Homeostasis in mice with genetically decreased angiotensinogen is primarily by an increased number of renin-producing cells.

Here we investigate the biochemical, molecular, and cellular changes directed toward blood pressure homeostasis that occur in the endocrine branch of the renin-angiotensin system of mice having one angiotensinogen gene inactivated. No compensatory up-regulation of the remaining normal allele occurs in the liver, the main tissue of angiotensinogen synthesis. No significant changes occur in expression of the genes coding for the angiotensin converting enzyme or the major pressor-mediating receptor for angiotensin, but plasma renin concentration in the mice having only one copy of the angiotensinogen gene is greater than twice wild-type. This increase is mediated primarily by a modest increase in the proportion of renal glomeruli producing renin in their juxtaglomerular apparatus and by four times wild-type numbers of renin-producing cells along afferent arterioles of the glomeruli rather than by up-regulating renin production in cells already committed to its synthesis.     

利用紧缩线性模型和贝叶斯模型对猪总产仔数和产活仔数性状的全基因组关联研究

全基因组关联分析策略已逐渐成为家畜重要经济性状研究的强有力工具。文章使用猪60K SNP芯片对一个具多胎繁殖性状记录的商业母猪群(n=820)进行分型检测,共计57 814个SNP通过设定质控标准。主成分分析显示群体内不存在显著的群体分层现象,而后分别运用两种统计模型Compressed Mixed Linear Model(GAPIT程序包)、Bayes CPi(GenSel软件)进行第1和第2胎次总产仔数和产活仔数性状的全基因组关联分析。从两种分析方法所得结果中各取最显著的50个SNP位点进行比较:对于第1胎次总产仔数,两种方法分析结果存在31个重合SNP位点,对于第1胎次产活仔数,有20个重合SNP位点;且两种统计分析结果中最显著的SNP位点都在另一方法中得到验证。与第1胎次总产仔数显著关联的SNP位于1、2、3、7、13、16和18号染色体,与第1胎次产活仔数显著关联的SNP位于1、3、4、13和16号染色体上的11个区域内。在1、3、13和16染色体上共有5个区域同时与这两个性状显著关联。与第2胎次总产仔数和产活仔数显著关联的区域主要位于7、10、12、13、14和16号染色体的6个重叠区域内。     

Selection for increased length of reproductive life in mice

Summary An experiment was conducted in mice to examine whether selection can increase reproductive life and lifetime production of progeny. Mice in two lines with litter size standardized at birth and in two lines without standardization were pair-mated at 7 weeks of age and maintained as long as they produced litters up to 382 days. Progeny from the sixth litters were used to maintain the four selected lines, while progeny from the first litters were bred to maintain unselected control lines. Selected and control lines were compared at five and six generations of the selected lines. Contemporary comparisons revealed that the length of reproductive life and most lifetime production traits were significantly greater in the selected than in control lines. Realized heritability of the length of reproductive life ranged from 0.08 to 0.13. It was concluded that the length of reproductive life and lifetime production in mice can be increased by selection.Animal Research Centre Publication No. 1618     

Selection for increased allocation to offspring number under environmental unpredictability

According to life-history theory, the evolution of offspring size is constrained by the trade-off between allocation of resources to individual offspring and the number of offspring produced. Existing models explore the ecological consequences of offspring size, whereas number is invariably treated simply as an outcome of the trade-off with size. Here I ask whether there is a direct evolutionary advantage of increased allocation to offspring number under environmental unpredictability. Variable environments are expected to select for diversification in the timing of egg hatch and seed germination, yet the dependence of the expression of diversification strategies, and thus parental fitness, on offspring number has not previously been recognized. I begin by showing that well-established sampling theory predicts that a target bethedging diversification strategy is more reliably achieved as offspring number increases. I then use a simulation model to demonstrate that higher offspring number leads to greater geometric mean fitness under environmental uncertainty. Natural selection is thus expected to act directly to increase offspring number under assumptions of environmental unpredictability in season quality.     

Selection for increased abdominal bristle number in Drosophila melanogaster with concurrent irradiation

Summary Replicate lines, each, with one hundred pairs of parents selected at 50% intensity, were derived from an inbred line. For twenty generations three lines were selected without irradiation and five with 1000 r X-rays per generation given to both females and males. After adjustment for level of crowding in the cultures, the final mean was 1.3 bristles higher in females and 1.0 bristles higher in males in the irradiated lines than in the unirradiated lines. In terms of phenotypic standard deviations in each sex in the base population, these total responses were 0.74 and 0.59 respectively. Radiation can induce mutations useful in increasing responses in selection programmes, but the average response attributable to radiation is small, and heterogeneity between replicate lines is to be expected.This work was carried out while B. H. was on leave from the New South Wales Department of Agriculture, and held a Commonwealth Research Studentship. Our thanks to Robin Hall and Tricia Brown for technical assistance, to Dr. B. L. Sheldon, C.S.I.R.O. Division of Animal Genetics, for providing the inbred line, and to the Radio-Therapy Unit, Royal Prince Alfred Hospital, for the use of their equipment.     

Selection for increased abdominal bristle number in Drosophila melanogaster with concurrent irradiation

Summary Replicate lines, each initially with one hundred pairs of parents selected at 50% intensity, were derived from the Canberra strain. In later generations population size was reduced and selection intensity increased. Three lines were selected without irradiation and five with 1000 r X-rays per generation for thirty generations. Selection was continued until generation 66. Long-term responses were similar in unirradiated and irradiated lines, and there was evidence that genes with large effects influenced response patterns in both groups of lines.This work was carried out while B.H. was on leave from the New South Wales Department of Agriculture, and held a Commonwealth Research Studentship. Robin Hall and Tricia Brown provided much appreciated technical assistance, and we are indebted to the Radio-Therapy Unit, Royal Prince Alfred Hospital, for the use of their equipment.     

Selection for increased nodule number in common bean (Phaseolus vulgaris L.)

Common bean (Phaseolus vulgaris L.) plants were grown for 21–28 days in plastic container-modified Leonard jar assemblies and placed in a controlled-environment room. The nodules on each plant were removed, counted; selected plants were repotted, grown and intercrossed to produce progenies for the next cycle of recurrent selection. Among the ten parent lines, Puebla 152 and WBR 22–34 produced the most nodules and Rio Tibagi and Negro Argel the fewest, when averaged over five experiments. An analysis of number of nodules on F₁ plants resulting from crosses made in a partial diallel design among the ten parents revealed highly significants variation for general combining ability (GCA) but not for specific combining ability (SCA). After three cycles of recurrent selection for nodule number per plant, the mean nodule number was 211% of the mean for the 10 parents control. Total nodule weight on selected plants also increased, but individual nodule weight decreased. Nineteen C₁ and 18 C₂ lines resulting from the individual plants selected for greater nodule number, along with the ten parents and two non-nodulating soybean lines included as non-fixing check plants were grown in a single experiment in a low-N field. C₂ lines on average accumulated significantly more N per plant than either the parents or C₁ lines, providing evidence for increased N₂ fixation measured by the N difference method. These data show that more nodules, possibly resulting from greater susceptibility to nodulation, are an important, heritable component of symbiosis and that selection for increased nodule number resulted in lines capable of fixing more atmospheric N₂.     

Quantitative evaluation of the total number and distribution of lymphocytes in young pigs.

In young pigs, the spleen, thymus and all lymph nodes were dissected out and weighed. The relative content of lymphoid cells was determined from histological sections. The number of nucleated cells was evaluated by two different methods: firstly, by measuring the DNA content of samples of lymphoid tissue and dividing by the DNA content of a single nucleus; and, secondly, by counting all lymphoid cells in histological sections of defined volumes of these organs. The number of lymphoid cells in tonsils, gut, bone marrow and lung were determined using histological evaluations and the volumes or weights of these organs. The resulting average number of lymphocytes was 321 times 10 (9) for a pig of 26 kg body weight. The lymphocytes showed the following distribution in lymphoid and non-lymphoid organs: thymus 44%, spleen 9%, mesenteric lymph nodes 17%, cervical lymph nodes 9%, other peripheral lymph nodes 3%, gut-associated lymphocytes 5%, tonsils 2%, bone marrow 5%, blood 3%, lung 0.2% and an estimated figure of 3% for all other tissues.     

CO2 uptake decreased and CH4 emissions increased in first two years of peatland seismic line restoration

Wetlands Ecology and Management - Oil and gas exploration has resulted in over 300,000 km of linear disturbances, known as seismic lines, throughout boreal peatlands across Canada. Sites...     

Immunoregulation in MRL/Mp-lpr/lpr mice: evidence for decreased helper-T-cell and increased suppressor-T-cell function with age

In vivo and in vitro plaque-forming cell (PFC) responsiveness to sheep erythrocytes (SRBC) was used to assess immunoregulatory function in the autoimmune MRL mouse strain. MRL/Mp-lpr/lpr (MRL/l) mice had good primary and secondary IgM and IgG responses in vivo compared to MRL/Mp-+/+ (MRL/n) mice when young, but with age the MRL/l responses declined markedly. In vitro primary SRBC-specific PFC responses in MRL/l mice declined at the same time as in vivo responses, indicating that the in vivo autoimmune environment could not account for cellular dysfunction. When varied mixtures of T and B cells from MRL/l and MRL/n mice were cultured, abnormalities in MRL/l T-cell function became apparent. T-helper-cell (T_H) function declined rapidly with age, beginning by 2 to $\text{2}\text{1}\text{2}$ months of age. T cells from MRL/l mice 2 months of age and older also had increased suppressor activity when cultured with B cells and MRL/n T cells. The degree of suppressor activity increased with age. The correlation of these findings with results of previous studies by others and with autoimmune disease is discussed.     

Selection response for litter size at birth and litter weight at weaning in the first parity in mice

Summary Five 60-pair lines of mice were selected for seven generations for the following criteria: number born alive (LSO), random selection of litters (LC), number born alive divided by the weight of the dam at 9 weeks (LSO/DWT), total litter weight weaned divided by the weight of the dam at 9 weeks (LWT/DWT), and weight of litter weaned (LWT). All traits were measured in the first parity only and litters were not standardized. Realized heritabilities for LSO, LWT, LSO/DWT, and LWT/ DWT were 0.10± 0.06, 0.11±0.07, 0.22 ± 0.04, and 0.22 ± 0.08, respectively. Selection response for the two ratio lines was due to correlated responses in the respective numerators, LSO and LWT, as DWT did not decrease. In terms of improving LWT, selection for LWT/ DWT was three times as effective as selection for LSO/ DWT.     

Selection of Merino sheep for increased and decreased resistance to Haemonchus contortus: peri-parturient effects on faecal egg counts.

Peri-parturient worm egg counts were compared in 395 Merino ewes bred for either increased (IRH) or decreased (DRH) resistance to Haemonchus contortus, or from an unselected control flock (CH). Following a 10 month period with no anthelmintic treatment, a rise in egg counts began about 4 weeks before parturition and continued into lactation. At all stages, egg counts were significantly lower in IRH ewes, even those failing to conceive. Before lambing, IRH ewes averaged 263 epg, compared with 1113 epg in CH and 1618 epg in DRH ewes. After 2 weeks of lambing, lactating ewes averaged 1050, 2173 and 3708 epg, respectively, in the three lines. At the end of lambing, egg counts had increased to 1645, 3959 and 4124 epg, respectively. Counts appeared to have peaked in IRH ewes but not in DRH ewes. Ewes with twins had higher counts than those with singles, and ewes suckling lambs had higher counts than those losing lambs. No significant variation was associated with age of ewe (2-7 years). Although there were several nematode species present, the results suggest that, in comparison with DRH ewes, IRH ewes were particularly effective in reducing pasture contamination with H. contortus, both before and during the peri-parturient period.