四品种黄牛正常牛体细胞染色体畸变分析

通过淋巴细胞培养对４个黄牛品种共６３头正常牛体细胞染色体的畸变类型和频率进行了观察统计分析。结果表明，蒙古牛，岭南牛和西镇年多倍体细胞出现率分别为４．１２％，４．５７％和５．２１％，平均为４．８７％。多倍体包括三倍体，四倍体和六倍体。结构变异有缺失，染色单体裂隙，染色单体断裂，染色体间隙，染色体断裂和断片几种类型。蒙古牛，秦川牛，岭南牛和西镇牛总的结构变异率分别为２．８７％，２．６５％，１．９４和     

草莓果实的流变特牲及其在贮藏过程中的变化规律

利用自制的应力－应变试验台，对草莓果实的应力－应变特性和蠕变特性进行了测定与研究，建立了草莓果实应力－应变的数学模型，指出了草莓果实的极限屈服点变动范围。同时对草莓在不同贮藏条件下流变特性的变化规律进行了初步的研究，发现草莓的成熟度、贮藏温度及贮藏时间对果实的硬度、屈服应力均有较显著的影响，建立了屈服应力随时间变化的不同阶段的回归方程，可用于预测在相应贮藏条件下的草莓果实的屈服应力。     

Seroprevalence of porcine and human influenza A virus antibodies in pigs between 1986 and 1988 in Hassia

1,268 sera collected from slaughtered pigs in Hassia (FRG) from 1986 to 1988 were tested for antibodies against porcine and human influenza A virus strains using the single radial haemolysis test (SRHT). Antibodies against the porcine strains (subtype H1N1) A/Swine/Arnsberg/1/81, A/Swine/Iowa/15/30 and A/New Jersey/7/76 were detected in 411 (32.4%), 318 (25.1%) and 304 (24.0%) of sera, respectively. Up to 1988 a slight increase (10%) in the seroprevalence to A/Swine/Arnsberg/1/81 was noticed, whereas the results obtained with the other strains showed little variation. Antibodies against the human H1N1 strain A/Singapore/6/86 were only found in sera collected 1987 and 1988 in rates of 1.6% and 3.0%. Serological indication of infections with the human H3N2 strains A/Victoria/1/75, A/Hong Kong/1/68 and A/Philippines/2/82 could be shown in 286 (22.6%), 178 (14.4%) and 135 (10.6%) of the serum samples. Within the three year period the rate of sera positive for antibodies against A/Philippines/2/82 increased from 6.5% to 23.0%, whereas no variation in the rates were found using the other H3N2 strains. Antibodies simultaneously against porcine (H1N1) and human (H3N2) virus strains were detected in 9.9% of all sera tested.     

Use of cyproterone acetate to lower circulating corticosterone and its effects on lymphocytes in domestic fowl

Chickens were given daily injections of cyproterone acetate (CA) and the effects on plasma corticosterone, bodyweight, weights of the adrenals and lymphoid organs, numbers of circulating peripheral blood lymphocytes and their proliferation in the presence of lectins, concanavalin A (Con A) and phytohaemagglutinin (PHA), were investigated. Five daily doses of 10 or 30 mg CA kg-1 bodyweight each week over a three-week period caused a decrease in weight gain and a reduction in the relative weights of the bursa and thymus but not the spleen. There was a small decrease in the adrenals after treatment with 10 mg CA kg-1. When daily injections of CA were given over a seven-day period doses of 6 and 10 mg CA kg-1 bodyweight caused a significant (P less than 0.05) decrease in plasma corticosterone concentration after four days. However, after eight daily injections of CA a single injection of corticotrophin (10 iu ACTH kg-1) increased circulating corticosterone indicating CA had not completely blocked adrenal synthesis. CA had no effect on numbers of circulating peripheral blood lymphocytes or their ability to proliferate in the presence of Con A or PHA. The results indicate that CA is effective in lowering circulating corticosterone in the fowl but this did not affect the numbers or responsiveness of peripheral blood lymphocytes.     

Comparison of media to isolate Staphylococcus aureus from teat skin and milking unit liners.

Four procedures were compared for isolation of Staphylococcus aureus from swabbing solutions of teat skin and milking unit liners from commercial dairies. In 2 procedures, 0.1 ml of swabbing solutions were added to either 5 ml Vogel-Johnson or Baird Parker broth media and enriched at 37 degrees C, 4 h. Following enrichment, 0.1 ml culture was transferred to modified Baird-Parker agar and incubated at 37 degrees C, 48 h. In the other 2 procedures, 0.1 ml of swabbing solution was directly placed on either blood or modified Baird-Parker agar plates and incubated at 37 degrees C 48 h. Combining results from all methods, Staphylococcus aureus were isolated from 72 of 913 (7.9%) skin samples, and 34 of 268 liners (12.6%). On average, 43.1% (31/72) of the S. aureus isolates were found by the enrichment in liquid Vogel-Johnson procedure. The average isolation percentage for other methods ranged from 19.4% to 25.0%. Isolation of S. aureus from milking unit liner or teat skin swabbing solutions was approximately twice as likely after enrichment in Vogel-Johnson liquid media as opposed to other methods of isolation. This indicates that enrichment in Vogel-Johnson liquid media improved recovery of S. aureus from swabbing solutions.     

负刚度的工作原理及应用初探

This paper deals with the vibration isolation principle of a system with a negative stiffness spring and the energy analysis for this system.As an application of the method, an example of vibration systems with equal frequencies is given. It shows that th     

Growth patterns of two lines of Angus cattle selected using predicted growth parameters.

Linear functions of body weight and condition score at weaning and 18 mo of age were used to predict the mature weight (A) and maturing rate (k) parameters of an asymptotic growth model of Angus cows at the Subtropical Agricultural Research Station, Brooksville, FL. From 1981 through 1988 a heavy-mature-weight line (Line A) and a rapid-maturing line (Line K) were selected based on predicted A and k values. Linear contrasts (A-K) of least squares means for weight at fixed ages indicated that the weight difference between lines increased from birth to maturity during the period of the study. Animals from Line A were heavier (P less than .01) at all ages. A negative response in maternal ability, relative to increased growth potential of their calves, seems to have occurred in the cows of Line A. Mature weight was reached at approximately 4.5 yr of age in Line K and at approximately 5.5 yr in Line A. Brody's three-parameter and Richards' four-parameter functions were fitted to 2,855 quarterly weights of cows, from birth to 6.5 yr of age, to estimate the average growth curve for each line. Brody's model gave better estimates of weights from 18 mo to maturity, but the asymptotic residual mean squares were slightly higher because early weights were overestimated. Linear and nonlinear regression analyses of weight-age data and comparisons of degree of maturity at different premature ages showed differences in the growth patterns of the two lines selected for early predicted values of A and k.     

Transforming growth factor type beta (TGF-beta) and adipogenesis in pigs

The present study was performed on s.c. adipose tissue of fetal pigs at 35 to 110 d of gestation to examine the distribution of TGF-beta-positive cells, to localize TGF-beta immunoreactivity at the cellular level using electron microscopy (EM), and to determine the effect of TGF-beta on primary cultures of pig adipose tissue cells. Tissues for EM were fixed and embedded in LR white resin. Sections then were incubated with a polyclonal antibody specific for TGF-beta and TGF-beta was located using 20 nm colloidal gold conjugated second antibody. Tissues were fixed and embedded in paraffin for localization of TGF-beta at the light microscope (LM) level. Tissues were incubated with anti-TGF-beta followed by localization using biotinylated second antibody. Using LM, only a few cells stained positively for TGF-beta within developing blood vessels at 35 d. By 50 d, more TGF-beta-positive cells were associated with forming capillary networks. Between 70 d and 110 d, positively stained adipocytes usually were clustered around blood vessels. Cells surrounding hair follicles stained positive for TGF-beta between 90 to 110 d. Electron microscopy revealed TGF-beta labeling within fat cells. Fibroblasts and endothelial cells did not exhibit TGF-beta immunoreactivity. The addition of TGF-beta to primary cultures of s.c. adipose tissue cells from newborn pigs prevented lipid filling in fat cells. This effect was dose-dependent, with half-maximal inhibition occurring at 3 pM maximum inhibition occurred at 40 pM. These results indicate that TGF-beta may regulate angiogenic activity and lipid filling in s.c. adipose tissue of fetal pigs. Although TGF-beta was present in adipocytes and in cells associated with developing capillary networks, the physiological role of TGF-beta during early adipose tissue development is not known.     

Selective measurement of lipoprotein lipase and hepatic triglyceride lipase in heparinized plasma from horses.

Affinity chromatography on heparin sepharose was used to identify 2 lipolytic enzymes in heparinized plasma from horses. One enzyme was typical of hepatic triglyceride lipase (HTGL), because it was resistant to inactivation by high concentrations of NaCl, and it did not require the addition of serum for activity. The other enzyme was identified as lipoprotein lipase (LPL), because of its inactivation at NaCl concentrations in excess of 0.2M, and its dependency on addition of serum as a source of apolipoprotein C-II activator. The enzymes were purified by 347-(HTGL) and 442- (LPL) fold, with yields of 54 and 58%, respectively. The partially purified enzymes were used to design incubation conditions that gave optimal activities for each enzyme in vitro. A selective assay was then developed for direct measurement of LPL and HTGL activities in heparinized plasma from horses. Analysis of HTGL took advantage of the almost complete inactivation of LPL when serum cofactor was excluded from the assay at the NaCl concentration that gave optimal HTGL activity. Prior incubation of heparinized plasma with sodium dodecyl sulfate to inhibit HTGL was necessary for measurement of LPL, because HTGL retained 67% of its activity at the NaCl concentration required for optimal LPL activity. Activity of each enzyme was measured in heparinized plasma from 12 Shetland ponies. The mean activity +/- SD for LPL was 3.22 +/- 1.04 mumol of fatty acids/ml of heparinized plasma/h (mumol of FA/ml/h. The mean activity for HTGL was 4.9 +/- 1.56 mumol of FA/ml/h. The performance of the assay was assessed by replicate analysis of pools of each enzyme with high and low activities.(ABSTRACT TRUNCATED AT 250 WORDS)