The fine structure of Ameson pulvis (Microspora,Microsporida) and its implications regarding classification and chromosome cycle

Nosema pulvisPerez, 1905, Ameson pulvis (Perez) Sprague, 1977, in muscles of the crabs Carcinus maenas and C. mediterraneus from the coast of France, was observed with the electron microscope. It was found to be structurally similar to the type species A. michaelis (Sprague, 1970). Sprague, 1977, having moniliform sporogonial plasmodia, unikaryotic sporoblasts, and hirsute sporulation stages. It is treated as distinct from A. michaelis because it has slightly smaller spores (by comparison with syntype material of A. michaelis) and appears to have fewer coils in the polar filament. The results require the removal of the genus Ameson from the family Nosematidae Labbé, 1899, where Sprague (1977) had placed it under the erroneous supposition that its sporoblasts are diplokaryotic. Ameson is transferred to family Unikaryonidae Sprague, 1977. Ameson is distinguished from PereziaLéger and Duboscq, 1909, shown by Ormieres et al. to have a similar developmental pattern, by presence of appendages on its sporulation stage. A. nelsoni (Sprague, 1950), the third, and only other species of Ameson, lacks the appendages and is transferred to genus Perezia.     

Host--virus interactions in the control of T4 prereplicative transcription. I. tabC (rho) mutants.

In this paper we describe properties of old (Takahashi, 1978) and new tabC^ts and tabC^cs bacterial mutants. We find that under non-permissive conditions they differently inhibit the synthesis of specific T4 prereplicative gene products. Among such products, that we have been able to identify, are P43 and PrIIA. In contrast, P32 and PrIIB are not affected.Inhibition of P43 (T4 DNA polymerase) synthesis is sufficient to account for depressed DNA synthesis in tabC (Takahashi, 1978).In heterodiploids: (1) all tabC mutants are recessive; (2) all tabC mutants do not complement with each other; (3) at least one, tabC^ts-5521, becomes dominant at 42.6 °C if rho mutant ts15 (Tab⁺) (Das et al., 1976) is situated in trans; (4) tabC^ts-5521 also becomes dominant at 42.6 °C if tabC^cs-110 and tabC^cs-18 are situated in trans (42.6 °C is non-permissive for T4 development on tabC^cs-5521 and permissive for T4 development on tabC^cs mutants).We discuss the possibility that in tabC mutants rho protein is altered and insensitive to T4-specific anti-termination functions. We also discuss a model that accounts for the differential effect of tabC mutants on the synthesis of T4 prereplicative proteins.     

Kinship and covariance

Price's (1970) covariance theorem can be used to derive an expression for gene frequency change in kin selection models in which the fitness effect of an act is independent of the genotype of the recipient. This expression defines a coefficient of relatedness which subsumes r(Wright, 1922), b(Hamilton, 1972), ρ (Orlove &; Wood, 1978), and R(Michod &; Hamilton, 1980). The new coefficient extends the domain of Hamilton's rule to models in which the average gene frequency of actors differs from that of recipients.     

Template preferences of DNA polymerase and nuclease activities appearing during early development of Xenopus laevis.

The three DNA polymerase activities identified in early embryos of Xenopus laevis(Benbow et al., 1975) were further distinguished by their template preferences, pH optima and sensitivity to monovalent cations. In addition, endo and exonuclease activities at pH 7.5 were identified and monitored through early development. Endonuclease activity increased throughout early development while exonuclease activity remained nearly constant. These nuclease activities were not responsible for the different template preferences of the partially purified DNA polymerase activities.     

Trehalose-6-phosphate synthetase activity in extracts of Dictyostelium discoideum.

Trehalose-6-phosphate (T-6-P) synthetase activity in extracts of Dictyostelium discoideum has been reexamined in an effort to resolve discrepancies between the results of previous studies (R. Roth and M. Sussman (1966). Biochim. Biophys. Acta, 122, 225; K. A. Killick and B. E. Wright (1972). J. Biol. Chem., 247, 2967). We find that T-6-P synthetase is not cold sensitive as reported by Killick and Wright (1972), is not present in bacterial-grown vegetative cells (though subject to some modulation by other nutritional conditions), and is not in our hands unmasked or activated by ammonium sulfate fractionation. We conclude that the pattern of T-6-P synthetase accumulation and disappearance during fruiting body construction in D. discoideum is as originally described by R. Roth and M. Sussman (1968). J. Biol. Chem., 243, 5081) and confirmed elsewhere (P. C. Newell et al. (1972). J. Mol. Biol., 63, 373; R. W. Brackenbury et al. (1974). J. Mol. Biol., 90, 529; B. D. Hames and J. M. Ashworth (1974). Biochem. J., 142, 301).     

Proteolysis in eucaryotic cells: Aminopeptidases and dipeptidyl aminopeptidases of yeast revisited

Using nine different l-aminoacyl-4-nitroanilides and four different dipeptidyl-4-nitroanilides, aminopeptidases and dipeptidyl aminopeptidases active at pH 7.5 and (or) pH 5.5 in logarithmically growing and stationary-phase cells of Saccharomyces cerevisiae were searched for. Ion-exchange chromatography was used to separate the proteins of the soluble cell extract. Besides the three already-characterized aminopeptidases—aminopeptidase I (P. Matile, A. Wiemken, and W. Guyer (1971) Planta (Berlin)96, 43–53; J. Frey and K. H. Röhm (1978) Biochim. Biophys. Acta527, 31–41), aminopeptidase II (J. Frey and K. H. Röhm (1978) Biochim. Biophys. Acta527, 31–41; J. Knüver (1982) Thesis, Fachbereich Chemie, Marburg, FRG), and aminopeptidase Co (T. Achstetter, C. Ehmann, and D. H. Wolf (1982) Biochem. Biophys. Res. Commun.109, 341–347)—12 additional aminopeptidase activities are found in soluble cell extracts eluting from the ion-exchange column. These activities differ from the characterized aminopeptidases in one or more of the parameters such as charge, size, substrate specificity, inhibition pattern, pH optimum for activity and regulation. Also, a particulate aminopeptidase, called aminopeptidase P, is found in the nonsoluble fraction of disintegrated cells. Besides the described particulate X-prolyl-dipeptidyl aminopeptidase (M. P. Suarez Rendueles, J. Schwencke, N. Garcia-Alvarez and S. Gascon (1981) FEBS Lett.131, 296–300), three additional dipeptidyl aminopeptidase activities of different substrate specificities are found in the soluble extract.     

Replication of polyoma DNA in isolated nuclei. VII. Initiator RNA synthesis during nucleotide depletion.

Earlier experiments demonstrated that the Okazaki fragments synthesized during discontinuous polyoma DNA synthesis in isolated nuclei at their 5′ ends contained structural elements consisting of polyribonucleotides starting with ATP or GTP (Reichard et al., 1974). These structures could be released by digestion with pancreatic DNAase and were named initiator RNA. They consist of a large family of polyribonucleotides differing in base sequence but having a common size of about a decanucleotide. We now demonstrate that limitation of DNA synthesis by low concentrations of deoxyribonucleoside triphosphates in parallel limits the synthesis of initiator RNA. This is additional evidence for the primer function of initiator RNA. When ribonucleoside triphosphates other than ATP were deleted from the incubation medium only a small decrease of DNA and initiator RNA synthesis occurred. Under those conditions deoxyribonucleotides substituted for ribonucleotides and were incorporated internally into the primer. From this result as well as the insensitivity of initiator RNA synthesis to α-amanitin (Reichard &; Eliasson, 1979) we suggest that a mammalian counterpart to primase, the dnaG gene product of Escherichia coli(Rowen &; Kornberg, 1978a), catalyzes the synthesis of initiator RNA.     

An approach to a physico-chemical model of olfactory stimulation in vertebrates by single compounds

During recent years, numerous attempts have been made to correlate both quantitative (Davies &; Taylor, 1959; Engen, 1962; Beck, 1964; Engen, Cain &; Rovee, 1968; Cain, 1969; Dravnieks &; Laffoit, 1970; Laffort, 1969a,b) and qualitative (Davies, 1965; Amoore &; Venstrom, 1965; Döving, 1966a,b; Wright &; Michels, 1964; Leveteau &; MacLeod, 1969) odorous properties of single compounds to their molecular properties. These attempts have been only partially successful.In the present paper we will try to explain the several odorous properties of single compounds on the basis of the non-specific properties of odorants involved in solubility.This model is a first approach, and although it gives statistically highly significant relations, it is not as accurate as those advanced with respect to the physical and sensory dimensions of stimuli in the fields of vision and audition.We will first give the present definitions of the most suitable physicochemical parameters, and then advance quantitative and qualitative models for single compounds. Quantitative odorous properties are: odour threshold, rate of change of odour intensity with odorant concentration in the suprathreshold region, and the somewhat controversial upper odour intensity. Qualitative properties refer to odour character.     

Crystalline aggregation of a proteolytic fragment of the major head protein of bacteriophage T4.

An analysis has been made of the composition and structure of the two types of sheets assembled from material from dissociated bacteriophage T2 (Poglazov &; Mesyhanzhinov, 1967) and T4 capsids. Serological techniques have been used to show that both types of sheet are assembled from proteolytic fragment of P23¹, the major capsid constituent. The two types of sheets have been found to interconvert depending on the concentration of Mg²⁺ ions in the buffer. Computer modelling experiments show that the “hexagonal” and “rectangular” morphologies observed in the negative stain are due to in-register and staggered associations, respectively, of a single basic hexagonal lattice. Analysis by polyacrylamide gel electrophoresis of samples of sheets and dissociated capsids, together with previous results from immune electron microscopy (Kistler et al., 1978), suggest that hexamers of the proteolytic fragment are derived conservatively from capsomers of the phage head.The value of this proteolytic P23 fragment has been twofold: (1) it has proved to be a useful peptide in the ongoing primary sequence determination of P23 and (2) antibodies raised against it have been employed to follow the fate of P23 antigenic sites during various steps of phage capsid maturation (Kistler et al., 1978).     

The Plasmodium vaughani--Complex

Plasmodium vaughaniNovy and MacNeal, 1904, Plasmodium tenueLaveran and Marullaz, 1914, and Plasmodium merulaeCorradetti and Scanga, 1972 are shown to differ. It is suggested that P. tenue and P. merulae should be considered as subspecies belonging to Plasmodium vaughani-complex.More investigations are needed for a sufficient knowledge of the complex, particularly because at least 36 species of birds harbor P. vaughani-like parasites and cover an immense geographical area in all the parts of the world.     

A general theory of chromosome pairing based on the palindromic DNA model of Sobell with modifications and amplifications

A model for chromosome pairing is presented. It is based on the presence of segments of symmetric sequences of bases (palindromes) in the DNA at specific places in the chromosome. Palindromic DNA has been characterized by Wilson &; Thomas (1974), who state that these sequences are a regular feature of eukaryotic DNA. Sobell (1972) has suggested that they may be involved in synapsis and genetic recombination. Sobell's model is modified and amplified in an attempt to develop a general theory of chromosome pairing that explains congressional pairing, synapsis, non-homologous pairing, the initiation of crossing over, and interference.     

Dinucleotide fold proteins. Interaction of arabinose binding protein with Cibacron Blue 3G-A.

Cibacron Blue 3G-A, the dye moiety of Blue dextran-Sepharose, has been shown to not specifically bind a protein with a dinucleotide fold-like supersecondary structure, L-arabinose binding protein from Escherichia coli. This shows that Cibacron Blue 3G-A is not suitable as a definitive probe for the dinucleotide fold as suggested earlier (Thompson et al., 1975; Stellwagen, 1977). An explanation for the large predominance of proteins containing this protein supersecondary structure that bind to this dye is presented.     

Visualization of drug--nucleic acid interactions at atomic resolution. V. Structure of two aminoacridine--dinucleoside monophosphate crystalline complexes, proflavine--5-iodocytidylyl (3'-5') guanosine and acridine orange--5-iodocytidylyl (3'-5') guanosine

Acridine orange and proflavine form complexes with the dinucleoside monophosphate, 5-iodocytidylyl(3′–5′)guanosine. The acridine orange-iodoCpG² crystals are monoclinic, space group P2₁, with unit cell dimensions $\text{a = 14.36}\text{A}\text{?}\text{, b = 19.64}\text{A}\text{?}\text{, c = 20.67}\text{A}\text{?}$, β = 102.5 °. The proflavine-iodoCpG crystals are monoclinic, space group C2, with unit cell dimensions $\text{a = 32.14}\text{A}\text{?}\text{, b = 22.23}\text{A}\text{?}\text{, c = 18.42}\text{A}\text{?}$, β = 123.3 °. Both structures have been solved to atomic resolution by Patterson and Fourier methods, and refined by full matrix least-squares.Acridine orange forms an intercalative structure with iodoCpG in much the same manner as ethidium, ellipticine and 3,5,6,8-tetramethyl-N-methyl phenanthrolinium (Jain et al., 1977, Jain et al., 1979), except that the acridine nucleus lies asymmetrically in the intercalation site. This asymmetric intercalation is accompanied by a sliding of base-pairs upon the acridine nucleus and is similar to that observed with the 9-aminoacridine-iodoCpG asymmetric intercalative binding mode described in the previous papers (Sakore et al., 1977, Sakore et al., 1979). Basepairs above and below the drug are separated by about 6.8 Å and are twisted about 10 °; this reflects the mixed sugar puckering pattern observed in the sugar-phospate chains: C3′ endo (3′–5′) C2′ endo (i.e. each cytidine residue has a C3′ endo sugar comformation, while each guanosine residue has a C2′ endo sugar conformation), alterations in glycosidic torsional angles and other small but significant conformational changes in the sugar-phosphate backbone.Proflavine, on the other hand, demonstrates symmetric intercalation with iodoCpG. Hydrogen bonds connect amino groups on proflavine with phosphate oxygen atoms on the dinucleotide. In contrast to the acridine orange structure, base-pairs above and below the intercalative proflavine molecule are twisted about 36 °. The altered magnitude of this angular twist reflects the sugar puckering pattern that is observed: C3′ endo (3′–5′) C3′ endo. Since proflavine is known to unwind DNA in much the same manner as ethidium and acridine orange (Waring, 1970), one cannot use the information from this model system to understand how proflavine binds to DNA (it is possible, for example, that hydrogen bonding observed between proflavine and iodoCpG alters the intercalative geometry in this model system).Instead, we propose a model for proflavine-DNA binding in which proflavine lies asymmetrically in the intercalation site (characterized by the C3′ endo (3′–5′) C2′ endo mixed sugar puckering pattern) and forms only one hydrogen bond to a neighboring phosphate oxygen atom. Our model for proflavine-DNA binding, therefore, is very similar to our acridine orange-DNA binding model. We will describe these models in detail in this paper.     

An autoradiographic analysis of the time of appearance of neurons in the developing chick neural retina

The pattern of incorporation of [³H]thymidine into the chick neural retina has been used to establish the time and order in which different classes of neuroepithelial cells withdraw from the cell cycle and initiate migration and differentiation.The posterior pole of the retina is the first to form during development. In this region most neuroepithelial cells complete mitotic activity between the third and sixth day of incubation. Presumptive ganglion cells initiate the withdrawal process, and they are soon followed by the neuroepithelial precursors of amacrine, horizontal, and receptor cells. Bipolar cell precursors are the last to begin and the last to complete cell cycle activity. It is worthy of note, however, that, in any given region of the retina, neuroepithelial cells of all types cease mitosis in close, overlapping succession.These results are in reasonable agreement with those previously published on the chick retina by Fujita and Horii (1963), and other investigators on the mouse (Mus), killifish (Fundulus), and toad (Xenopus). The present data are also consistent with those proposals of Angevine (1970), Jacobson, 1968a, Jacobson, 1968b, Jacobson, 1970, and others that relate the cessation of mitotic activity of neuroepithelial cells to the determination of neuronal size, axon length, and the specification of neuronal connections.     

Iron-ethylenediaminetetraacetic acid (EDTA)-catalyzed superoxide dismutation revisited: An explanation of why the dismutase activity of Fe-EDTA cannot be detected in the cytochrome c/xanthine oxidase assay system

The recent assertion of J. Diguiseppi and I. Fridovich (1980, Arch. Biochem. Biophys., 203, 145–150) that Fe-EDTA does not catalyze superoxide dismutation is disputed. By directly observing superoxide generated during pulse radiolysis, we have confirmed the results of a previous study (G. J. McClune, J. A. Fee, G. A. McClusky, and J. T. Groves, 1977, J. Amer. Chem. Soc., 99, 5220–5222) which concluded that Fe-EDTA catalyzed superoxide dismutation. We also demonstrate that the reaction of Fe(II)-EDTA, formed during catalyzed superoxide dismutation, with cytochrome c, the probe molecule in the cytochrome c/xanthine oxidase/xanthine assay system for superoxide dismutase activity, is sufficiently rapid (H. L. Hodges, R. A. Holwerda, and H. B. Gray, 1974, J. Amer. Chem. Soc., 96, 3132–3137) to obscure the weak catalysis of superoxide dismutation by Fe-EDTA.     

Liberation of labile sulfur from ferredoxins by alkaline zinc reagent: an appraisal of the methylene blue method.

In disagreement with reported observation by Suhara and her colleagues (K. Suhara, S. Takemori, M. Katagiri, K. Wada, H. Kobayashi, and H. Matsubara, 1975, Anal. Biochem.68, 632–636) we found that more than 90% of labile sulfur was liberated from adrenodoxin within 5 min at 22°C. This rate was faster than those of spinach and clostridial ferredoxins, a result also at variance with Suhara's observation. At low temperature, the reaction was clearly biphasic, and spinach ferredoxin showed a similar profile. In the absence of zinc acetate, activation energies of the decomposition reaction of iron-sulfur center of OH^? were obtained as 39, 26, and 11 kcal/mol for adrenal, spinach, and clostridial ferredoxins, respectively. The adrenal reaction became faster as the dipole moment of the solvent increased. In the presence of 4 m urea and 1 m KCl, the rate was enhanced by approximately 26-fold, relative to the reaction without the addition of urea. In conclusion, the liberation reaction of adrenal labile sulfur with alkaline zinc reagent is fast at 22°C, indicating no need for modification of the original method (T. Kimura and K. Suzuki, 1967, J. Biol. Chem.242, 485–491; P. E. Brumly, R. W. Miller, and V. Massey, 1965, J. Biol. Chem.240, 2222–2228).     

A note on the sampling theory for infinite alleles and infinite sites models

This note considers sampling theory for a selectively neutral locus where it is supposed that the data provide nucleotide sequences for the genes sampled. It thus anticipates that technical advances will soon provide data of this form in volume approaching that currently obtained from electrophoresis. The assumption made on the nature of the data will require us to use, in the terminology ofKimura (Theor. Pop. Biol.2, 174–208 (1971)), the “infinite sites” model of Karlin and McGregor (Proc. Fifth Berkeley Symp. Math. Statist. Prob.4, 415–438 (1967)) rather that the “infinite alleles” model of Kimura and Crow (Genetics49, 174–738 (1964)). We emphasize that these two models refer not to two different real-world circumstances, but rather to two different assumptions concerning our capacity to investigate the real world. We compare our results where appropriate with corresponding sampling theory of Ewens (Theor. Pop. Biol.3, 87–112 (1972)) for the “infinite alleles” model. Note finally that some of our results depend on an assumption of independence of behavior at individual sites; a parallel paper byWatterson (submitted for publication (1974)) assumes no recombination between sites. Real-world behavior will lie between these two assumptions, closer to the situation assumed by Watterson than in this note. Our analysis provides upper bounds for increased efficiency in using complete nucleotide sequences.     

Lambda phage cro repressor: Non-specific DNA binding

The interaction of lambda phage cro repressor with double-stranded non-specific DNA has been investigated by monitoring the quenching of its intrinsic tyrosyl fluorescence. The McGhee & von Hippel (1974) analysis of the binding of cro repressor to DNA showed that cro repressor undergoes structural variations in the ionic strength range from 0.04 to 0.18m-KCl. Under these salt conditions, the excluded binding site size of cro repressor on the DNA lattice changes from three to four base-pairs (6 to 8 nucleotides) at the lower ionic strengths, to seven to eight base-pairs (14 to 16 nucleotides) at the higher ionic strength. Quaternary structure variation, which does not cause the excluded site size variation, was also noted at low ionic strengths. Evidence is presented to indicate that cro repressor binds only one side of the DNA helix, such that cro repressor covers a stretch of 14 to 16 nucleotides along one side of the helix in the presence of 0.2 m-salt. Under conditions where the cro repressor structure is constant, approximately nine ion-pairs are formed in the cro repressor-non-specific DNA complex. These results are in agreement with the model proposed by Anderson et al. (1981).