秦川牛保种情况的分析(续) Ⅱ、群体留种方式与世代间隔

根据陕西省秦川牛场秦川牛保种群30多年的记录统计,分析了该群体的世代间隔与留种方式。结果表明,该群体平均世代间隔为6.9年,采取的是对保种不利的合并留种,导致各种家系后代供量方差增大,尤其是公牛的女儿供量方差高达77.39,比平均女儿供量(5.84头)高13倍。不同始祖个体在后裔群中的血统分布也极不均匀。若能改进留种方式或设法降低选择强度,则可大大提高保种效果。     

Contribution of Metallogenium-Siderococcus bacteria to the postvolcanic transformation of igneous material (Kamchatka)

The transformation of recent igneous rock occurs with participation of microorganisms associated with the deposition of iron and aluminum on their cell surface. An identity of morphological structures was found in the microorganisms in both cases, and this fact counts in favor of their similarity and wide distribution in the rock being transformed. The polymorphous acid-resisting organism identified by our studies was tentatively classified with the Metallogenium-Siderococcus group.     

Distribution of calcium in peat deposits of the central part of Western Siberia

Distribution patterns of calcium in peat deposits of seventeen bogs in the middle and southern taiga of Western Siberia have been studied. Four types of Ca distribution patterns related to the genesis of peat deposits are specified. Up to three Ca-enriched peat layers are distinguished in thick deposits. This Ca distribution pattern is typical of different peat deposits formed under various conditions. It is shown that Ca accumulation in particular layers of peat deposits is related to the warm stages of the Holocene.     

朝阳东大桥承台砼施工技术

叙述了朝阳东大桥主桥两个承台大体积砼的施工经过。总结了施工方案优选过程和大体积低水化热砼的配合比试验情况,并在实际施工中,证明,该技术措施可行,方案经济合理,取得了比较成功的经验。     

Osteosarcoma of the distal femur, combined with multiple bone infarcts: the case of a 10-year-old poodle

A ten-year-old female poodle was presented for left hindlimb lameness. Radiographically, irregular intramedullary densities of long bones (bone infarcts) and a lytic lesion in the left distal femur were detected. Two years after the first examination, the lesions in the distal femur were definitely identified as osteosarcoma and the dog was euthanized. Pathological and histological changes of the bone infarcts as well as of the osteosarcoma are described. Regarding bibliographical data, occurrence and aetiopathogenesis of osteosarcoma associated with multifocal bone infarction in man and dog are discussed.     

Pasteurella haemolytica A1 and Bovine Respiratory Disease: Pathogenesis

The severe fibrinonecrotic pneumonia associated with pneumonic pasteurellosis usually results from colonization of the lower respiratory tract by Pasteurella haemolytica biotype A, serotype 1(A1). Despite recent research efforts, the authors lack a detailed understanding of the interactions and host response to P. haemolytica in the respiratory tract. The authors hypothesize that management and environmental stress factors or viral infection alters the upper respiratory tract (URT) epithelium allowing P. haemolytica to colonize the epithelium. Once the URT is colonized, large numbers of organisms enter the lung where they interact with alveolar macrophages. Endotoxin, released from the bacteria, crosses the alveolar wall where it activates pulmonary intravascular macrophages, endothelium, neutrophils, lymphocytes, platelets, complement, and Hageman factor leading to complex interactions of cells and mediators. It is the progression of this inflammatory response with neutrophil influx that is ultimately responsible for the pulmonary injury. Leukotoxin is a major virulence factor of P. haemolytica that allows it to survive by destroying phagocytic cells. At subcytolytic concentrations it may also enhance the inflammatory response by activating cells to produce mediators and release reactive oxygen metabolites and proteases.     

Characteristics of cytotoxic cells induced by Toxoplasma lysate antigen in mouse spleen.

Spleen cells from Toxoplasma lysate antigen (TLA)-sensitized BALB/c mice showed the strong cytotoxic activity against both natural killer (NK)-sensitive cells (YAC-1 and RL male-1) and NK-insensitive cells (P-815), when incubated with TLA or recombinant human IL-2 (rhIL-2). The increment of TLA concentration in culture medium increased the cytotoxic activity. Treatment of effector cells; spleen cells from TLA-sensitized mice incubated with TLA, with anti-asialo GM1 or anti-Thy-1 plus complement inhibited the cytotoxic activity of effector cells, whereas treatment with anti-mouse Lyt-2.2 serum plus complement had no effect on the cytotoxic activity. Treatment of spleen cells from TLA-sensitized mice with anti-asialo GM1 and/or anti-Thy-1 plus complement inhibited cytotoxic activities of effector cells. These results suggested that spleen cells sensitized with TLA both in vivo and in vitro were asialo GM1 positive and Thy-1 positive, and the majority of cytotoxic cells induced by TLA were similar to lymphokine-activated killer (LAK) cells induced by IL-2.     

Effects of Pasteurella haemolytica A1 leukotoxin on bovine neutrophils: degranulation and generation of oxygen-derived free radicals.

To further define the role of Pasteurella haemolytica A1 leukotoxin in the pathogenesis of bovine pneumonic pasteurellosis, its in vitro effects on bovine neutrophils were investigated. Leukotoxin-containing culture supernatant, from P. haemolytica, stimulated a neutrophil respiratory burst as measured by the generation of oxygen-derived free radicals O2- and H2O2. This effect was immediate because preincubation of neutrophils with the culture supernatant for 5 min or longer substantially suppressed this respiratory burst. This suppression was due to cytolysis of the neutrophils. Prolonged incubation of neutrophils with the same culture supernatant caused further cytolysis and degranulation. Heat-inactivated P. haemolytica culture supernatant that had lost its cytotoxic properties failed to stimulate respiratory burst by neutrophils. Furthermore, the respiratory burst, cytolysis and degranulation were abrogated only by leukotoxin-neutralizing monoclonal and polyclonal antibodies, but not by antibodies against the lipopolysaccharide. These studies show that the leukotoxin component in the culture supernatant was responsible for the generation of oxygen-derived free radicals and proteolytic enzymes from neutrophils which may participate in direct lung injury.     

Dietary selenate versus selenite for cattle, sheep, and horses.

Food and Drug Administration regulations currently permit addition of .3 mg of Se per kilogram of diet for chickens, turkeys, ducks, swine, sheep, and cattle. However, field reports indicate that this level may not be adequate for ruminants in all situations. Because sodium selenite is the most common supplemental form and is known to be readily absorbed to particles or reduced to insoluble elemental Se or selenides in acid, anaerobic environments, studies were conducted with dairy cattle, sheep, and horses fed sodium selenate to determine whether Se from this source was more bioavailable than Se from sodium selenite. A 2-wk period of no Se supplementation was followed by 49 or 56 d of Se supplementation at .3 mg/kg of dietary DM. Serum Se concentrations and glutathione peroxidase (GSHPx) activities measured initially and periodically thereafter revealed no difference between Se forms in sheep and horses and only a small (P less than .05) advantage for selenate in supporting serum Se concentration in dairy cattle. Selenium concentrations in skeletal muscle and liver of sheep were not different between Se forms. Serum Se, but not GSHPx, increased with time, and .3 mg of supplemental Se per kilogram of dietary DM from either sodium selenate or sodium selenite supported normal serum Se concentrations in sheep, dairy cattle, and horses.