RESUMEN
OBJECTIVE: The efficacy of topical anesthesia during retinopathy of prematurity (ROP) screening has been a controversial issue. To determine the efficacy of proparacaine eye drops (0.5%), we compared the Premature Infant Pain Profile (PIPP) scores in 40 preterm infants undergoing ROP screening. STUDY DESIGN: Prospective randomized double masked cross-over clinical trial. The study was conducted in the neonatal intensive units for infants undergoing routine ROP screening exams. Baseline PIPP scores and post-examination PIPP scores at 1 and 5 min were compared for: (1) those receiving saline vs proparacaine eye drops (2) first ROP screening vs second ROP screening, regardless of the type of eye drops used. Wilcoxon signed-ranks test was used to pair pain scores. RESULT: Forty preterm infants were included in the study. Mean gestational age (GA) at first and second examinations was 33.3 and 35.3 weeks, respectively. Proparacaine use significantly lowered mean PIPP scores (P=0.027) and delta scores (P=0.013) at 1 min after examination, but there was no difference at 5 min after examination. Second examinations showed significantly lower mean PIPP scores after examination (1 min (P=0.003) and 5 min (P=0.025)), regardless of the type of drop used. CONCLUSION: Proparacaine eye drops offer significant relief of pain that is apparently short lived. Significantly lower PIPP scores at second ROP examinations suggested that infants of older GA may have a greater ability to tolerate ROP screening. We recommend the use of proparacaine eye drops for the short term, immediate relief of pain during ROP screening in preterm infants of lesser GA.
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Dimensión del Dolor/efectos de los fármacos , Propoxicaína , Retinopatía de la Prematuridad/diagnóstico , Anestésicos Locales , Estudios Cruzados , Método Doble Ciego , Edad Gestacional , Humanos , Recién Nacido , Recien Nacido Prematuro , Tamizaje Neonatal/métodos , Soluciones Oftálmicas , Dolor/prevención & control , Dimensión del Dolor/instrumentaciónRESUMEN
OBJECTIVE: To investigate the safety, pharmacokinetics (PK), binding activity and immunogenicity of CR002, a human monoclonal antibody (mAb) directed against platelet-derived growth factor-D (PDGF-D), administered as a single intravenous (i.v.) infusion over a range of doses. SUBJECTS: 40 healthy male subjects received increasing doses of CR002 at 0.3, 1, 3, 10, 30 mg/kg or placebo. METHOD: This was a randomized, double-blind, placebo-controlled, dose-escalation Phase I study. The trial had a duration of 90 days, with dosing on Day 1 and follow-up visits on Days 2, 4, 7, 14, 21, 30, 45 and 90. Serum was collected for PK, binding activity and immunogenicity analysis at screening and up to Day 90. Safety was recorded throughout the study by performing laboratory tests, recording vital signs and electrocardiograms (ECGs), by monitoring the occurrence of adverse events (AEs). The use of concomitant medications was also recorded. RESULTS: All 40 subjects received CR002 or placebo, and completed the trial. No dose-limiting toxicities (DLTs) occurred, the maximum tolerated dose (MTD) was not reached and was estimated as > 30 mg/kg. There were no deaths during this study and no SAEs or other significant AEs reported. The most frequent drug-related treatment-emergent AE (TEAE) was headache in 4 of 30 subjects (13.3%) in the CR002 group vs. 0 of 10 subjects in the placebo group. CR002 exhibited linear PK parameters, had a long half-life (t1/2 in the range 15.5 â 48.1 days) and a volume of distribution at steady state in the range 4.7 â 6.5. Free PDGF-D in the serum bound to CR002 in a reversible manner, as shown in the lowest dose cohort. However, levels of total circulating PDGF-D remained constant throughout the study. There were no anti-CR002 antibodies detected in subjects dosed with CR002. CONCLUSIONS: CR002 was safe and well-tolerated at all doses tested as a single i.v. administration. The MTD was estimated to be above 30 mg/kg, the highest dose tested. CR002 had a long half-life, low clearance and a limited tissue distribution. Although total levels of PDGF-D at all dose levels remained relatively constant, there was no detectable circulating free PDGF-D after CR002 administration. At the lowest CR002 dose tested (0.3 mg/kg), PDGF-D was detectable again by Day 21 and the levels increased near to pre-infusion levels by Day 90. In this study, CR002 was not immunogenic during the 90-day study period.
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Anticuerpos Monoclonales/farmacocinética , Linfocinas/antagonistas & inhibidores , Factor de Crecimiento Derivado de Plaquetas/antagonistas & inhibidores , Anticuerpos Monoclonales/administración & dosificación , Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales Humanizados , Método Doble Ciego , Humanos , Infusiones Intravenosas , Linfocinas/inmunología , Linfocinas/metabolismo , Masculino , Factor de Crecimiento Derivado de Plaquetas/inmunología , Factor de Crecimiento Derivado de Plaquetas/metabolismo , Unión ProteicaRESUMEN
Peroxisome proliferator-activated receptor gamma (PPAR gamma) agonists, including the glitazone class of drugs, are insulin sensitizers that reduce glucose and lipid levels in patients with type 2 diabetes mellitus. To more fully understand the molecular mechanisms underlying their therapeutic actions, we have characterized the effects of the potent, tyrosine-based PPAR gamma ligand GW1929 on serum glucose and lipid parameters and gene expression in Zucker diabetic fatty rats. In time-course studies, GW1929 treatment decreased circulating FFA levels before reducing glucose and triglyceride levels. We used a comprehensive and unbiased messenger RNA profiling technique to identify genes regulated either directly or indirectly by PPAR gamma in epididymal white adipose tissue, interscapular brown adipose tissue, liver, and soleus skeletal muscle. PPAR gamma activation stimulated the expression of a large number of genes involved in lipogenesis and fatty acid metabolism in both white adipose tissue and brown adipose tissue. In muscle, PPAR gamma agonist treatment decreased the expression of pyruvate dehydrogenase kinase 4, which represses oxidative glucose metabolism, and also decreased the expression of genes involved in fatty acid transport and oxidation. These changes suggest a molecular basis for PPAR gamma-mediated increases in glucose utilization in muscle. In liver, PPAR gamma activation coordinately decreased the expression of genes involved in gluconeogenesis. We conclude from these studies that the antidiabetic actions of PPAR gamma agonists are probably the consequence of 1) their effects on FFA levels, and 2), their coordinate effects on gene expression in multiple insulin-sensitive tissues.
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Perfilación de la Expresión Génica , Expresión Génica/fisiología , Insulina/fisiología , Receptores Citoplasmáticos y Nucleares/fisiología , Factores de Transcripción/fisiología , Tejido Adiposo/efectos de los fármacos , Tejido Adiposo/fisiología , Tejido Adiposo Pardo/efectos de los fármacos , Tejido Adiposo Pardo/fisiología , Animales , Benzofenonas/farmacología , Diabetes Mellitus/sangre , Diabetes Mellitus/genética , Diabetes Mellitus/metabolismo , Diabetes Mellitus/fisiopatología , Ácidos Grasos/metabolismo , Expresión Génica/efectos de los fármacos , Glucosa/metabolismo , Homeostasis , Hígado/efectos de los fármacos , Hígado/fisiología , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/fisiología , Obesidad , Ratas , Ratas Zucker , Receptores Citoplasmáticos y Nucleares/agonistas , Factores de Transcripción/agonistas , Tirosina/análogos & derivados , Tirosina/farmacologíaRESUMEN
Regulation of the concentration of Ca2+ in the apoplast of plants is essential in order to allow Ca(2+)-dependent processes, such as Ca(2+)-mediated signal transduction in stomatal guard cells, to function correctly. This is particularly important for plants growing with high levels of Ca2+ in the rhizosphere. Recently, we have shown that in two calcicoles, Leontodon hispidus L. and Centaurea scabiosa L., trichomes play a key role in this regulatory process. Ozone is known to have a marked effect on plant Ca2+ homeostasis. Therefore, we have examined the effect of this pollutant on the regulation by trichomes of apoplastic Ca2+ in the calcicole L. hispidus. Treatment with 100 nl l-1 ozone resulted in a reduction in stomatal conductance of approximately 25% in plants grown with 15 mM Ca2+ in the rhizosphere. Analysis of total Ca2+ levels revealed that these changes in stomatal behaviour reflect a decrease in the ability of trichomes to sequester Ca2+. The amount of Ca2+ present in the trichome tip cell was reduced by approximately 38%. This was accompanied by an increase in the levels of Ca2+ in the guard cells and other tissues of the leaf. These data suggest that ozone has a detrimental effect on the ability of trichomes to regulate the concentration of apoplastic Ca2+ in L. hispidus, resulting in altered stomatal behaviour, and hence gaseous exchange, possibly due to the disruption of guard-cell Ca(2+)-mediated signal transduction. This has important implications for the growth and survival of plants growing in Ca(2+)-rich soils.
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Asteraceae/metabolismo , Cloruro de Calcio/metabolismo , Ozono/toxicidad , Estructuras de las Plantas/metabolismo , Adaptación Fisiológica/fisiología , Contaminantes Atmosféricos/toxicidad , Asteraceae/efectos de los fármacos , Cloruro de Calcio/administración & dosificación , Extensiones de la Superficie Celular/metabolismo , Pared Celular/metabolismo , Ozono/administración & dosificación , Estructuras de las Plantas/efectos de los fármacos , Transducción de Señal , Suelo/análisisRESUMEN
The choice of fixation for occipitocervical arthrodesis remains controversial, especially in oncologic patients who need further radiographic evaluation or postoperative radiotherapy. We studied the long-term outcome of 20 patients who underwent occipitocervical fusions using onlay corticocancellous bone graft and wiring, with postoperative halo vest immobilization. Eight of these patients had postoperative radiotherapy for spinal tumors (group I), and 12 patients had occipitocervical fusions for other pathologies that did not require postoperative radiotherapy (group II). All patients had solid arthrodeses; however, there was a difference in the average time to fusion between patients who received pre- or postoperative radiotherapy and those who did not (p = 0.11). At an average follow-up of 54.5 months (range 24-92 months) 15 of 20 patients (75%) had excellent or good outcomes. A high fusion rate can be expected with reasonable intraoperative or postoperative complications.
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Articulación Atlantoaxoidea/cirugía , Articulación Atlantooccipital/cirugía , Trasplante Óseo/métodos , Fijadores Internos/estadística & datos numéricos , Fusión Vertebral/métodos , Neoplasias de la Columna Vertebral/complicaciones , Neoplasias de la Columna Vertebral/cirugía , Adulto , Anciano , Articulación Atlantoaxoidea/diagnóstico por imagen , Articulación Atlantoaxoidea/patología , Articulación Atlantooccipital/diagnóstico por imagen , Articulación Atlantooccipital/patología , Niño , Cordoma/complicaciones , Cordoma/patología , Cordoma/cirugía , Fijadores Externos/estadística & datos numéricos , Femenino , Humanos , Lactante , Masculino , Meningioma/complicaciones , Meningioma/patología , Meningioma/cirugía , Persona de Mediana Edad , Complicaciones Posoperatorias , Radiografía/estadística & datos numéricos , Reoperación/métodos , Reoperación/estadística & datos numéricos , Fracturas de la Columna Vertebral/patología , Fracturas de la Columna Vertebral/cirugía , Fusión Vertebral/instrumentación , Neoplasias de la Columna Vertebral/patología , Insuficiencia del Tratamiento , Terapia por Rayos X/efectos adversosRESUMEN
The association of inheritance of different apolipoprotein E (APOE, gene; apoE, protein) alleles with the risk and rate of onset of Alzheimer's disease (AD) is now well established and widely confirmed. While there are now a collection of hypotheses concerning the specific relationship of APOE polymorphisms to various phenotypic manifestations of AD, no single compelling theory has been tested and universally accepted. The only clear fact emerging during the past 6 years is that differences in APOE genotype affect the average rate of disease onset as a predictable function of the inheritance of this polymorphic gene. Methods now exist to enable experimental designs to study the metabolic effects of inheriting different APOE alleles, addressing what differences that may be present for many years, perhaps over the entire lifetime, can lead to earlier or later manifestations of the disease and are therapeutically tractable. This review summarizes part of an experimental approach to identify biological pathways influenced by the different APOE polymorphisms that are relevant to the pathogenesis of AD.
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Enfermedad de Alzheimer/tratamiento farmacológico , Apolipoproteínas E/metabolismo , Alelos , Enfermedad de Alzheimer/genética , Animales , Apolipoproteína E3 , Apolipoproteína E4 , Apolipoproteínas E/genética , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Marcación de Gen , Técnicas Genéticas , Genotipo , Humanos , Polimorfismo Genético , ARN Mensajero/metabolismoRESUMEN
Two large-scale yeast two-hybrid screens were undertaken to identify protein-protein interactions between full-length open reading frames predicted from the Saccharomyces cerevisiae genome sequence. In one approach, we constructed a protein array of about 6,000 yeast transformants, with each transformant expressing one of the open reading frames as a fusion to an activation domain. This array was screened by a simple and automated procedure for 192 yeast proteins, with positive responses identified by their positions in the array. In a second approach, we pooled cells expressing one of about 6,000 activation domain fusions to generate a library. We used a high-throughput screening procedure to screen nearly all of the 6,000 predicted yeast proteins, expressed as Gal4 DNA-binding domain fusion proteins, against the library, and characterized positives by sequence analysis. These approaches resulted in the detection of 957 putative interactions involving 1,004 S. cerevisiae proteins. These data reveal interactions that place functionally unclassified proteins in a biological context, interactions between proteins involved in the same biological function, and interactions that link biological functions together into larger cellular processes. The results of these screens are shown here.
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Proteínas Fúngicas/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas Fúngicas/genética , Sistemas de Lectura Abierta , Biblioteca de Péptidos , Unión Proteica , Estructura Terciaria de Proteína , Técnicas del Sistema de Dos HíbridosRESUMEN
Small changes in the gaseous composition of the atmosphere have many different impacts on terrestrial plants. Some of the most important involve changes in stomatal control of leaf conductance. Evolution has provided highly complex mechanisms by which stomata respond to a wide range of environmental factors to balance the conflicting priorities of carbon gain for photosynthesis and water conservation. These mechanisms involve direct responses of the guard cells to aspects of the aerial environment, and hormonal communication within the plant enabling conductance to be adjusted according to soil moisture status. Various aspects of these delicately balanced mechanisms can be disturbed by air pollutants. Impairment of the regulation of plant water use by SO2 and O3 has been known for some years, but there are still many obstacles to our understanding of the variations in response between species, or even between genotypes of the same species. A surprising outcome of some recent studies is the suggestion that CO2 pollution may disrupt the control of water relations in some species because their stomata do not close sufficiently in CO2-enriched air. It has often been taken for granted that the elevation of atmospheric CO2 would lead to economies in water use by plant canopies, but the underlying assumptions are now being seriously questioned.
RESUMEN
Analysis of patients with inherited hypokalaemic alkalosis resulting from salt-wasting has proved fertile ground for identification of essential elements of renal salt homeostasis and blood-pressure regulation. We now demonstrate linkage of this phenotype to a segment of chromosome 1 containing the gene encoding a renal chloride channel, CLCNKB. Examination of this gene reveals loss-of-function mutations that impair renal chloride reabsorption in the thick ascending limb of Henle's loop. Mutations in seventeen kindreds have been identified, and they include large deletions and nonsense and missense mutations. Some of the deletions are shown to have arisen by unequal crossing over between CLCNKB and the nearby related gene, CLCNKA. Patients who harbour CLCNKB mutations are characterized by hypokalaemic alkalosis with salt-wasting, low blood pressure, normal magnesium and hyper- or normocalciuria; they define a distinct subset of patients with Bartter's syndrome in whom nephrocalcinosis is absent. These findings demonstrate the critical role of CLCNKB in renal salt reabsorption and blood-pressure homeostasis, and demonstrate the potential role of specific CLCNKB antagonists as diuretic antihypertensive agents.
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Síndrome de Bartter/genética , Canales de Cloruro/genética , Mutación , Síndrome de Bartter/clasificación , Síndrome de Bartter/metabolismo , Secuencia de Bases , Canales de Cloruro/química , Canales de Cloruro/metabolismo , Cromosomas Humanos Par 1/genética , Intercambio Genético , Cartilla de ADN/genética , Exones , Femenino , Ligamiento Genético , Humanos , Intrones , Asa de la Nefrona/metabolismo , Masculino , Linaje , Fenotipo , Reacción en Cadena de la Polimerasa , Eliminación de SecuenciaRESUMEN
Essential hypertension is a common multifactorial trait. The molecular basis of a number of rare diseases that after blood pressure in humans has been established, identifying pathways that may be involved in more common forms of hypertension. Pseudohypoaldosteronism type II (PHAII, also known as familial hyperkalaemia and hypertension or Gordon's syndrome; OMIM #145260), is characterized by hyperkalaemia despite normal renal glomerular filtration, hypertension and correction of physiologic abnormalities by thiazide diuretics. Mild hyperchloremia, metabolic acidosis and suppressed plasma renin activity are variable associated findings. The pathogenesis of PHAII is unknown, although clinical studies indicate an abnormality in renal ion transport. As thiazide diuretics are among the most efficacious agents in the treatment of essential hypertension, understanding the pathogenesis of PHAII may be of relevance to more common forms of hypertension. Analysis of linkage in eight PHAII families showing autosomal dominant transmission demonstrates locus heterogeneity of this trait, with a multilocus lod score of 8.1 for linkage of PHAII to chromosomes 1q31-q42 and 17p11-q21. Interestingly, the chromosome-17 locus overlaps a syntenic interval in rat that contains a blood pressure quantitative trait locus (QTL). Our findings provide a first step toward identification of the molecular basis of PHAII.
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Cromosomas Humanos Par 17 , Cromosomas Humanos Par 1 , Ligamiento Genético , Hiperpotasemia/genética , Hipertensión/genética , Seudohipoaldosteronismo/genética , Animales , Mapeo Cromosómico , Femenino , Humanos , Hiperpotasemia/complicaciones , Hipertensión/complicaciones , Masculino , Linaje , Seudohipoaldosteronismo/complicaciones , RatasRESUMEN
Monoliths of two contrasting vegetation types, a species-rich grassland on a brown earth soil over limestone and species-poor community on a peaty gley, were transferred to solardomes and grown under ambient (350 µ 1-1 ) and elevated (600 µ11-1 ) CO2 for 2 yr. Shoot biomass was unaltered but root biomass increased by 40-50% under elevated CO2 . Root production was increased by elevated CO2 in the peat soil, measured both as instantaneous and cumulative rates, but only the latter measure was increased in the limestone soil. Root growth was stimulated more at 6 cm depth than at 10 cm in the limestone soil. Turnover was faster under elevated CO2 in the peat soil, but there was only a small effect on turnover in the limestone soil. Elevated CO2 reduced nitrogen concentration in roots and might have increased mycorrhizal colonization. Respiration rate was correlated with N concentration, and was therefore lower in roots grown at elevated CO2 . Estimates of the C budget of the two communities, based upon root production and on net C uptake, suggest that C sequestration in the peat soil increases by c. 0.2 kg C m -2 yr-1 (= 2 t ha yr-1 ) under elevated CO2 .
RESUMEN
We have investigated the cellular basis for the effects of oxidative stress on stomatal behavior using stomatal bioassay and ratio photometric techniques. Two oxidative treatments were employed in this study: (a) methyl viologen, which generates superoxide radicals, and (b) H2O2. Both methyl viologen and H2O2 inhibited stomatal opening and promoted stomatal closure. At concentrations [less than or equal to]10-5 M, the effects of methyl viologen and H2O2 on stomatal behavior were reversible and were abolished by 2 mM EGTA or 10 [mu]M verapamil. In addition, at 10-5 M, i.e. the maximum concentration at which the effects of the treatments were prevented by EGTA or verapamil, methyl viologen and H2O2 caused an increase in guard cell cytosolic free Ca2+ ([Ca2+]i), which was abolished in the presence of EGTA. Therefore, at low concentrations of methyl viologen and H2O2, removal of extracellular Ca2+ prevented both the oxidative stress-induced changes in stomatal aperture and the associated increases in [Ca2+]i. This suggests that in this concentration range the effects of the treatments are Ca2+-dependent and are mediated by changes in [Ca2+]i. In contrast, at concentrations of methyl viologan and H2O2 > 10-5 M, EGTA and verapamil had no effect. However, in this concentration range the effects of the treatments were irreversible and correlated with a marked reduction in membrane integrity and guard cell viability. This suggests that at high concentrations the effects of methyl viologen and H2O2 may be due to changes in membrane integrity. The implications of oxidative stress-induced increases in [Ca2+]i and the possible disruption of guard-cell Ca2+ homeostasis are discussed in relation to the processes of Ca2+-based signal transduction in stomatal guard cells and the control of stomatal aperture.
RESUMEN
The DCC (deleted in colorectal cancer) candidate tumor suppressor gene spans greater than 1350 kilobases at chromosomes 18q21.1 and encodes a transmembrane protein of unknown function. Although DCC is expressed in a number of adult tissues, its expression is highest in the brain and we have, therefore, undertaken studies to determine if DCC inactivation might contribute to tumors arising there. Decreased or absent DCC protein expression was noted in more than 50% of the thirty brain tumors studied. Although specific mutations in the DCC gene were not identified, a variety of mechanisms appeared to contribute to the altered DCC expression, including allelic loss, aberrant splicing of transcripts and allele-specific loss of transcripts. In total, the data suggest that DCC inactivation may be important in brain tumor pathogenesis.
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Neoplasias Encefálicas/genética , Genes DCC , Glioblastoma/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Deleción Cromosómica , Cromosomas Humanos Par 18 , ADN de Neoplasias , Heterocigoto , Humanos , Ratones , Ratones Desnudos , Datos de Secuencia Molecular , Mutación , Trasplante de Neoplasias , Reacción en Cadena de la Polimerasa , Empalme del ARN , ARN Mensajero/genéticaRESUMEN
Responses to elevated CO2 have been studied using Agrostis capillaris L., an upland grass which is abundant on nutrient-poor soils. Plants were grown in sand culture with a wide range of nitrogen, phosphorus and potassium concentrations, and the impact of CO2 on the demand for nutrients was determined using isotopic root bioassays. Plants grown with the smallest concentrations of N and P showed typical foliar symptoms associated with deficiency of these elements. However, even when supplies of N and P were limiting to growth, additional CO2 (250 ppm above ambient) influenced neither total N nor total P in above-ground tissues, nor nutrient demands as indicated by the bioassay. The estimates of the demand of the plants for K from the 86 Rb bioassay indicated an appreciable increase when plants were raised in elevated CO2 . For plants of the same size with the same nutrient supply, those grown in elevated CO2 consistently displayed an increased internal demand for K. Uptake of K was not however, enhanced by elevated CO2 even in non-limiting conditions and it might therefore be limited by a factor other than K supply. The overall conclusion from the experiments is that when A. capillaris is grown in elevated CO2 , uptake of N, P and K fails to increase proportionally with dry mass. This was true even when nutrient supplies were adequate, and it appears that nutrient-use-efficiency might increase to enable the plants to maintain growth in elevated CO2 .
RESUMEN
Bud break and growth of beech trees were measured during the growing season of 1992. The trees had previously been exposed, through the growing season of 1991, to one of four treatments: (1) episodic ozone for 128 d, total dose = 46-3 ppm h; (2) air purified by filtration through Purified and charcoal; (3) ozone together with a period of water shortage: (4) filtered air with a period of water shortage. Despite uniform growth conditions during 1992. the previous water stress treatment caused bud break to begin slightly earlier, but the rates of shoot growth and the length of the first flush branches were reduced (40%). In well-watered plants ozone caused a reduced Tate of shoot growth during the first week after bud break. The total amount of growth during 1992 was shown to be reduced (36%) by the previous water stress treatment, In the case of the well-watered trees, exposure to ozone in the previous year reduced the amount of new growth by 17%, which was the result of reduced internal expansion. When ozone was combined with water stress, there was no further reduction in the amount of new growth, but there was a fall in the number of internodes relative to water-stressed plants grown in filtered air. Ozone and water stress applied singly reduced growth. A combination of the two stresses, however, caused no additional reduction in growth, but reduced the number of internodes. The possible implications of the aftereffects of these stresses are discussed in relation to reduced productivity and canopy structure.
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The response of photosynthetic gas exchange to oxides of nitrogen (NOx) was studied in leaves of lettuce (Lactuca sativa L.) at different temperatures. Exposure to > high concentrations (e.g. 13 µmol NOx mol-1 ), similar to those often found in commercial glasshouses, caused a rapid inhibition of the net assimilation of CO2 . This appeared to be by a direct effect on photosynthesis rather than by a change in the stomatal conductance. In ambient CO2 , (345 µmol mol-1 ), the percentage inhibition at 10 and 5°C was approximately 3× and 5×, respectively, that measured at 20°C. This effect of temperature also occurred when measured in CO2 , enriched air (1050 µmol mol-1 ), which would normally accompany NOx in a glasshouse. The extent of photosynthetic inhibition caused by NOx was, however, always less in high than in low CO2 . The results suggest that when burning fuel to raise the CO2 , concentration and heat the glasshouse air, growers should avoid generating high concentrations of NOx , in conditions of low temperature.
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Polyamines (PA) are known to be involved in the areas of plant physiology and biochemistry which are related to the response of a plant to air pollution. This study examines the role of arginine decarboxylase (ADC), an important rate-limiting enzyme in polyamine synthesis, in barley plants exposed to ozone (O(3)). The activity of ADC increased significantly in O(3)-treated leaves when visible injury was hardly apparent. The increase in ADC activity may be a mechanism to increase the PA levels in O(3)-treated leaves and so minimize the damaging effects of O(3). Supporting this, foliar applications of DL-alpha-difluoromethylarginine (DFMA), a specific inhibitor of ADC, prevented the rise in ADC activity and visible injury was considerable on exposure to O(3). This damage was not due to the foliar sprays, as little visible injury was seen in leaves in the O(3)-free controls. The results are discussed in terms of the roles of PA in conferring O(3) resistance in plants.
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The effects of a mixture of SO(2) and NO(2) at a concentration of 0.08 to 0.10 ppm (in microg m(-3): 164-205 for NO(2); 229-286 for SO(2)) were tested for four weeks on two old varieties of winter wheat, Little Joss and Holdfast, introduced in 1908 and 1938, respectively, grown in simulated autumn conditions. After two weeks, root dry weights of both varieties were significantly decreased but, although there was some leaf necrosis, shoot dry weights were unaltered. After a further two weeks, the dry weights of the shoots as well as the roots were significantly decreased. These effects, amounting to a combined 40% decrease in total dry weight, were greater than those in identical experiments carried out with the present day variety Avalon, in which the decrease was 20%. The results suggest that the modern cultivar Avalon is more tolerant of SO(2) and NO(2) than Little Joss and Holdfast, which were grown many years ago.
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The effects of SO2 and NO2 on the control of water loss by birch trees were investigated using clonal populations of both Betula pendula Roth, (silver birch) and Betula pubescens Khr. (downy birch). Plants were grown in controlled environments and were fumigated in a 2 × 2 factorial experiment with 65 nl l-1 SO2 and/or NO2 , or with equal concentrations of both SO2 and NO2 in four treatments, namely zero, 20, 40 and 60 nl l-1 . Excised leaves showed in increased rate of water loss approximately corresponding to the concentration of pollutant to which they had been previously exposed. When petroleum jelly was applied to the abaxial epidermal surface of polluted leaves the increased rate of water loss was not found, strongly implying that the damage had occurred only at this site, and not on the adaxial epidermis, which is virtually devoid of stomata. Measurements of gas exchange were made on B. pubescens exposed to the four doses of the mixture of the two gases. The rate of transpiration was approximately doubled as a result of the two higher pollution treatments, judging from measurements made later in clean air. When transpiration was measured in high and low CO2 concentrations, polluted plants had a slightly reduced and more variable response to the change in CO2 concentration. Both clones were also exposed first to the four doses of the gas mixture, and then to drought. There was a more rapid onset of water stress, accompanied by an earlier decrease in effective leaf area in the polluted plants, when compared with the unpolluted plants. The abaxial surface of frozen hydrated leaves of the Betula pubescens clone were examined at low temperature with a scanning electron microscope. Damaged epidermal cells were clearly visible on the polluted leaves and thought to be responsible for areas of wide open stomata. It is concluded that leaves of these species are less efficient in the utilization of water after a period of exposure to pollution and are less able to restrict water loss in a time of shortage.
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Restriction-site variation in and around the alpha 1-antitrypsin gene has been studied using two genomic probes. With use of restriction enzymes SstI, MspI, and AvaII, three polymorphic sites have been described with a 4.6-kb probe in the 5' portion of the gene. With use of a 6.5-kb probe, polymorphisms in the coding and 3' regions of the gene have been detected with AvaII, MaeIII, and TaqI. All of these polymorphisms are of sufficiently high frequency to be useful in genetic mapping studies. The polymorphisms with AvaII and MaeIII (6.5-kb probe) are particularly useful for prenatal diagnosis. PI types and M subtypes tend to be associated with specific DNA haplotypes; there are two different types of DNA haplotypes associated with PI M1. The extent of linkage disequilibrium differs throughout the region of the alpha 1-antitrypsin gene.