bluuebunny/crossref_metadata_2025_split huggingface dataset:
Covalently closed, circular DNA in kappa endosymbionts ofParamecium
Authors: Dilts Judith A. 
Published: September 2009

SUMMARYCaedobacter taeniospiralis(kappa), a bacterial endosymbiont isolated fromParamecium tetraureliastock 51, contains, in addition to the bacterial chromosome, covalently closed circular DNA molecules as shown by isolation on dye-buoyant-density gradients. The closed circular molecule has a contour length of 13·75 ± 0·04 µm with a buoyant density of 1·698 g/cm3. The buoyant density of the bacterial chromosome is 1·700–1·701 g/cm3. Kappa of the 51 group isolated from stock 298 and stock 6g2,P. tetraurelia, also contain the closed circular DNA. Two forms of kappa coexist in paramecia: brights and nonbrights. Examination by density-gradient centrifugation of the DNA of brights and nonbrights shows the extrachromosomal DNA to be associated mainly with brights. It is suggested that the extrachromosomal DNA might be the determinant for the refractile bodies and the helical phage-like structures found in brights.
Synchrony of division in mass cultures of Paramecium tetraurelia by a selective density-labelling technique
Authors: Aufderheide Karl 
Published: September 2009

SUMMARYA technique has been developed for achieving synchrony of division by selection for immediate pre- and post-fission cells of Paramecium tetraurelia. Cell populations are fed granular tantalum, followed by density-gradient centrifugation. Dividing cells, which do not feed, are separated from feeding interphase cells. The selected cells are division-synchronous for at least two generations when resuspended in fresh culture fluid. This technique provides a rapid means of obtaining large numbers of synchronously dividing paramecia for cell-cycle studies and has general application for selective enrichment of non-feeding sub-populations of cells.
A study on the mate-killer toxin by microinjection inParamecium
Authors: Koizumi Sadaaki , Kobayashi Sumiko 
Published: September 2009

SUMMARYThe killing action by mu toxin, which is contained in the cytoplasm of stock 540,Paramecium primaurelia, was demonstrated against the various stocks of paramecia by means of microinjection. Most of the toxin is present in the soluble fraction of the host cytoplasm. The toxin was precipitated by ammonium sulphate at 50–80% saturation, and was almost completely inactivated by incubation at 60 °C for 30 min. Pre-autogamous paramecia were more sensitive than post-autogamous ones to the toxin. Paramecia which bear endosymbionts were generally resistant to the mate-killer toxin.
Longitudinal microtubules and their functions during asexual reproduction inParamecium tetraurelia
Authors: Sundararaman V. , Hanson Earl D. 
Published: September 2009

SUMMARYLongitudinal microtubules appear inParamecium tetraureliawhen cells are ready to divide (ca.interfission age 0·9). They arise in the longitudinal cortical ridges between kineties and form, in each ridge, an incomplete circlet of 15–18 microtubules, disappearing 10–15 min after separation of the fission products (ca.interfission age 0·03–0·04). Vinblastine, colchicine, colcemid, mercaptoethanol, and cold treatments all result in loss of these microtubules, rounding up of the cells, and some suppression of cell division. The tubules are thought to play a role in cellular elongation, morphogenesis, and separation.
Laser microbeam induction of incomplete doublets of Oxytricha fallax
Authors: Grimes Gary W. 
Published: September 2009

SUMMARYDestruction by laser microbeam of oral and ventral cirral primordia for the future opisthe of 1/2 of a pre-fission doublet results in the permanent loss of ability to form oral and ventral cirral primordia on the irradiated half. This observation provides further evidence for the postulated ‘determinative region’ present on each ventral surface of these organisms. The opisthe of the irradiated doublet retains both original rows of marginal cirri, which are located mid-dorsally with respect to the remaining ventral surface. These two rows of marginal cirri are reproduced faithfully in all future opisthes, but are lost in most proter lines. The pattern of loss in proters involves migration of the extra rows of marginal cirri to the cell's right margin followed by aberrant morphogenesis and subsequent resorption. These results show that the reproduction of marginal cirri is at least partially dependent upon the presence of marginal cirri and their inherent structural characteristics as well as upon their position on the cell surface.
Maintenance of genetic homogeneity in systems with multiple genomes
Authors: Birky C. William , Skavaril Russell V. 
Published: September 2009

SUMMARYGenes or sequences of DNA present in multiple copies per cell include entire genomes of mitochondria and chloroplasts, nuclear ribosomal RNA genes, and highly repetitive sequences in heterochromatin. All copies are nearly identical, in spite of mutational pressure and weak selection. A zygote containing mitochondrial or chloroplast genophores of two different genotypes quickly produces progeny pure for one genotype or another (vegetative segregation). Evidence from yeast andChlamy-domonassuggests that organelle genophores undergo repeated rounds of random mating and recombination. When two molecules carrying different alleles at a locus recombine, gene conversion can result in the cell becoming pure for one allele. Stochastic matching and conversion (SMAC) has been studied by computer simulations which suggest that it will tend to eliminate new mutations in yeast mitochondrial DNA and speed up vegetative segregation. We have verified previous suggestions that gene conversion, occurring during unequal mitotic sister-strand crossing-over, provides an efficient mechanism for maintaining the homogeneity of repeated sequences in eukaryotic chromosomes.
Effects of actinomycin D and puromycin upon excystment ofDidinium nasutum
Authors: Butzel H. M. , Mayer L. 
Published: September 2009

SUMMARYActivated cysts ofDidinium nasutumcontinue excystment after treatment with actinomycin D or puromycin. Cysts treated at developmental stages 19–20 emerge holociliated and lacking the seizing organ. No effect of the antibiotics at any other stages was found, suggesting that it is at stage 19–20 that the initiation of normal ciliation and of mouth formation occurs. Treatment with other metabolic inhibitors either blocks excystment completely or has no effect on normal development depending upon dosage, suggesting that the action of the antibiotics is specific.
Evidence that HT mutant strains of bacteriophage P22 retain an altered form of substrate specificity in the formation of transducing particles inSalmonella typhimurium
Authors: Chelala Cesar A. , Margolin Paul 
Published: September 2009

SUMMARYThe effects of two different deletions of the tryptophan operon on the cotransduction linkage of the nearbycysBandpyrFmarkers were studied using three sets of donor lysates, each produced by a different HT mutant P22 phage strain. Eachtrpoperon deletion (present in both donor and recipient to preserve homology) caused changes in the cotransduction frequencies. This indicated that the HT mutant phage encapsulating mechanism, whose ability to discriminate phage DNA from host-cell DNA is absent or diminished, could still distinguish among nucleotide sequences in selecting bacterial chromosome sites at which to initiate transducing particle formation. The three HT mutant phage strains each produced different sets of cotransduction linkage values, indicating that this aspect of substrate specificity was altered differently and uniquely by each HT mutation.
The association of tryptophan synthetase subunits fromEscherichia coliandSalmonella typhimuriumin homologous and heterologous combinations
Authors: DiCamelli Ralph Francis , Balbinder Elias 
Published: September 2009

SUMMARYThe association of α and β2subunits of tryptophan synthetase fromEscherichia coliandSalmonella typhimuriumin homologous and heterologous combinations was studied by sucrose density gradient centri-fugation. Under conditions allowing for optimal association of subunits derived from the same source, subunit association in the mixtureE. coliα–S. typhimuriumβ2was weaker than normal while in the reciprocal combination ofS. typhimuriumα–E. coliβ2it was tighter than normal.These observations suggest that a certain degree of binding between the α and β2subunits of tryptophan synthetase could have had a selective advantage during the evolutionary divergence of the species of Entero-bacteriaceae, so that a mutation leading to the substitution of an amino acid involved in α–β2association in one of the subunits could have been compensated by a mutation in the complementary one.
Lysogenization by phage P22 carrying amber mutations in Genes 12 and 18
Authors: Ronen Amiram , Levine Myron 
Published: September 2009

SUMMARYTemperature-sensitive mutants in genes 12 and 18 of phage P22 show recessive DNA-negative phenotypes, but dominant integration-negative phenotypes. In contrast, am mutants in genes 12 and 18 are recessive for both DNA synthesis and lysogeny. The data are interpreted to indicate that the active forms of these two gene products are multimers.
Quantitation of nuclear DNA inAscaris lumbricoides: DNA constancy and chromatin diminution
Authors: Pasternak J. , Barrell R. 
Published: September 2009

SUMMARYThe DNA contents of nuclei during gametogenesis and embryogenesis inAscaris lumbricoideswere measured by Feulgen-microspectrophoto-metry. The variability in the mean value for the haploid amount of DNA in sperm from different males processed at different times was not significant when sperm cell samples were taken from the same region of the seminal vesicle. As the sperm mature, the extent of uptake of Feulgen dye decreases nonsystematically. A similar phenomenon occurs during embryogenesis, and as noted by others, primary oocytes in the terminal portion of the oviduct become Feulgen-negative. Feulgen-positive primary oocytes maintain a 4C DNA value without significant variation. Notwithstanding the differences in Feulgen-DNA values in certain types of nuclei, our evidence supports the view that inAscaris lumbricoidesthe amount of intraspecific DNA has a constant value between individual organisms and from one generation to the next. About 34% of the DNA of the zygote is lost through chromatin diminution at the third embryonic cleavage. This quantity represents 0·23 pg DNA per haploid equivalent.
Plasmid-mediated transmission of chromosomal genes inPseudomonas glycinea
Authors: Lacy George H. , Leary John V. 
Published: September 2009

SUMMARYComplementing diauxotrophic mutants ofP. glycineawere mated in combination in which one or both mutants contained a resistance plasmid. The transfer of chromosmal markers was scored by the appearance of prototrophy at one or more of the auxotrophic loci. The resistance plasmid RP1 was equally or slightly more efficient than R6886 in the transmission of chromosomal genes.
The effects of selection at different ages for high and low body weight on the pattern of fat deposition in mice
Authors: Hayes J. F. , McCarthy J. C. 
Published: September 2009

SUMMARYTwo pairs of lines of mice, selected for High and Low weight at 5 weeks of age (H5and L5) and at 10 weeks of age (H10and L10) over 15 generations, were compared with each other and an unselected control line (QC) at three different ages, i.e. at 5, 10 and 21 weeks of age. Differences in percentage fat between High and Low lines were small at 5 weeks, clearcut at 10 weeks and at 21 weeks the High lines were almost twice as fat as the Low ones. The H5line was slightly fatter than the H10line at all three ages and the L10line was fatter than the L5line at two ages. The developmental pattern of fat deposition was unaffected by selection for high or low weight at 5 weeks, i.e. the relationship between fat weight and carcass weight was similar in the H5, L5and QC lines. Selection at 10 weeks affected the level of fat at low carcass weights and the relative rate at which fat was subsequently deposited. The different correlated responses resulting from selection at 5 and 10 weeks are explained in terms of genetic variation in (1) the rate of food consumption, (2) the efficiency of energy utilization for growth, and (3) the relative amount of fat deposited up to the age at selection.
The effect of selection for body weight on the skeletal variation of the mouse
Authors: Truslove Gillian M. 
Published: September 2009

SUMMARYThe incidence of many minor skeletal variants in the inbred mouse strain C57BL can be influenced by the diet on which the parents live: in many cases, the effect is mediated by a correlation with body size. This also seems to be true in Falconer's (1973) Q-strain in which body size has been increased or decreased by selection. However, there was so much heterogeneity between replicates within selection lines that variants influenced by body size could be detected as a group, but not identified individually.
The survival of RP 1–1 inEscherichia coliand the influence of therecandpolAgenes on the process
Authors: Moillo-Batt Agnes , Richmond M. H. 
Published: September 2009

SUMMARYThe survival of the plasmid RP 1–1 inE. colidepends on the presence of a functionalpolAgene. Unlike other plasmids that have this requirement, the replication of RP 1–1 is inhibited by chloramphenicol. RP 1–1 cannot be inherited byE. coli recAmutants, and inactivation of therecAgene product in arecAtsmutant leads to destruction of the plasmid. RP 1–1 cannot be inherited byrecBorrecC E. coliunless the strains also carry a suppressor of these genes, such assbcAorsbcB. The pattern of replication of RP 1–1 inE. coliK12 and its mutants suggests that the survival of this plasmid in this species is the outcome of a balance between DNA polymerase I-specified replication and exonuclease destruction.
A selective model for electrophoretic profiles in protein polymorphisms
Authors: Moran P. A. P. 
Published: September 2009

SUMMARYIn a previous paper the theory of a model of electrophoretic profiles due to Ohta & Kimura was considered. This model assumes a finite population with a linear series of possible alleles with mutation between nearest types but no selection. In the present paper a model with both mutation and selection is constructed which results in a stable population distribution closely fitting empirically observed features of the Ohta–Kimura model. The problem of discriminating between selective and non-selective models for electrophoretic models is considered.
Behavioural pleiotropy of theyellowgene inDrosophila melanogaster
Authors: Wilson R. , Burnet B. , Eastwood L. , Connolly K. 
Published: September 2009

SUMMARYTheyellowmutant (y− 1:0·0) ofDrosophila melanogastershows a reduction in body pigmentation associated with a decrement in locomotor activity and in male competitive mating ability. The effects of the mutant gene are specific to locomotor activity in the adult fly, measures of larval activity being unaffected. In the presence of active femalesyellowmales offer a reduced intensity of sexual stimulation because they are less able to maintain contact during courtship. However, the impaired locomotor performance ofyellowmales is not the general cause for their reduced competitive mating ability, since the stimuli provided byyellowmutants courting inactive females appear to be both quantitatively and qualitatively indistinguishable from those of their wild-type male sibs. Nor is there any good evidence, as measured by the frequency of rejection responses, that the courtship stimulation offered by theyellowmales is less acceptable to the females. The mutant males are nevertheless unsuccessful in achieving copulation with such females. It is suggested that impairment of mating ability inyellowmales may be caused by changes in the efficiency for mating of their secondary sexual structures due to the effect of theyellowgene on the properties of the cuticle.
Tetrapyrrole biosynthesis:N-methyl-N′-nitrosoguanidine-induced mutants ofPropionibacterium shermanii
Authors: Georgopapadakou N. H. , Petrillo J. , Scott A. I. , Low B. 
Published: September 2009

SUMMARYAn isolation method forN-methyl-N′-nitrosoguanidine-induced catalase negative mutants ofP. shermaniibased on replica plating is described. In contrast to previous methods, it extends to the early stages of tetrapyrrole biosynthesis which are common in both corrins and porphyrins. It may thus aid in elucidating the mechanism and control of porphyrin and corrin biosynthesis. Some preliminary results are discussed.
Strain variation in spermatozoal β-glucuronidase in mice
Authors: Erickson Robert P. 
Published: September 2009

SUMMARYVariation in spermatozoal β-glucuronidase levels of inbred strains of mice was found to parallel the known variation usually studied in liver with one outstanding exception: BALB/cJ spermatozoa, but not other tissues, showed an anomalously low level. This difference in spermatozoal β-glucuronidase activity was studied in hybrids and backcrosses but the data did not establish the number of loci affecting the difference. The levels of β-glucuronidase in F1's between C3H/HeJ and A/J depended markedly on the sex direction of the cross.
Recombination of recessivev+transformants inDrosophila melanogaster
Authors: Fox Allen S. , Kreber Robert A. , Liu Chih Ping , Yoon Sei Byung 
Published: September 2009

SUMMARYRecessive transformants (col) obtained fromv(vermilion) embryos treated withv+DNA are shown to map at 1−0·02, a position not distinguishable from that ofsu(s) (suppressor-of-sable) and in agreement with observations indicating phenotypic allelism ofcolwithsu(s) mutants. Recombination in they–col–gtsegment of theXchromosome, over a total map length of O·3 units, was studied among the progeny ofcolv1/y1gtE6cvv1fandy1colgtE6cvv1f/v1females. The data from both crosses exhibit the following features: (1) recovery of reciprocal recombinants betweeny1andcol; (2) recovery of reciprocal recombinants betweencolandgtE6and (3) striking negative interference in they–col–gtsegment. These results allow three alternative interpretations: (1) that recombination in they–col–gtsegment results from conventional crossing-over, with high coincidence of crossovers in the two subsegments; (2) that it results from symmetrical gene conversion at thecolsite (coltocol+, andcol+tocol), which may be accompanied by single cross-overs in either of the adjacent regions; (3) thatcolbehaves like a transposable element, formally symbolizedsu(s)+·col, and that recombination insu(s)+·col/su(s)+(i.e.col/col+) heterozygotes results from transposition of thecolelement from homolog to homolog, accompanied sometimes by crossing-over, either in they–colsubsegment or in thecol-gtsubsegment.
Choline-O-sulphate utilization inAspergillus nidulans
Authors: Gravel Roy A. 
Published: September 2009

SUMMARYThe role of choline-O-sulphate (COS) as a sulphur storage compound inAspergillus nidulanswas examined by comparing a normal strain and one unable to utilize COS in a sulphur-starvation experiment designed to measure the mobilization of sulphur stores. Efforts to isolate the necessary mutants deficient in choline sulphatase activity produced two nutritionally distinct classes of mutants unable to utilize COS. They were found to be allelic on the basis of genetic complementation and fine structures mapping and represent either leaky or tight mutants with respect to choline sulphatase activity. One of these mutants with no detectable choline sulphatase activity was selected for a growth experiment which demonstrated that COS is a major, though not the only source of the endogenous sulphur supply which can be mobilized during growth in sulphur-limiting conditions.
Maternal inheritance of extranuclear mitochondrial markers inAspergillus nidulans
Authors: Rowlands Robert T. , Turner Geoffrey 
Published: September 2009

SUMMARYMaternal inheritance of extranuclear mitochondrial genes has been demonstrated inAspergillus nidulansusing the ‘blue’ ascospore colour mutants in combination with heterokaryon incompatible strains. It appears that heterokaryosis is not a prerequisite of sexual outcrossing, and that recombination of extranuclear mitochondrial markers does not occur in the sexual stage of the cell cycle.
DNA syntheses in course of meiotic development in Neurospora crassa
Authors: Iyengar G. A. S. , Deka P. C. , Kundu S. C. , Sen S. K. 
Published: September 2009

SUMMARYNuclear DNA syntheses have been measured microspectrophotometrically in course of meiotic nuclear development inNeurospora crassa. The purpose of the study has been to establish the timing of these DNA syntheses in relation to meiosis and in the formation of its final products in an ideal genetic material, where the products of the meiotic division can be recovered and identified. Spectrophotometric analysis has indicated that the last premeiotic DNA replication is completed before caryogamy; a postmeiotic DNA replication takes place at the tetrad of the nuclei level; and finally a second postmeiotic DNA replication occurs in the ascospores to result in eight binucleated ascospores. The timing of postmeiotic replication is compatible with the models explaining gene conversion through the postulated mechanisms involving heteroduplex formation.
Genetic analysis of a cross between two homothallic strains ofPhysarum polycephalum
Authors: Poulter R. T. M. , Honey N. K. 
Published: September 2009

SUMMARYThe homothallic amoebal clones ofPhysarum polycephalumare of potential use in understanding the developmental genetics of this organism. Such an application requires that complementation and recombination analysis be possible between pairs of homothallic clones. This paper is a report of the formation of mixed plasmodia by pairs of homothallic amoebal clones. In order to detect such mixed plasmodia use was made of two marker genes involved in plasmodial fusion,fusA andfusB. Sporulation of a mixed plasmodium formed from two homothallic (delayed) amoebal clones yielded progeny amoebae which were genetically recombinant. It is deduced from the ratios of various genotypes in these progeny clones that the mixed plasmodium was diploid and that meiosis was associated with sporulation. There is therefore no impediment to the use of the homothallic strains for genetical analysis. The progeny amoebal clones were observed to be showing segregation for the characters homothallic (rapid) and homothallic (delayed). This observation, taken together with other related observations, suggests that the homothallic (delayed) character is produced by mutation of the homothallic (rapid) character. The rare plasmodia formed by a homothallic (delayed) amoebal clone are the result of reversion of this mutation. Amoebal clones of the homothallic (delayed) type are therefore developmental mutants unable to perform the differentiation from amoeba to plasmodium.
Selection for conditional lethals: A general negative selective system for Schizophyllum commune
Authors: Anderson Miriam Rich , Deppe Carol S. 
Published: September 2009

SUMMARYThis paper describes a method for selecting for conditional lethal mutations in the filamentous fungus Schizophyllum commune. The method is, to our knowledge, the only successful application of filtration enrichment to Basidiomycetes. In addition, it is far more powerful than filtration enrichment methods reported previously for any fungus; it permits recovery of up to 80% auxotrophs starting with material untreated with any mutagen.
Some bryozoan karyotypes and chromosome numbers
Authors: Backus B. T. 
Published: September 2009

SUMMARYA technique for obtaining bryozoan chromosome spreads is described. Karyotypes were prepared for the following phylactolaemate species: Plumatella emarginata, 2n = 14; Hyalinella punctata, 2n = 14; Fredericella sultana, 2n = 14; and Pectinatella magnifica, 2n = 18. Approximate numbers were obtained for Lophopodella carteri, 2n 18–22, and three ctenostomes, Pottsiella erecta, 2n = 22 or 24; Amathia semiconvoluta, 2n about 30; and Paludicella articulata, 2n about 20. Differences between the bryozoan karyotypes seen in this study correlate with taxonomy.