Stable long-period cycling and complex dynamics in a single-locus fertility model with genomic imprinting

Although long-period population size cycles and chaotic fluctuations in abundance are common in ecological models, such dynamics are uncommon in simple population-genetic models where convergence to a fixed equilibrium is most typical. When genotype-frequency cycling does occur, it is most often due to frequency-dependent selection that results from individual or species interactions. In this paper, we demonstrate that fertility selection and genomic imprinting are sufficient to generate a Hopf bifurcation and complex genotype-frequency cycling in a single-locus population-genetic model. Previous studies have shown that on its own, fertility selection can yield stable two-cycles but not long-period cycling characteristic of a Hopf bifurcation. Genomic imprinting, a molecular mechanism by which the expression of an allele depends on the sex of the donating parent, allows fitness matrices to be nonsymmetric, and this additional flexibility is crucial to the complex dynamics we observe in this fertility selection model. Additionally, we find under certain conditions that stable oscillations and a stable equilibrium point can coexist. These dynamics are characteristic of a Chenciner (generalized Hopf) bifurcation. We believe this model to be the simplest population-genetic model with such dynamics.     

Germinal stage vitrification is superior to MII stage vitrification in prepubertal mouse oocytes

This study investigated if in vitro maturation (IVM) before or after vitrification would be more successful for prepubertal oocytes. To mimic prepubertal conditions in an experimental setup, oocytes were collected from healthy 14, 21 and 28day old Swiss albino mice. The germinal vesicle (GV) stage oocytes and in vitro matured MII oocytes were subjected to vitrification-warming. Both structural (meiotic spindle morphology, mitochondrial integrity, cortical granules) and functional (sperm zona binding, fertilization) characteristics were assessed in oocytes after warming. This study demonstrated that IVM was more detrimental to prepubertal oocytes than to young adults. Further, vitrification of the IVM oocytes resulted in an increase in the number of abnormal meiotic spindles, a change in the cortical distribution pattern, a reduction in sperm zona binding and the fertilization rate. Importantly, oocyte integrity was better when prepubertal oocytes were vitrified before, rather than after, IVM. The above observations support GV stage vitrification for prepubertal oocytes requiring fertility preservation. Understanding the mechanisms behind the differing outcomes for oocytes from immature females will help in refining current protocol, thereby retaining the oocytes' maximum structural and functional integrity Further investigation is necessary to determine whether human prepubertal oocytes also behave in a similar way. It is to be noted here, with great emphasis, that a major limitation of this study is that the oocytes’ abilities were tested only until fertilisation, as a consequence of which the study cannot reveal the developmental potentials of the embryos beyond fertilisation.     

Strategic treatment of anovular dairy cows with GnRH

The primary objective was to evaluate fertility of anovular dairy cows given GnRH 4 d after first postpartum timed AI (TAI). Secondary objectives were to determine ovulatory response to treatment, effect of treatment on serum progesterone (P(4)) concentrations, and the proportion with a short luteal phase. Lactating Holstein cows (n=1047) were submitted for first postpartum TAI using a Presynch+Ovsynch protocol. Anovular cows were identified from an initial 1047 lactating Holstein cows using transrectal ultrasonography, based on the absence of a CL at the first GnRH injection of a Presynch+Ovsynch protocol, and anovular cows were randomly assigned to receive either no further treatment (Control, n=85), or 100 microg of GnRH 4 d after TAI (GnRH treated; n=71). For GnRH treated cows, 51% responded by ovulating a follicle in response to GnRH treatment 4 d after TAI; however, pregnancies per AI (P/AI) did not differ between GnRH treated cows that ovulated (36%) compared to GnRH treated cows that did not ovulate (21%). There was a quadratic effect of P(4) at the PGF(2 alpha) injection of Ovsynch on P/AI, and cows with P(4)>or=1 ng/mL at the PGF(2 alpha) injection of Ovsynch had greater P/AI (41%) than cows with P(4)<1 ng/mL (12%); however, no treatment difference was detected. Overall, P/AI did not differ between control (30.1%) and GnRH treated (29.6%) treatments for synchronized cows. Although treatment of anovular cows with GnRH 4 d after TAI failed to improve fertility, variation among cows in serum P(4) at the PGF(2 alpha) injection of Ovsynch dramatically affected fertility of anovular dairy cows.     

Population homeostasis in sub-Saharan Africa

Global population growth remains one of the major challenges of the twenty-first century. This is particularly true for African countries which have been undergoing their demographic transitions. To investigate whether predicted increasing population density and urbanization can help to stabilize African population, we construct a database for 84 georeferenced Demographic and Health Survey (DHS) samples including 947,191 individuals in sub-Saharan Africa and match each location with gridded population density from NASA. We apply a proportional hazard model to evaluate the quantitative impact of local population density on the transitions from childlessness to motherhood, and from celibacy to marriage. Moving from the 5th to the 95th percentile of population density increases the median age at first birth by 2.2 years. This roughly decreases completed fertility by half a child. The same increase in population density increases the median age at first marriage by 3.3 years. These findings contribute to the understanding of why fertility has not dropped in Africa as fast as expected. One part of the answer is that population density remains low. Yet the total effect of increased density on fertility remains limited and counting on it to stabilize the population would be unrealistic.     

合成甘蓝型油菜中双隐性雄性核不育材料的发现及遗传规律分析

从甘蓝型油菜与白菜型油菜的种间杂交获得的甘蓝型油菜(Brassica napus)中发现了雄性不育单株,兄妹交株系和不育株与甘蓝型油菜常规杂交F1和F2株系的育性分离分析表明,该不育材料属于双隐性雄性核不育类型.利用育性分离株系的可育株自交和可育株与不育株间兄妹交等方法筛选出7个纯合可育株系,等位测验表明这7个纯合可育株系(B1～B7)中存在两种基因型:Ms1Ms1ms2ms2和ms1ms1Ms2MS2.该材料对油菜核不育基因定位和杂种优势利用研究有重要意义.     

The relationship between sperm quality in cool-shipped semen and embryo recovery rate in horses

The relationship between the quality of cool-shipped stallion semen and fertility has not been adequately described. This study evaluated sperm quality of cool-shipped semen from 459 ejaculates (N = 130 stallions) that were used for insemination of 196 embryo donor mares (n = 496 estrous cycles). Embryo recovery rate (ERR; %) increased, as all sperm measures (e.g., motility, viability, DNA quality, morphology, concentration, and total number) increased. Threshold values are reported for each sperm quality measure (e.g., total sperm motility ≥ 65%) that separate two ERR groups (e.g., average: ∼50% ERR; high: ∼65% ERR).     

光温条件对短光低温不育水稻育性转换的影响

短光低温不育水稻是一类与长光高温不育水稻育性转换特性相反的新种质,通过对分期播种材料自然条件下的育性及人工短光处理后的育性比较分析表明,宜DIS的光敏期为第一苞分化期至第二次枝梗原基和小穗原基分化期（幼穗分化I－III期）,在常温下光敏期的短日处理可使育性趋于不育,但在高温下光敏期短日不育效应被削弱,宜DIS的花粉育性在高,低温作用下育性的均出现下降,根据高,低温影响育性的资料分析得到的敏感期基本一致,即花粉母细胞形成期至花粉内容物充实期（幼穗分化V－Ⅶ期）。     

Mapping complementary genes in maize: positioning the rf1 and rf2 nuclear-fertility restorer loci of Texas (T) cytoplasm relative to RFLP and visible markers

There are three major groups of cytoplasmic male-sterile cytoplasms in maize; C (Charrua), S (USDA), and T (Texas). These cytoplasms can be classified by the unique nuclear genes that suppress the male-sterility effects of these cytoplasms and restore pollen fertility. Typically, plants that carry Texas (T) cytoplasm are male fertile only if they carry dominant alleles at two unlinked nuclear restorer loci,rf1 andrf2. To facilitate analysis of T-cytoplasm-mediated male sterility and fertility restoration, we have mappedrf1 andrf2 relative to closely-linked RFLP markers using five populations. Therf1 locus and/or linked visible markers were mapped in four populations; therf2 locus was mapped in two of the populations. Data from the individual populations were joined with the aid of JoinMap software. The resulting consensus maps placerf1 between umc97 and umc92 on chromosome 3 andrf2 between umc153 andsus1 on chromosome 9. Markers that flank therf1 andrf2 loci have been used to identify alleles atrf1 andrf2 in segregating populations. These analyses demonstrate the possibility of tracking separate fertility restorer loci that contribute to a single phenotype.R. P. Wise and P. S. Schnable should both be considered first authors as they contributed equally to this workJoint contribution of the Field Crops Research Unit, USDA-Agricultural Research Service and the Iowa Agriculture and Home Economics Experiment Station. Journal Paper No. 15416 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project Nos. 2447 and 3152     

论大白菜及其近缘芸薹属作物核不育材料的育性遗传兼基因互作的抑制效应

根据大白菜及其近缘芸薹属作物核不育材料育成的纯合两型系和杂合两型系可育株间互交F~1|可育株自交,其子代可能出现无育性分离情况或者产生13(可育株)∶3(不育株)两种表型的育性比资料,认为前者宜用复等位基因假说解释,而后者用抑制作用解释为妥。抑制作用的内涵有两种可能,一是由一对决定育性表现的育性基因与另一对不决定育性表现的抑制基因互作表现抑制作用,即抑制作用假说;二是由性质相同、作用相反且可育基因起上位作用的两对育性基因彼此互作产生抑制效应,权称之为上位抑制假说解释其育性遗传现象。 Abstract:The heading Chinese cabbage-pe-tsai and related crops genic male sterile materials can breed up homozygous two-type line and hyterozygous two-type line,intercrossing between fertile plants of this two lines,its F1 fertile plant selfed,generation show two possibles,one is being without fertility segregation,another is fertility segregation rate of 13 (fertile) ∶3(sterile).According literature above,its considerd that the former is proper to be interpreted by means of multiple alleles hypothesis,and the fertility heredity of the latter is appropriate to be interpreted using inhibition.The implecation of the inhibition has two possibilities,one is that a pair of fertility genes controlling fertility and another pair of inhibition genes not controlling fertility interact showing inhibition,i.e.,inhibiting effect hypothesis,and the other is that two pairs of fertility genes with identical property and contrary action and its fertile genes acting epistatically interact demonstrating inhibiting effect.It was temporarily here defined as epistatic inhibition hypothesis interpreting its fertility inheritance phenomenon.     

Effect of low density lipoproteins in extender on freezability and fertility of buffalo (Bubalus bubalis) bull semen

This study was designed to determine whether low-density lipoporoteins (LDLs) extracted from egg yolk in extender improve the freezability and fertility of buffalo bull semen. Semen from three Nili-Ravi buffalo bulls was diluted at 37 °C with tris-citric acid extender (50 × 10⁶ motile spermatozoa mL⁻¹) containing LDLs 2.5%, 5%, 10%, and 15% extracted from egg yolk and extender containing 20% egg yolk was kept as control. Diluted semen was cooled to 4 °C in 2 h, equilibrated at 4 °C for 4 h, filled in 0.5 mL French straws, and kept on liquid nitrogen vapors for 10 min. Straws were then plunged and stored in liquid nitrogen (-196 °C). Sperm motility (visually; %), plasma membrane integrity (%; with supravital hypo-osmotic swelling test), and viability (%; with dual staining test using Trypan-blue Giemsa) were assessed at post-dilution, pre-freezing and post-thawing. At post-dilution and pre-freezing, sperm progressive motility, plasma membrane integrity and viability was similar (P > 0.05) in extender containing 10% LDLs or the control. However, at post-thaw the aforementioned parameters were higher (P < 0.05) in extender containing 10% LDLs compared with the control and other experimental extenders. The fertility rate of inseminations performed were higher (P < 0.05) with extender containing 10% LDLs than the control. It was concluded that LDLs (10%) in extender improved the freezability and fertility of buffalo bull spermatozoa.