The primary cilium as the cell's antenna: signaling at a sensory organelle   总被引：1，自引：0，他引：1  

Singla V  Reiter JF 《Science (New York, N.Y.)》2006,313(5787):629-633

Almost every vertebrate cell has a specialized cell surface projection called a primary cilium. Although these structures were first described more than a century ago, the full scope of their functions remains poorly understood. Here, we review emerging evidence that in addition to their well-established roles in sight, smell, and mechanosensation, primary cilia are key participants in intercellular signaling. This new appreciation of primary cilia as cellular antennae that sense a wide variety of signals could help explain why ciliary defects underlie such a wide range of human disorders, including retinal degeneration, polycystic kidney disease, Bardet-Biedl syndrome, and neural tube defects.  相似文献   

Ausfilterung von Schwefelverbindungen aus der Luft durch einen Buchenbestand     

B. Ulrich  R. Mayer  P. K. Khanna  J. Prenzel 《植物养料与土壤学杂志》1978,141(3):329-335

Filtering of Sulfur compounds from air by beech forest In a mature beech (Fagus silvatica) forest the amounts of sulfate-S per ha and year in open land precipitation, throughfall, stem flow and seepage in 100 cm soil depth have been measured from 1969 to 1976. From the fluxes measured quantitative data on plant leaching and dry deposition in the form of plant filtering are derived. Dry deposition amounts to 26kg S · ha^?1 · y^?1 and is of the same size as wet deposition (24 kg). The leaching of sulfate takes place only in autumn and amounts to ca. 3 kg S. The acid soil in the range of Al-buffering increases its sulfate storage annually by ca. 17 kg S/ha.  相似文献   

Effect of fertilizer phosphorus on transport of P and other ions through an undisturbed column of an acid brown earth     

B. Mishra  P. K. Khanna 《植物养料与土壤学杂志》1979,142(4):562-569

Application of mono-calcium phosphate (500 kg P/ha) to undisturbed soil columns of an acid brown earth under steady state unsaturated flow conditions (6 mm/day) showed that phosphorus was leached up to a depth of 19.5 cm after 96 days when 4 pore volumes of water were replaced. Among the cations studied, Al < Mg < Mn < Na were lost in that order- the amount of calcium retained was much higher than the amount of cations lost. A significant increase in the concentration of Si in the leachates was observed together with the decrease in H ions. The possible predominant processes occurring in the column have been discussed.  相似文献   

Concentration of lipocalin region of collagen XXVII alpha 1 in the serum of dogs with hemangiosarcoma     

Kirby GM  Mackay A  Grant A  Woods P  McEwen B  Khanna C  Macri J  Hayes MA  Stalker M 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2011,25(3):497-503

Background: Hemangiosarcoma (HSA) is a common malignancy of dogs with characteristic early, aggressive metastasis. Diagnosis of HSA is challenging because of lack of sensitive and specific diagnostic tests. Hypothesis: Specific proteins that are increased in serum of dogs with HSA might represent useful biomarkers of the disease. Animals: Thirty‐four dogs with HSA and 42 healthy dogs from the Ontario Veterinary College Teaching Hospital. Methods: This case‐control study compared serum proteins in dogs with HSA and healthy dogs. Proteins were separated by 2‐dimensional difference gel electrophoresis and identified by liquid chromatography and tandem mass spectrometry. Results: Western blot analysis showed that serum collagen XXVII peptide concentration in serum of dogs with large metastatic HSA burdens (1,488, 231–3,754 DU; median, minimum‐maximum); was, on average, 9.5‐fold higher than in healthy dogs (156; 46–2,101 DU). While concentrations for dogs with osteosarcomas (678; 124–3,251 DU), lymphomas (423; 92–2,777 DU), carcinomas (1,022; 177–3,448 DU), and inflammatory disease were also increased, values were consistently lower than those for HSA. Receiver operating characteristic curves revealed an estimated area under the curve of 83% for HSA cases whereas areas for other neoplastic and nonneoplastic diseases were nondiscriminatory. Serum collagen XXVII peptide concentration before splenectomy (1,350; 1,156–1,929 DU) was reduced after tumor removal (529; 452–562 DU) and chemotherapy but increased in 2 dogs with tumor recurrence (511–945 DU; 493–650 DU). Conclusions and Clinical Importance: Collagen XXVII peptide might be useful for diagnosis and monitoring of advanced HSA.  相似文献   

Effect ofAcacia nilotica on mustard crop     

J. P. Yadav  K. K. Sharma  P. Khanna 《Agroforestry Systems》1993,21(1):91-98

Performance of mustard (Brassica campestris) crop cultivated underAcacia nilotica single tree, grown under irrigated and rainfed situations was studied for plant population and biomass production. Root behaviour of trees and mustard crop under tree canopy and open areas was also studied. Plant density and biomass production of mustard crop declined with increasing tree canopy depth towards tree trunk. There was a 64.58% reduction in biomass production under an irrigated field upto 4 m and cent percent up to 3 m in rainfed fields as compared to per unit mean yield data recorded at 21 m distance from the tree base in an open field. The plant density and biomass production data and root behaviour of both trees and crop showed a close relationship. The plant density and yield of crop tend to increase with the increase in depth of tree roots. Irrigating the mustard field enhances crop yield and plant density in the affected area as compared with the rainfed field.  相似文献   

Carbon and nitrogen in forest soils: Potential indicators for sustainable management of eucalypt forests in south-eastern Australia   总被引：1，自引：0，他引：1  

Peter Hopmans  Jürgen Bauhus  Partap Khanna  Chris Weston 《Forest Ecology and Management》2005,220(1-3):75-87

Soil organic matter (SOM) has been adopted as an indicator of soil fertility based on the rationale that SOM contributes significantly to soil physical, chemical, and biological properties that affect vital ecosystem processes of forests in Australia. A study was undertaken to evaluate the utility of SOM as an indicator of SFM at two long-term experimental sites in native eucalypt forests, including Silvertop Ash (E. sieberi L. Johnson) and Mountain Ash (E. regnans F. Muell.) in Victoria. This study examines the relative contributions made by various sources of carbon in soil profiles (0–30 cm) of forest soils, viz. mineral soil (<2 mm), plant residues, charcoal (>2 mm), and rock fragments (>2 mm). The long-term changes in these fractions in response to management-induced soil physical disturbance and fire (unburnt, moderate and high intensity) were evaluated. After 10 years, carbon levels in the fine soil fraction (soil <2 mm including fine charcoal) were similar across the range of fire disturbance classes in Mountain Ash forest (20–25 kg/m²) and Silvertop Ash forest (7–8 kg/m²). Likewise differences in carbon associated with other fractions, viz. microbial biomass, labile carbon, plant residues and rock fragments were comparatively small and could not be attributed to fire disturbance. Burning increased the charcoal carbon fraction from 5 to 23 kg/m² in Mountain Ash forest and from 1 to 3 kg/m² in Silvertop Ash forest. Taking into account, the percentage area affected by fire, increases in total soil carbon in these forests were estimated at 25 and 7 t/ha, respectively.

The effects of physical disturbance of soils were examined at one site in Mountain Ash forest where soil cultivation was used as site preparation rather than the standard practice of burning of logging residues. Total carbon in soil profiles decreased from 29 to 21 kg/m² where soil disturbance was severe, i.e. topsoil removed and subsoil disturbed. This was mainly due to a decrease in charcoal carbon from 6.8 to 1.7 kg/m² but severe soil disturbance also increased the amount of carbon associated with rock fragments from 1.6 to 3.5 kg/m².

Management-induced fire increased the coarse charcoal content of soil profiles substantially, thus increasing total carbon content as well as the proportion of recalcitrant carbon in SOM. In contrast, there was little change in the carbon content of the fine soil fraction including the labile and biologically active fractions indicating that these SOM fractions most relevant to ecosystem processes showed little long-term impact from soil disturbance and fire. Conventional sampling of the fine soil fraction (<2 mm) only represented between 50% and 70% of total carbon in the soil profiles. In contrast, total nitrogen in this fraction represented between 75% and 90% of the nitrogen in soil profiles and was less affected by changes in the contributions of N made by coarse fractions. Monitoring of soil N rather than C as an indicator of soil fertility and SFM may be more appropriate for forest soils with significant charcoal content.  相似文献   

Hot water extractable C and N in relation to microbiological properties of soils under beech forests     

Marcin?ChodakEmail author  Partap?Khanna  Friedrich?Beese 《Biology and Fertility of Soils》2003,39(2):123-130

Hot water extraction is sometimes recommended as an easy method to estimate the readily mineralizable fractions of total C (C_t) and total N (N_t) in arable soils. However, the usefulness of this method for forest soils has not been adequately studied. The objectives of this study were to relate the hot water extractable C (C_hw) and N (N_hw) to microbiological and chemical properties of the forest soils under beech (Fagus sylvatica L.) stands and to test the ability of near infrared spectroscopy (NIRS) to predict chemical and microbial properties of these soils. Soils differing in humus type, soil type and soil texture were collected from five locations and five depths. In all soils the amount of C_hw was higher than the microbial biomass C (C_mic) indicating that a considerable part of C_hw was of non-microbial origin. The amount of C_hw in mineral soil correlated significantly (r =–0.30–0.53) with C_mic, basal respiration (BAS) and C_t/N_t ratio but was not related to C_mic/C_t ratio. The amount of N_hw was correlated with C_mic, BAS, C_mic/C_t ratio, and C_t/N_t ratio (r =–0.59–0.78). However, C_t and N_t values showed better relationships (r =–0.42–0.88) with all the parameters, indicating no advantage in using C_hw and N_hw in forest soils. NIRS predicted satisfactorily C_t, N_t, C_hw, N_hw, C_mic, C_mic/C_t ratio and BAS in the mineral soils [the regression coefficients (a) of linear regression (measured against predicted values) ranged from 0.84 to 1.17 and the correlation coefficients (r) ranged from 0.86 to 0.94] indicating the applicability of NIRS to estimate these properties.  相似文献   

氧化铁饱和滤纸用于森林土壤有效磷测定的研究   总被引：2，自引：1，他引：1  

田昆  Partap Khanna 《土壤学报》1998,35(3):419-422

磷的测定研究,取得了很多新进展,日前采用的都是一些经典的测磷方法,这些方法因用化学试剂提取土壤中的有效磷而受到了诸如pH等土壤性质的影响,而使测定值偏高或偏低^[1]。Val。DerZee等1987年提出一种滤纸测磷方法^[2],近似根系在土壤中对有效磷的吸收,但为室内实验研究。作者把滤纸作为一种吸附介体直接用于森林土壤有效磷的测定,省去了土样采集和处理等步骤,简单易行,能较真实地反映土壤中游离的供植物根系吸收的有效磷含量。  相似文献   

Hypomagnesemia in 188 Dogs: A Hospital Population-Based Prevalence Study     

Chand Khanna  Elizabeth M. Lund  Marc Raffe  P. Jane Armstrong 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1998,12(4):304-309

Magnesium is a divalent cation involved in more than 300 metabolic processes. Magnesium acts as an intracellular regulator of most energy-demanding pathways. Clinical investigation in the human medical field has determined risk factors for hypomagnesemia and its relationship to a number of disease processes. Experimental studies have established the effects of hypomagnesemia in dogs, but little is known of its prevalence, risk factors, or clinical associations in a hospital population of dogs. To study the prevalence, risk factors, and clinical associations of hypomagnesemia in dogs, a retrospective cross-sectional study of dogs admitted to the University of Minnesota Veterinary Teaching Hospital over a 2.5-year period was undertaken. The prevalence of hypomagnesemia in the study population was 6.1% (188 of 3,102 dogs). Using both categorical and continuous variables in a univariate analysis, significant associations with hypomagnesemia were identified and used to construct a multivariate analysis of the relative risk of hypomagnesemia. Results from evaluation of 3,102 dogs indicate that the most significant predictors of hypomagnesemia were albumin ( P ≤ .0001; odds ratio [OR] = 0.2), potassium ( P ≤ .0001; OR = 0.5), total CO₂ ( P ≤.05; OR = 0.9), and blood urea nitrogen concentrations ( P < .0001; OR = 0.9), a diagnosis of cardiovascular disease ( P < .02; OR = 1.9); and being a Collie ( P < .02; OR = 3.9) or German Shepherd Dog ( P < .002; OR = 2.2). These results can be used to better understand and predict hypomagnesemia in dogs.  相似文献   

Kalkitoxin Inhibits Angiogenesis,Disrupts Cellular Hypoxic Signaling,and Blocks Mitochondrial Electron Transport in Tumor Cells     

J. Brian Morgan  Yang Liu  Veena Coothankandaswamy  Fakhri Mahdi  Mika B. Jekabsons  William H. Gerwick  Frederick A. Valeriote  Yu-Dong Zhou  Dale G. Nagle 《Marine drugs》2015,13(3):1552-1568

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