Sequence comparison and transmission of <Emphasis Type="Italic">Blackcurrant reversion virus</Emphasis> isolates in black,red and white currants with black currant reversion disease and full blossom disease symptoms

We collected samples from black, red and white currants showing symptoms of blackcurrant reversion disease (BRD) and full blossom disease (FBD), cultivated in the Czech Republic. Blackcurrant reversion virus (BRV) was detected in all symptomatic plants. After amplification, a substantial part of the 3′ non-translated region (3′-NTR) of RNA2 of 15 new isolates of BRV was sequenced and compared with sequences available in the literature and GenBank. We did not find significant sequence diversity among isolates associated with either FBD or BRD. BRV was graft-transmitted from FBD infected red currant to black currant where symptoms of BRD were observed. Further sequence analysis of BRV isolates resulted in a phylogenetic tree with four branches, each consisting of six to nine isolates. No correlation with geographic origin was visible on the tree as isolates from various countries occurred in all four branches. We also found no correlation between the host and the topology of the tree: most of black currant isolates occurred in branches 3 and 4, but also occurred in branches 1 and 2. Only one white currant and one red currant isolate occurred in branches 3 and 4, respectively. The sequence identity of the Czech isolates in this region ranged from 91.9 to 99.8%. The 17 plant species growing within and in the close vicinity of the BRD-infested plantation were tested negative for BRV by RT-PCR as natural hosts of BRV. BRV was successfully transmitted by mechanical inoculation from black currant to Nicotiana occidentalis and N. tabacum cv. Xanthi, the latter being a new host for BRV. The infection was confirmed by PCR and sequencing.     

2Ai-2染色体在小麦部分同源染色体代换背景中的遗传

用中间偃麦草2Ai-2染色体特异的EST-PCR标记检测5个小麦-中间偃麦草二体异代换系(包括端体代换系)与普通小麦中国春(CS)杂交后代群体,研究外源染色体2Ai-2通过杂种向后代的传递率及其结构变异,并用基因组原位杂交进行验证。结果表明,第二部分同源群不同染色体代换背景对外源染色体传递的影响不同,在2B代换系的杂种中外源染色体或片段显示优先传递,而在2D代换系的杂种中其传递力则较低,2B代换背景更有利于2Ai-2染色体或片段的传递;外源染色体在杂种后代传递过程中会发生变异,在多数组合中,变异出现在着丝粒处;与短臂相比,外源染色体长臂更容易在世代中丢失;端体代换系中的外源染色体端体在杂种后代传递过程中容易丢失,且也会发生结构变异。基因组原位杂交结果证明了分子标记跟踪外源染色体的可靠性。     

Proliferation and transmission patterns of <Emphasis Type="Italic">Pasteurella multocida</Emphasis> B:2 in goats

This report describes the proliferation and transmission patterns of Pasteurella multocida B:2 among stressful goats, created through dexamethasone injections. Thirty seven clinically healthy adult goats were divided into three groups consisted of 15 goats in group A, 11 goats in group B and the remaining 11 in group C. At the start of the study, all goats of group A were exposed intranasally to 1.97 × 10¹⁰ CFU/ml of live P. multocida B:2. Dexamethasone was immediately administered intramuscularly for 3 consecutive days at a dosage rate of 1 mg/kg. The exposed goats were observed for signs of HS for a period of 1 month. At the end of the 1-month period, 11 goats from group B were introduced into and commingled with the surviving goats of group A before all goats from both groups were immediately injected intramuscularly with dexamethasone for 3 consecutive days. The treatment with dexamethasone was then carried out at monthly interval throughout the 3-month study period. Goats of group C were kept separately as negative control. Three surviving goats from each group were killed at 2-week interval for a complete post-mortem examination. Two (13%) goats of group A were killed within 24 hours after intranasal exposure to P. multocida B:2 while another two (13%) goats from the same group were killed on day 40, approximately 10 days after the second dexamethasone injection. All four goats showed signs and lesions typical of haemorrhagic septicaemia. Bacteraemia was detected in 3 goats of group A that were having rectal temperature higher than 41°C. The P. multocida B:2 isolation pattern was closely associated with dexamethasone injections when significantly (p < 0.05) higher rate of isolations from both groups were observed after each dexamethasone injection. Transmission of P. multocida B:2 from goats of group A to group B was successful when P. multocida B:2 was isolated from goats of group B for a period of 28 days. There was a strong correlation between dexamethasone injections, rate of bacterial isolation and serum cortisol level. The IgG level showed an increasing trend 2 weeks after exposure to P. multocida B:2 and remained high throughout the study period.     

Transmission of classical swine fever virus within herds during the 1997-1998 epidemic in The Netherlands

In this paper, we describe the transmission of Classical Swine Fever virus (CSF virus) within herds during the 1997–1998 epidemic in the Netherlands. In seven herds where the infection started among individually housed breeding stock, all breeding pigs had been tested for antibodies to CSF virus shortly before depopulation. Based upon these data, the transmission of CSF virus between pigs was described as exponential growth in time with a parameter r, that was estimated at 0.108 (95% confidence interval (95% CI) 0.060–0.156). The accompanying per-generation transmission (expressed as the basic reproduction ratio, R₀) was estimated at 2.9. Based upon this characterisation, a calculation method was derived with which serological findings at depopulation can be used to calculate the period in which the virus was with a certain probability introduced into that breeding stock. This model was used to estimate the period when the virus had been introduced into 34 herds where the infection started in the breeding section. Of these herds, only a single contact with a herd previously infected had been traced. However, in contrast with the seven previously mentioned herds, only a sample of the breeding pigs had been tested before depopulation (as was the common procedure during the epidemic). The observed number of days between the single contact with an infected herd and the day of sampling of these 34 herds fitted well in the model. Thus, we concluded that the model and transmission parameter was in agreement with the transmission between breeding pigs in these herds.

Because of the limited sample size and because it was usually unknown in which specific pen the infection started, we were unable to estimate transmission parameters for weaned piglets and finishing pigs from the data collected during the epidemic. However, from the results of controlled experiments in which R₀ was estimated as 81 between weaned piglets and 14 between heavy finishing pigs (Laevens et al., 1998a. Vet. Quart. 20, 41–45; Laevens et al., 1999. Ph.D. Thesis), we constructed a simple model to describe the transmission of CSF virus in compartments (rooms) housing finishing pigs and weaned piglets. From the number of pens per compartment, the number of pigs per pen, the numbers of pigs tested for antibodies to CSF virus and the distribution of the seropositive pigs in the compartment, this model gives again a period in which the virus most probably entered the herd. Using the findings in 41 herds where the infection started in the section of the finishers or weaned piglets of the age of 8 weeks or older, and of which only a single contact with a herd previously infected was known, there was no reason to reject the model. Thus, we concluded that the transmission between weaned piglets and finishing pigs during the epidemic was not significantly different from the transmission observed in the experiments.     

西气东输管道工程与我国天然气工业发展

西气东输管道工程是一项世界级的宏大工程，该工程作为我国西部大开发标志性工程之一，不但有利于加快新疆以及我国西部地区经济的发展，促进我国能源结构的调整，有效治理大气污染，促进长江三角洲地区的经济快速发展，而且标志着我国天然气工业发展新时期的到来，极大地带动了整个天然气工业的全面发展，是一个非常重要而具有划时代意义的里程碑，从四个方面论述了西气东输管道工程对我国天然气工业发展的重要意义。     

机械传动系统扭矩及功率的动态测试（一）

针对目前林木及运输机械传递扭矩估算与实测值(均值)相差悬殊，本从实时检测动态扭矩及功率入手，提出中低速大扭矩及功率的数据采集方法。     

脱毛剂量环磷酰胺对貉皮肤组织及毛被脱换的影响

用脱毛剂量（２８ｍｇ／ｋｇ体重）的环磷酰胺。对春季换毛前的貉（Ｎｙｃｔｅｒｅｕｔｅｓ ｐｒｏｃｙｏｎｏｉｄｅｓ）进行肌注。研究其脱毛机理。在注药后的不同时间,取其背部皮肤样品少许,分别固宇下１０％的福尔马林和２％的戊二醛中。采用常规的石蜡和超薄切片法制片。对其毛皮、毛被及皮脂等影响的组织进行观察。结果表明,注药后第１天毛囊结构已发生变化;第７天针毛囊和毛球角质经;第１５天毛囊结构基本正常。毛囊上升     

Back-calculation method shows that within-flock transmission of highly pathogenic avian influenza (H7N7) virus in the Netherlands is not influenced by housing risk factors

To optimize control of an avian influenza outbreak knowledge of within-flock transmission is needed. This study used field data to estimate the transmission rate parameter (β) and the influence of risk factors on within-flock transmission of highly pathogenic avian influenza (HPAI) H7N7 virus in the 2003 epidemic in The Netherlands. The estimation is based on back-calculation of daily mortality data to fit a susceptible-infectious-dead format, and these data were analysed with a generalized linear model. This back-calculation method took into account the uncertainty of the length of the latent period, the survival of an infection by some birds and the influence of farm characteristics. After analysing the fit of the different databases created by back-calculation, it could be concluded that an absence of the latency period provided the best fit. The transmission rate parameter (β) from these field data was estimated at 4.50 per infectious chicken per day (95% CI: 2.68–7.57), which was lower than what was reported from experimental data. In contrast to general belief, none of the studied risk factors (housing system, flock size, species, age of the birds in weeks and date of depopulation) had significant influence on the estimated β.     

Inhibitory action of intravenously administered ammonium acetate on the motility of the rumen in sheep

Summary

The effect of 60 minutes’ intravenous infusions, before morning feeding, of ammonium acetate (18.6 micromole/min/kg of body weight) and ammonium acetate with propranolol (11 μg/min/kg of body weight) on the ruminal motility of sheep was examined. Ammonia has an adrenaline‐like action therefore propranolol, a beta‐receptor blocking agent, was administered in order to eliminate the possible effect of adrenaline on ruminal motility. The contractions of the dorsal sack of the rumen were registered by means of the balloon method, with the gauge inserted through the rumen fistula. The infusion of ammonium acetate caused an increase of the ammonia concentration in the blood to 0.6 mmolel/at the end of 60 minutes’ infusion. Already during the first 5 minutes of the intravenous infusion of ammonium acetate there was a decreased frequency of ruminal contractions, which was observed throughout the infusion. After the infusion there was a radical decrease of the concentration of ammonia in the blood, and at the same time an increase in the frequency of rumen contraction was observed.

Blocking of the beta‐adrenergic receptors by propranolol did not eliminate the inhibiting action of ammonium ion on rumen motility. The infusion of the ammonium acetate caused an increase of adrenaline and glucose concentration. This response was eliminated by propranolol in the case of adrenaline but not glucose. It is assumed that the action of ammonium ion on the rumen motility is derived primarily by the central nervous system.     

太行山干旱低山丘陵区林草复合系统能量环境特征研究

研究了太行山干旱低山丘陵区林草复合系统能量环境特征,结果表明复合系统年太阳总辐射量为49868.65GJ.hm-2.a-1,光合有效辐射为24244.67GJ.hm-2.a-1,复合系统的平均反射率为22.5%,高于单作苹果系统,平均透射率为18.0%,低于单作苹果系统,说明林草复合系统可以截获和利用更多的光能。