Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 14 de 14
Filtrar
1.
Tree Physiol ; 30(6): 689-704, 2010 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-20453002

RESUMEN

The periodic production of large seed crops by trees (masting) and its interaction with stem growth has long been the objective of tree physiology research. However, very little is known about the effects of masting on stem growth and total net primary productivity (NPP) at the stand scale. This study was conducted in an old-growth, mixed deciduous forest dominated by Fagus sylvatica (L.) and covers the period from 2003 to 2007, which comprised wet, dry and regular years as well as two masts of Fagus and one mast of the co-dominant tree species Fraxinus excelsior (L.) and Acer pseudoplatanus (L.). We combined analyses of weather conditions and stem growth at the tree level (inter- and intra-annual) with fruit, stem and leaf production, and estimates of total NPP at the stand level. Finally, we compared the annual demand of carbon for biomass production with net canopy assimilation (NCA), derived from eddy covariance flux measurements, chamber measurements and modelling. Annual stem growth of Fagus was most favoured by warm periods in spring and that of Fraxinus by high precipitation in June. For stem growth of Acer and for fruit production, no significant relationships with mean weather conditions were found. Intra-annual stem growth of all species was strongly reduced when the relative plant-available water in soil dropped below a threshold of about 60% between May and July. The inter-annual variations of NCA, total NPP and leaf NPP at the stand level were low (mean values 1313, 662 and 168 g C m(-2) year(-1), respectively), while wood and fruit production varied more and contrarily (wood: 169-241 g C m(-2) year(-1); fruits: 21-142 g C m(-2) year(-1)). In all years, an annual surplus of newly assimilated carbon was calculated (on average 100 g C m(-2) year(-1)). The results suggest that stem growth is generally not limited by insufficient carbon resources; only in mast years a short-term carbon shortage may occur in spring. In contrast to common assumption, stem growth alone is not a sufficient proxy for total biomass production or the control of carbon sequestration by weather extremes.


Asunto(s)
Clima , Fagus/crecimiento & desarrollo , Tallos de la Planta/crecimiento & desarrollo , Árboles/crecimiento & desarrollo , Fraxinus/anatomía & histología , Fraxinus/crecimiento & desarrollo , Frutas/crecimiento & desarrollo , Hojas de la Planta/crecimiento & desarrollo , Estaciones del Año , Suelo , Árboles/anatomía & histología , Tiempo (Meteorología)
2.
Theriogenology ; 121: 1-6, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30121493

RESUMEN

To determine relationships of ovarian antral follicle count (AFC) on d 28 postpartum with postpartum interval (PPI) and AFC on d 8 post-estrus, three-dimensional ultrasonography was performed on multiparous (n = 47) and primiparous (n = 20) Brahman cows on d 28 postpartum and on d 8 post-estrus. Follicles were evaluated to determine numbers of total, small (≤17 mm3), medium (17 mm3-67 mm3), and large follicles (≥67 mm3) on each ovary. Estrus was detected using vasectomized, penile-deviated bulls fitted with chin-ball markers during the AI period and with tail paint during the natural service period. Cows with AFC ≥ ½ SD above the mean were classified as high, those within ½ SD of the mean were classified as intermediate, and those ≥ ½ SD below the mean were classified as low. Classes of AFC for total follicles included low (L ≤ 73), intermediate (74 ≤ I ≤ 112), and high (H ≥ 113). Classes of AFC for small follicles included low (L ≤ 55), intermediate (56 ≤ I ≤ 87), and high (H ≥ 88). Classes of AFC for medium follicles included low (L ≤ 13), intermediate (14 ≤ I ≤ 23), and high (H ≥ 24). Classes of AFC for large follicles included low (L ≤ 2), intermediate (3 ≤ I ≤ 4), and high (H ≥ 5). Cows with PPI ≥ ½ SD above the mean were classified as long, those within ½ SD of the mean were classified as intermediate, and those ≥ ½ SD below the mean were classified as short. Classes of PPI included short (S ≤ 47 d), intermediate (48 d ≤ I ≤ 75 d), and long (L ≥ 76 d). The PROC MIXED procedure of SAS was used to analyze potential differences among classes of AFC and PPI. The PROC REG procedure of SAS was used to analyze relationships between AFC and PPI and between AFC on d 28 postpartum and on d 8 post-estrus. The PPI differed among classes of total (P < 0.01; L = 76.2 ±â€¯6.0, I = 61.7 ±â€¯4.5, H = 43.8 ±â€¯6.5), small (P < 0.01; L = 74.3 ±â€¯5.6, I = 64.6 ±â€¯4.8, H = 42.9 ±â€¯5.9), and medium AFC (P = 0.04; L = 72.3 ±â€¯5.9, I = 59.3 ±â€¯5.8, H = 52.1 ±â€¯5.8). The PPI did not differ among classes of large AFC (P = 0.81). As total AFC on d 28 postpartum increased, PPI decreased (P < 0.01, Adj.R2 = 0.13). Total AFC on d 8 post-estrus was positively associated with total AFC on d 28 postpartum (P < 0.01, Adj.R2 = 0.66). These results suggest that: a) populations of total, small, and medium follicles in the postpartum period predict PPI in Brahman females and b) total AFC in Brahman females are consistent.


Asunto(s)
Bovinos/fisiología , Folículo Ovárico/crecimiento & desarrollo , Animales , Cruzamiento/métodos , Estro , Femenino , Folículo Ovárico/diagnóstico por imagen , Periodo Posparto , Embarazo , Índice de Embarazo , Factores de Tiempo
3.
Arch Ophthalmol ; 94(4): 597-8, 1976 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-1267639

RESUMEN

A malignant teratoma of the ovary was resected in a 14-year-old girl. Within the tumor, a partially developed eye was found.


Asunto(s)
Ojo , Neoplasias Ováricas/patología , Teratoma/patología , Adolescente , Ojo/embriología , Femenino , Humanos , Epitelio Pigmentado Ocular
4.
Surv Ophthalmol ; 21(3): 285-90, 1976.
Artículo en Inglés | MEDLINE | ID: mdl-1013882

RESUMEN

A four-year survey of all ocular trauma cases admitted to a large metropolitan eye hospital was conducted for the purpose of generally documenting ocular trauma and evaluating prophylactic, demographic and etiologic factors. Of 6254 eye admissions, 7.5% were for ocular trauma; hyphema was the most common diagnosis. Injuries were evaluated according to site, cause, and age, sex and race distribution.


Asunto(s)
Lesiones Oculares/epidemiología , Adolescente , Adulto , Factores de Edad , Catarata/etiología , Niño , Preescolar , Lesiones de la Cornea , Cuerpos Extraños en el Ojo/epidemiología , Párpados/lesiones , Femenino , Fracturas Óseas , Humanos , Hipema/etiología , Lactante , Masculino , Persona de Mediana Edad , Órbita/lesiones , Desprendimiento de Retina/etiología , Estudios Retrospectivos , Esclerótica/lesiones , Factores Sexuales , Cuerpo Vítreo/lesiones , Heridas Penetrantes
5.
Am J Ophthalmol ; 79(1): 18-24, 1975 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-45922

RESUMEN

Four full-thickness corneal buttons and tissue from one lamellar keratoplasty, derived from four patients with granular corneal dystrophy recurring in previously transplanted corneas, were studied by light and transmission electron microscopy. Fibrous tissue without vascularization was present between the epithelium and Bowman's membrane and contained deposits characteristic of granular dystrophy in both light and electron microscopy. The recurrence of dystrophy in the normal donor cornea is the result of infiltration of the grafted cornea by host invasion. The donor stroma is spared.


Asunto(s)
Córnea/patología , Distrofias Hereditarias de la Córnea/patología , Adolescente , Adulto , Córnea/ultraestructura , Trasplante de Córnea , Lámina Limitante Posterior/ultraestructura , Epitelio/ultraestructura , Femenino , Fibroblastos/ultraestructura , Humanos , Masculino , Membranas/ultraestructura , Microscopía Electrónica , Microscopía de Polarización , Persona de Mediana Edad , Recurrencia , Coloración y Etiquetado , Trasplante Homólogo , Agudeza Visual
6.
Bioorg Khim ; 22(5): 387-9, 1996 May.
Artículo en Ruso | MEDLINE | ID: mdl-8929226

RESUMEN

alpha-Subunit of the Torpedo californica nicotinic acetylcholine receptor was isolated by preparative SDS-PAGE followed by reversed-phase HPLC on a C4 column in an acetonitrile-isopropanol gradient in water. After removal of the organic solvents and solubilization in beta-octylglucoside, the purified alpha-subunit binds alpha-bungarotoxin with high affinity (Kd 28 nM).


Asunto(s)
Bungarotoxinas/metabolismo , Receptores Nicotínicos/metabolismo , Animales , Bungarotoxinas/química , Cromatografía Líquida de Alta Presión , Electroforesis en Gel de Poliacrilamida , Receptores Nicotínicos/química , Receptores Nicotínicos/aislamiento & purificación , Solubilidad , Torpedo
7.
Ther Umsch ; 61(5): 325-8, 2004 May.
Artículo en Alemán | MEDLINE | ID: mdl-15195718

RESUMEN

Tonsillectomy (TE) is one of the most frequent as well as one of the most controversial surgical interventions. The objective of this paper was to assess the evidence of the most common indications for TE. For this purpose the literature of the past 25 years was analysed using the criteria of evidence based medicine. In children seventy-five percent of TEs are performed because of recurrent tonsillitis. Several randomised clinical trials (RCTs) have demonstrated the efficacy of TE in this disease. This indication is based on evidence grade I-II. No consensus has yet been reached, however, about the number of annual episodes that justify TE. The remaining paediatric TEs are performed to relieve symptoms of airway obstruction. TE has been shown to improve obstructive symptoms in up to 100% of patients. It is the accepted treatment of paediatric obstructive sleep apnoea, although the evidence is not based on major RCTs. In adults, too, the majority of TEs are performed for recurrent or chronic tonsillitis. There are no good RCTs, but the indication can be based on a series of well controlled studies (evidence grade III). Obviously, TE is indicated if there is suspicion of neoplasm. Peritonsillar abscess per se is no indication for TE, unless the abscess cannot be drained otherwise. TE plays no role in the standard management of OSAS and mononucleosis.


Asunto(s)
Obstrucción de las Vías Aéreas/cirugía , Medicina Basada en la Evidencia , Tonsilectomía , Tonsilitis/cirugía , Adulto , Obstrucción de las Vías Aéreas/diagnóstico , Niño , Medicina Familiar y Comunitaria , Humanos , Hiperplasia , Mononucleosis Infecciosa/diagnóstico , Mononucleosis Infecciosa/cirugía , Tonsila Palatina/patología , Absceso Peritonsilar/diagnóstico , Absceso Peritonsilar/cirugía , Prevención Secundaria , Tonsilitis/diagnóstico , Resultado del Tratamiento
11.
J Protein Chem ; 16(3): 161-70, 1997 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-9155087

RESUMEN

Here we report on the use of iodination of the membrane-bound nicotinic acetylcholine receptor (nAChR) from Torpedo californica electric tissue in order to define surface-exposed portions of the receptor molecule. Membrane-bound nAChR was 125I-iodinated using the oxidation agent Iodo-Gen. The iodinated subunits were separated by preparative gel electrophoresis, desalted, and cleaved with trypsin. The resulting peptides were separated by reverse-phase HPLC and the radioactive peptides were identified by mass spectrometry and protein sequencing. For the delta-subunit, we identified five iodinated peptides containing the tyrosine residues deltaTyr17, deltaTyr74, deltaTyr365, deltaTyr372, and deltaTyr428. The surface exposition of these amino acids is in agreement with the four-transmembrane-segment model (4TM model) of the nAChR, but the assignment to the intra- or extracellular surface is doubtful. According to this model, the N-terminal portion of the receptor subunits including the iodinated residues deltaTyr17 and deltaTyr74 is extracellular and deltaTyr372 as a site of tyrosine phosphorylation is located on the cytoplasmic side. But since this latter residue is among the first to be iodinated using an immobilized iodination agent, its true position with respect to the membrane bilayer is not clear.


Asunto(s)
Monoyodotirosina , Receptores Nicotínicos/química , Secuencia de Aminoácidos , Animales , Cromatografía Líquida de Alta Presión , Órgano Eléctrico/metabolismo , Radioisótopos de Yodo , Sustancias Macromoleculares , Espectrometría de Masas , Datos de Secuencia Molecular , Fragmentos de Péptidos/química , Fragmentos de Péptidos/aislamiento & purificación , Mapeo Peptídico , Conformación Proteica , Torpedo , Tripsina , Urea/análogos & derivados
12.
Tree Physiol ; 17(12): 777-86, 1997 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-14759887

RESUMEN

Mineral nutrition of Norway spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) was investigated along a transect extending from northern Sweden to central Italy. Nitrogen (N) concentrations of needles and leaves in stands growing on acid soils did not differ significantly between central Italy and southern Sweden (1.0 +/- 0.1 mmol N g(-1) for needles and 1.9 +/- 0.14 mmol N g(-1) for leaves). In both species, foliar N concentrations were highest in Germany (1.2 mmol N g(-1) for needles and 2.0 mmol N g(-1) for leaves) and decreased by 50% toward northern Sweden (0.5 mmol N g(-1)). Both species showed constant S/N and P/N ratios along the transect. Calcium, K and Mg concentrations generally reflected local soil conditions; however, Mg concentrations reached deficiency values in Germany. Leaf area per unit dry weight varied significantly along the transect with lowest values for Norway spruce recorded in northern Sweden and Italy (3.4 m(2) kg(-1)) and a maximum in central Europe (4.7 m(2) kg(-1)). A similar pattern was observed for beech. Despite the low variation in foliar N concentrations on the large geographic scale, local and regional variations in N concentrations equalled or exceeded the variation along the entire continental transect. Furthermore, nutrient contents (i.e., nutrient concentration x dry weight per needle or leaf) showed a greater variation than nutrient concentrations along the transect. Nitrogen contents of Norway spruce needles reached minimum values in northern Sweden (2.4 micro mol N needle(-1)) and maximum values in Denmark (5.0 micro mol N needle(-1)). The N content of beech leaves was highest in Denmark (242 micro mol N leaf(-1)). At the German site, foliar N content rather than N concentration reflected the seasonal dynamics of foliar growth and N storage of the two species. During foliage expansion, there was an initial rapid increase in N content and a decrease in N concentration. This pattern lasted for about 2 weeks after bud break and was followed by 6 weeks during which dry weight and N content of the foliage increased, resulting in a further decrease in N concentration. During summer, dry weight and N content of mature needles of Norway spruce increased further to reach a maximum in autumn, whereas N concentration remained constant. In spring, reallocation of N from 1- and 2-year-old needles was 1.5 and 1.0 micro mol N needle(-1), respectively. This remobilized N was a major source of N for the development of new needles, which had an N content of 1.5 micro mol N needle(-1) after bud break. The seasonal remobilization of N from old foliage decreased with increasing needle age. Needle N content and dry weight decreased progressively with age (1 micro mol N needle(-1) between age classes 2 and 5), whereas N concentrations remained constant. For Norway spruce, annual stemwood production was correlated with needle N content but not with foliar N concentration or with the total amount of N in the canopy. Interspecific and geographical differences in plant nutrition are discussed on the basis of competitive demands for C and N between growth of foliage and wood.

13.
Artículo en Inglés | MEDLINE | ID: mdl-1079116

RESUMEN

Corneal deposits of granular dystrophy were studies in six corneas from five patients. Two additional corneas from two patients with lattice dystrophy were used for comparison. The diagnoses were confirmed by light and electron microscopy. Three types of ultrastructural features were distinguished in the electron-dense rod-shaped deposits of granular dystrophy, i.e., Type 1 with homogenous structure, Type 2 with fibrillar constituents, and Type 3 with a moth-eaten or sponge-like appearance. In polarization microscopy of Congo-red stained sections, the Type 2 tended to show an increased birefringence without green dichroism, while the other types were less birefringent than the stroma. Three different components were found immediately around the deposits, i.e., 1. normal collagen fibrils, 2. finely filamentous substance, and 3. areas of thin fibrils (70-100 A in diameter). While the second component appeared non-specific, the third component was found only in two corneas, superimposed on the lesions of granular dystrophy, and showed light and electron microscopic characteristics of the lesions of amyloid as well as of lattice dystrophy.


Asunto(s)
Distrofias Hereditarias de la Córnea/patología , Anciano , Amiloide , Birrefringencia , Colágeno , Rojo Congo , Gránulos Citoplasmáticos/ultraestructura , Histocitoquímica , Humanos , Masculino , Microscopía Electrónica , Microscopía Fluorescente , Microscopía de Polarización
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA