The F1 genes of the F1F0 ATP synthase from the acidophilic bacterium Thiobacillus ferrooxidans complement Escherichia coli F1unc mutants

Abstract Because of the allelic variations within the M protein gene ( emm gene) of group A streptococci, reliable typing of this important human pathogen can be accomplished by the use of emm gene-specific oligonucleotide probes. Two technical modifications (a reverse dot blot and a reverse line blot hybridization assay) of a novel approach for the type-specific identification of emm genes have been developed. Both procedures involved amplification of an emm gene by polymerase chain reaction. The non-radioactively labeled amplicon was subsequently hybridized to a membrane carrying an array of immobilized emm gene-specific oligonucleotide probes, thus allowing the simultaneous analysis of the gene polymorphism in a single hybridization reaction. The feasibility of these rapid and easy to perform methods was shown for the unequivocal identification of reference strains and clinical isolates belonging to 16 different M serotypes.     

Predictors of marker-informativeness for an outbred F2 design

Generalization of the polymorphism information content (PIC) index to represent marker informativeness (MI) for a three-generation F2 design requires that two additional sources of non-informativeness be added to the PIC formula: the probability of matings between like-heterozygous F1 individuals, of which one is non-informative; and that of matings between like-heterozygous F1 individuals, which are both fully informative but where line of origin of the same alleles is reciprocal. Given the dense marker-maps currently available for some species, this F2 informativeness parameter constitutes the natural criterion for marker selection in F2 designs, and two computer programs to predict MI from grandparental marker-genotypes were developed for an F2 population originating from two divergent selection lines of outbred mice (F approximately 0.2). A total of 403 markers had been genotyped for the F0 grandparents (n=31), and 14 markers had also been genotyped in the complete pedigree including 559 F2 individuals. One program was based on assumptions of random-mating (RM), while the other (PED) accounted for the pedigreed mating structure. For the 403 markers, the correlation between MI from RM and from PED was 0.95, and the average deviation between the two predictions was 0.005 MI units (MI ranged from 0 to 1). Correlations between predicted and realized MI for the 14 fully genotyped markers were 0.97 for PED and 0.94 for RM, while the corresponding average of deviations between predicted and actual values were 0.01 and 0.04, respectively. Absolute deviations from realized MI never exceeded 0.09 and 0.16 for PED and RM, respectively. Simulated optimization of the mating system to maximize average MI of 28 markers on one chromosome led to improvements in the range of 15-20% average MI (0.07-0.09 MI units). The degree of relative advantage conferred by the F2 generalization of the PIC index over the traditional index was found to be of minor significance.     

Time-resolved microfluorescence for measuring coenzyme F420 in Methanobacterium thermoautotrophicum

Abstract The time course of photobleaching and the nanosecond fluorescence decay have been measured from microscopic samples of methanogenic bacteria, to our knowledge the first application of these methods in this field. Decay times of about 1 ns and 3 ns were obtained for the specific coenzymes F₄₂₀ and 7-methylpterin, respectively. In contrast to methylpterin and other fluorescent compounds the intensity of F₄₂₀ fluorescence was reduced selectively due to photobleaching. This effect, as well as the different decay time constants could be used to discriminate F₄₂₀ from other fluorescent components. In addition, active and inactive bacterial cells could be differentiated following the course of photobleaching.     

The restoration of male fertility in F1 wheat hybrids

The yield of F₁ wheat hybrids is often limited by reduced male fertility. Improvement depends upon selecting male and female parents capable of allowing good fertility ‘restoration’ in the F₁ hybrids. Assessment of restoring potential in growth rooms was difficult because fertility was much lower than in field grown plants. In the field, two experiments showed differences between parent lines but also that the fertilities of the F₁ hybrids were site-specific, and that this factor might be considered during further selection. Variation between reciprocal crosses, possibly due to cytoplasmic differences, rendered a proposed test for the early assessment of fertility restoration capacity amongst potential male-sterile lines to be of doubtful value with present stocks.     

Functional asymmetry of the F0 motor in bacterial ATP synthases

F₁F₀ ATP synthases use the electrochemical potential of H⁺ or Na⁺ across biological membranes to synthesize ATP by a rotary mechanism. In bacteria, the enzymes can act in reverse as ATP-driven ion pumps creating the indispensable membrane potential. Here, we demonstrate that the F₀ parts of a Na⁺- and H⁺-dependent enzyme display major asymmetries with respect to their mode of operation, reflected by the requirement of ∼100 times higher Na⁺ or H⁺ concentrations for the synthesis compared with the hydrolysis of ATP. A similar asymmetry is observed during ion transport through isolated F₀ parts, indicating different affinities for the binding sites in the a/c interface. Together with further data, we propose a model that provides a rationale for a differential usage of membrane potential and ion gradient during ATP synthesis as observed experimentally. The functional asymmetry might also reflect an important property of the ATP synthesis mechanism in vivo . In Escherichia coli , we observed respiratory chain-driven ATP production at pH 7–8, while P -site pH values < 6.5 were required for ATP synthesis in vitro . This discrepancy is discussed with respect to the hypothesis that during respiration lateral proton diffusion could lead to significant acidification at the membrane surface.     

Estimating sib percentages from small samples of F1 hybrid populations

Plant breeders raising F_x hybrid populations cannot usually grow more than about 300 plants from one seed lot. If not more than k sibs are observed in a random sample of size N, they then need to estimate the probability that the proportion of sibs in the population is at most p. For sample sizes of not more than 300 this note describes the required statistical procedure which, though not new, may be unfamiliar to plant breeders.     

Regional Distribution of Prostaglandins D2, E2, and F2α and Related Enzymes in Postmortem Human Brain

Abstract: The presence of prostaglandins D₂, E₂, and F_2α was demonstrated and their contents measured in various regions of postmortem human brain, pineal body, and pituitary by using specific radioimmunoassays and gas chromatography-mass spectrometry. The three prostaglandins were widely distributed in similar concentrations ranging from several hundred pg/g wet weight to about 40 ng/g wet weight. Prostaglandins D₂ and E₂ showed consistent and similar regional distributions in all six brains tested; amounts were high in pineal body, pituitary, olfactory bulb, and hypothalamus. On the other hand, prostaglandin F_2α was distributed more evenly. Prosta- glandin D synthetase and prostaglandin E synthetase activities were found in cerebrum homogenate from a single subject and were recovered from the 100,000 × g supernatant. The presence of 1 m M glutathione, reduced form, markedly stimulated the activity of prostaglandin E synthetase, but did not affect prostaglandin D synthetase activity. Activity of 15-hydroxyprostaglandin dehydrogenase was found in the cerebrum homogenate and was partially purified. This enzyme required NADP as a cofactor and copurified with prostaglandin E 9-ketoreductase.     

A Chemical Indicator for the Rapid Measurement of F0 Values

A new chemical indicator for monitoring steam sterilization processes has been calibrated in F ₀ units. The effective temperature range for F ₀ measurements using this device has been shown to lay between 115 and 123°C. The effective F ₀ range of the device has been shown to be 4–23 F ₀ units. Using the device, measurements can be made within 0.5 units of conventionally calculated F ₀ values.     

CATABOLISM OF PROSTAGLANDIN ENDOPEROXIDES INTO PROSTAGLANDIN E2 AND F2x BY THE RAT BRAIN

Abstract— Tritium labeled prostaglandin (PG) endoperoxides PGG₂ and PGH₂ were rapidly transformed (2 min, 37°C) in good yield (> 50%) by homogenates of whole rat brain into a mixture of products including prostaglandin E₂ and F_2x: under similar conditions (10min. 37°C) tritium labeled arachidonic acid remained essentially unoxidised. The ratio of PGE-like products: PGF_2x formed was approx 0.5 as determined by radio thin layer chromatography. This ratio changed to unity when homogenates of cerebral cortex or cerebral hemispheres were employed. On the other hand cerebellar homogenates formed PGF_2x in much greater amounts. The structures of the products were confirmed by mass spectrometry and were further supported by experiments using octadeuterio-endoperoxides. In the latter experiments the resulting PGE₂ and PGF_2x contained the expected seven and eight deuterium atoms respectively. Evidence for the formation of heptadeuterio PGD₂. heptadeuterio-6-keto-PGF₁, and hexadeuterio 12-hydroxyheptadecatrienoic acid was also obtained by mass spectrometry. These experiments demonstrate for the first time in brain tissue the biosynthesis of labeled prostaglandins from exogenous tritiated and deuterated precursors.     

Assembly of the Escherichia coli F1F0 ATPase, a large multimeric membrane-bound enzyme

The F₁F₀ proton translocating ATPase of Escherichia coli is a large membrane-bound enzyme complex consisting of more than 20 polypeptides that are encoded by the unc operon. Besides being a system for analysing the enzymology of ATP synthesis and energy coupling, the ATPase is a model system for determining how large oligomeric membrane-bound proteins are synthesized and assembled. The assembly of the ATPase involves differential gene expression and assembly of the subunits within the membrane and with each other. This review discusses the influence of F₁ subunits on the assembly and proton permeability of the F₀ proton channel, and the possible advantages to assembly of the particular arrangement of genes in the unc operon.     

Factors affecting field-scale production of seed of F1 hybrid Brussels sprouts

The two main factors involved in field-scale production of seed of F₁ hybrid Brussels sprouts are pollen availability and honeybee behaviour. Pollen availability depends upon the extent of winter survival of the parent inbreds, their flowering times, plant size and on the number of flowers per plant. Plant losses varied between inbreds and between sites and seasons. Differences in the commencement of flowering time in pairs of inbreds varied from 7 to 21 days, and plant size affected flower number. In hybrid seed-production there was a direct relationship between the number of mature flowers on each inbred and the percentage of non-hybrid seed produced from that inbred. Bees were highly selective in their visits to inbreds, and a mean selfing-to crossing-movement ratio of 30:1 was observed. This behaviour, together with pollen availability, greatly influenced the production of ‘sibs’. Radioactive experiments showed that the amount of cross-pollen carried by a bee decreased by about 30% at each flower visited but radioactive pollen grains were detected on the tenth flower visited. Of a number of factors investigated as possibly influencing bee behaviour, differences in flower colour and plant height were associated with discrimination between inbred lines.     

Confirmation of the F2 allele in the bovine F blood group system

Serological evidence is presented to prove the presence of an F₂ allele in the F system of British Friesian cattle.     

Inheritance of Pathogenicity of Progeny from an F1 Culture of Melampsora lini

Abstract Races 1 and 400 of Melampsosau bni the causal agent of flax [Lmum usitatissimum]), were crossed and the resulting F² progeny evaluated on near-isogcnic fiax lines. The infection type of the parental cultures, the F¹² and the segregating f² progeny were used to evaluate the inheritance of pathogenicity. Races 1 and 400 as well as the F² and all the F² progeny were avirulent on lines N and P⁴ genes. This indicated both races to be homozygous avirulent. The F² and all the F² progeny were virulent on lines containing L9, M1, M4, and P. This indicated the F to be homuzygous for virulence at these loci. Segregation ratios of the F² cultures fit monogenic ratios on lines with host genes K. L2, L5, L6, L7, L11, M, M2, M3, N1, P1, P2, and P3. Race 1 was avirulent, race 400 virulent and tht F, avirulent on these lines. Several linkage groups were indicated including close linkage at A^p1, A^p2 and A^p3. Segregation on lines L, L3, M5, M6 and cultivars Flor, Dufferin, Linott, and Wishek fit a digenic model. The infection tvpes of the parents, the F¹ and the F², segregations could usually be explained by classical gene-for-gene interactions. Possible exceptions were segregations on L4, L8 and N2 which did not fit a 3: 1 ratio but did fit a 9: 7 ratio. Segregation on L 10 fit a 7: 9 ratio but line L10 may be temperature sensitive. Segregation on L1 indicated a single dominant gene for pathogenicity.     

Non-association between Rfp-Y major histocompatibility complex-like genes and susceptibility to Marek's disease virus-induced tumours in 63× 72 F2 intercross chickens

Marek's disease (MD) is a lymphoproliferative disease caused by a member of the herpesvirus family, and the best understood genetic resistance to MD involves the chicken major histocompatibility complex (MHC) B -complex. Preliminary observations have suggested that MHC-like Rfp-Y genes might also influence the incidence of MD. This study describes the differentiation and definition of unique Rfp-Y genes in inbred lines 6₃ and 7₂, lines that possess identical B -complex genes, but that are resistant or susceptible to MD, respectively. To assess if Rfp-Y genes affect susceptibility to MD, 265 6₃× 7₂ F₂ chickens were challenged with the JM strain of MD virus at 1 week of age and were evaluated for MD lesions at up to 10 weeks of age. Genotyping of the F₂ chickens for Rfp-Y haplotypes was performed by restriction fragment length polymorphism analysis of genomic DNA using Taq I and a B-FIV probe. Analysis of variance and interval mapping procedures were used to determine association between the Rfp-Y haplotypes and the phenotypic MD values of the F₂ chickens. The cosegregation analysis of 265 F₂ chickens indicated that there was no association between Rfp-Y haplotypes and MD susceptibility. Furthermore, the fact that the Rfp-Y haplotypes fit the 1:2:1 segregation ratio and the Rfp-Y allele frequencies did not differ significantly from 0·5 in the full population or in selected subpopulations (of either 40 MD-resistant or 39 MD-susceptible chickens) also indicated that Rfp-Y haplotypes do not significantly influence MD susceptibility. We conclude that Rfp-Y haplotypes do not play a major role in determining the genetic susceptibility to MD in 6₃× 7₂ F₂ White Leghorn chickens.     

F4 - Isoprostanes as Specific Marker of Docosahexaenoic Acid Peroxidation in Alzheimer's Disease

Abstract : F₂-isoprostanes are prostaglandin-like compounds derived from free radical-catalysed peroxidation of arachidonic acid. Peroxidation of eicosapentaenoic acid produces F₃-isoprostanes, whereas peroxidation of docosahexaenoic acid would give F₄-isoprostanes. This study demonstrates the presence of esterified F₄-isoprostanes in human brain and shows that levels are elevated in certain brain cortex regions in Alzheimer's disease. Our data with Alzheimer's disease suggest that analysis of F₄-isoprostanes will provide new opportunities to study lipid peroxidation in the neurodegenerative diseases.     

The F1FO ATP synthase genes in Methanosarcina acetivorans are dispensable for growth and ATP synthesis

There is a long-standing discussion in the literature, based on biochemical and genomic data, whether some archaeal species may have two structurally and functionally distinct ATP synthases in one cell: the archaeal A₁A_O together with the bacterial F₁F_O ATP synthase. To address a potential role of the bacterial F₁F_O ATP synthase, we have exchanged the F₁F_O ATPase gene cluster in Methanosarcina acetivorans against a puromycin resistance cassette. Interestingly, the mutant was able to grow with no difference in growth kinetics to the wild type, and cellular ATP contents were identical in the wild type and the mutant. These data demonstrate that the F₁F_O ATP synthase is dispensable for the growth of M. acetivorans .     

Effect of plant density and nitrogen on wheat F1 hybrids and their parents

The autonomous spread of Gaeumannomyces graminis var. tritici from discrete sources of inoculum, consisting of naturally infected stubble and roots, was measured in three field experiments. Spread occurred from only half of the inoculum sources and when it did occur it averaged a distance of only 10 cm.