Transposable Elements in Mendelian Populations. III. Statistical Results

Methods are proposed for estimating the parameters in the frequency spectrum derived from the model of Langley, Brookfield and Kaplan for the evolution of a transposable element in a finite Mendelian population. Statistical properties of these estimates are studied, and the results are supported with simulation data. The effects on the estimates caused by possible insensitivities of the experimental technique are also discussed. To illustrate the proposed methodology, the data of Montgomery and Langley are analyzed.     

The innervation of the hepatic portal vein in the rabbit: Ultrastructural evidence against “purinergic” neurotransmission

Summary The relative density of adrenergic and non-adrenergic nerves in the hepatic portal vein of the rabbit has been determined ultrastructurally. Adrenergic nerves were visualised with the modified chromaffin procedure of Tranzer and Richards (1976). Nearly equal numbers of adrenergic and non-adrenergic nerve profiles were found, indicating a much greater density of innervation by non-adrenergic nerves than that described by Burnstock et al. (1979) using light microscopic histochemical methods. These results imply that part of the argument used by Burnstock et al. (1979) to support purinergic transmission in rabbit portal vein is probably invalid.     

Breeding systems and population structure in Limnanthes

Summary The breeding systems of seven Limanthes (Limanthaceae) populations, including one inbreeding and three outbreeding taxa, were quantified using a multilocus outcrossing rate estimator (t_m) and autofertility estimates. Along with the assays of heterozygosity levels, these data were used to separate components of effective outcrossing in terms of Wright's equilibrium inbreeding coefficient (F_e) and adult (F_A) and zygotic (F_Z) fixation indices. The patchy distribution of alleles as a potential source of substructure inbreeding was tested from the allelic frequencies mapped along a linear transect. Evidence for consanguineous matings in restricted neighborhoods and for selection at two different life cycle stages, and the efficiency of the protandrous breeding system were noted and discussed. Multilocus estimates of outcrossing are useful for their greater precision and unbiased nature while single locus estimates can help in detecting the effects of selection and population substructure. The data generally support the heterozygosity paradox noted by Brown (1979) but further suggest that the paradox may often result from a lack of precision of outcrossing estimates and from overlooking the stages of the life cycle being sampled.     

Evolutionary analysis ofα andβ hemoglobin genes by reh theory under the assumption of the equiprobability of genetic events

Summary It is shown how REH theory in conjunction with mRNA or gene sequence data can be used to obtain estimates of the fixation intensity, the number of varions, and the total mutations fixed between homologous pairs of nucleic acids. These estimates are more accurate than those that can be derived from amino acid sequence data. The method is illustrated for and hemoglobin genes and these improved estimates are compared with those made from the amino acid sequences for which those genes code. Significant differences are found between the estimates made by these two methods. For the hemoglobin gene sequences examined here, the fixation intensity is some-what less than the protein data had suggested, and the number of rations is considerably greater. Depending on the gene sequences examined, between 62 and 83% of the codons appear able to fix mutations during the divergences considered. This reflects the constraints of natural selection on acceptable mutations. The total number of base replacements separating the genes for human, mouse, and rabbit hemoglobin varies from 61 to 105 depending on the pair examined. Rabbit and hemoglobin are separated by at least 290 fixed mutations. For such distantly related sequences estimates made from protein and mRNA data differ less, reflecting the higher quality of information from the many observed changes in primary structure. The effects of nonrandom gene structure on these evolutionary estimates and the fact that various genetic events are not equiprobable are discussed.     

Attacking the bottlenecks of backfilling schedulers

Backfilling is a simple and effective way of improving the utilization of spacesharing schedulers. Simple firstcomefirstserved approaches are ineffective because large jobs can fragment the available resources. Backfilling schedulers address this problem by allowing jobs to move ahead in the queue, provided that they will not delay subsequent jobs. Previous research has shown that inaccurate estimates of execution times can lead to better backfilling schedules. In the first part of this study, we characterize this effect on several workloads, and show that average slowdowns can be effectively reduced by systematically lengthening estimated execution times. Further, we show that the average job slowdown metric can be addressed directly by sorting jobs by increasing execution time. Finally, we modify our sorting scheduler to ensure that incoming jobs can be given hard guarantees. The resulting scheduler guarantees to avoid starvation, and performs significantly better than previous backfilling schedulers. In the second part of this study, we show how queue randomization and even more a combination of queue randomization and sorting by job length can improve performance. We show that these improvements are better than with queue sorting by job length alone in the simulation with actual estimates of job running times. We investigate the real characteristics of these estimates, and show the wide range of overestimation. To exploit even more randomization and queue sorting, we eliminate guarantees from backfilling algorithm, and show significant improvements. Finally, we show a limited usefulness of these guarantees, and show that queue sorting criteria can be modified to prevent starvation in the modified backfilling algorithm.     

Maximum-likelihood models for mapping genetic markers showing segregation distortion. 2. F2 populations

In F₂ populations, gametic and zygotic selection may affect the analysis of linkage in different ways. Therefore, specific likelihood equations have to be developed for each case, including dominant and codominant markers. The asymptotic bias of the classical estimates are derived for each case, in order to compare them with the standard errors of the suggested estimates. We discuss the utility and the efficiency of a previous model developed for dominant markers. We show that dominant markers provide very poor information in the case of segregation distortion and, therefore, should be used with circumspection. On the other hand, the estimation of recombination fractions between codominant markers is less affected by selection than is that for dominant markers. We also discuss the analysis of linkage between dominant and codominant markers.     

The estimation of optimum applications of a quantitative factor to crops grown in rotation

Summary Given certain prior information about residues from earlier applications of a quantitative factor Q to crops grown in rotation, this paper shows how relatively simple experiments can be used to provide estimates of the optimum applications of Q to successive crops; the estimates obtained allow for the presence of residues. The prior information in the particular case discussed is that if x units of the factor are applied then the residues one, two, three ...t... seasons later are rx, rpx, rp²x, ...rp^t–1x..., where r and p are constants such that 0r<1, 0p<1.     

Imitieren Buchfinken(Fringilla coelebs) auf Bornholm den Alarmruf des Sprossers(Luscinia luscinia)?

Zusammenfassung 1979 und 1980 wurde in Ostbornholm ein einheitlicher Regenrufdialekt des Buchfinken gefunden, der dem Alarmruf des Sprossers sehr ähnlich klingt. Auch im Sonagramm zeigen sich morphologische Entsprechungen. Nach demMann-Whitney-Test sind die Mittelwerte der Frequenzen und Impulsdauer hochsignifikant verschieden, was jedoch im felde ohne direkten Vergleich nicht wahrnehmbar ist. Trotz der Differenzen wird Fremdimitaton für sehr wahrscheinlich gehalten, Zufallskonvergenz jedoch nicht ganz ausgeschlossen.

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A case of vocal appropriation in the Chaffinch to the alarm-call of the Thrush Nightingale at Bornholm?

Summary In 1979 and 1980 in the east of Bornholm (Baltic Sea, Danmark), an uniform dialect of the rain-call was found in the Chaffinch, which resembles the alarm call of the Thrush Nightingale(Luscinia luscinia). The sonagrams of the two calls are very similar in structure. The frequency and duration differ significantly. In the field, however, one can hardly take apart the two calls without direct comparison. Despite these differences, it is speculated, that the rain-call is an imitation, but convergence by chance can not be excluded.

     

Parasitic gastro-enteritis in lambs — A model for estimating the timing of the larval emergence peak

The life history of the nematode parasites of domestic ruminants usually involves the development and survival of free-living stages on pasture. The pasture is, therefore, the site of deposition, development and transmission of nematode infection and meteorological factors affecting the pasture will affect the parasites. Recently Thomas and Starr (1978) discussed an empirical technique for forecasting the timing of the summer wave of gastro-intestinal parasitism in North-East England in the lamb crop using meteorological data and in particular estimates of the duration of surface wetness. This paper presents an attempt to model surface wetness and the temperature limitation to nematode development.Presented at the Eighth International Congress of Biometeorology, 8–14 September 1979, Shefayim, Israel.     

Facts on optic flow

We employ an optimal solution to both the shape from motion problem and the related problem of the estimation of self-movement on a purely optical basis to deduce practical rules of thumb for the limits of the optic flow information content in the presence of perturbation of the motion parallax field. The results are illustrated and verified by means of a computer simulation.The results allow estimates of the accuracy of depth and egomotion estimates as a function of the accuracy of data sampling and the width of field of view, as well as estimates of the interaction between rotational and translational components of the movement.     

De novo mutations producing unstable Hbs or Hbs M.

Summary Cases of unstable hemoglobin and hemoglobin M disease that have appeared as de novo mutants over a span of approximately 50 years were used in derivingminimal, direct estimates of mutation rates per nucleotide per generation in man. The estimates are based upon analysis of data related to 40 cases of unstable Hbs and 15 of Hbs M that arose in 13 countries. The estimated rate calculated using all de novo -gene mutants is 7.4×10^-9 per nucleotide per generation; that derived using de novo -gene mutants is 10.0×10^-9. Subsequent calculations of mutation rates per - and -chain gene and extrapolation of these rates to a hypothetical gene of 1000 nucleotides yield an estimated mutation rate of 8.6×10^-6 per 1000 nucleotides per generation. Even though some instances of false paternity may have biased these estimates in an upward direction, underreporting of Hb M cases, and particularly of unstable hemoglobins, makes it likely that the cited values are minimal estimates of mutation rates at the molecular level.     

An algorithmic model of heading perception

On the basis of Hanada and Ejimas (2000) model, an algorithmic model was presented to explain psychophysical data of van den Berg and Beintema (2000) that are inconsistent with vector-subtractive compensation for the rotational flow. The earlier model was modified in order not to use vector-subtractive compensation for the rotational flow. The proposed model computes the center of flow first and then estimates self-rotation; finally, heading is recovered from the center of flow and the estimate of self-rotation. The model explains the data of van de Berg and Beintema (2000). A fusion model of rotation estimates from different sources (efferent signals, proprioceptive feedback, vestibular signals about eye and head rotation, and visual motion) was also presented.     

Physiological comparisons of two soybean cultivars differing in canopy photosynthesis. I. Variation in vertical 14CO2 labelling and dry weight partitioning

Differences in canopy apparent photosynthesis (CAP) among soybean [Glycine max (L.) Merr.] genotypes have been shown to be correlated to seed yields. Since the physiological basis for such differences in CAP is unknown, two cultivars known to differ in CAP, Tracy and Davis, were studied during the 1978–1980 growing seasons. The CAP and dry weights of component plant parts were determined. In 1978 and 1979, ¹⁴CO₂ uptake by vertical leaf strata was determined and specific leaf weight (SLW) and leaf area index (LAI) were determined for corresponding strata in 1979 and 1980. Measurements were taken on several dates during reproductive growth. With the exception of CAP, all measurements (¹⁴C uptake, dry weights) were made in layers within the canopy. CAP on some dates were significantly higher in Tracy than in Davis and integrated CAP values from a certain growth period, labeled as R5 to R7, averaged 16 percent higher in Tracy for the three years studied. No differences in the relative recovery of ¹⁴C from different layers of leaves in the canopy were found. This indicates that variations in canopy structure or leaf orientation did not play a major role in the CAP differences between cultivars. The differences seem related to variations in leaf dry weights. Overall, Tracy exhibited 13.5, 19.2, and 13.2 percent greater leaf dry weights than Davis during 1978, 1979, and 1980, respectively. These differences in leaf dry weight seem largely due to a differences in the SLW. Data from these experiments indicate that differences in soybean CAP values were associated with differences in SLW.Abbreviations CAP Canopy Apparent Photosynthesis - CER Carbondioxide Exchange Rates - EST Eastern Standard Time - LAI Leaf Area Index - LSD Least Significant Difference - POPOP 1,4-bis-[2(5-phenyloxazdyl)]-benzene - PPO 2,5-diphenyloxazole - SLW Specific Leaf Weight     

The mating system in natural and shelterwood stands of Douglas-fir

Summary Mating systems in two pairs of old-growth uncut and adjacent shelterwood stands of Douglas-fir (Pseudotsuga menziesii var. menziesii) were compared by estimating the proportions of viable progenies due to outcrossing (t) with both single-locus and multilocus techniques. Single-locus population estimates (_s), ranging from 0.41 to 1.16, were significantly (P<0.05) heterogeneous among loci in three of four stands; mean single-locus estimates for shelterwoods were not significantly different from those for uncut stands. Multilocus population estimates (_m) ranged from 0.94 to 1.00; again, estimates for shelterwoods were not significantly different from those for uncut stands. Multilocus estimates were slightly higher than mean single-locus estimates for uncut stands but were nearly equivalent for shelterwoods, suggesting that related matings other than selfs may be associated with uncut stands, but not shelterwoods. Individual-tree outcrossing rates (_{m i}), estimated for six trees in each shelterwood, ranged from 0.90 to 1.10 and were significantly heterogeneous among trees at one of the two shelterwoods. Outcrossing was high (> 0.90) in both uncult and shelterwood stands, and no evidence indicated that low parent-tree density had affected stand outcrossing rates.FRL 1918, Forest Research Laboratory. Oregon State University, Corvallis, USA     

Gentamicin resistance among salmonellae. A ten-year study, 1973–1982

A total of 8579 Salmonella strains received during 1973–1982 were tested for their antibiogram patterns against nine routinely used antibiotics including gentamicin. Of these, 380 strains (4.4%) showed resistance to gentamicin at levels of 10 g/ml and above. A high degree of resistance to gentamicin was recorded in 1979 (18.7%) and 1980 (9.4%). M.I.C. levels of strains received during 1982 were determined and it was found that some strains had levels as high as 160 g/ml. The comparative results of gentamicin resistance from 1973 to 1982 are presented and the public health significance of the alarming increase in two years (1979–1980) is discussed.     

The phylogenetic significance of sperm morphology in the Platyhelminthes

The phylogenetic significance of flatworm sperm morphology is discussed against the background of general spermatology. The modified type of spermatozoon of the Nemertodermatida, a group of primitive flatworms, indicates that the Platyhelminthes evolved from forms characterized by the primitive type of metazoan sperm and by the primitive mode of fertilization, implying the release of sperm freely into sea water.The occurrence of aberrant types of spermatozoa in most platyhelminths is obviously a consequence of early evolution of the internal mode of fertilization, which characterizes all true members of this group. It can be concluded, from the ultrastructure of these aberrant spermatozoa that higher metazoans cannot have evolved from seriated flatworms related to the recent Seriata (Proseriata and Tricladida). Even the seemingly primitive Acoela have such aberrant spermatozoa that evolution of higher metazoans from acoels related to the recent Acoela seems highly improbable.The ultrastructure of the spermatozoa of the parasitic groups of flatworms (Monogenea, Digenea, Cestoda) is very similar to that found in the Kalyptorhynchia, a further indication that the parasitic groups are related to the rhabdocoel turbellarians.     

Martian channels and the search for extraterrestrial life

Summary The origin of the channels on Mars has been a subject of intense interest since they were first recognized on early Mariner 9 images (Driscoll, 1972; Masursky, 1973). Their presence on the planet, and their striking resemblance to terrestrial flood channels related to glacial outbursts or to dendritic river systems has suggested to most investigators (Baker, 1974, 1977; Nummedal, 1978; Carr, 1979; Masursky et al., 1977) that they were formed by running water. Because life as we know it is dependent on water, the discovery by the Mariner cameras, of watercut channels and volcanoes as a source for water, and water ice in the residual north polar cap by Viking, has reaffirmed the choice of Mars as the best target for the search for extraterrestrial life.     

An index of weed size for assessing the soil productivity of ancient crop fields

A method is presented for generating data on archaeological weed species relevant to soil productivity and consequently crop husbandry. Three plant attributes (maximum canopy height, maximum canopy spread and maximum dry leaf weight per node) which are functionally related to habitat productivity were measured for 161 British annual species. These three attributes were combined to produce an index of weed size. Index values were found to differ significantly between character species of phytosociological classes from fertile and infertile habitats and to provide an objective assessment of CSR (Competitor/Stress-tolerator/Ruderal) strategysensu Grime (1974, 1979). Further work is required, however, to distinguish medium-sized species that exploit highly disturbed and productive habitats from those of less disturbed and less productive situations.     

Branchinecta belki n. sp. (Branchiopoda: Anostraca), a new fairy shrimp from Mexico,hybridizing withB. packardi Pearse under laboratory conditions

A new fairy shrimp,Branchinecta belki n.sp., endemic to the south of Coahuila state is described and figured. A total of nine species of phyllopods, including the new species, occur in ponds in the type area.The laboratory hybridization ofB. belki andB. packardi through no-choice mating tests in reciprocal crosses is discussed. A mixture of characteristics of parental species is present in male F1 and F2 hybrids. This may provide a biological tool, or search image (sensu Wiman, 1979a), for detecting male hybrids, should such exist, between theBranchinecta species of this study in nature. In addition to the reported interspecific hybridizations inStreptocephalus (Wiman, 1979a & 1979b) and inArtemia (Bowenet al., 1985) under laboratory conditions, the new evidence inBranchinecta suggests that absence of efficient premating mechanisms may be common in Anostraca.     

Photochemical reactivity of the homologous proteinsα-lactalbumin and lysozyme

Summary The fluorescent behaviour and the photodynamic effect was studied in native and structurally modified lysozyme and-lactalbumin.The Tyr residues in lysozyme and-lactalbumin show different sensitivities to the photodynamic effect. The effect is zero in the case of Tyr from native lysozyme. In contrast, the Tyr residues in-lactalbumin are susceptible to photooxidation, which indicates a greater degree of exposure to the solvent. The three His residues of-lactalbumin have different degrees of exposure and show two different kinetics of photooxidation whereas the His residue of lysozyme is photooxidized with a single kinetic.Two photooxidation kinetics were obtained for the Trp residues of both native proteins, an indication that in both cases there are Trp residues that are differently exposed to the solvent. The wavelengths of maximum fluorescent emission of the Trp residues were different for the two proteins, an effect which can also be explained in terms of a difference in the environment of these residues. The modified form of these proteins emit at wavelengths longer than those of the native forms. When modified the proteins photooxidize with noticeably greater quantum yields.