D Old (d + old)

Distribution by Scientific Domains

Selected Abstracts

Toxicity of dispersed weathered crude oil to early life stages of Atlantic herring (Clupea harengus)

Stephen McIntosh
Abstract Reports of the chronic toxicity of dispersed crude oil to early life stages of fish perpetuate uncertainty about dispersant use. However, realistic exposures to dispersed oil in the water column are thought to be much briefer than exposures associated with chronic toxicity testing. To address this issue, the toxicity of dispersed weathered oil to early life stages of Atlantic herring (Clupea harengus) was tested for short exposure durations, ranging from 1 to 144,h. Toxicity was a function of concentration and duration of exposure, as well as of the life stage exposed. Medium South American crude oil dispersed with Corexit 9500 caused blue sac disease in embryos, but not in free-swimming embryos. The age of embryos was negatively correlated with their sensitivity to oil; those freshly fertilized were most sensitive. Sensitivity increased after hatch, with free-swimming embryos showing signs of narcosis. Gametes were also tested; dispersed oil dramatically impaired fertilization success. For exposures of less than 24,h, gametes and free-swimming embryos were the most sensitive life stages. For those of more than 24,h, young embryos (<1 d old) were most sensitive. The results are presented as statistical models that could assist decisions about dispersant use in the vicinity of fish spawning habitats. Environ. Toxicol. Chem. 2010;29:1160,1167. © 2010 SETAC [source]

Toxic responses of medaka, D-rR strain, to polychlorinatednaphthalene mixtures after embryonic exposure by in ovo nanoinjection: A partial life-cycle assessment

Sergio A. Villalobos
Abstract Polychlorinated naphthalenes (PCNs) are organic compounds with some chemical properties and uses similar to polychlo-rinated biphenyls. Polychlorinated naphthalenes have been detected in biota from certain aquatic environments. The toxicities of several PCN technical mixtures (Halowax) to medaka (Oryzias latipes) were determined by use of an embryo nanoinjection method. Medaka eggs (early gastrula) were injected with 0.5 nl of triolein (vehicle control) or 0.5 nl of four to five graded doses (0.3,30 ng/egg) of Halowax 1014, Halowax 1013, or Halowax 1051 in triolein. Following exposure, embryos developed, and fry were reared to sexual maturity (4 months), at which time they were euthanized. Responses were evaluated as early life stage (ELS) and early adult life stage (EALS) assessments. For ELS, lethality and sublethal alterations in embryos and larvae (<16 d old), such as craniofacial, cardiovascular, and myoskeletal deformities and abnormal or delayed hatch, were monitored for the first 9 d, and a dose severity index was computed. The EALS assessment examined the survival of 16-d-old larvae until early adulthood (123 ± 3 d old), including gonadosomatic index (GSI) and morphometry. Halowax 1014 was found to be the most toxic mixture (LD50 4.2 ng/egg), whereas Halowax 1013 and 1051 were significantly less toxic (LD50s could not be determined). The gonadosomatic index of females was significantly less in fish dosed with Halowax 1014 or 1051. The LD50 for medaka embryos nanoinjected with 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) is about 0.75 pg/egg. Thus, Halowax 1014 was 5,585-fold less potent than TCDD. For Halowax 1014, ELS assessments accurately predicted the results of EALS assessments. [source]

Innate and Learned Shoaling Preferences Based on Body Coloration in Juvenile Mollies, Poecilia latipinna

ETHOLOGY, Issue 11 2008
Jessica M. Ledesma
Shoaling offers fish enhanced protection from predators through a phenomenon known as the confusion effect. This phenomenon depends on a high degree of phenotypic homogeneity within a shoal, which may confuse predators that have difficulty in targeting a single individual as prey. Accordingly, fish typically choose shoalmates with similar phenotypic characteristics to themselves. In the molly (Poecilia latipinna), dramatic differences in body coloration have been shown to affect shoalmate choice in adults. Here, we show that juvenile mollies (50 d old) were capable of shoaling and that early experience impacted shoalmate choice. When raised in isolation, mollies chose shoalmates with similar body coloration to their own. When raised with other juvenile mollies, test fish chose to associate with individuals of the same coloration as the fish with whom they had been reared. These results show that P. latipinna are capable of the behavioral plasticity that has been demonstrated in other fish species, and that early experience affects the impact of body coloration on shoaling decisions in this species. [source]

Variation and Repeatability of Female Choice in a Chorusing Katydid, Ephippiger ephippiger: an Experimental Exploration of the Precedence Effect

ETHOLOGY, Issue 4 2004
Michael D. Greenfield
Female choice in various species of acoustic insects and anurans entails a psychoacoustic preference for male calls that lead their neighbors by a brief time interval. This discrimination, which can be termed a precedence effect, may select for various mechanisms with which males adjust call rhythm and thus reduce their incidence of ineffective following calls. At a collective level, alternating and synchronous choruses may emerge from these call timing mechanisms. Using playback experiments, we characterized the precedence effect in females of the katydid Ephippiger ephippiger, an alternating choruser in which males use a rhythm adjustment mechanism that prevents calling during brief intervals following their neighbors' calls. E. ephippiger females oriented toward leading male calls in >75% of trials when relatively young (<40 d old) and when playbacks were timed so that following calls began within 100,250 ms of the leading ones. However, this preference declined to below 60% as females aged and the interval separating leading and following call onsets increased. The strength of this precedence effect varied greatly between females, but within broad age classes the effect in a given female was statistically repeatable. Such repeatability indicates the possibility that additive genetic variance could be a significant component of variation in the precedence effect. We discuss the implications of our findings and inference on genetic variance for evolution of the precedence effect and for chorusing. [source]

Observations of predation by corvids at a Marbled Murrelet nest

Percy N. Hébert
ABSTRACT Unlike other alcids, Marbled Murrelets (Brachyramphus marmoratus) typically nest solitarily on large platforms in the upper canopy of old-growth coniferous trees. Although Marbled Murrelets exhibit characteristics that minimize the risk of predation, habitat fragmentation has likely increased the risk of nest predation by corvids. Using a video camera at a nest in northern California, we observed nest fates for 4 yr (2002,2005). These recordings revealed two cases of egg predation by a Steller's Jay (Cyanocitta stelleri) and a Common Raven (Corvus corax), respectively. In both instances, the egg was carried from the nest site, leaving no evidence that nesting had occurred. Our observations revealed (1) the need to be conservative in estimates of nesting attempts and nesting success of Marbled Murrelets based only on the presence or absence of eggshell fragments or feces, (2) that not all predation attempts were successful, and (3) that murrelets may be more susceptible to predation early in the incubation period when adults may be less attentive to eggs and, after hatching, when young are less than 14 d old. We encourage efforts to minimize anthropogenic activities that may increase local corvid densities or disturb murrelets during the early incubation period. SINOPSIS Contrario a otros álcidos, la uria (Brachyramphus marmoratus), anida comunmente, de forma solitaria en grandes plataformas en el docel de bosques maduros de coníferos. Aunque estas aves exhiben características que minimizan el riesgo de depredación, la fragmentación de habitat ha incrementado el mismo, particularmente por parte de córvidos. Utilizando una cámara de video en un nido en el norte de California,observamos el fracaso de nidos por cuatro años (2002,2005). Las grabaciones revelaron dos casos de depredación de huevos por parte de Cyanocitta stelleri y Corvus corax, respectivamente. En ambos casos, los huevos fueron cargados, y no se dejo evidencia de depredación. Nuestras observaciones revelan: (1) la necesidad de ser conservador cuando hace estimados de intentos de anidamiento y éxito de anidamiento de urias basado en la presencia o ausencia de fragmentos de cascarones o heces fecales, (2) que no todos los intentos de depredación fueron exitosos, y (3) que el ave estudiada pudiera ser más suceptibles a la depredación temprano en el periodo de incubación, cuando los adultos pudieran darle menor atención a los huevos, y luego del eclosionamiento, cuando los pichones tienen menos de 14 días. Fomentamos los esfuerzos para minimizar actividades antropogénicas que puedan incrementar las densidades locales de córvidos o el disturbio de urias durante las etapas tempranas de incubación. [source]

Determination of Regional Flavor Differences in U.S. Cheddar Cheeses Aged for 6 Mo or Longer

M.A. Drake
ABSTRACT:, Cheddar cheese is a widely popular food in the United States. This product is produced in facilities across the United States and often marketed based on region of manufacture, implying that regional differences in flavor character of the cheese exist. This study was conducted to determine if regional differences in flavor exist in the aged U.S. Cheddar cheeses. Three times per year for 2 y, triplicate 18-kg blocks of Cheddar cheese (< 60 d old) were obtained from 19 manufacturing facilities located in 4 major cheese- producing regions/states: California, Northwest, Midwest, and Northeast. A trained sensory panel documented the flavor characteristics of cheeses after 6-, 9-, 12-, 18-, and 24-mo ripening at 7 °C. Regional differences were observed for specific flavors for cheeses manufactured in the Northwest, Midwest, and Northeast across ripening (P < 0.05), but the specific flavors responsible for these effects were not consistent across ripening. Similarly, cheese make procedure effects were also observed for specific flavors across ripening (P < 0.05), but these differences were also not consistent across ripening. The impact of region and cheese make procedure on flavor of the aged Cheddar cheeses was small in comparison to consistently documented, facility-specific flavor differences (P < 0.0001). Flavor profiles of aged Cheddar cheeses were most strongly influenced by practices specific to manufacturing facility rather than region of manufacture. [source]

Carbon use efficiency depends on growth respiration, maintenance respiration, and relative growth rate.

A case study with lettuce
ABSTRACT Carbon use efficiency (CUE, the ratio between the amount of carbon incorporated into dry matter to the amount of carbon fixed in gross photosynthesis) is an important parameter in estimating growth rate from photosynthesis data or models. It previously has been found to be relatively constant among species and under different environmental conditions. Here it is shown that CUE can be expressed as a function of the relative growth rate (rGR) and the growth (gr) and maintenance respiration coefficients (mr): 1/CUE = 1 + gr + mr/rGR. Net daily carbon gain (Cdg), rGR, and CUE were estimated from whole-plant gas exchange measurements on lettuce (Lactuca sativa L.) ranging from 24 to 66 d old. Carbon use efficiency decreased from 0.6 to 0.2 with increasing dry mass, but there was no correlation between CUE and Cdg. The decrease in CUE with increasing dry mass was correlated with a simultaneous decrease in rGR. From the above equation, gr and mr were estimated to be 0.48 mol mol,1 and 0.039 g glucose g,1 dry matter d,1, respectively. Based on the gr estimate, the theoretical upper limit for CUE of these plants was 0.68. The importance of maintenance respiration in the carbon balance of the plants increased with increasing plant size. Maintenance accounted for 25% of total respiration in small plants and 90% in large plants. [source]

Accelerated ventricular rhythm in the neonatal period: a review and two new cases in asymptomatic infants with an apparently normal heart

M Anatoliotaki
Accelerated ventricular rhythm (AVR) was observed in two newborn infants. In the first case, arrhythmia was noted during the foetal period. Both neonates were asymptomatic and had no evidence of cardiac disease. The arrhythmia eventually disappeared when the infants were 4 mo and 24 d old, respectively. AVR in the neonatal period is reviewed in this report and recent information regarding appropriate diagnostic evaluation, differentiation from ventricular tachycardia and treatment is outlined. Conclusion: Accelerated ventricular rhythm is a benign and self-limited arrhythmia in the neonatal period. However, it is important to differentiate it from other serious rhythm disorders, mainly ventricular tachycardia, in order to avoid unnecessary and potentially harmful treatment and to relieve parental anxiety. [source]

Folic acid supplementation on red kidney bean-induced diarrhoea and enteric bacterial translocation into mesenteric lymph nodes in rats: a pilot study

R Shoda
Deaths following childhood diarrhoea, a major health problem in developing countries, are often associated with malnutrition and septicaemic complications. Folic acid has been used in the treatment of acute and chronic diarrhoea in the tropics. Using a rat model, we evaluated the protective effect of large doses of folic acid on diarrhoea, small intestinal bacterial overgrowth and translocation of enteric bacteria into mesenteric lymph nodes induced by a raw red kidney bean-based diet containing lectin (phytohemagglutinin). Long-Evans rats in 2 groups of 5 each (60 g to 70 g in weight, 28 d old) were used. All 10 rats, individually kept in metabolic cages, received a raw red kidney bean-based diet for 10 d, and 5 of them also received a daily folic acid supplement (160 ,g/g feed) both during and for 10 d before the experiment. The faecal weight was measured and a quantitative aerobic bacterial culture of the small intestinal mucosal scrapings and of the mesenteric lymph nodes was made. Folic acid supplementation did not reduce faecal output nor did it prevent loss of body weight associated with lectin-induced diarrhoea. However, the mean total count of enteric bacteria translocated to the mesenteric lymph nodes was significantly reduced in the supplemented rats (1.27 ± 0.61 vs 2.66 ± 0.84, p= 0.028) and a trend towards reduced bacterial count in the small intestinal mucosal scrapings (0.40 ± 0.89 vs 1.42 ± 1.31, p= 0.16) was documented. A significant positive correlation was also seen between the bacterial count in the jejunal mucosal scrapings and in the mesenteric lymph nodes. Conclusion: Although large-dose folic acid supplementation did not prevent diarrhoea and malnutrition induced by a lectin-based diet, it substantially reduced the count of enteric bacteria translocated into the mesenteric lymph nodes and showed a trend towards a reduction in indigenous bacteria adhering to jejunal mucosa. These findings could be of relevance in the prevention of septicaemic complications following many clinical conditions, including diarrhoea with malnutrition in children known to have bacteraemic and septicaemic complications. [source]