Negative Segregation Distortion in the Sd System of Drosophila Melanogaster: A Challenge to the Concept of Differential Sensitivity of Rsp Alleles

Current models of segregation distortion based on previous experimental results predict that, in the Sd heterozygous Rspi/Rsps male, the chromosome carrying the sensitive Rsps allele is distorted or transmitted in a frequency smaller than that of the expected Mendelian 0.5 relative to the chromosome carrying the insensitive Rspi allele. The present study presents a case where this does not occur, that is, when the genotype of the males is supp-X(SD)/Y; Sd E(SD)Rspi M(SD)+/Sd+ E(SD)+ Rsps M(SD)+ where supp-X(SD) is an X chromosome carrying a strong suppressor or suppressors of SD activity and SD+ E(SD)+ Rsps M(SD)+ is the standard cn bw chromosome. Following the "inseminated female transfer" procedure, young males of the above genotype carrying the standard-X instead of the supp-X(SD) chromosome show k values for the SD chromosome (frequencies of the SD chromosome recovered among progeny) of about 0.75, but with the supp-X(SD) chromosome, the k values are reduced to 0.36-0.41. Several possibilities other than the mechanism of segregation distortion to explain the reduced k values are ruled out. The occurrence of "negative segregation distortion" is clearly demonstrated, where the chromosome carrying the Rspi allele is distorted but the chromosome with the Rsps allele is not. This result requires a major modification of the current models or even a new model for the mechanism of segregation distortion to accommodate Rsp allele sensitivity or insensitivity. The present study also shows that males of the genotype, Sd Rspss M(SD)+/Sd+ Rspss M(SD), are almost completely sterile, but their fertility is considerably increased when SD activity is suppressed by the presence of the supp-X(SD) chromosome. This result suggests that the amount of the Sd product is not limited with respect to the interacting sites available, that is, the amount is large enough to interact with both of the Rspss alleles.     

Deletion of internal twenty-one amino acid residues of Escherichia coli prolipoprotein does not affect the formation of the murein-bound lipoprotein.

Mutation pgsA affecting the phosphatidylglycerol phosphate synthesis is lethal for all but certain E. coli strains such as strains deleted for the lpp gene or strains containing unmodifiable prolipoprotein like lppD14. Strain SD312 pgsA3 is tolerant to pgsA mutation, which suggests the lpp alleles in strain SD312 pgsA3 and its parental strain SD12 may be defective. DNA sequence analysis of the lpp genes in Escherichia coli strains SD12 and SD312 pgsA using asymmetric polymerase chain reaction showed that the lpp alleles in these two strains contained a 63 base pair deletion corresponding to the 37th to 57th codons of the wild-type lpp gene. [3H]Palmitate labeling of strains SD12 and SDS312 showed that the mutant lipoprotein in SD12 strain was modified with lipid, while the prolipoprotein in SD312 was not modified. The shortened mature lipoprotein in SD12 and the lipid-modified prolipoprotein in globomycin-treated SD12 were found to be covalently attached to the peptidoglycan, while the unmodified prolipoprotein in SD312 did not form significant amounts of murein-bound lipoprotein.     

Factors Influencing the Effect of Segregation Distortion in Natural Populations of DROSOPHILA MELANOGASTER

The major components of the SD system have been examined in two natural populations of D. melanogaster to investigate how SD behaves and is maintained in nature and to estimate its impact and efficiency. A twofold approach was used: (1) direct measurements of segregation distortion in wild males and (2) measurement of sensitivity of wild SD (+) chromosomes to SD action. Characterization of newly isolated SD chromosomes and of a large number of SD( +) chromosomes from nature demonstrated that (1) SD can operate efficiently in the wild genome: 45% of SD/SD(+) males collected from nature had k values larger than 0.70. (2) Forty-three of 44 newly recovered SD chromosomes are of the SD-72 type, having a small pericentric inversion that maintains tight linkage among the Sd, E(SD) and Rsp loci in the SD complex. In 1956, most SD chromosomes in Madison lacked this inversion. (3) Only 12 of the 44 SD chromosomes carried a recessive lethal (compared with five of six in 1956), and many of the viable SD chromosomes were fertile as homozygotes, indicating that SD homozygotes need not have obvious reductions in fitness. (4) Among more than 500 wild chromosomes assayed for response to distortion by a strong SD, at least 40-50% were sensitive, about 33% were partially sensitive and 17% were insensitive. This frequency of sensitives is higher than in reports from some other populations. An estimated 12% of the wild chromosomes were classified as true Rsp(i) by their constellation of effects, including a special test of ability to cause self-distortion of a "suicide" chromosome, R(cn)-10. In a direct assay with R(cn)-10, an independent sample of 99 chromosomes from nature gave 30% putative Rsp(i). Thus, these populations contain in the range of 12-30% Rsp(i). (5) Chromosomes supersensitive to SD, previously described for certain laboratory stocks, were also found to coexist in nature with SD. (6) Profiles of wild chromosomes with a panel of three or four different SD testers suggest a series of allelic alternatives at the Rsp locus including supersensitive, sensitive, semisensitive and insensitive, and that loci other than Rsp may also be important in determining the effect of SD in nature.     

The Independent Distorting Ability of the Enhancer of Segregation Distortion, E(sd), in Drosophila Melanogaster

Segregation distortion is a meiotic drive system, discovered in wild populations, in which males heterozygous for an SD chromosome and a sensitive SD+ homolog transmit the SD chromosome almost exclusively. SD represents a complex of three closely linked loci in the centromeric region of chromosome 2: Sd, the Segregation distorter gene; E(SD), the Enhancer of Segregation Distortion, required for full expression of drive; and Rsp, the target for the action of Sd, existing in a continuum of states classifiable into sensitive (Rsps) and insensitive (Rspi). In an SD/SD+ male which is Sd E(SD) Rspi/Sd+ E(SD)+ Rsps, the Sd and E(SD) elements act jointly to induce the dysfunction of those spermatids receiving the Rsps chromosome. By manipulating the number of copies and the position of the Enhancer region, I demonstrated that: (1) E(SD), whether in its normal position or translocated to the Y chromosome, is able to enhance the degree of Sd-caused distortion in a dosage-dependent manner; (2) even in the absence of Sd, the E(SD) allele in two doses can cause significant distortion, in Sd+ or Df(Sd)-bearing genotypes; (3) quantitative differences among Enhancers of different sources suggest allelic variation at E(SD), which could account at least in part for differences among wild SD chromosomes in strength of distortion; (4) E(SD)/E(SD)-mediated distortion, like that of Sd, is directed at the Rsp target, whether Rsp is on the second or the Y chromosome; (5) E(SD), like Sd, is suppressed by an unlinked dominant suppressor of SD action. These results show that E(SD) is independently capable of acting on Rsp and is not a simple modifier of the action of Sd. E(SD) provides an example of a trans-acting gene embedded in heterochromatin that can interact with another heterochromatic gene, Rsp, as well as parallel the effect of a euchromatic gene, Sd.     

中国黑腹果蝇中分离变相因子[Segregation Distorter(SD)]的初步研究

黑腹果蝇（Ｄｒｏｓｏｐｈｉｌａ ｍｅｌａｎｏｇａｓｔｅｒ）中的分离变相因子「Ｓｅｇｒｅｇａｔｉｏｎ Ｄｉｓｔｏｒｔｅｒ（ＳＤ）」是一种非常典型的具有减数分裂驱动性质的特殊遗传因子，ＳＤ在世界不同地区的黑腹果蝇群体中广泛存在，通过杂交的方法测得其频率在１％－５％范围之内。首次在中国北京，青岛采集大量野生黑腹果蝇样本，对ＳＤ进行频率测定，发现ＳＤ在中国野生黑腹果蝇群体中也广泛存在，且频率与世界其他地区     

A New Crystal Structure of the Bifunctional Antibiotic Simocyclinone D8 Bound to DNA Gyrase Gives Fresh Insight into the Mechanism of Inhibition

Simocyclinone D8 (SD8) is an antibiotic produced by Streptomyces antibioticus that targets DNA gyrase. A previous structure of SD8 complexed with the N-terminal domain of the DNA gyrase A protein (GyrA) suggested that four SD8 molecules stabilized a tetramer of the protein; subsequent mass spectrometry experiments suggested that a protein dimer with two symmetry-related SD8s was more likely. This work describes the structures of a further truncated form of the GyrA N-terminal domain fragment with and without SD8 bound. The structure with SD8 has the two SD8 molecules bound within the same GyrA dimer. This new structure is entirely consistent with the mutations in GyrA that confer SD8 resistance and, by comparison with a new apo structure of the GyrA N-terminal domain, reveals the likely conformation changes that occur upon SD8 binding and the detailed mechanism of SD8 inhibition of gyrase. Isothermal titration calorimetry experiments are consistent with the crystallography results and further suggest that a previously observed complex between SD8 and GyrB is ~ 1000-fold weaker than the interaction with GyrA.     

Ultrasonographic observations of the maturation of basic movements in guinea pig fetuses

Ultrasonography has not previously been used for studying fetal movements in precocial rodents. The objective of this study was to ultrasonographically determine the sequence of the appearance of basic movements in a guinea pig fetus. The research included eight guinea pig females carrying one fetus each. Fetal movements were observed for 10 minutes each day, from the 25th to 38th day of gestation. The time and sequence of the appearance of movements was observed as follows: whole body flexion (mean 27.6 SD ± 1.68), whole body extension (mean 28.1 SD ± 1.12), head flexion (mean 28.1 SD ± 1.80), head extension (mean 30.5 SD ± 2.67) forelimbs flexion (mean 30.5 SD ± 2.32), forelimbs extension (mean 30.7 SD ± 1.84), trunk rotation (mean 31.9 SD ± 2.23), forelimbs alternating flexion and extension (mean 32.1 SD ± 2.1), hind limbs extension (mean 32.2 SD ± 3.2), hind limbs flexion (mean 32.4 SD ± 3.16), and hind limbs alternating flexion and extension (mean 33.5 SD ± 2.39). The identical sequences of basic movement appearances in guinea pigs, sheep, and rats suggest that the rostrocaudal gradient of basic movement appearance could be a general developmental pattern in mammalian species.     

Changes in structure and function of the human left ventricle after acclimatization to high altitude

To analyse the role of changes in structure and function of the left ventricle in determining cardiac function at rest and during exercise, several two-dimensional and Doppler echocardiographic measurements were performed on 11 healthy subjects immediately before an Himalayan expedition (Nun, 7135 m), during acclimatization (3 weeks) and 14 days after the return. At rest decreases were found in cardiac index (CI) (3.23 l.min-1.m-2, SD 0.4 vs 3.82 l.min-1.m-2, SD 0.58, P less than 0.01), left ventricular mass (55.3 g.m-2, SD 9.4 vs 65.2 g.m-2, SD 13.5, P less than 0.005) and left ventricular end-diastolic volume (LVEDV) (53.9 ml.m-2, SD 6.9 vs 64.8 ml.m-2, SD 9.1, P less than 0.001) after acclimatization; by contrast the coefficient of peak arterial pressure to left ventricular end-systolic volume (PAP/ESV) (7.8, SD 1.6 vs 6.0, SD 1.8, P less than 0.005) and mean wall stress [286 kdyn.cm-2, SD 31 vs 250 kdyn.cm-2, SD 21 (2.86 N.cm-2, SD 0.31 vs 2.50 N.cm-2, SD 0.21), P less than 0.005] increased. After return to sea level, low values of CI and mass persisted despite a return to normal of LVEDV and preload. A reduction of PAP/ESV was also observed. At peak exercise, PAP/ESV (8.7, SD 2.4 vs 12.8, SD 2.0, P less than 0.0025), CI (9.8 l.min-1.m-2, SD 2.5 vs 11.6 l.min-1.m-2, SD 1.6, P less than 0.05) and the ejection fraction (69%, SD 6 vs 76%, SD 4, P less than 0.05) were lower after return to sea level than before departure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bacillus subtilis mutants dependent on streptomycin

Summary Six streptomycin-dependent mutants of Bacillus subtilis, two of which were asporogenous, were isolated. All six mutants, SD1, SD2, SD6, SD7, SD9 and SD10, contained a single mutation causing streptomycin dependence and asporogeny, but four of these mutants (SD6, SD7, SD9, SD10) contained a second mutation which phenotypically suppressed the asporogenous character of the streptomycin dependence mutation. All six mutants grew more slowly than the wild type strain BR151, but those defective in sporulation grew the slowest. The streptomycin dependence mutations of SD9 and SD10B (a sporeplus transformant from SD10 carrying both the dependence mutation and the phenotypic suppressor) lie near or possibly within the strA locus. Ribosomes from SD9, SD10A (a spore-minus transformant from SD10 carrying only the dependence mutation), and SD10B were stimulated in vitro by concentrations of streptomycin that inhibit the activity of wild type strain BR151 ribosomes. The level of misreading as measured by poly(U)-directed isoleucine incorporation was greatly enhanced by streptomycin in wild type strain BR151 ribosomes, but misreading of mutant SD9, SD10A, and SD10B ribosomes, irrespective of the sporulation phenotype, was little affected by streptomycin. There were no apparent differences in the patterns obtained by two-dimensional polyacrylamide gel electrophoresis of the 70S ribosomal proteins of the mutants SD9, SD10A, SD10B, and wild type strain BS151.     

Spiral waves of spreading depression in the isolated chicken retina

Existence of the theoretically predicted spiral waves of excitation in intact two-dimensional networks of excitable elements has been experimentally confirmed in the isolated chicken retina. The preparation supports the waves of Leão's spreading depression (SD) the concentric propagation of which from the point of origin can be directly observed as a change of the optical properties of the retinal tissue. The propagation rate of 3.7 mm/min (35°C) decreased to 1.5 mm/min for SD waves elicited during relative refractory period. When a several-mm long segment of the SD wave had been blocked by anodal polarization, the laterally opened ends of the wavefront started to spread after termination of polarization into the previously blocked tissue, gradually turning around and penetrating into the region recovering from the original SD. One or two simultaneously generated spiral waves of SD continued to rotate for several cycles. Spiral SD could also be elicited by punctiform cathodal polarization (1 mA) applied to the SD wave-rear. Since the new SD wave could only spread into the recovering tissue it formed a laterally open wavefront, the free ends of which eventually turned around and started spiral SD. With continued reverberation the nucleus of the spiral SD wave gradually migrated across the retina until it approached an obstacle (e.g., pecten) which stopped further spiral propagation. Spiral SD waves were elicited in 31 retinal preparations and lasted for 4.5 cycles on the average. Average cycle duration was 4.7 min. Spontaneous spiral SD waves were observed in preparations incubated in Mg²⁺-free media. The spiral SD waves in retina are compared with mathematical models of analogous phenomena. It is argued that spiral SD waves probably exist in the cerebral cortex of rats and account for generation of repetitive SD waves sometimes elicited by overlapping stimulation of two cortical regions.     

A mutant rat strain deficient in induction of a phenobarbital-inducible form of cytochrome P-450 in liver microsomes

Two phenobarbital-inducible forms of cytochrome P-450, P-450(PB-1), and P-450(PB-4), were purified from the liver microsomes of phenobarbital-treated rats and identified with P-450b and P-450e, respectively. It was found, however, that the content of P-450(PB-4) in the liver microsomes of a strain of SD rat, Qdj:SD, was very low even after phenobarbital-induction. The levels of the mRNAs for P-450(PB-1) and P-450(PB-4) were separately determined using Northern blot hybridization with specific oligonucleotide probes. It was found that the level of P-450(PB-4) mRNA in the livers of phenobarbital-treated Qdj:SD rats was much lower than that of phenobarbital-treated Slc:SD rats. Slc:SD rats are widely used in Japanese laboratories. Genetic analysis using the crossbred animals between Qdj:SD and Slc:SD rats showed that the low expression of P-450(PB-4) in Qdj:SD rats is a recessive trait and is caused by a single gene mutation. However, no difference in the 5' flanking region in P-450(PB-4) gene was found between Qdj:SD rats and Slc:SD rats.     

Principles of morphometric grading

Grading of the severity of lesions has increased in importance in histopathology. The simplest grading system has 2 grades. If there is variation in the measuring system, the grading will not be perfect, and there are also misgraded samples. We estimated the fraction of falsely graded cases by applying th NAG (Numerical Algorithm Group) Fortran Library. If all possible measurement values are equally probable the grades based on measurements within +/- 1 SD around the division line are false in 31.6% of cases. The corresponding figures for regions +/- 2 SD, +/- 3 SD, 1 to 2 SD, 1 to 3 SD, and 2 to 3 SD are 19.6, 13.3, 7.5, 4.2, and 0.8%, respectively. Detailed calculations were made which allowed accurate determination of the probability of a grade being false in different positions of the measurement scale. The results suggest that for diagnostic grading a borderline region should be defined (e.g. +/- 2 SD or +/- 3 SD around the division line).     

Suppression of gamma EEG activity as an index of a spreading depression wave in the neocortex of a waking rabbit

A spreading depression (SD) can spontaneously develop in seizures, attacks of migraine, vascular disorders and other pathological states of the brain. However, problems in technique of recording the DC-potential in the neocortex of humans and waking animals substantially restrict the possibilities of studying functional consequences of the SD. In this article, the EEG pattern was studied in detail at the moment of the SD development. Specific features were revealed, which make it possible to detect the SD without recording shifts of the DC-potential. At the moment of the SD arrival, the interhemispheric balance drastically disturbs because of a strong decrease in the high-frequency activity. By the time indices, the course of the suppression of the gammal and gamma2 EEG frequencies is the most reliable symptom of the SD wave development. The EEG spectral power in the delta band increases with a certain delay in reference to the deep depression of the high-frequency activity and is, in essence, an SD aftereffect. The found EEG signs of an SD wave can substantially simplify the identification of this phenomenon both in experiment and clinical conditions in certain pathological states of the brain.     

Effect of exercise on cerebral perfusion in humans at high altitude.

The effects of submaximal and maximal exercise on cerebral perfusion were assessed using a portable, recumbent cycle ergometer in nine unacclimatized subjects ascending to 5,260 m. At 150 m, mean (SD) cerebral oxygenation (rSO2%) increased during submaximal exercise from 68.4 (SD 2.1) to 70.9 (SD 3.8) (P < 0.0001) and at maximal oxygen uptake (.VO2(max)) to 69.8 (SD 3.1) (P < 0.02). In contrast, at each of the high altitudes studied, rSO2 was reduced during submaximal exercise from 66.2 (SD 2.5) to 62.6 (SD 2.1) at 3,610 m (P < 0.0001), 63.0 (SD 2.1) to 58.9 (SD 2.1) at 4,750 m (P < 0.0001), and 62.4 (SD 3.6) to 61.2 (SD 3.9) at 5,260 m (P < 0.01), and at .VO2(max) to 61.2 (SD 3.3) at 3,610 m (P < 0.0001), to 59.4 (SD 2.6) at 4,750 m (P < 0.0001), and to 58.0 (SD 3.0) at 5,260 m (P < 0.0001). Cerebrovascular resistance tended to fall during submaximal exercise (P = not significant) and rise at .VO2(max), following the changes in arterial oxygen saturation and end-tidal CO(2). Cerebral oxygen delivery was maintained during submaximal exercise at 150 m with a nonsignificant fall at .VO2(max), but at high altitude peaked at 30% of .VO2(max) and then fell progressively at higher levels of exercise. The fall in rSO2 and oxygen delivery during exercise may limit exercise at altitude and is likely to contribute to the problems of acute mountain sickness and high-altitude cerebral edema.     

Epidemics and Frequent Recombination within Species in Outbreaks of Human Enterovirus B-Associated Hand,Foot and Mouth Disease in Shandong China in 2010 and 2011

The epidemiology and molecular characteristics of human enterovirus B (HEV-B) associated with hand, foot and mouth disease (HFMD) outbreaks in China are not well known. In the present study, we tested 201 HEV isolates from 233 clinical specimens from patients with severe HFMD during 2010–2011 in Linyi, Shandong, China. Of the 201 isolates, 189 were fully typed and 18 corresponded to HEV-B species (six serotypes CVA9, CVB1, CVB4, Echo 6, Echo 25 and Echo 30) using sensitive semi-nested polymerase chain reaction analysis of VP1 gene sequences. Phylogenetic analysis based on the VP1 region showed that eight E30SD belonged to a novel sub-genogroup D2; E25SD belonged to a novel sub-genogroup D6; E6SD belonged to sub-lineage C6 and five CVB1SD belonged to subgroup 4C; and B4SD belonged sub-lineage D2. The full viral genomes of the CVB1SD, E6SD, E25SD and E30SD isolates were sequenced. Analysis of phylogenetic and similarity plots indicated that E25SD recombined with E25-HN-2, E30FDJS03 and E4AUS250 at noncontiguous P2A–P3D regions, while E30SD, E30FDJ03, E25-HN-2 and E9 DM had shared sequences in discrete regions of P2 and P3. Both E6SD and B1SD shared sequences with E1-HN, B4/GX/10, B5-HN, and A9-Alberta in contiguous regions of most of P2 and P3. Genetic algorithm recombination detection analysis further confirmed the existence of multiple potential recombination points. In conclusion, analysis of the complete genomes of E25SD, E30SD, CVB1SD and E6SD isolated from HFMD patients revealed that they formed novel subgenogroup. Given the prevalence and recombination of these viruses in outbreaks of HFMD, persistent surveillance of HFMD-associated HEV-B pathogens is required to predict potential emerging viruses and related disease outbreaks.     

An Intact U5-Leader Stem Is Important for Efficient Replication of Simian Immunodeficiency Virus

Previous work has shown that four deletions in simian immunodeficiency virus (SIV), termed SD1a, SD1b, SD1c, and SD6, which eliminated sequences at nucleotide positions 322 to 362, 322 to 370, 322 to 379, and 371 to 379, respectively, located downstream of the primer binding site, impaired viral replication capacity to different extents. Long-term culturing of viruses containing the SD1a, SD1b, and SD6 deletions led to revertants that possessed wild-type replication kinetics. We now show that these revertants retained the original deletions in each case but that novel additional mutations were also present. These included a large deletion termed D1 (nt +216 to +237) within the U5 region that was shown to be biologically relevant to reversion of both the SD1a and SD1b constructs. In the case of SD6, two compensatory point mutations, i.e., A+369G, termed M1, located immediately upstream of the SD6 deletion, and C+201T, termed M2, within U5, were identified and could act either singly or in combination to restore viral replication. Secondary structure suggests that an intact U5-leader stem is important in SIV for infectiousness and that the additional mutants described played important roles in restoration of this motif.