Half-life,clearance and production rate for oxytocin in cattle during lactation and mammary involution I

Basal concentration, production rate, metabolic clearance rate and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for oxytocin were measured in Holstein cows at three lactational stages and during mammary involution. At each lactational stage, oxytocin was given intravenously at .5 IU/min or 1.0 IU/min for 60 min. Infusions were preceded by priming. During involution, the high dose was used. Mean basal concentrations of oxytocin ranged from 8.7 to 21.4 uU/ml. Mean basal values at early, middle, late lactation and involution were 17.57, 12.33, 15.15, 21.13 uU/ml, respectively and differed significantly. The mean “rapid” $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ was 3.87 ± .1 min. Early, middle, late lactation and involution $\text{T}\text{1}\text{2}\text{s}$ were 4.2, 3.7, 4.0 and 3.5 min, respectively. The rapid $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ was not affected by lactational stage. The mean “slow” $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ was 25.53 ± 1 min. Early lactation and dry period means differed significantly. The overall mean oxytocin clearance rate was 8.41 ± .1 ml/kg^·min. Clearance rate declined through lactation and into the dry period. Mean values of 9.3, 8.8, 7.8 and 7.1 ml/kg^·min were obtained at early, middle, late lactation and involution, respectively. Clearance rates at late lactation and involution differed significantly from one another and from the early and middle stages. Mean entry rates for oxytocin at early, middle, late lactation and involution were 168.79, 106.03, 111.1 and 146.8 uU/kg^·min, respectively. Measurements at early lactation and involution were greater than values for middle and late lactation. To summarize, basal oxytocin concentrations can be measured in cows that are lactating or undergoing mammary involution and changes in concentrations during lactation are related to hormone production (entry rate) and metabolic clearance rates.     

Analysis and in vivo assay of B. abortus agglutinating and non-agglutinating antibodies

Studies were made of physicochemical and immunochemical characteristics of Brucella abortus agglutinating and non-agglutinating antibodies in the sera of cattle repeatedly injected with living B. abortus (Strain 1119). Both agglutinating and non-agglutinating antibody were shown to be IgG1, and by immunodiffusion against rabbit anti-cattle gamma-globulin, agglutinating antibody gave a precipitation line of identity with that given by non-agglutinating antibody. Whilst agglutinating antibody increased clearance of antigen from the blood of passively protected mice, non-agglutinating antibody did not enhance clearance. Determination of the spleen infection index in mice pre-treated with agglutinating and non-agglutinating antibody showed that in animals passively immunized with non-agglutinating antibody the number of living (infecting) bacteria was approximately 4 times higher than in the case of agglutinating antibody. The possible potentiation of chronic B. abortus infection by non-agglutinating antibody is discussed.     

A protective antigen for Turkeys purified from a type 1 strain of Pasteurella multocida

A protective antigen was purified from a saline extract of a Type 1 strain of Pasteurella multocida by chromatographic methods, and its chemical and immunological ccharacteristics were studied. Three protein peaks were obtained from crude extract by gel filtration with Sephadex G-200. A bacteria-specific antigen was detected only in the first peak fraction, which, after passing through an immunoadsorbent column to remove any components originating from the growth medium, was adsorbed onto DEAE-cellulose followed by elution with a gradient of NaCl. From the first peak fraction of the gel filtration, 4 protein peaks were obtained, the second and third peaks being the major ones. Carbohydrate/protein ratios of the peak fractions varied from 0.06 to 1.0. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that 2 proteins of molecular weights 44 000 and 25 000 were present in all the fractions. The 4 DEAE-cellulose fractions (DP-1 to DP-4) contained a single antigenically identical material, and induced protective immunity in turkeys against challenge exposure. The second peak fraction from DEAE-cellulose (DP-2) protected turkeys when subcutaneously injected as 2 doses of 10 μg protein with a 14-day interval between doses. The DP-2 fraction induced antibodies in rabbits which formed a single precipitin line against the crude extract. The purified antigen (DP-2) from a Type 1 strain was antigenically distinct from a similar antigen purified from a Type 3 strain; there was no significant cross protection in turkeys between the 2 antigens. These results indicate that protective antigens purified from soluble extracts of a Type 1 or Type 3 strain possess similar physicochemical properties, but that they are immunologically distinct from each other.     

Growth hormone secretion in chicks during dietary calcium deficiency

The role of calcium in the secretion of growth hormone (GH) has been examined in vivo in immature domestic fowl. Chicks reared on a low calcium (0.16% calcium in the feed) diet showed a reduced growth rate, compared with those on a normal (0.86%) calcium diet and had lower basal levels of plasma GH 1, 5, 10 and 15 d after calcium deprivation, but not after 20, 25, 30 or 35 d of calcium deficiency. No consistent changes in the concentration of immunoreactive somatomedin C were observed during calcium restriction. In both the control and low calcium fed birds the plasma concentrations of GH were elevated by the intravenous administration of human pancreatic GH releasing factor (hpGRF) and by thyrotropin releasing hormone (TRH). The GH responses to these provocative stimuli were not reduced in magnitude by calcium deficiency. It is suggested, therefore, that the effect of calcium deprivation on the secretion of GH is mediated via the reduced release of stimulatory hypophysiotrophic factors from the hypothalamus.

Pharmacological alterations in calcium status also suggest that calcium deprivation inhibits GH secretion. Plasma concentrations of GH were acutely depressed in young chicks following the administration of a calcium chelator (ethylene diaminotetraacetic acid) a calcium channel blocker (verapamil) and after calmodulin inhibition (by chlordiazapine and trifluorpenazine administration). These data therefore demonstrate the importance of calcium in the stimulation of GH secretion in the domestic fowl.     

Progesterone production in granulosa cells of the domestic fowl: effects of incubation media, pH, cell density and some other factors

The objective of this study was to determine the optimal conditions for the short term incubation of chicken granulosa cells. Compared to mechanically-dispersed cells, collagenase-treatment yielded granulosa cells of greater viability and responsiveness to ovine LH (oLH) stimulation. The rate of progesterone secretion by enzyme-dispersed chicken granulosa cells was subsequently compared in five different culture media during incubation periods of up to 24 hr. Under room air as the gas phase, Medium 199 (M199) containing Hank's salts and Ham's F-12 medium (F-12) were the most effective, whereas Krebs-Ringer bicarbonate-buffered glucose solution (KRBG) and Dulbecco's medium were the poorest. When pH and the ionic strength of KRBG was maintained by continuous gassing with O₂:CO₂ (95:5), progesterone production was similar to that obtained with Hepes-buffered M199. The pH optimum was found to be 7.4, although within the range of 6.6–8.5 granulosa cells remained responsive to LH stimulation. The optimal cell density was observed to be 1 × 10⁴ to 5 × 10⁵/ml. Although time course studies showed that both basal and stimulated progesterone production peaked by about 12 hr of incubation regardless of the media composition, the amounts released were significantly greater in M199 and F-12 during more prolonged (up to 24 hr) incubations. Glucose, a key medium ingredient for hormone-stimulated steroidogenesis, could be replace by pyruvate. On the other hand, lactate was inhibitory. It is concluded that the mature ovarian follicles of the domestic fowl are an excellent source of pure granulosa cells that can be obtained in high yield after a brief treatment with collagenase. These cells remain viable up to 24 hr and continue to produce large amounts of progesterone in response to LH when incubated in an appropriate medium and at optimal cell density.     

中山市四旁绿化调查与分析

以典型三阶抽样和一阶抽样方法,建立调查样本,数据推算面积结果,全市现已完成绿化总面积8236hm^2,化树种丰富,城区、乡镇和道路的绿化投入大、起点高、对中山市乡镇和自然村四旁绿化进行抽样调查。以调查人均公共绿地48．27m^2。调查结果表明,中山市四旁绿配置合理,管护措施得力,绿化美化效果好。     

全钒液流电池运行条件对其性能影响的数值模拟研究

建立了适合全钒液流电池计算的电化学模型,并对部分电化学模型进行了简化;利用建立起来的电化学模型,数值模拟了在一个充放电循环过程中钒离子浓度、质子浓度、电流、温度与电解液流量对电堆性能的影响,数值模拟表明:电流越大,电堆的充放电时间越短,电堆的电压效率与能量效率越小;总钒离子浓度越大,电堆的充放电时间越长,电堆的电压效率与能量效率也越大;硫酸浓度、温度和电解液流量,不影响电堆的充放电时间,但影响电堆的电压效率与能量效率。     

切削速度对Inconel 718加工表面完整性的影响

随着机械加工对于更快的材料去除率和更好的表面完整性的需求,高速切削高强度镍基高温合金Inconel 718的应用是必然的发展趋势。通过赛阿龙(Sialon)陶瓷刀具高速铣削Inconel 718试验,研究切削速度对Inconel 718加工表面完整性的影响规律。结果表明,随着切削速度的提高加工表面完整性越来越好,在试验条件范围内,当切削速度达到1 400 m/min时,获得的表面完整性最好。     

哈尔滨交通干道两侧土壤重金属潜在生态危害评价

以哈尔滨市公滨路、香成路、哈-腰堡路3条交通干道两侧的土壤为主要研究对象,用原子吸收光谱法分析土壤中重金属Cu、Cd、Pb、Zn、Cr、Ni含量,采用松嫩平原土壤重金属背景值作为参比值,应用地质累积指数法和潜在生态危害评价法对重金属污染进行评价,以研究公路交通引起的土壤中重金属污染以及潜在的生态危害。结果表明:研究区土壤中Cu、Cd、Pb、Zn、Cr、Ni的含量显著高于背景值。Cd和Pb为中等污染,土壤对重金属元素的污染程度:ZnPbCdCrNiCu。污染源主要为机动车燃料、轮胎、机械中所含微量重金属成分。     

Effect of microwave irradiation on composition,structure and properties of rice (Oryza sativa L.) with different milling degrees

Effects of microwave irradiation on composition, structure, thermal and storage properties of rice with different milling degrees were investigated. Microwave irradiation partially inactivated the lipase and lipoxidase, damaged thiamine, and created puffed rice. In addition, the transition temperatures (T_o and T_P) of rice were shifted to higher temperatures, and the enthalpy of gelatinization decreased after irradiation. The effect was more obvious when the power of microwave was increased. Microstructure analysis showed that stress cracks and some “explosion” were created in rice kernels after microwave irradiation. Storage property analysis indicated that free fatty acid content of all rice samples increased gradually in the process of storage. Microwave irradiation reduced the release of free fatty acids during storage. The higher the power, the lesser the free fatty acids generated. The results suggested that microwave irradiation was potentially applicable for improving storage properties of brown and milled rice.