清醒羊低氧性肺动脉高压及逆转中肺血管对外源性血小板活化因子的反应

本实验复制了清醒羊低氧性肺动脉高压（ＨＰＨ）及其逆转模型,动态观察了在ＨＰＨ发生、发展及逆转中肺、体循环对外源性血小板活化因子（ＰＡＦ）的反应。结果表明：（１）ＰＡＦ对清醒羊常氧期、ＨＰＨ及ＨＰＨ逆转期均为一强效应肺血管收缩剂,且呈剂量依赖性;（２）ＨＰＨ期：ＰＡＦ对肺血管加压反应增值百分离较常氧期及ＨＰＨ逆转期低;（３）ＰＡＦ对三期体动脉压、心率无明显影响,却能降低各期心输出量。     

Immunocytochemical localisation of prolactin and growth hormone in the perinatal sheep pituitary

Summary The peroxidase anti-peroxidase immunocytochemical staining technique has been used to identify prolactin and growth hormone cells in pituitaries from fetal and neonatal sheep. The size of the secretory granules in these cell types has been measured using the image analysing computer Quantimet 720. The area size distributions of the fetal prolactin and growth hormone granules were compared with those in the neonate and the adult. It appears that the gestational age of the fetus may influence the size range of prolactin secretory granules.     

Hybridization of Australian Haemonchus placei (place, 1893), Haemonchus contortus cayugensis (Das & Whitlock, 1960) and Haemonchus contortus (Rudolphi, 1803) from Louisiana

There were distinct ecotypie differences in the ability to develop to third stage larvae at a constant 11 or 13°C for two weeks. H. conforms cayugensis could develop at both 11 and 13°C; H. contortus from Louisiana could develop at 13°C but not 11°C and H. placei could not complete development at either temperature. Eggs produced from the first cross between ecotypes had the same cold tolerance as their maternal parent. F₁ eggs were intermediate between parental ecotypes, while F₂ eggs, when fertile, developed at the same temperature as the most cold-tolerant parent in the first cross. The H. placei knobbed vulvar morph type was dominant to H. contortus cayugensis smooth morph type and recessive to the H. contortus (Louisiana) smooth morph type. Knobbed morph type of H. contortus (Louisiana) was dominant to smooth of H. contortus cayugensis. Dominance of morph type was enhanced by a matroclinous effect in the between species matings but not in the within species matings. No fertile eggs were produced by the F1 of the mating between female H. placei × male H. contortus (Louisiana) or by the F₂ of the reciprocal mating. Reciprocal matings between H. placei × H. contortus cayugensis produced an F₁ and F₂ that had reduced fertility but were not completely sterile. No decrease in fertility was observed in the F₂ and F₁ from the H. contortus cayugensis × H. contortus(Louisiana)matings. Cytological studies revealed several kinds of meiotic disturbances in the between species F₁ and F₂. The most frequent were aneuploidy, failure of chromosome pairing, and pairing between non-homologous chromosomes. Males were more seriously affected than females by meiotic disturbances. The H. placei X chromosome appeared to be selected against by the hybrid genetic background. Within species hybrids showed no meiotic disturbances and the percentage of male offspring from these crosses was the same as for female offspring.     

Fusion of erythrolysosomes in epithelial cells of the sheep placenta

Summary In trophoblastic epithelial cells of the sheep placenta the breakdown of erythrocytes within complex erythrolysosomes was studied at the ultrastructural level.It was found that the formation of complex erythrolysosomes containing from two to several erythrocytes as a result of fusion of erythrolysosomes within the epithelial cells was a common occurrence when the epithelial cells engulfed a large number of erythrocytes. The erythrocytes enclosed in complex erythrolysosomes appear to be either in the same or in different stages of hemolysis.In the process of breakdown of erythrocytes within complex erythrolysosomes five successive stages of hemolysis could be distinguished. Acid phosphatase activity was demonstrated in the complex erythrolysosomes and appeared to be located in the angular interspaces between the erythrocytes and the lysosomal membrane. The fragmentation of complex erythrolysosomes with formation of small hemoglobin-containing lysosomes also occurred.The fusion of erythrolysosomes with formation of complex erythrolysosomes can be considered as an additional mechanism in the process of erythrocyte breakdown in the epithelial cells of the sheep placenta.     

Cytotoxic immune cells with specificity for defined soluble antigens. I. Assay with antigen-coated target cells

An in vitro cytotoxic system is described, in which immune cells specific for a given soluble antigen exert a specific cytotoxic effect on target cells to which this antigen has been covalently linked. The nature of the target cell is important in this system. When antigen-coated P 815-X2 mastocytoma cells and antigen-coated chicken red blood cells were incubated for several hours in culture medium at 37 °C, the presence of membrane-bound antigen could still be demonstrated on the latter, but not on the former target cells. This might be the reason why antigen-specific target cell destruction by specific immune cells was observed only with antigen-coated chicken red blood cells as target cells. The specificity of the cytotoxic effect was controlled in each experiment in a criss-cross way by using two non cross-reacting antigens both as immunogens and for coating the target cells. Specific cytotoxicity was demonstrable with both guinea pig and mouse immune cells and with different kinds of antigens: foreign proteins, hapten-heterologous protein conjugates and hapten-autologous protein conjugates.     

Effect of grazing removal on aboveground vegetation and soil seed bank composition in sub-alpine grasslands of northern Iran

Background: Knowledge about vegetation and soil seed bank composition and the processes that contribute to vegetation recovery after the removal of heavy grazing is lacking in sub-alpine ecosystems.

Aims: In order to assess the effects of large herbivores on above-ground vegetation (AGV) and soil seed bank (SSB) characteristics, intensively sheep-grazed areas were compared to adjacent areas where grazing had been removed 10 years previously in a sub-alpine grassland of northern Iran.

Methods: A total of 40 4-m² (2 m × 2 m) plots were established in each treatment, and soil samples were collected from each plot within a depth of 10 cm. Plant species composition was determined for each plot during the flowering stage of herbaceous species in June 2011. The seedling emergence method was used to estimate SSB composition.

Results: A total of 45 species (23 annuals and 22 perennials) emerged from the soil samples of the grazed area, while the number of species emerged from the soil samples of the previously grazing area was 76 (37 annuals and 39 perennials). The removal of grazing led to a significant increase in species richness and seed density in the SSB. Species turnover of AGV was higher, and that of the SSB was similar for grazed areas compared with areas that were formerly grazed. Detrended correspondence analysis ordination of AGV composition showed a clearly separate structure between grazed plots and plots where grazing has been removed, while the segregation was less clear for SSB composition.

Conclusions: We concluded that restoration of locally degraded sites cannot rely on the SSB when grazing is stopped simultaneously and unvegetated gaps are colonised by vegetative growth rather than by seed.     

Stable isotope evidence (δ13C, δ18O) for winter feeding on seaweed by Neolithic sheep of Scotland

The antiquity of the use of seaweed to feed domestic animals was investigated through carbon ( δ ¹³C) and oxygen ( δ ¹⁸O) isotope analysis of tooth enamel bioapatite. The analysis was performed on sheep and cattle teeth from two Neolithic sites in Orkney (Scotland). At the Knap of Howar, c . 3600 bc , carbon isotopes reflect grazing on terrestrial plants throughout the year for both sheep and cattle, with no contribution of seaweed to their diet. At the Holm of Papa Westray North (HPWN), c . 3000 bc , significant contribution of seaweed to the sheep diet during winter is indicated by bioapatite δ ¹³C values as high as −5.7‰, far outside of the range of values expected for the feeding on terrestrial C₃ plants, and δ ¹⁸O values higher than expected during winter, possibly caused by ingestion of oceanic water with seaweed. Ingestion of seaweed by sheep at HPWN might have been necessitated by severe reduction of pastures during winter. Results suggest that sheep ingested fresh seaweed rather than dry fodder, perhaps directly on the shore as sheep do nowadays on North Ronaldsay. A significant difference between the two populations is the exclusive reliance on seaweed by the North Ronaldsay sheep, which have developed physiological adaptations to this diet. Contribution of seaweed to the sheep winter diet at HPWN might have been a first step towards this adaptation.     

Factors that affect fertility in a feral population of sheep

Feral livestock offer an excellent opportunity lo study factors affecting fertility as the physiology of their husbanded relatives is well known and social and environmental influences can be studied free of man's interference. This is so in the population of about 1250 sheep of the primitive Soay breed on the islands of St Kilda, Scotland. There is a high coincidence of oestrus amongst the ewes in mid November, and the breeding season is constant within a few days, from year to year. The breeding season in other British breeds of sheep demonstrates a strong correlation with latitude. On St Kilda, mortality rates in male sheep are higher than in females so that the ratio of rams to ewes at mating time is about 1:5. Competition amongst rams is intense. The optimal time for mating and the place of ram lambs in the social system are discussed.