THE DISTRIBUTION OF LEAF AREA AND LIGHT INTENSITY WITHIN WHEAT CROPS DIFFERING IN ROW DIRECTION, ROW SPACING AND RATE OF SOWING; A CONTRIBUTION TO THE STUDY OF UNDERSOWING PASTURE WITH CEREALS

The distribution of leaf area and light intensity within wheat crops differing in row direction, row spacing and rate of sowing is described. Regardless of the manner of planting, 75% of the total leaf area was found within a band 31/2 in. wide, centred on the centre of the row. Light penetration within crops spaced at 14 in. was greater than within those spaced at 7 in. Light penetration within rows running N.–S. was more uniform and higher, particularly around noon, than within rows running E.-W. Within N.-S. rows the position midway between rows received the highest amount of light, but light decreased on either side until it was least beneath the rows. Within E.-W. rows at 14 in. spacing, maximum light was recorded at 101/2 in. on the southern side of a row, decreasing progressively as the row was approached.     

The protein,non-protein and total nitrogen inSolanum tuberosum,ssp.andigena potatoes

Total protein estimated from 80% ethanol insoluble nitrogen in residue ofS. tuberosum, ssp.andigena tubers agreed well with results obtained by Potty method and estimation of non-dialyzable nitrogen. The method is simple, rapid and applicable for screening large numbers of samples. Dry matter, total nitrogen, protein nitrogen and non-protein nitrogen were analyzed for 50 clone samples harvested in Huancayo, Peru, and correlations between the various constituents are statistically analyzed and discussed. An increase in total nitrogen with an increase of protein nitrogen was observed. Clones with higher dry matter normally showed lower % of non-protein nitrogen. The percentage of protein nitrogen to total nitrogen varied from 40 to 74% in the 50 clone samples and clonal differences in protein production were evident.     

UV‐B radiation constrains the photosynthesis of Quercus robur through impacts on the abundance of Microsphaera alphitoides

Quercus robur saplings were exposed at an outdoor facility in the UK to supplemental levels of UV‐B radiation (280–315 nm) under arrays of cellulose diacetate‐filtered fluorescent lamps which also produced UV‐A radiation (315–400 nm). Saplings were also exposed to supplemental UV‐A radiation under arrays of polyester‐filtered lamps and to ambient levels of solar radiation under arrays of unenergized lamps. The UV‐B treatment was modulated to maintain a 30% elevation above the ambient level of erythemally weighted UV‐B radiation. Naturally occurring infections by oak powdery mildew (Microsphaera alphitoides) were more abundant, and developed more rapidly, on lammas leaves of saplings which were exposed to treatment levels of UV‐B radiation than on leaves of saplings exposed to supplemental UV‐A or to ambient levels of solar radiation over 12 weeks in summer and autumn 1996. An analysis of leaf photosynthetic capacities revealed that M. alphitoides infection reduced the quantum efficiency of photosystem (PS) II by 14% at moderate irradiance. Although there was no direct effect of UV‐B radiation on PSII photochemistry, exposure of saplings to supplemental UV‐A radiation under polyester‐filtered lamps resulted in a 17.5% decrease in PSII quantum efficiency, compared with saplings exposed to ambient solar radiation. The results from our study suggest that photosynthesis of Q. robur may be constrained by exposure to UV‐B radiation in the natural environment through impacts on the abundance of M. alphitoides.     

Growth,dry matter production,phenotypic plasticity,and nutritive value of three natural populations of Dactylis glomerata L. under various shading treatments

Dactylis glomerata L. is a widespread perennial grass species, which has been reported to be adapted to shaded conditions. Its populations thrive in a variety of environments. However, little information is available concerning the comparative response of its natural populations from contrasting environments under the reduced light intensity conditions that exist in silvopastoral systems. The objective of the present study was to estimate the comparative ability of three populations of D. glomerata from northern, central and southern Greece to grow under full sun, 60 % shade and 90 % shade in terms of their growth characteristics, phenotypic plasticity, dry matter production and nutritive value. Shade reduced tillering and dry matter production, increased tiller height and modified leaf characteristics. Under shade fewer leaves were grown simultaneously on the same tiller, but these were longer and thinner compared to full sun. Differentiation in response to shade among the populations examined of D. glomerata was observed mainly for leaf characteristics. The population from Pertouli (central Greece) responded better, particularly to moderate shade as it had a higher leaf area, longer leaf and higher dry matter production, compared to the others. Evidence for adaptive phenotypic plasticity to moderate shade was suggested only for this population. Additionally, Pertouli had higher nutritive value compared to Taxiarchis (northern Greece) and Crete (southern Greece) under shade. The divergent responses of natural populations of D. glomerata could justify breeding germplasm with enhanced shade tolerance.     

Identification of bovine viral diarrhea virus type 1 in yaks (Bos poephagus grunniens) in the Himalayan region

Since cattle are widely infected by bovine viral diarrhea virus (BVDV) in India, we searched for pestivirus infection in yaks. Of 71 pure and crossbred yaks from Himalayan region, pestivirus antigen was detected by Ag-ELISA in three animals. Pestivirus in leukocyte and cell culture isolated virus samples originating from positive yaks was also confirmed by RT-PCR using panpestivirus specific primers selected from 5'-untranslated region (5' UTR). The 5' UTR, N(pro) and E2 regions were sequenced and used for genetic typing. Phylogenetic analysis revealed that pestiviruses detected in three Himalayan yaks were similar genetically, belonging to BVDV-1. Antigenic characterisation of yak pestivirus also confirmed the typing as BVDV-1. This is the first report on the identification of BVDV type 1 in yaks.     

Pharmacokinetics of topically applied ciprofloxacin in tears of mesocephalic and brachycephalic dogs

OBJECTIVE: To evaluate the pharmacokinetics of ophthalmic ciprofloxacin in the tear film of normal mesocephalic and brachycephalic dogs. ANIMALS STUDIED: Twenty mesocephalic dogs and 15 brachycephalic dogs. PROCEDURES: Thirty-five microliters of ciprofloxacin were placed on the cornea of both eyes of each dog. Five brachycephalic dogs were used twice. A tear-test strip placed in the ventral cul de sac for 30 s was used to obtain samples. The tear film of each eye was sampled once at eight time-points post administration, resulting in five samples at each time-point. Samples were evaluated using high performance liquid chromatography. Data from the two skull types were compared using the unpaired two-tailed t-test. RESULTS: The mean concentration of ciprofloxacin in the tears of mesocephalic dogs was 192.8 +/- 269.97, 140.6 +/- 91.06, 56.60 +/- 28.47, 13.6 +/- 6.3, 43.25 +/- 59.71, 16.6 +/- 10.62, 15.6 +/- 13.16 and 6.25 +/- 9.84 microg/g at 5, 10, 15, 30 min and 1, 2, 4 and 6 h, respectively. The mean concentration of ciprofloxacin in the tears of brachycephalic dogs was 272.6 +/- 106.21, 144.4 +/- 142.32, 131.2 +/- 147.07, 75 +/- 80.07, 40.8 +/- 30.35, 35 +/- 21.98, 52.75 +/- 51.87 and 8.6 +/- 12.10 microg/g at 5, 10, 15, 30 min and 1, 2, 4 and 6 h, respectively. There was no statistical difference in tear concentration at any time-point between skull types. CONCLUSIONS: Topical application of ciprofloxacin resulted in a mean tear concentration of ciprofloxacin that remained above the MIC(90) levels for most pathogenic bacteria for 6 h in normal mesocephalic and brachycephalic dogs.     

Diphtheroid colitis in a Boa constrictor infected with amphibian Entamoeba sp

A female boa (Boa constrictor) from a zoological collection was submitted for necropsy after sudden death. Prominent pathological findings included a diphtheroid colitis, endoparasitism, focal pneumonia and inclusion bodies typical for inclusion body disease (IBD). In the colon entamoebae were identified, which differed in size and distribution from Entamoeba invadens. Gene sequence analysis of the 18S ribosomal RNA revealed 100% similarity with an Entamoeba species from the African bullfrog (Pyxicephalus adspersus), probably Entamoeba ranarum. The snake was possibly immunosuppressed, and the source of infection remains unclear. This is the first report of an infection with an amphibian Entamoeba species associated with colitis in a snake.     

猪生物医学模型的基因组学研究进展

本综述对猪生物医学模型的多样性和基因组学在这些模型持续开发中的重要性作了一个简要的更新。由于猪在体型大小、生理条件、器官发育和疾病发展等方面与人类相似,因而已作为一种重要的哺乳动物医学模型为人类所用。将猪作为人类医学模型,可以使研究人员从容不迫地安排研究时间,并可利用普通的人类医学技术对机体内部的血管和器官进行成像处理,且可以采集重复的外周样本,并且在扑杀后可采集复杂的粘膜组织样本。以猪为医学模型,能够利用同窝的猪或克隆猪和转基因猪,因而使比较分析和遗传作图更为容易。以猪作为人类医学的动物模型可获得大量代表各种组织的分化方向明确的细胞系,从而可更加有利于基因表达和药物敏感性的检测。因此,对人而言,猪是一种出色的生物医学模型。由于猪在基因序列和染色体结构上与人类高度同源,因而对基因组应用而言,其不失为一个宝贵的资源。由于目前猪基因组序列已被人类充分掌握,因而有改良型遗传学方法和蛋白质组学方法可供这些比较分析方法所利用。本综述将论述用于探测这些模型的基因组学方法中的某些方法,并将重点介绍黑色素瘤和抗传染性疾病的基因组学研究情况,论述在设计此类研究时应予以考虑的问题。本文最后将对利用基因组学方法开发控制具有最高经济价值的猪病—猪繁殖与呼吸综合征病毒(Porcine Reproductive and Respiratory Syndrome,PRRSV)—新型替代方法的可行性、和将从PRRSV研究中获得的知识应用到人传染性疾病研究中的可行性作简短讨论。