; difenidol ; dicyclidol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (R)-Hexahydro-difenidol has a higher affinity for M1 receptors in NB-OK 1 cells, pancreas M3 and striatum M4 receptors (pKi 7.9 to 8.3) than for cardiac M2 receptors (pKi 7.0). (S)-Hexahydro-difenidol, by contrast, is nonselective (pKi 5.8 to 6.1). Our goal in the present study was to evaluate the importance of the hydrophobic phenyl, and cyclohexyl rings of hexahydro-difenidol for the stereoselectivity and receptor selectivity of hexahydro-difenidol binding to the four muscarinic receptors. Our results indicated that replacement of the phenyl ring of hexahydro-difenidol by a cyclohexyl group (→ dicyclidol) and of the cyclohexyl ring by a phenyl moiety (→ difenidol) induced a large (4- to 80-fold) decrease in binding affinity for all muscarinic receptors. Difenidol had a significant preference for M1, M3, and M4 over M2 receptors; dicyclidol, by contrast, had a greater affinity for M1 and M4 than for M2 and M3 receptors. The binding free energy decrease due to replacement of the phenyl and the cyclohexyl groups of (R)-hexahydro-difenidol by, respectively, a cyclohexyl and a phenyl moiety was almost additive in the case of M4 (striatum) binding sites. In the case of the cardiac M2, pancreatic M3, or NB-OK 1 M1 receptors the respective binding free energies were not completely additive. These results suggest that the four (R)-hexahydro-difenidol “binding moieties” (phenyl, cyclohexyl, hydroxy, and protonated amino group) cannot simultaneously form optimal interactions with the M1, M2, and M3 muscarinic receptors. When each of the hydrophobic groups is modified, the position of the whole molecule, relative to the four subsites, was changed to allow an optimal overall interaction with the muscarinic receptor.
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    Björn Ringdahl: A remembrance (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 156-156 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030214
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    Synthesis of the [8] gingerol enantiomers (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 151-155 
    Details
    ISSN: 0899-0042
    Keywords: (-)-(R) and (+)-(S) [8] gingerol ; enantiomers synthesis ; chiral stationary phase ; HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (+)-(S)-5-Hydroxy-1-(4-hydroxy-3-methoxyphenyl)-3-dodecanone 1a commonly named (+)-(S)-[8] gingerol is a natural product known to have cardiotonic activity.1-5 A total synthesis of both enantiomers is described with details for the first time using a general synthetic scheme which was recently outlined in the literature.6 This synthesis relies both on the separation of the diastereoisomers 4a and 4b by simple column chromatography on silica gel and on an HPLC analysis on a chiral phase to determine the optical purity of the enantiomers 8a and 8b of protected [8] gingerol. The gingerol isomers were thus obtained in good chemical yields in greater than 96% enantiomeric excess.
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    Synthesis and effects on peripheral thyroid hormone conversion of (R)-4-hydroxypropranolol, a main metabolite of (R)-propranolol (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 145-150 
    Details
    ISSN: 0899-0042
    Keywords: hyperthyroidism ; (R)-4-hydroxypropranolol ; peripheral conversion ; metabolites of propranolol ; negative chronotropic effect ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The inhibiting effect of (R,S)-propranolol on peripheral T4/T3 conversion can be related to the (R)-isomer. The intention of this study is to clarify if (R)-4-hydroxypropranolol, a main metabolite of (R)-propranolol, develops the same or even a stronger effect on peripheral thyroxine metabolism as the parent drug. (R)-4-hydroxypropranolol was synthesized via (R)-4-methoxypropranolol and their optical purity was checked chromatographically. Twenty patients suffering from hyperthyroidism were divided into five groups and treated with (R)-4-hydroxypropranolol · HCl in dosages from 12 to 75 mg per day in a placebo controlled study over a period of 5 days. The serum hormone levels and resting pulse rate were measured. No significant changes of thyroid parameter could be observed but a significant decrease of resting pulse rate under treatment with 75 mg (R)-4-hydroxypropranolol occurred. It could be concluded that (R)-4-hydroxypropranolol possesses negative chronotropic effects but develops no changes in thyroid hormone metabolism in hyperthyroid patients.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030101
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    Second international symposium on Chiral discrimination (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 157-157 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/chir.530030215
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    Molecular graphic and modelling training course intensive four-day course with “hands-on” training (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 158-158 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/chir.530030216
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991) 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030301
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    On flying wedges, crashing wedges, and perspective-blind stereochemists (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 159-160 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/chir.530030302
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    Drug chirality: Impact on pharmaceutical regulation (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 161-164 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/chir.530030303
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    Optical resolution of two isomeric naphthylalanines by immobilized enyzmes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 170-173 
    Details
    ISSN: 0899-0042
    Keywords: β-(1-naphthyl)alanine ; β-(2-naphthyl)alanine ; alumina ; α-chymotrypsin ; subtilisin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical resolution of β-(1-naphthyl)alanine and β-(2-naphthyl)alanine have been efficiently carried out through enzymatic hydrolysis of their methyl ester and/or N-acetyl ester derivatives by immobilized enzymes. Difficulties related to the lipophilic character of these amino acids were overcome by using emulsions of n-butyl acetate-water as reaction medium. The use of an automatic recirculating apparatus allowed reproducible and repetitive use of the immobilized biocatalysts.
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    N-(n-Butylamide) of (S)-2-(phenylcarbamoyloxy)propionic acid: A new chiral solvating agent, derived from L-lactic acid, for the enantiomeric purity determination of derivatized amino acids (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 174-176 
    Details
    ISSN: 0899-0042
    Keywords: chiral ; chiral solvating agent ; stereochemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N-(n-butylamide) of (S)-2-(phenylcarbamoyloxy)propionic acid, easily prepared starting from the inexpensive L-ethyl lactate, can be used as convenient chiral solvating agent (CSA) to determine the enantiomeric composition of N-(3,5-dinitrobenzoyl)amino acid methyl esters.
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    Pharmacokinetics of ibuprofen enantiomers in dogs (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 165-169 
    Details
    ISSN: 0899-0042
    Keywords: ibuprofen ; enantiomer ; stereoselectivity ; chiral inversion ; pharmacokinetics ; dog ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inversion of inactive (R)-ibuprofen to active (S)-ibuprofen has been suggested to occur presystemically only. In order to investigate the site of inversion in dogs we administered both enantiomers either intravenously or intraduodenally (10 mg/kg) to adult, male beagle dogs (n = 3) in a crossover design. Plasma, urine, and bile were collected for up to 6 h and analyzed stereospecifically by HPLC, according to a previously published method. Pharmacokinetic parameters were calculated using a linear computer program. Absorption after intraduodenal administration occurred rapidly, resulting in maximum plasma concentrations 0.2 h after giving the enantiomer. Approximately 70% of the (R)-enantiomer (according to AUC) was inverted to the S-enantiomer independent of route of administration. No R-ibuprofen could be detected in plasma after (S)-ibuprofen administration. Mean residence time was found to be 2 to 3 times longer for (S)-than for (R)-ibuprofen. Total systemic clearance from plasma was twice as high for (R)- than for (S)-ibuprofen. There were no differences between plasma clearances after intravenous and intraduodenal administration. Between 8 and 17% of dose was recovered in bile [especially as free and conjugated (S)-ibuprofen] and 3-12% in urine [as (S)-ibuprofen, hydroxy- and carboxyibuprofen, free and conjugated forms]. Small amounts of (R)-ibuprofen were detected in bile after intraduodenal administration of (R)-ibuprofen only (1.8% of dose). In short, the unidirectional inversion of R-ibuprofen appears to occur systemically rather than presystemically in dogs.
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    Pharmacokinetic studies with the lipid-regulating agent beclobrate: Enantiospecific assay for beclobric acid using a new fluorescent chiral coupling component (S-FLOPA) (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 35-42 
    Details
    ISSN: 0899-0042
    Keywords: chiral derivatization ; pharmacokinetics ; enantiospecific assay ; fluorescent derivatization ; flunoxaprofen ; acyl glucuronides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The major biotransformation pathway for the chiral lipid-regulating agent beclobrate is conversion to the corresponding carboxylic acid, which is then metabolized to the acyl glucuronide. An enantiospecific assay for biological material was developed that is based on chiral derivatization with N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide (EDAC) and the primary amine S-FLOPA, a new chiral coupling component for carboxylic acids derived from the 2-arylpropionic acid S-flunoxaprofen. Conversion of beclobric acid to the acyl chloride prior to coupling with the amine is also feasible. From plasma or urine beclobric acid was extracted into n-hexane/ethanol (9:1) at pH 4 after addition of sodium chloride. Clofibric acid was used as internal standard. Derivatization with EDAC/FLOPA was performed under addition of 1-hydroxybenzotriazole in anhydrous dichloromethane containing trace amounts of pyridine (ambient temperature/2 h reaction time). The chromatographic separation was performed on a silica gel stationary phase (Zorbax Sil) using n-hexane-chloroform-ethanol (100:10: 0.75, by vol) as mobile phase [flow rate, 2 ml/min; fluorescence detection, 305/355 nm; elution order of the derivatives, (-) before (+)]. Coefficients of variation were between 1.3 and 9.3% for both plasma and urine. Limit of quantification was 20-25 ng/ml for plasma based on a sample volume of 0.2 ml. Application of the assay in a pilot pharmacokinetic study showed significant differences between the kinetics of the two enantiomers. In plasma and urine, the concentrations of the dextrorotatory enantiomer exceeded those of the levorotatory enantiomer significantly.
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    A chiral stationary phase which affords unusually high levels of enantioselectivity (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 183-187 
    Details
    ISSN: 0899-0042
    Keywords: (S)-N-(1-naphthyl)leucine ; N-(3,5-dinitrobenzoyl) ; amino acids ; derivatives ; 3,5-dinitroanilides of chiral acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chiral stationary phase (CSP) derived from N-(1-naphthyl) leucine has been prepared. This CSP is conceptually similar to the CSP derived from N-(2-naphthyl)alanine and was expected to separate the enantiomers of the same clientele of analytes as does the latter. The magnitudes of the separation factors observed on the two CSPs may differ markedly for a given analyte, the new CSP often affording much greater enantioselectivity.
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    Fast liquid chromatography for the resolution of chiral compounds (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 188-195 
    Details
    ISSN: 0899-0042
    Keywords: fast analysis times ; enantiomers ; chiral stationary phase ; Pirkle-concept ; achiral derivatization ; rapid screening ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Pirkle-concept chiral stationary phase (CSP) derived from N-(1-naphthyl)leucine was evaluated for developing methods to reduce analysis times and investigating techniques in the rapid screening of a variety of chiral compounds over a given chiral selector. The effects of reduced column lengths and elevated temperatures were studied to shorten analysis times.
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    Solid angle as steric parameter of acyclic saturated groups (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 242-253 
    Details
    ISSN: 0899-0042
    Keywords: steric effects ; geometric model ; ester hydrolysis ; ester conformation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: With the early aim of quantifying steric consequences of chirality, efforts to define a nonempirical steric parameter of chemical groups are reported. Steric hindrance of a reacting center by any acyclic saturated R group has been characterized by a geometric “axial steric parameter”: the solid angle of R. When the group is a “symmetric top substituent” (i.e., when all the terminal atoms are equivalent), the solid angle matches the solid angle of a cone envelope of R. The definition of this cone is compared with Tolman's definition of a ligand cone in organometallic complexes. The chemical significance of this parameter is shown by an excellent correlation with the Dubois' experimental steric parameter E′s. Modeling steric repulsion by the cone of R, and correcting solid angles for conformational effects, only 3 empirical coefficients are needed to calculate 33 values of E′s with less than 10% error. The cone model is suggested to be relevant within the limits of random and independent free rotations about all the bonds in the C-R group. A separation between “axial cone steric hindrance” and other steric effects is proposed. The basic model and the corrections proposed allow the conformational features of esters to be discussed.
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    URL: http://dx.doi.org/10.1002/chir.530030406
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    Direct measurement of enantiomeric ratios of enzymatic resolution by chiral high-performance liquid chromatography (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 67-70 
    Details
    ISSN: 0899-0042
    Keywords: enzymatic resolution ; chiral HPLC ; enantiomeric ratio ; enantiomeric excess ; 2-(phenoxy)propionate ; 2-(4-chlorophenoxy)propionate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (R)- and (S)-Methyl 2-(phenoxy)propionate and their acids could be separated simultaneously by a Chiralcel OD or OK column, while (R)- and (S)-methyl 2-(4-chlorophenoxy)propionate and their acids were separated concurrently only by an OK column. This is a novel and facile way to measure the enantiomeric excesses of the remaining substrate and product in the reaction of enzymatic resolution; enantiomeric ratios could then be calculated.
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    Chirality of isomers of aldosterone formed in dilute alkali (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 71-75 
    Details
    ISSN: 0899-0042
    Keywords: crystal structure ; aldosterone conformation ; correction of assigned configuration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of dilute alkali at room temperature aldosterone undergoes rearrangement to form 11β,18:18,21-diepoxy-20,21-dihydroxy-4-pregnen-3-one (V). X-Ray crystallographic analysis demonstrates that isomers of both 18R, 20S, 21S and 18R, 20S, 21R configuration are formed rather than the 18R, 20R, 21R isomer postulated on the basis of examination of 1H-NMR spectra. The spectra appears to be consistent with the major component of the mixture. The 20S configuration observed is in agreement with the chirality assigned to the degradation product obtained when the same alkaline solution of aldosterone is subjected to reflux. The crystals of (V) are monoclinic P21, Z = 4 with a = 20.891(2), b = 6.3848(5), c = 16.067(2)Å, β = 122.09°(1) with two molecules in the asymmetric unit. Molecule A has the 20S,21S configuration and the molecules in the second site are a mixture of the 20S, 21S and 20S, 21R configuration in the ratio of 3:2.
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    Separating enantiomers by HPLC on silica dynamically coated with a chiral stationary phase of permethylated β-cyclodextrin (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 136-138 
    Details
    ISSN: 0899-0042
    Keywords: solvent generated HPLC systems ; β-cyclodextrin derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The paper demonstrates that the technique of solvent generated liquid--solid chromatography can be used to create normal phase systems for chiral separations. The chiral adsorption layer was generated by pumping a binary hexane:ethanol eluent containing a small fraction of permethylated β-cyclodextrin through a column packed with microparticulate silica. This technique leads to columns with good time stability and reproducibility. The possibility of generating normal phase systems with permethylated β-cyclodextrin as chiral component via the mobile phase broadens the range of phase system which can be used to separate enantiomers by HPLC.
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    Stereospecific HPLC method for the quantitation of the enantiomers of MK-0571, a potent leukotriene D4 receptor antagonist, in biological specimens (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 129-135 
    Details
    ISSN: 0899-0042
    Keywords: chiral separation ; diastereomer ; racemate ; (+)-α-(1-naphthyl)ethylamine derivatives ; enantioselective ; drug disposition ; toxicokinetic studies ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereospecific HPLC bioanalytical method was developed for quantitation of the enantiomers of MK-0571, a leukotriene D4 receptor antagonist. The procedure involves the addition of an internal standard analog to the biological matrix followed by extraction of the free acids into ethyl acetate. The acids are subsequently reacted with the homochiral reagent, (+)-(R)-α-(1-naphthyl)ethylamine (NEA) to form diastereomers. Following removal of excess reagent and side products by a dilute acid wash, the NEA-MK-0571 diastereomers are separated on a phenyl urea chiral column using a mobile phase containing hexane, isopropanol, and acetonitrile and are detected with a fluorescence detector. The sensitivity of the method is such that 50 ng of each enantiomer can be quantitated. In the 0.05 to 10 μg range the recoveries of the enantiomers of MK-0571 from plasma were 100.4 ± 7.9% and 100.0 ± 7.2%. NMR and mass spectral data confirmed the structure of the derivative. The method has been utilized in drug safety evaluation studies to demonstrate enantioselectivity in disposition of the enantiomers of MK-0571 in rats and monkeys but not in mice.
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    URL: http://dx.doi.org/10.1002/chir.530030209
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    A method for the quantitative enantioselective HPLC analysis of ethambutol and its stereoisomers (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 139-144 
    Details
    ISSN: 0899-0042
    Keywords: benzoylation ; Pirkle phase ; absolute stereochemistry ; antituberculosis drug ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A rapid, quantitative, enantioselective HPLC method, using N,N′-dibenzylethylenediamine as internal standard, for the analysis of the three stereoisomers of the antituberculosis drug ethambutol and 2-aminobutan-1-ol is described. The derivatisation and chromatographic procedures and their reproducibility, durability, and sensitivity are discussed. Application to assays of raw material, tablet content, and synthetic reactions are illustrated. The method involves perbenzoylation, in pyridine, followed by direct HPLC on a “Pirkle covalent bonded column” containing a 3,5-dinitrobenzoyl-D-phenylglycine as chiral stationary phase (CSP) using hexane/IPA as mobile phase and detection at 230 nm.
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    URL: http://dx.doi.org/10.1002/chir.530030211
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    Cell division in Dictyostelium with special emphasis on actomyosin organization in cytokinesis (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 41-54 
    Details
    ISSN: 0886-1544
    Keywords: contractile ring ; mitotic spindle ; birefringence ; video-enhanced microscopy ; fluorescence microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study focuses on the dynamic reorganization of actin and myosin (“conventional” myosin, or myosin-II) during cytokinesis in D. discoideum. This is the first study identifying the birefringence of the spindle microtubules as well as three sets of microfilamentous structure in Dictyostelium. The change of organization in these fibrillar structures was followed in real-time with video microscopy, using a Universal Polarizing Microscope equipped with polarized-light (POL) and differential interference contrast (DIC) optics combined with digital image processing. High-frequency mitotic cells were obtained by semi-synchronous culture, and high-resolution observations were made by utilizing the agar-overlay method (Yumura et al.: Journal of Cell Biology 99:894-899, 1984). The molecular identity of the birefringent structures was determined by fluorescence microscopy. Through-focus observations were performed with an axial resolution of 0.3 μm depth of field.The actomyosin fibrils show a dramatic reorganization throughout mitosis. The fibrils at the leading lamellipodia disappear, and there is a striking assembly of the cortical actomyosin in pro-metaphase, which is accompanied by a decrease in cell volume. The cortical actomyosin gradually increases through anaphase. After late anaphase, very active polar lamellipodia, with an average life of less than 1 minute, are formed. We confirmed that the polar lamellipodia include actin, but not myosin-II. At the cleavage furrow, the microfilaments form two distinctive structures: circular contractile ring at the equator, and a cortical filament array parallel to the polar axis. Myosin is localized in the contractile ring, but not associated with the axial array of F-actin. Actomyosin in the contractile ring gradually transforms into cortical network at the posterior region of daughter cells. The constriction of the furrow is accompanied by a drastic efflux of water as evidenced by highly active contractile vacuole formation and turbulent motion of minute vesicles connected to the furrow. This study demonstrates the presence of a new microfilament structure, as well as the dynamic property of the contractile ring, and sheds new light on the contractile mechanisms underlying cytoki-nesis.
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    Announcement (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 76-76 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970180108
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    Variant cDNAs encoding proteins similar to the α subunit of chicken CapZ (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 204-214 
    Details
    ISSN: 0886-1544
    Keywords: actin-binding ; muscle ; Z-line ; capping ; isoform ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chicken adult muscle and liver cDNA libraries were screened with a cDNA, α1, previously isolated from a chicken embryo library by screening with antibodies against the α subunit of chicken CapZ. cDNAs with a new coding region, called α2, were found in addition to ones with the α1 coding region. α2 predicts a protein sequence that matches exactly the N-terminal sequence of 5 peptides prepared from CapZ α purified from chicken muscle, while the protein sequence predicted by α1 matches the peptides well, but not exactly. The predicted protein sequences of α1 and α2 are very similar to each other, and they are similar to those of the α subunit of capping protein from Dictyostelium [Hartmann et al., J. Biol. Chem. 163:5254-5254, 1989] and an actin-binding protein from Xenopus [Ankenbauer et al., Nature 342:822-824, 1989]. Other conserved features of the predicted primary and secondary structures are noted. Chicken α1 and α2 are transcribed in all of 7 adult chicken muscle and non-muscle tissues in comparable amounts by Northern analysis. α2 has four poly(A)+ RNA transcripts, one of which is rare in liver. α1 has two transcripts. α1 and α2 are encoded by different single-copy genes by Southern analysis of chicken genomic DNA.
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    Alpha-actinin and actin in the outer retina: A double immunoelectron microscopic study (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 15-25 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; microfilaments ; immunocytochemistry ; photoreceptors ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Actin has many diverse functions in the outer retina. To help elucidate its organization in this area, we have investigated the extent of its association with the actin cross-linking protein alpha-actinin. Ultrathin sections of chicken retina were double-immunolabelled with monospecific antibodies against actin and alpha-actinin. The highest relative amount of alpha-actinin to actin label was measured in the adherens junctions between the individual retinal pigmented epithelial (RPE) cells and between the photoreceptor and Mueller cells; in the photoreceptor myoid; and in the RPE basal microvilli. The lowest amount was in the Mueller cell microvilli, the RPE apical processes, and in the photoreceptor ellipsoid. It is likely that the areas containing the highest ratio of alpha-actinin to actin labelling are where the actin filaments are most highly cross-linked into bundles and linked to the plasma membrane by alpha-actinin. Actin filaments terminate in these areas, and, except for the myoid region, they are involved in cell-cell or cell-substrate adherens junctions.
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    Localization of the centrin-related 165,000-Mr protein of PtK2 cells during the cell cycle (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 1-14 
    Details
    ISSN: 0886-1544
    Keywords: centrin ; centrosome ; pericentriolar lattice ; pericentriolar material ; mitosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this study, we follow changes in localization of the centrin-related 165,000-Mr protein of PtK2 cells during the cell cycle. This protein is a component of a pericentriolar lattice that consists of pericentriolar satellites, pericentriolar matrix, and basal feet (Baron A.T., and J.L. Salisbury, J. Cell Biol. 107:2669-2678, 1988). By immunofluorescence microscopy, the 165,000-Mr protein is seen as a constellation of pericentrosomal spots. We observe that cells in late G1 and S are characterized by a dense centrosomal focus of spots with additional spots dispersed throughout the cytoplasm. In G2, one bright centrosomal focus of clustered spots is observed. As the cells proceed through prophase this single focus divides, forming two foci that move toward opposite sides of the nucleus. During prometaphase, each polar focus of spots disperses. At metaphase, the spots are distributed throughout each half-cytoplast from the poles to the chromosomes. During anaphase chromosome movement, some spots are seen beside and behind the trailing chromosome arms while others are clustered at the poles. At telo-phase, pericentrosomal spots radiate from the poles to surround each mass of chromatin. In early G1, pericentrosomal spots surround each newly formed nucleus. We conclude that the 165,000-Mr protein is a dynamic component of both the centrosome (pericentriolar matrix) and the mitotic apparatus (spindle matrix).
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970180401
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    Decrease of internal free calcium and human sperm movement (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 228-240 
    Details
    ISSN: 0886-1544
    Keywords: Quin-2/AM ; spermatozoa ; calcium depletion ; motility ; flagellum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to elucidate the effects of calcium on the movement of human spermatozoa, studies were conducted using motile cells selected by swim-up migration at 37°C in 5% CO2 in air in a synthetic BWW medium containing 1.7 × 10-3 M CaCl2 or BWW without added calcium (BWW-Ca). Preliminary experiments have confirmed that the addition of EGTA (5 × 10-3; 10-2 M) to BWW medium decreased the intracellular calcium concentration ((Ca++)i) of spermatozoa, as measured in cells loaded with a fluorescent Ca++ indicator, Quin-2. Concomitant measurements of (Ca++)i and sperm movement (analysed by videomicrography at 200 f/s at room temperature) were carried out on Quin-2 loaded cells incubated in BWW-Ca medium plus EGTA (10-5 M; 10-4 M; 10-3 M). Under these conditions a decrease in (Ca++)i was observed and associated with a decrease in mean amplitude of lateral head displacement (ALH). Analysis using an automatic analyser (Hamilton Thorn at 37°C) confirmed these results: the percentage of spermatozoa swimming with ALH ≤ 6 μm is decreased when the external free calcium in BWW-Ca is decreased by the addition of 10-5 M, 10-4 M, or 10-3 M EGTA. Flagellar analysis of the sperm population characterized by ALH ≤ 6 μm showed a large proximal curvature of the tail associated with a low propagation wave velocity and a low beat frequency as compared to the spermatozoa with ALH ≤ 6 μm with similar progressive velocities. These characteristics result in a high flagellar beat efficiency (in terms of head displacement per beat). The disappearance of this pattern of movement when intracellular calcium is lowered indicates that calcium plays a complex role in the relationship between curvature and wave propagation. The ability of spermatozoa to modulate their movement in response to an alteration in the intracellular calcium level confirms the role of calcium in controlling flagellar movement in intact cells.
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    An automated assay for quantifying the swimming behavior of Paramecium and its use to study cation responses (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 91-98 
    Details
    ISSN: 0886-1544
    Keywords: motion analysis ; motility ; adaptation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Paramecium letraurelia is a ciliated protist that alters its swimming behavior in response to various stimuli. Like the sensory responses of many organisms, these responses in Paramecium show adaptation to continued stimulation. For quantitative studies of the initial response to stimulation. and of the time course of adaptation, we have developed a computerized motion analysis assay that can detect deviations from the normal swimming pattern in a population of cells. The motion of an average of ten cells was quantified during periods ranging from 15 to 60 seconds, with a time resolution of 1/15 seconds. During normal forward swimming, the maximum deviation from a straight-line path was less than 17°. Path deviations above this threshold value were defined as changes in swimming direction. The percentage of total path time that cells spent deviating from forward swimming was defined as percent directional changes (PDC). This parameter was used to construct dose-response curves for the behavioral effects of various externally added cations known to induce behavioral changes and also to show the time course of adaptation to a depolarizing K+ stimulus. This assay is a valuable tool for studies of chemoeffectors or mutations that alter the swimming behavior of Paramecium and may also be applicable to other motile organisms.
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    Site-specific antibodies block kinase a phosphorylation of desmin in vitro and inhibit incorporation of myoblasts into myotubes (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 109-120 
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    ISSN: 0886-1544
    Keywords: intermediate filaments ; vimentin ; myogenesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Desmin and vimentin are two type III intermediate filament (IF) proteins, which can be phosphorylated in vitro by cAMP-dependent kinase (kinase A) and protein kinase C, and the in vitro phosphorylation of these proteins appears to favor the disassembled state. The sites of phosphorylation for desmin and vimentin have been mapped to their amino-terminal headpiece domains; in chicken smooth muscle desmin the most kinase A-reactive residues are ser-29 and ser-35. In this study we have examined the phosphorylation of desmin by the catalytic subunit of kinase A by using anti-peptide antibodies directed against residues 26-36. The antibodies, which we call anti-D26, recognize both native and denatured desmin and can discriminate between intact desmin and those derivatives that do not possess residues 26-36. Pre-incubation of desmin with affinity purified anti-D26 blocks total kinase A catalyzed incorporation of 32P into desmin by 75-80%. When antibody-treated IFs are subjected to phosphorylation, no filament breakdown is observed after 3 hours. Thus anti-D26 antibodies block phosphorylation of IF in vitro. We have also explored the role of desmin phosphorylation in skeletal muscle cell differentiation using these antibodies. Quail embryo cells, induced to differentiate along the myogenic pathway by infection with avian SKV retroviruses expressing the ski oncogene, were microinjected with affinity purified anti-D26 at the mononucleated, myoblast stage. By 24 h post-injection, the vast majority of uninjected cells had fused into multinucleated myotubes, but all microinjected cells were arrested in the process of incorporating into myotubes and remained mononucleated. This observation suggests that kinase A phosphorylation-induced dynamic behavior of the desmin/vimentin IF cytoskeleton may be one of the many cytoskeletal restructuring events that must take place during myoblast fusion.
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    Inhibition of intracellular granule movement by microinjection of monoclonal antibodies against caldesmon (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 109-120 
    Details
    ISSN: 0886-1544
    Keywords: nonmuscle tropomyosin ; Ca++/calmodulin-binding protein ; actin-binding protein ; epitope ; actomyosin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Monoclonal antibodies, C2, C9, C18, and C21, against chicken gizzard caldesmon (called high molecular weight isoform) were shown to crossreact with a low molecular weight isoform of caldesmon in chicken embryo fibroblasts (CEF). These antibodies were used in a microinjection study to investigate the in vivo function of caldesmon in nonmuscle cell motility. Injected cells did not appear to change their morphology significantly; the cells displayed a flat appearance and were able to ruffle and locomote normally. However, in the C21 injected cells, saltatory movements of granules and organelles appeared to be greatly inhibited. This inhibition of granule movement was reversible, so that by 3 hr after injection, granules in injected cells had already recovered to normal speed. The inhibition of granule movement by C21 antibody was also very specific; the average speeds of granule movement in cells injected with C2, C9, or C18 antibody, or with C21 antibody preabsorbed with caldesmon, were not significantly different from that in uninjected cells. In a previous epitope study, we demonstrated that, of the antibodies used in this study, only C21 antibody was able to compete with the binding of caldesmon to Ca++/calmodulin and to F-actin, although both C21 and C2 antibodies recognized the same carboxyl-terminal 10K fragment of gizzard caldesmon [Lin et al., 1991: Cell Motil. Cytoskeleton 20:95-108]. The caldesmon distribution in C21 injected cells changed from stress-fiber localization to a more diffuse appearance, when the injection was performed at 10-30 mg/ml of C21 antibody. We have previously shown that a monoclonal anti-tropomyosin antibody exhibited motility-dependent recognition of an epitope, and that micro-injection of this antibody specifically inhibited intracellular granule movements of CEF cells [Hegmann et al., 1989: J. Cell Biol. 109:1141-1152]. Therefore, it is likely that tropomyosin and caldesmon may both function in intracellular granule movement by regulating the contractile system in response to [Ca++] change inside nonmuscle cells.
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    The identification of mammalian centrosomal antigens using human autoimmune anticentrosome antisera (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 121-135 
    Details
    ISSN: 0886-1544
    Keywords: centrosome ; pericentriciar material ; spindle poles ; MTOCs ; autoimmunity ; autoantibodies ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human autoimmune sera were screened for the presence of anticentrosome autoantibodies. Two high titer sera were identified that reacted with HeLa, CHO, and PtK2 centrosomes by immunofluorescence, although the fluorescent patterns that were obtained using the two antisera were separate and distinct. Serum obtained from patient IJ contained antibodies that reacted with epitopes present only in mitotic centrosomes; staining of interphase centrosomes was never detected uing IJ antiserum. Immunoblot analysis demonstrated that antibodies present in IJ antiserum reacted with a 190 kD spindle pole antigen. Immunofluorescent staining of cultured mammalian cells demonstrated that antibodies present in serum obtained from patient SPJ reacted with both interphase and mitotic centrosomes. Characterization of SPJ antiserum by immunoblotting demonstrated that antibodies present in the SPJ serum recognized proteins of Mrs of 39, 185, and 220 kD, although the possibility that the 185 kD polypeptide was a proteolytic breakdown product of the 220 kD protein has not been eliminated. Neither antiserum was able to inhibit microtubule nucleation from centrosomes in a lysed cell system in which pure 6S tubulin was added to permeabilized cells following pretreatment of the cells with either SPJ or IJ antiserum. These antisera should be useful probes for studying the biochemistry of the mammalian centrosome.
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    A component of the interphase cytoskeleton is cyclically recruited into spindle poles during mitosis (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 80-90 
    Details
    ISSN: 0886-1544
    Keywords: centrosomes ; microtubules ; sea urchin embryos ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: During the transition from interphase to mitosis, proteins are recruited into forming spindle poles [Leslie, Cell Motil. Cytoskeleton 16:225-228, 1990]. Antibodies which recognize these recruited components clearly label spindle poles during mitosis but the location and character of such proteins during interphase remain a mystery. Competition assays using an antibody to a recruited spindle pole protein show that in its disperse form the spindle pole protein is a highly insoluble component of the Cytoskeleton which is dispersed to such an extent during interphase that it is difficult to identify by immunolocalization. The function of recruited spindle pole proteins is unknown but the aggregation/dispersion cycle and the antigen are highly conserved, appearing in sea urchin embryos and tissue culture cells.
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    Microtubule reorganization during the cell cycle in synchronized BY-2 tobacco suspensions (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 94-106 
    Details
    ISSN: 0886-1544
    Keywords: Nicotiana tabacum ; microfilament ; nuclear envelope ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tobacco BY-2 suspension cultures were synchronized with aphidicolin in order to assess the relationship between microtubules (MTs), microfilaments (MFs), and the nuclear envelope (NE) at different stages of the cell cycle. Using immunofluorescence techniques, ordered MT arrays were found in the cortex in G1; few MTs are evident deeper in the cytoplasm or near the nucleus. However, MTs radiate from the surface of the nucleus during S and G2 as the interphase cortical array is replaced by the preprophase band. Perinuclear fluorescence is also visible at the end of cytokinesis but does not overlap with new ordered cortical arrays early in G1. When isolated nuclei are examined, associated MTs are again evident in S and G2, but not in G1. Microfilaments are colocalized with the MTs in the radiating arrays, as ascertained by dual staining of cells with rhodamine phalloidin. Propyzamide treatment leads to the loss of MTs at all stages, while cytoplasmic and perinuclear MF networks persist. Conversely, cytochalasin D disrupts MFs, including those radiating from the nucleus during S and G2, without any apparent effect on MTs. The results cast doubt on a proposed role for the NE in the generation of cortical MTs in plants. A universal role for MFs in the deployment of MTs is also in question.
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    Reorganization of cytoskeletal and junctional proteins during cochlear hair cell degeneration (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 215-227 
    Details
    ISSN: 0886-1544
    Keywords: guinea pig ; organ of Corti ; cytokeratins ; actin ; cingulin ; phalangeal scar ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Experiments were carried out to elucidate changes in cytoskeletal elements and intercellular junctions in the organ of Corti, when hair cells degenerate and phalangeal scars form. Hair cell damage was induced by exposing guinea pigs to high intensity noise. The spatial and temporal changes in the organization of micro-filaments, intermediate filaments, and tight junction-specific proteins were investigated using scanning and transmission electron microscopy and histochemistry. The results show that microfilaments, cytokeratins, adherens junctions, and tight junctions rearrange their distribution in damaged areas. From the temporal sequence of these changes it appears that phalangeal scars develop simultaneous with hair cell degeneration, and that the integrity of the luminal membranes in the organ of Corti is not interrupted. Each scar is formed by two supporting cells which expand and invade the sub-apical region of the dying hair cell. This region becomes cytokeratin-positive. The two supporting cells meet at the mid-line of the scar, where a new junctional complex is formed. The junctional complex consists of tight junction and adherens-type junction, but desmosomes are absent.
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    Calyculin-A increases the level of protein phosphorylation and changes the shape of 3T3 fibroblasts (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 26-40 
    Details
    ISSN: 0886-1544
    Keywords: vimentin ; phosphatase inhibitors ; intermediate filaments ; stress fibers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Calyculin-A, an inhibitor of type 1 and 2A phosphatases, was applied extracel-lularly to 3T3 fibroblasts. At 0.1 μM, calyculin-A caused a marked increase in protein phosphorylation in both the cytosolic and insoluble cellular fractions. This effect was independent of external Ca2+. An immunoprecipitate, formed with an antibody to myosin, contained several cytoskeletal components. Increased phos-phorylation following treatment with calyculin-A was observed in vimentin, the 20-kD myosin light chain, and an unidentified 440-kD component. An enhanced level of vimentin phosphorylation was found in intermediate filament preparations from treated cells.Calyculin-A also caused marked shape changes of 3T3 cells. Within minutes after addition of calyculin-A (0.1 μM) cells became rounded and lost attachment to the substratum. Stress fibers, intermediate filaments, and microtubules, prominent in the attached control cells, were not evident in the rounded cells. Shape changes were reversible and after removal of calyculin-A the rounded cells attached to the substratum, resumed a flattened shape, and were active mitotically. In the cells treated with calyculin-A an unusual “ball-like” structure was observed with transmission electron microscopy. This unique structure was 2-3 μM in diameter and was located close to the nucleus.The use of calyculin-A adds further support to the idea that cell shape is controlled, at least in part, by concerted actions of a kinase-phosphatase couple.
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    Flagellar photoresponses of Chlamydomonas cells held on micropipettes: II. Change in flagellar beat pattern (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 269-278 
    Details
    ISSN: 0886-1544
    Keywords: high-speed microcinematography ; photophobic response ; phototaxis ; beat frequency ; rate of flagellar movement ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In response to step-up as well as step-down blue or white light stimuli, changes of beat pattern were observed in the two flagella of Chlamydomonas. The front amplitude was either increased or decreased, always in reverse in the two flagella. Again, two opposite combinations of step-up and step-down responses were found roughly in parallel to the two types of beat frequency changes. It is shown that positive phototaxis is probably achieved by the first type [called type (+)] and negative phototaxis by the second one [called type (-)]. Comparative measurements have revealed that frequency is not only related to the rate of flagellar movement, but also to the beat pattern. The rate of movement may change in different ways in the recovery and in the effective stroke. Though beat frequency and pattern changes are opposite in the two types, the rates of movement of the two flagella during the effective stroke are not always. In type (-) divergent changes were found in the rates of effective stroke movement, perhaps indicating the involvement of an additional mechanism.
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    Post-mitotic cellular reorganisation in the diatom Cymatopleura solea: The role of microtubules and the microtubule centre (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 279-292 
    Details
    ISSN: 0886-1544
    Keywords: morphogenesis ; diatoms ; intracellular movement ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cell division in Cymatopleura requires precise and major relocations of the nucleus and chioroplast which have been followed by time-lapse cinematography and with the electron microscope. These movements are (1) the premitotic nucleus migrating to one end of the cell; (2) after cytokinesis, the daughter nuclei moving back to the cell centre, often oscillating several times while establishing their final location; (3) the single chloroplast folding over and sandwiching the central nucleus; and (4) the folded end of the chloroplast stretching back to fill the empty half of the cell. In all cases, straight, actively moving, transient strands of cytoplasm are associated with the movement of the nucleus and chloroplast, and these often appear to be pulling on the surface or the fold of the chloroplast which undergoes transient distortion.These movements are rapid and colchicine-sensitive. Ultrastructurally, they appear to be mediated by the prominent microtubule centre (MC) and its associated cytoskeleton of microtubules (MTs) although MTs do not attach directly to either nucleus or chloroplast. The MC is located close to the moving nucleus. Later, it moves ahead of the moving chloroplast and its MTs ensheath the tip. Later still, it is seen embedded in the fold of the chloroplast. In all three situations, MTs from it are seen in the strands of cytoplasm radiating from this area across the vacuole. After these events, the MC resumes its usual interphase situation on the nuclear surface.
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    Dictyostelium discoideum essential myosin light chain: Gene structure and characterization (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 83-94 
    Details
    ISSN: 0886-1544
    Keywords: cDNA clone ; polypeptide ; contractile protein ; motility ; non-muscle myosin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have used a Dictyostelium essential myosin light chain (EMLC) cDNA clone to isolate additional cDNA clones which supply a different 3′ sequence from that previously described. The revised cDNA sequence encodes a polypeptide of 150 amino acids. Amino acid residues 147-167 of the previously reported sequence are replaced by new residues 147 to 150. The new cDNA encodes a polypeptide with 66% amino acid sequence identity with the Physarum polycephalum EMLC, and approximately 30% identity with mammalian EMLC sequences. These new cDNA clones were used to isolate two genomic DNA fragments which contain the entire EMLC gene. The Dictyostelium EMLC gene contains a single intron located immediately 3′ of the translation initiation codon and encodes a product most similar to MLC3 isoform of vertebrates. Primer extension analysis places the transcription initiation site approximately 90 nucleotides upstream of the translation initiation site. A DNA fragment containing 350 bases of sequence upstream of the putative transcription initiation site is sufficient to drive expression of a reporter gene upon reintroduction into growing Dictyostelium cells. In addition, the CAT reporter mRNA produced by this construct showed a pattern of developmental regulation similar to that previously reported for the endogenous EMLC mRNA. Based on comparison with published EMLC sequences from a variety of sources, the Dictyostelium EMLC shows slightly higher similarity to vertebrate EMLCs from striated musele sources than nonmuscle sources. While Dictyostelium and human nonmuscle sequences display only 28% identity over their entire sequence, the region from residue 88 to 108 shows much higher identity (67%). The high evolutionary conservation of this region of the EMLC suggests it may play an important role in EMLC function, and as such, represents a good target for future mutagenesis studies.
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    Epitope mapping of monoclonal antibodies against caldesmon and their effects on the binding of caldesmon to Ca++/calmodulin and to actin or actin-tropomyosin filaments (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 95-108 
    Details
    ISSN: 0886-1544
    Keywords: actomyosin ; smooth muscle contraction ; nonmuscle cell motility ; microinjection ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of monoclonal anti-caldesmon antibodies, C2, C9, C18, C21, and C23, on the binding of caldesmon to F-actin/F-actin-tropomyosin filaments and to Ca++/calmodulin were examined in an in vitro reconstitution system. In addition, the antibody epitopes were mapped by Western blot analysis of NTCB (2-nitro-5-thiocyanobenzoic acid) and CNBr (cyanogen bromide) fragments of caldesmon. Both C9 and C18 recognize an amino terminal fragment composed of amino acid residues 19 to 153. The C23 epitope lies within a fragment ranging from residues 230 to 386. Included in this region is a 13-residue repeat sequence. Interestingly this repetitive sequence shares sequence similarity with a sequence found in nuclear lamin A, a protein which is also recognized by C23 antibody. Therefore, it is likely that the C23 epitope corresponds to this 13-residue repeat sequence. A carboxyl-terminal 10K fragment contains the epitopes for antibodies C2 and C21. Among these antibodies, only C21 drastically inhibits the binding of caldesmon to F-actin/F-actin-tropomyosin filaments and tc Ca++/calmodulin. When the molar ratio of monoclonal antibody C21 to caldesmon reached 1.0, a maximal inhibition (90%) on the binding of caldesmon to F-actin filaments was observed. However, it required double amounts of C21 antibody to exhibit a maximal inhibition of 70% on the binding of caldesmon to F-actin-tropomyosin filaments. These results suggest that the presence of tropomyosin in F-actin enhances caldesmon's binding. Furthermore, C21 antibody also effectively inhibits the caldesmon binding to Ca++/calmodolin. The kinetics of C21 inhibition on caldesmon's binding to Ca++/calmodulin is very similar to the inhibition obtained by preincubation of caldesmon with free Ca++/calmodulin. This result suggests that there is only one Ca++/calmodulin binding domain on caldesmon and this domain appears to be very close to the C21 epitope. Apparently, the Ca++/calmodulin-binding domain and the actin-binding domain are very close to each other and may interfere with each other. In an accompanying paper, we have further demonstrated that microinjection of C21 antibody into living chicken embryo fibroblasts inhibit intracellular granule movement, suggesting an in vivo interference with the functional domains [Hegmann et al., 1991: Cell Motil. Cytoskeleton 20:109-120].
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    Detection of spindle pushing forces in vivo during anaphase B in the fungus Nectria haematococca (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 18-24 
    Details
    ISSN: 0886-1544
    Keywords: Fusarium ; mitosis ; mitotic mechanisms ; motion analysis ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Forces that elongate the spindle during anaphase B of mitosis might be generated in the asteis, in the spindle, or in both. In the fungus Nectria haematococca, it has already been shown that the asters pull on the spindle pole bodies (SPBs) through-out anaphase B. In this study, we used computerized video motion analysis to characterize brief episodes of spindle bending and straightening to find out if such bending is caused by spindle pushing forces. In three episodes there were two distinct components of spindle bending and straightening: one spanning the entire episode and comprising spindle elongation and another, superimposed on the first, involving a shortening of the distance between the SPBs. In a fourth episode, only spindle elongation was involved. All four spindles elongated rapidly while bending and underwent net growth during the overall bending-straightening episode at an average rate of 4.2 μm/min. The path of one aster of a fifth mitotic apparatus was blocked by a large, occluding vacuole. This obstacle caused the migration of the mitotic apparatus to stop, resulting in a long (25 sec) episode of spindle curving and bending, usually without any substantial reduction in the distance between the SPBs as well as a marked reduction (from 4.7 to 0.65 μm/min) in the rate of spindle elongation. The results provide evidence that spindle pushing forces are active in vivo during anaphase B in N. haematococca and that they, along with astral pulling forces, help to elongate the spindle at a mostly constant rate. This is the first demonstration of both kinds of spindle elongation forces in the same organism.
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    Substrate-bound factors stimulate engorgement of growth cone lamellipodia during neurite elongation (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 255-268 
    Details
    ISSN: 0886-1544
    Keywords: confocal-microscopy ; neurite growth factor ; tubulin ; video-microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The surfaces on which neurons grow greatly affect neurite elongation, but it is unclear how substrates influence the events within the growth cone that bring about elongation. Neurite elongation by Aplysia californica neurons in culture occurs through a series of transformations of the structures of the growth cone (Goldberg and Burmeister, J. Cell Biol., 103:1921-1931, 1986). The growth cone produces actin-rich protrusions, veils, and lamellipodia, which can then mature into the central body of the growth cone through the net advance of microtubules and membranous organelles from contiguous central regions, a process called “engorgement.” Aplysia neurons form growth cones on poly-l-lysinetreated substrates, but their rate of neurite elongation is greatly enhanced on substrates additionally exposed to Aplysia hemolymph. The acute application of hemolymph to slowly growing neurites brings about a rapid acceleration of neurite elongation and engorgement. The enhancement of engorgement was effected with material eluted from hemolymph-treated substrates and was not seen when hemolymph was added to neurons cultured on hemolymph-treated substrates inactivated by exposure to UV radiation. Thus, we conclude that the rapid acceleration of engorgement caused by hemolmph is, in large part, a substrate-mediated effect. We propose that extracellular substrate molecules can modulate the rate of neurite growth through the regulation of the engorgement of lamellipodia.The microtubule disrupters colcemid and nocadazole inhibit the advance of vesicular elements into the lamellipodia following hemolymph treatment, but taxol, which promotes the polymerization and stabilization of microtubules, does not itself enhance engorgement. The microfilament disrupter cytochalasin B, however, stimulates engorgement. Our results suggest that regulating the resistance of the peripheral actin meshwork to penetration by microtubules and vesicles may be a mechanism by which substrate-attached molecules regulate neurite advance.
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    Microtubule sliding in flagellar axonemes of Chlamydomonas mutants missing inner- or outer-arm dynein: Velocity measurements on new types of mutants by an improved method (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 275-281 
    Details
    ISSN: 0886-1544
    Keywords: sliding velocity ; mechanochemistry ; dynein mutant ; axonemal motility ; cilia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To help understand the functional properties of inner and outer dynein arms in axonemal motility, sliding velocities of outer doublets were measured in disintegrating axonemes of Chlamydomonas mutants lacking either of the arms. Measurements under improved solution conditions yielded significantly higher sliding velocities than those observed in a previous study [Okagaki and Kamiya, 1986, J. Cell Biol. 103:1895-1902]. As in the previous study, it was found that the velocities in axonemes of wild type (wt) and a mutant (oda1) missing the outer arm differ greatly: 18.5 ± 4.1 μm/sec for wt and 4.4 ± 2.3 μm/sec for oda1 at 0.5 mM Mg-ATP. In contrast, axonemes of two types of mutants (ida2 and ida4) that lacked different sets of two inner-arm heavy chains displayed velocities almost identical with the wild-type velocity. Moreover, axonemes of a non-motile double mutant ida2 × ida4 underwent sliding disintegration at a similar high velocity, although less frequently than in axonemes of single mutants. These observations support the hypothesis that the inner and outer dynein arms in disintegrating axonemes drive microtubules at different speeds and it is the faster outer arm that determines the overall speed when both arms are present. The inner arm may be important for the initiation of sliding. The axoneme thus appears to be equipped with two (or more) types of motors with different intrinsic speeds.
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    Erratum (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 290-290 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970190408
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970200101
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    α-, β-, and γ-tubulins: Sequence comparisons and structural constraints (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 181-189 
    Details
    ISSN: 0886-1544
    Keywords: α-tubulin ; β-tubulin ; γ-tubulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Comparison of ≏ 160 α-, β-, and γ-tubulins, and excluding the highly divergent C-terminal peptide, indicates that the three subclasses have similar tertiary structures. Conserved sequences within or between the subclasses have been identified, together with the locations of known epitopes, chemical modifications, and mutations. Evidence is also reviewed concerning the identity of the GTP-binding sites, about which residues are exposed in the assembled microtubule and at subunit:subunit interfaces. These characteristics constrain the possible tertiary structure of the tubulin subunit.
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    Annoucement (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 134-134 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Effects of interferon-β on the translocation rate and stationary time in human fibroblasts in culture (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 99-108 
    Details
    ISSN: 0886-1544
    Keywords: inhibition of cell motility and proliferation by interferon-β ; interferon-β increases stationary time in fibroblasts ; interferon-β decreases translocation rate in fibroblasts ; fibroblast motility in culture ; cell motility: translocation rate and stationary time ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The rate of translocation and the percent of the time that cells are stationary have been measured by computer-assisted time-lapse cinemicrography in over 1,000 freshly planted human foreskin fibroblasts (FS-4 cell strain) for periods of up to a week and the effects of interferon-β (IFN-β) on these parameters have been determined. Cells were planted at 2.5 × 103 cells/cm2 in Eagle's minimal essential-medium (MEM) with 10% fetal bovine serum (FBS). Frames were taken every 2 or 4 minutes and data were collected on both cell location and cell division as a function of time. After planting FS-4 cells require ∼48 hr to reach maximum motility both with respect to the translocation rate when moving and percent time cells are moving. Recombinant human IFN-β (800 μ/ml) caused a marked increase in the fraction of time cells were stationary and a decrease of lesser magnitude in the translocation rate, as quantitated during the period during which the stationary fraction for control cells was at a minimum. IFN-β also decreased the rate of cell proliferation, without any evidence of degeneration or death of cells. Our results contribute new evidence that the fraction of time cells spend moving directionally is an important determinant of their locomotory behavior and that this determinant is responsive to modulation by cytokines.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Regulation of smooth muscle myosin (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 81-85 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Microtubules in the fission yeast Schizosaccharomyces pombe contain only the tyrosinated form of α-tubulin (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 86-93 
    Details
    ISSN: 0886-1544
    Keywords: tubulin ; detyrosination ; cdc mutants ; D2O ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The state of tubulin tyrosination in the fission yeast Schizosaccharomyces pombe was investigated using a combination of indirect immunofluorescence microscopy and Western blotting. Antibodies specific for the tyrosinated form of α-tubulin stained all microtubule arrays in wild type cells and recognised the two α-tubulin polypeptides in Western blots of cell extracts enriched for tubulin by DEAE-Sephadex chromatography. Antisera that specifically recognised the detyrosinated, glu, form, on the other hand, gave consistently negative results, both in cells undergoing rapid exponential growth and in those allowed to accumulate in stationary phase. Neither the “ageing” of microtubules, by arresting cells at different points (late G1 or G2/M) in the cell division cycle, nor stabilising them, using D2O, lead to any detectable tubulin detyrosination. These results suggest that S. pombe lacks the carboxypeptidase that carries out the tubulin detyrosination reaction. This is the first report of an organism that possesses the correct C-terminal α-tubulin sequence yet fails to carry out this post-translational modification. The implication of this novel finding for the biological role of these events is discussed.
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    Effect of cytochalasins on actin in dividing root tip cells of Allium and Triticum: A comparative immunocytochemical study (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 107-112 
    Details
    ISSN: 0886-1544
    Keywords: cell division ; cytoskeleton ; root cell ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A collaborative effort was initiated to resolve differences in two recent papers on the effects of cytochalasins in root cells. While both studies reported similar effects on interphase cells (i.e., replacement of microfilaments by many small specks and rods), Palevitz (Cell Motil. Cytoskeleton 9:283-298, 1988) maintained that cytochalasins B and D induce actin aggregation at the poles of dividing Allium root cells at a concentration of 10 μM with rhodamine phalloidin as a reporter probe, whereas McCurdy and Gunning (Cell Motil. Cytoskeleton 15:76-87, 1990) could not find these aggregates following antiactin immunocytochemistry in Triticum roots treated with CB at 50 μM. Employing identical methods and materials in the same laboratory, we found that CD induces polar actin aggregates in dividing cells of both species. However, the aggregates in Triticum are smaller and occur less frequently than those in Allium. A similar pattern is seen with CB.
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    Calcium sensors in sea urchin sperm flagella (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 123-130 
    Details
    ISSN: 0886-1544
    Keywords: calmodulin ; motility ; spermatozoa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The asymmetry of ATP-reactivated flagellar bending waves of Triton-demem-brated sea urchin spermatozoa has been measured over a range of free Ca2+ ion concentrations from 10-9 to 10-4 M. Detailed examination of the gradual response of asymmetry to Ca2+ ion concentration over this wide range indicates the presence of two Ca2+ sensors. A high-affinity sensor operates at Ca2+ concentrations near 10-7.5 M. A lower-affinity sensor operates at Ca2+ concentrations above 10-6 M, in the typical range for calmodulin-mediated responses. Incubation of demembranated sperm flagella at high Ca2+ concentrations to release calmodulin is required to enable these Ca2+ responses to be observed. This treatment also causes a decrease in the apparent affinity of the flagella for cal-modulin, as determined by measuring the increase in asymmetry in response to addition of exogenous calmodulin at low Ca2+ concentration.
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    Production and specificity of monoclonal antibodies against calmodulin from dictyostelium discoideum (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 113-122 
    Details
    ISSN: 0886-1544
    Keywords: calcium ; immunoblot ; PVDF membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Monoclonal antibodies were raised against calmodulin purified from Dictyostelium discoideum. To increase its antigenicity, the calmodulin was conjugated to keyhole limpet hemocyanin; mice were immunized with the conjugate. Hybridomas producing antibodies against calmodulin were identified by screening culture supernatants with calmodulin coupled to bovine serum albumin. The specificity of antibodies from hybridoma culture supernatants was tested by Western blot of Dictyostelium cell lysates. For this purpose, methods were developed that permitted sensitive detection of calmodulin bound to membranes. The key elements of the blotting protocol were use of PVDF membrane, transfer conducted in phosphate buffer, and glutaraldehyde fixation after transfer. These methods permitted detection of as little as 0.1 ng of calmodulin spotted directly onto the membrane, or 10 ng transferred from an SDS polyacrylamide gel. Ten calmodulin-specific antibodies were identified; most of these reacted preferentially with the calcium-containing form of Dictyostelium calmodulin. Several of the monoclonal antibodies cross-reacted with calmodulin from bovine brain.
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    Cytoskeleton of the mouse egg and embryo: Reorganization of planar elements (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 143-154 
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    ISSN: 0886-1544
    Keywords: mouse ; intermediate filaments ; detergent-extracted mouse eggs ; cytoskeletal networks ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Examination of detergent-extracted mouse eggs and embryos reveals the existence of two cytoskeletal networks. One network is the typical thin filament network observed in somatic cells while the other is composed of large planar elements. These latter cytoskeletal structures, with individual widths of 60.0±6.8 nm, alter their spatial organization in a developmental stage-specific manner. The planar elements are composed of filaments with a diameter of 10 nm aligned side-by-side with these filaments exhibiting a linear periodicity of 20.0±1.6 nm. A biochemical fraction containing components of the planar elements has been prepared from different stages of development and disappearance of prominent polypep-tides from this fraction correlates with the altered spatial organization of the planar elements. Ultrastructure and biochemistry of cytoskeletal planar elements in eggs and embryos of the mouse are comparable with cytoskeletal sheets of Syrian hamster eggs and embryos, suggesting these cytoskeletal components may have a functional role in mammalian embryogenesis. Because such structures have not been identified in eggs or embryos of species other than mammals, their function may be unique to mammalian embryogenesis.
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    Chromosome fiber dynamics and congression oscillations in metaphase PtK2 Cells at 23°C (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 131-142 
    Details
    ISSN: 0886-1544
    Keywords: mitosis ; microtubules ; tubulin incorporation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A bioriented chromosome is tethered to opposite spindle poles during congression by bundles of kinetochore microtubules (kMts). At room temperature, kinetochore fibers are a dominant component of mitotic spindles of PtK2 cells. PtK2 cells at room temperature were injected with purified tubulin covalently bound to DTAF and congression movements of individual chromosomes were recorded in time lapse. Congression movements of bioriented chromosomes between the poles occur over distances of 4.5 μm or greater. DTAF-tubulin injection had no effect on either the velocity or extent of these movements. Other cells were lysed, fixed, and the location of DTAF-tubulin incorporation was detected from digitally processed images of indirect immunofluorescence of an antibody to DTAF. Microtubules were labeled with an anti-beta tubulin antibody. At 2-5 minutes after injection, concentrated DTAF-tubulin staining was seen in the kinetochore fibers proximal to the kinetochores; a low concentration of DTAF-tubulin staining occurred at various sites through the remaining length of the fibers toward the pole. Kinetochore fibers in the same cell displayed different lengths (0.2 to 4 μm) of concentrated DTAF-tubulin incorporation proximal to the kinetochore, as did sister kinetochore fibers. Ten minutes after injection, the lengths of DTAF-containing chromosomal fibers were greater than expected if incorporation resulted solely from the lengthening of kinetochore microtubules due to congression movements of the chromosomes. Besides incorporation as a result of chromosome movement, two other mechanisms might explain the length of the DTAF-containing segments: (1) a poleward flux of tubulin subunits (Mitchison, 1989) or (2) capture of DTAF-containing nonkinetochore microtubules.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970180301
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    Genetic aspects of microtubule biology in the nematode Caenorhabditis elegans (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 159-163 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970180302
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    Microvascular endothelial-derived autacoids regulate pericyte contractility (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 180-188 
    Details
    ISSN: 0886-1544
    Keywords: microvessels ; endothelin ; contraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A silicone rubber assay is used in conjunction with morphometric measurements to characterize in vitro the contractile properties of retinal pericytes in response to endothelial secreted factors. Factor(s) present in conditioned media derived from pulmonary and retinal microvascular endothelial cells and pulmonary artery endothelial cells promote pericyte contractions. Using a radioimmunoassay significant levels of endothelin immunoreactivity are measured in conditioned media obtained from all three cell lines. Thrombin treatment enhanced endothelin-like secretions by pulmonary microvascular endothelial cells, but significantly reduced levels of endothelin-like immunoreactivity secreted by retinal microvascular endothelial cells. Synthetic endothelin and thromboxane A2 (TxA2) stimulate pericyte contractions, whereas prostaglandin I2 (PGI2) promotes pericyte relaxation. Thrombin and angiotensin II (ang II) have no effect on pericyte contractility. However, using cocultures of pericytes and endothelial cells we observe endothelial-dependent pericyte contractions in response to thrombin and ang II. Thrombin and ang II stimulate the release of endothelial-derived contracting factors, with characteristics similar to endothelin. These data suggest microvascular endothelial cell-pericyte interactions may regulate, at least in part, microvessel contractility.
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    Direct binding of F-actin to ponticulin, an Integral plasma membrane glycoprotein (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 164-179 
    Details
    ISSN: 0886-1544
    Keywords: actin-binding proteins ; actin-membrane interactions ; blot overlays ; cytoskeleton ; Dictyostelium discoideum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have developed an 125I-labeled F-actin blot overlay assay for the identification of F-actin-binding proteins after transfer to nitrocellulose from SDS-polyacryl-amide gels. Two major F-actin-binding proteins from Dictyostelium discoideum, a cytoplasmic 30 kDa protein and a 17 kDa integral membrane protein, and two minor membrane polypeptides of 19 kDa and 15 kDa were detected by this method. Using F-actin affinity and immunoaffinity chromatography, the 17 kDa polypeptide was identified as ponticulin, a previously described actin-binding glycoprotein from D. discoideum plasma membranes (Wuestehube, L.J., and Luna, E.J. [1987]: J. Cell Biol. 105:1741-1751). The binding of F-actin to ponticulin on blots is specific because unlabeled F-actin competes with 125I-labeled F-actin and because G-actin does not bind. Nitrocellulose-bound ponticulin displays binding characteristics similar to those of purified plasma membranes in solution, e.g., F-actin binding is sensitive to high salt and to elevated temperatures. Under optimal conditions, 125I-labeled F-actin blot overlays are at least as sensitive as are immunoblots with an antibody specific for ponticulin. When blotted onto nitrocellulose after 2-D gel electrophoresis, all isoforms of ponticulin and of the 19 kDa and 15 kDa polypeptides appear to bind F-actin in proportion to their abundance. Thus the actin-binding activities of these proteins do not appear to be regulated by modifications that affect isoelectric point. However, the actin-binding activity of nitrocellulose-bound ponticulin is diminished when the protein is exposed to reducing agents, suggesting an involvement of disulfide bond(s) in ponticulin function. The 125I-labeled F-actin blot overlay assay also may enable us to identify F-actin-binding proteins in other cell types and should provide a convenient method for monitoring the purification of these proteins.
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    The cytoplasmic domain of adherens-type junctions (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 1-6 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    Diversity of microtubular doublets in insect sperm tails: A computer-aided image analysis (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 282-289 
    Details
    ISSN: 0886-1544
    Keywords: sperm flagellum ; microtubular protofilaments ; dynein arms ; computer reconstruction ; computer analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Axonemal doublets of some insect spermatozoa were fixed in a mixture of glutaraldehyde and tannic acid, post-fixed in uranyl acetate, and examined by electron microscopy, in order better to characterize the protofilament pattern. Most species had outer and inner dynein arms; others had only the inner one or none. Electron micrographs show the individual protofilaments to be well resolved and to be separated by an electron dense material. A certain “noise” inherent in the electron-microscopical technique was found and is believed to be due to irregularities in fixation, embedding, and section staining, and to beam damage. The noise level was reduced by using a computer program in which similar picture elements are averaged. The resulting averaged images of the axonemal doublets show a few widened “gaps” in the wall of protofilaments. These widened gaps coincide with the location of dynein arms, spokes, or intertubular material. There were, on the other hand, no widened gaps at the level of attachement of the accessory tubules. We tentatively conclude that at least some of the proteins that associate with microtubules are inserted deep inside the microtubular wall rather than having a superficial attachement. The internal structure of the A-subtubule is rather constant in species where both sets of dynein arms are present, whereas that of the B-tubule is more variable.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970190201
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    Recent insights into the assembly, dynamics, and function of intermediate filament networks (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 67-79 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970190202
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    Cell locomotion: New research tests old ldeas on membrane and cytoskeletal flow (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 245-257 
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    ISSN: 0886-1544
    Keywords: lipid flow ; cytoskeleton ; actin ; microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Recent studies on the mobility of membrane markers on crawling cells indicate that there is no long-range centripetal flow of membrane proteins or lipids during cell locomotion. In this article we reflect on the history of ideas about membrane flow in cells, and we discuss how these new findings will shift the focus of research in cell locomotion away from the cell surface to the molecular interactions and dynamics of the actin cytoskeleton.
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    Microtubule binding and translocation by inner dynein arm subtype i1 (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 258-268 
    Details
    ISSN: 0886-1544
    Keywords: flagella ; motility ; Chlamydomonas ; cilia ; ATPase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Structural, biochemical, and genetic evidence has demonstrated there are three inner dynein arm subforms, I1, I2, and I3, which differ in organization and composition (see Piperno et al.: J. Cell Biol. 110:379-389, 1990). Using dynein extracted from Chlamydomonas outer dynein armless mutant pf28, we have begun to define the structural and functional properties of isolated inner arm subforms. Inner dynein arm I1 was purified either by sucrose density gradient centrifugation or microtubule binding affinity. I1, composed of heavy chains 1α and 1β, sedimented at 21S and selectively bound to and cross-linked purified microtubules in and ATP-sensitive manner. Deep etch electron microscopy revealed that the 21S sedimenting fraction contained two-headed structures in which large globular heads are connected by long, flexible-stem domains. In contrast, components derived from I2 and I3 sedimented as a mixture of 11S particles with single globular heads which did not bind to purified microtubules. Both the 21S and 11S sedimenting fractions supported microtubule translocation in in vitro motility assays. In 1 mM MgATP the I1-containing fraction produced very slow microtubulegliding velocities (0.76 μm/sec) compared to the I2, I3-containing fraction (4.1 μm/sec).
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    Pseudopodial activity at the active edge of migrating fibroblast is decreased after drug-induced microtubule depolymerization (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 152-158 
    Details
    ISSN: 0886-1544
    Keywords: video-enhanced contrast microscopy ; colcemid ; lamellipodia ; mitochondria ; intermediate filaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: It is known that depolymerization of microtubules by colcemid or other similar drugs abolishes polarization of pseudopodial activity in migrating fibroblasts. In this work the effect of colcemid on the intensity of protrusion and retraction of lamellipodia at the active edges of human fibroblasts migrating into the wound was investigated with video-enhanced contrast microscopy. To characterize the pseudopodial activity quantitatively the outlines of the active edges in the pairs of frames taken at adjacent 20-sec intervals were compared and mean areas of protrusions and retractions per unit length of the perimeter of the edge were measured. The mean rates of protrusions and retractions were 4-6 times less in colcemid-treated cells than in controls. Thus, microtubules depolymerized by colcemid, and/or intermediate filaments undergoing perinuclear collapse in the presence of this drug, are essential not only for the restriction of pseudopodial activity to one particular zone of the cell edge but also for the development of maximal activity in this zone.
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    βVLDL uptake by pigeon monocyte-derived macrophages: Correlation of binding dynamics with three-dimensional ultrastructure (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 139-151 
    Details
    ISSN: 0886-1544
    Keywords: lipoprotein ; receptor-mediated endocytosis ; nonspecific endocytosis ; microvilli ; membrane ruffles ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Endocytosis of pigeon beta migrating very-low-density lipoprotein (βVLDL) by monocyte-derived macrophages (monocyte/macrophages), cultured from Random Bred White Carneu (RBWC) pigeons, occurs by both coated and non-coated regions of the plasma membrane (Henson et al.: Exp. Mol. Pathol. 51:243-263, 1989). Secondary to binding, the βVLDL is translocated to lysosomes for degradation. Ultimately these events lead to foam cell formation in vitro. Utilizing video-enhanced contrast light microscopy in conjunction with whole mount intermediate-voltage transmission electron microscopy (IVEM) and high-resolution scanning EM, the dynamics of βVLDL binding have been correlated with ultrastructure. Beta VLDL conjugated to gold colloids was visualized at the surface of living cells by using Allen video-enhanced contrast-differential interference contrast microscopy (AVEC-DIC). Subsequent to AVEC-DIC, direct observation of the identical cells by IVEM and SEM was facilitated through the use of gold finder grids, and these EM observations confirmed identification of the videoobserved βVLDL particles.Upon addition of βVLDL, pigeon monocyte/macrophages underwent gross morphological changes. These changes were recorded by video as movements at the cytoplasmic periphery, and the movements involved extension of microvilli, expression of retraction fibers, and elaboration of membrane ruffles. When secondarily observed by stereo (3-D) IVEM and SEM, the identification of microvilli, retraction fibers, and membrane ruffles was confirmed and the lipoprotein-gold conjugates were associated with these ligand-induced membrane structures. Beta VLDL-gold conjugates were also associated with pit-like regions at the base of microvilli, while at the base of ruffles, βVLDL-gold conjugates were located in membrane invaginations and cytoplasmic vesicles.
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    Relation of nucleolar structure and position to the cytoplasmic microtubule system in Dictyostelium (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 293-303 
    Details
    ISSN: 0886-1544
    Keywords: cell movement ; microtubule-organizing center ; nucleus ; rapid-freeze substitution ; immuno-fluorescence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cytoplasmic microtubule system seems to influence the position and structure of nucleoli in Dictyostelium discoideum amoebae in several growing and migrating states. For example, nucleoli were usually excluded from the nuclear periphery near the microtubule-organizing center (MTOC) in all cases; and in migrating adherent cells, more than half the nucleoli were located opposite the MTOC. This localization was disrupted by nocodazole treatment, after which the nucleoli were largely dispersed except near the MTOC. More extensive effects of microtubules on nucleolar structure were seen in aggregating cells. In contrast to the normal oval structure in growing cells, nucleoli took on a different morphology: they protruded from the leading edge of nuclei and elongated to form nozzle-like structures. Analysis by rapid-freeze substitution and indirect immunofluorescence showed each nozzle surrounded by more than 10 microtubules; and in the presence of nocodazole, the microtubules shortened as expected and the nozzles disappeared. Between microtubules and the outer nuclear envelope, various-sized cross-bridges were seen. The implication that microtubules were associated with the nucleoli in aggregating cells was verified in vitro: nuclei isolated from growing cells contained the MTOC but few if any detectable microtubules; but nuclei from aggregating cells were surrounded by them. These data are consistent with the notion the microtubule system may help regulate the position and conformation of nucleoli during early development of Dictyostelium.
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    Announcement (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 319-320 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970180408
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970190101
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    A monoclonal antibody recognizing a common antigen on Drosophila embryos and human fibroblasts (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 1-8 
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    ISSN: 0886-1544
    Keywords: anti-vimentin antibody ; nuclear envelope ; centrosomes ; Drosophila early embryogenesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We used a monoclonal antibody specific for vimentin from human fibroblasts to stain whole mounts of Drosophila embryos. In immunofluorescence observations this antibody cross-reacts with an antigenic determinant localized throughout mitosis at the nuclear boundary. Double fluorescence observations with the Rb188 antibody that specifically recognizes a centrosomal protein of the Drosophila embryo [Whitfield et al., 1988] showed that the anti-vimentin antibody cross-reacts with an antigen localized in the centrosomal region.
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    Alterations in microtubule assembly caused by the microtubule-active drug LY195448 (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 9-17 
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    ISSN: 0886-1544
    Keywords: β-tubulin ; CHO ; taxol ; colcemid ; drug resistance ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: LY195448 is an experimental drug that blocks cells at metaphase (Boder et al.:Microtubules and Microtubule Inhibitors 1985: 353-361, 1985). A 4 hour exposure of NRK cells to a drug concentration of 46 μM (15 μg/ml) increased the number of mitotic cells in the population from 4.9% to 18.5%. Examination of treated cells by immunofluorescence showed increased numbers of cells blocked at prometaphase, with short microtubules extending from the spindle pole to the kinetochores. The cytoskeleton of interphase cells remained intact at these concentrations. However, the number of microtubules appeared to be reduced, and those that remained appeared kinkier and curled, particularly toward the periphery of the cells. When cytoskeletal microtubules of NRK cells were depolymerized with nocodazole, they reassembled within minutes of transfer to drug-free media. However, nocodazole-treated cells transferred to fresh media containing 15 μg/ml of LY 195448 required 2-3 times longer to reassemble cytoplasmic microtubules. Previously isolated Chinese hamster ovary cell microtubule mutants resistant to either taxol or Colcemid were tested for cross-resistance to this drug. Cell lines resistant to the depolymerizing drug Colcemid exhibited increased resistance to LY 195448 compared to wild-type cells, whereas taxol resistant cell lines were more sensitive. Of eleven newly isolated mutant CHO cell lines selected for increased resistance to LY 195448, seven exhibited an altered β-tubulin protein by two-dimensional polyacrylamide gel electrophoresis. These 11 cell lines also showed a heterogenous pattern of resistance to several microtubule-active drugs. These data demonstrate that LY 195448 is cytotoxic to mammalian cells because it inhibits microtubule assembly, most likely through a direct interaction with tubulin.
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    Inhibition of spindle elongation by taxol (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 136-144 
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    ISSN: 0886-1544
    Keywords: interzonal microtubules ; anaphase B ; PtK1 cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: During anaphase B spindle elongation, interzonal microtubules lengthen to accomplish pole-pole separation, while at the same time remaining highly dynamic [Shelden and Wadsworth, J. Cell Sci. 97:273-281, 1990]. To further examine the role of microtubule polymerization and dynamics during spindle elongation, cells have been treated with taxol, which induces microtubule polymerization and stabilizes microtubules. Taxol was added to PtK1 cells 3 minutes after initial chromatid separation, so that the effect on anaphase B could be observed with minimal disruption to anaphase A movement. In 20 μM taxol, the rate and extent of pole-pole separation, measured from time-lapse video records, are reduced to 4% and 9.5% of controls, respectively. The organization of microtbules in taxol treated cells was examined using tubulin immunofluorescence and confocal fluorescence microscopy. Taxol induces a dramatic reorganization of interzonal microtubules resulting in a narrow gap, which is nearly completely lacking in MTs, across the center of the interzone. Furthermore, microtubules in taxol treated cells are resistant to nocodazole induced microtubule disassembly. Our results reveal that taxol rapidly inhibits anaphase B spindle elongation; inhibition is accompanied by a depletion of interdigitated interzonal microtubules and a reduction in microtubule dynamic behavior.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991) 
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    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1002/cm.970200301
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    Analysis of inducible contractile rings suggests a role for protein kinase C in embryonic cytokinesis and wound healing (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 145-157 
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    ISSN: 0886-1544
    Keywords: amphibian ; cleavage regulation ; in vitro ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A semi-in vitro system derived from Xenopus oocytes which allows induction of contractile ring (CR) formation and closure is described and exploited to elucidate regulatory and structural features of cytokinesis. The inducible CRs (ICRs) are composed of actin filaments and closure is actin filament-dependent as is cytokinesis in vivo. ICR closure in this system is calcium-dependent and pH-sensitive, as is cytokinesis in permeabilized cells (Cande: Journal of Cell Biology 87:326, 1980). Closure of ICRs proceeds at a rate and with a kinetic pattern similar to embryonic cytokinesis. Collectively, these data demonstrate that this system is a faithful mimic of cytokinesis in vivo. ICR formation and closure is protein kinase C (PKC)-dependent and neomycin-sensitive, indicating that the PKC branch of the polyphosphoinositide pathway regulates formation of the actomyosin ring which is the effector of cytokinesis. Kinetic measurements show that the rate of ICR closure reaches a peak of 4-8 μm/sec. Since the maximum measured velocity of actin filament translocation by vertebrate, non-muscle myosins is 0.04 μm/sec, the later observations support a model in which the CR is segmented, containing multiple sites where filaments overlap in a “sliding filament” fashion. Because the rate decreases after reaching a peak, the results also suggest that the number of overlap sites decrease with time.
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    Post-translational incorporation of actin into myofibrils in vitro: Evidence for isoform specificity (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 158-168 
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    ISSN: 0886-1544
    Keywords: myofibril assembly ; protein isoforms ; confocal microscopy ; muscle development ; cell-free translation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The incorporation of actin into myofibrils has been examined in a cell-free system [Bouché et also Journal of Cell Biology 107:587-596, 1988; Goldfine et all Cellular and Molecular Biology of Muscle Development, 1989]. Actin was translated in a reticulocyte lysate in the presence of 35S-methionine (35S-actin) or purified from muscle and labeled with fluorescein-5-isothiocyanate (FITC-actin). Myofibrils were incubated with either 35S-actin or FITC-actin and then analyzed by gel electrophoresis or fluorescence microscopy. When myofibrils were incubated with FITC-actin monomer in the reticulocyte lysate buffer, strong fluorescent labeling was observed in Z-band regions and less so in I-bands. No fluorescence was detected in non-overlap regions of A-bands. Confocal microscopic analysis of these myofibrils indicated that FITC-actin was distributed evenly across the diameter of the myofibrils. These observations suggest that actin incorporation in the reticulocyte lysate buffer occurred at sites in the sarcomere which contain actin. In contrast, FITC-actin showed a variety of non-physiological incorporation patterns when incubated with myofibrils in the presence of an isotonic buffer (I-buffer). However, when ATP was added to I-buffer, FITC-actin showed a pattern of incorporation into myofibrils similar to that seen in the reticulocyte lysate buffer. Immunoblots indicated that actin of native size was released from myofibrils during incubation in the reticulocyte lysate buffer. No actin release was detected when the myofibrils were incubated in I-buffer lacking ATP. We used this system to compare the incorporation of actin isoforms into myofibrils. Both α- and β-actins exhibited incorporation into the myofibrils but there was a three-fold greater incorporation of the α isoform. We propose that the differential affinities of actin isoforms for myofibrils and other cytoskeletal structures could provide a mechanism for actin isoform targeting within the cytoplasm.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970200208
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    Analysis of cDNA clones for Acanthamoeba profilin-I and profilin-II shows end to end homology with vertebrate profilins and a small family of profilin genes (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 169-177 
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    ISSN: 0886-1544
    Keywords: sequence ; isoforms ; evolution ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have cloned and sequenced full length cDNAs for Acanthamoeba profilin-I and profilin-II. The genes and the encoded proteins are nearly identical except for the region between bp 121 and 210 where 35% of the nucleotides and 47% of amino acids differ. Most of these substitutions are conservative, although three of them are responsible for the differences in the isoelectric points of the isoforms [Kaiser et al., Cell Biol., 102:221-226, 1986]. The DNA sequence revealed six corrections in the previously published protein sequence of profilin-I [Ampe et al., J. Biol. Chem. 260:834-840, 1985] and for the first time resolved the ambiguities at the five positions where profilin-IA and -IB differ. The DNA sequence of profilin-II also allowed us to make two corrections in the protein sequence [Ampeet al., FEBS Lett. 228:17-21, 1988a]. Probes prepared from the cDNAs revealed 1 profilin-IA gene. one strongly cross-hybridizing profilin-I gene and one strongly reacting profilin-II gene on Southern blots of Acanthamoeba DNA. Weaker reactions with other genomic DNA fragments leave open the possibility of one additional gene each for profilin-I and profilin-II. Four different profilin RNAs were resolved on Northern blots. It possible to align the sequences of the three Acanthamoeba profilins with the sequences of nine other profilins from five different phyla. There are only two invariant residues in these profilin sequences, but many pairwise identities and conservative substitutions that indicate considerable divergence of this family of proteins from its ancestral precursor.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970200209
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    Vinculin in relation to stress fibers in spread platelets (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 190-202 
    Details
    ISSN: 0886-1544
    Keywords: platelets ; spreading ; talin ; fibrinogen ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To investigate the function of vinculin in blood platelets, we studied its localization in relation to other cytoskeletal proteins as well as its state of phosphorylation in platelets allowed to spread on fibrinogen-coated surfaces. By 5 minutes after loading the platelets onto the surfaces the 47 and 20 kDa polypeptides became phosphorylated, indicating activation. By 30 minutes, platelets formed small, typical bundles of fibers which stained brilliantly with rhodamine phalloidin. Myosin and tropomyosin, detected with specific antibodies, were localized in periodic arrays along these bundles. By indirect immunofluorescence, a discrete patch of vinculin was observed at each end of every actin-containing bundle. Vinculin phosphorylation was not detected in immunoprecipitates protected against phosphatases. Interference reflection images showed that regions of close binding to the substratum (adhesion plaques) closely matched the vinculin staining sites. Talin appeared diffusely localized. It could be shown to be present in the plaques when platelets were stabilized with ZnCl2 by the method of Geiger and then sonicated to remove some of the surface membrane. Localizations of vinculin and myosin were unaltered by this treatment. Talin phosphorylation or proteolysis could not account for vinculin translocation.We conclude that platelets, in response to an appropriate physiological surface, form typical actin bundles with vinculin at the termination of each bundle, in close relation to adhesion plaques. The signal for this translocation does not appear to depend on phosphorylation of vinculin or on phosphorylation or proteolysis of talin. Our findings support the conclusion that in platelets, as in nucleated cells, vinculin serves as at least part of the connection between bundled actin fibers and the extracellular matrix. Such a connection seems required for platelets' known ability to exert tension on surfaces.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970200303
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