A layered structure in the organic envelopes of the prismatic layer of the shell of the pearl oyster Pinctada margaritifera (Mollusca, Bivalvia).

The organic interprismatic layers of the mollusc Pinctada margaritifera are studied using a variety of highly spatially-resolved techniques to establish their composition and structure. Our results show that both the interlamellar sheets of the nacre and interprismatic envelopes form layered structures. Additionally, these organic layers are neither homogeneous in composition, nor continuous in their structure. Both structures play a major role in the biomineralization process and act as a boundary between mineral units.

Reproductive and Environmental Drivers of Time and Activity Budgets of Striped Skunks.

The regulation of daily and circannual activity patterns is an important mechanism by which animals may balance energetic requirements associated with both abiotic and biotic variables. Using collar-mounted accelerometers, we assess the relative importance of reproductive stage and environmental conditions on the overall dynamic body acceleration (ODBA) of free-living striped skunks (Mephitis mephitis). We found that activity timing relative to photoperiod varied across seasonal stages for both sexes. Surprisingly, male skunks did not commence activity earlier than females during the mating interval. Moreover, while female skunks began activity before dusk and terminated activity after dawn during mid- through late summer (lactation period), the duration of activity bouts in females during this period was not different from other seasons. Both male and female skunks exhibited high variability and fragmentation in daily activity rhythms except during the lactation period, when females appear to switch to prolonged bouts of nocturnal activity. Overall, ODBA varied by season and sex, with changes in ODBA indicative of seasonal reproductive requirements such as conspecific competition for mates in males and lactation in females. Weather conditions had little effect on skunk activity levels except during the winter season, when snow cover and temperature negatively influenced daily ODBA. Taken together, the activity patterns of striped skunks appear to be primarily driven by seasonal investment in reproduction and secondarily by thermoregulatory constraints during the non-winter months. Our results highlight the importance of considering how environmental and reproductive drivers may interact to affect activity across both the daily and seasonal cycle.

Regulación de la energía en mofetas rayadas ante la reproduccin y el ambiente La regulación de los patrones de actividad diaria y circanual es un mecanismo importante mediante el cual los animales pueden equilibrar los requerimientos energéticos asociados con las variables bióticas y abióticas. Usando acelerómetros montados en collar, evaluamos la importancia relativa de la etapa reproductiva y las condiciones ambientales en la aceleración global dinámica del cuerpo (ODBA, por sus siglas en inglés) de las mofetas rayadas (Mephitis mephitis). Encontramos que el tiempo de actividad en relación con el fotoperíodo varió a lo largo de las etapas estacionales para ambos sexos. Sorprendentemente, las mofetas macho no comenzaron la actividad antes que las hembras durante el intervalo de apareamiento. Además, las mofetas hembra comenzaron la actividad antes del anochecer y terminaron la actividad después del amanecer durante la mitad del verano (período de lactancia), la duración de los episodios de actividad en las hembras durante este período no fue diferente de otras estaciones. Tanto las mofetas macho como las hembra mostraron una alta variabilidad y fragmentación en los ritmos de la actividad diaria, excepto durante el período de lactancia, cuando las hembras parecen cambiar a episodios prolongados de actividad nocturna. En general, la ODBA varió según la temporada y el sexo, con cambios en la ODBA indicativos de los requisitos reproductivos estacionales, como la competencia específica para los machos en los machos y la lactancia en las hembras. Las condiciones climáticas tuvieron poco efecto en los niveles de actividad de la mofeta, excepto durante la temporada de invierno, cuando la capa de nieve y la temperatura influyeron negativamente en la ODBA diaria. Tomados en conjunto, los patrones de actividad de las mofetas rayadas parecen estar impulsados principalmente por la inversión estacional en la reproducción y, en segundo lugar, por las restricciones de termorregulación durante los meses que no son de invierno. Nuestros resultados resaltan la importancia de considerar cómo los impulsores ambientales y reproductivos pueden interactuar para afectar la actividad a lo largo del ciclo diario y estacional. Translated to Spanish by S Hinojosa (hinojosa.silvia@gmail.com).

Deciphering the distribution of organic components in brachiopod shells by confocal laser scanning microscopy.

Characterization of the nature and distribution of organic components is crucial to understand shell formation in marine invertebrates. Although several techniques can provide detailed information at high spatial resolution, few of them are non-destructive and informative in a larger structural context. We explore the use of confocal laser scanning microscopy (CLSM) to obtain a better understanding of the distribution of organic components in calcitic shells of brachiopods focusing on perforations (punctae) across the shell. Resulting intensities and patterns of fluorescence correspond well with the distribution of polysaccharides and proteins as reported in previous histological and biochemical studies. Confocal laser microscopy is, therefore, a useful tool to be combined with other techniques to improve our knowledge of biomineral structures in marine invertebrates.

Thermogenic capacity at subzero temperatures: how low can a hibernator go?

Abstract Hibernation in mammals is a physiological and behavioral adaptation to survive intervals of low resource availability through profound decreases in metabolic rate (MR), core body temperature (Tb), and activity. Most small mammalian hibernators thermoconform, with Tb approximating ambient temperature (Ta); arctic species are an exception, since they must actively defend what can be large thermal gradients between Tb and Ta. Here we compare the thermogenic capacity of the arctic ground squirrel (Urocitellus parryii) to that of the golden-mantled ground squirrel (Callospermophilus lateralis), a temperate-zone montane hibernator. We allowed animals to reenter torpor at sequentially lower Ta's and found that arctic ground squirrels maintained steady state torpor at Ta's as low as -26°C, through a 36-fold increase in torpid MR (TMR), compared to their minimum TMR, exhibited at a Ta of 0°C. Golden-mantled ground squirrels are able to maintain steady state torpor at Ta's at least as low as -8°C, through a 13.5-fold increase in MR, compared to their minimum TMR at a Ta of 2°C. In a second experiment, torpid animals were exposed to continuously decreasing Ta's (0.25°C/30 min); individuals of both species increased their metabolism while remaining torpid at low Ta's (as low as -30°C for arctic ground squirrels and -10°C for golden-mantled ground squirrels). Although the capacity to hibernate at subfreezing Ta's is not unique to arctic ground squirrels, their large body size, greater torpid metabolic scope, and previously ascribed capacity to supercool allow them to occupy much colder hibernacula for prolonged seasons of hibernation.

Magnetic resonance imaging of the mini-pig heart: the effect of gadolinium-DTPA on normal myocardium.

The effect of gadolinium-diethylene-triamine-penta-acetic acid (Gd-DTPA) on normal, mini-pig myocardium was investigated with magnetic resonance imaging. Results indicate that intravenous administration of Gd-DTPA produces a significant enhancement of mini-pig myocardial signal intensity, which in all cases was maintained in excess of 50 min. No significant enhancement was demonstrated in skeletal muscle.

Buffer zone widths for honeybees from ground and aerial spraying of insecticides.

The relative field hazards of insecticides to honeybees have been estimated by considering intrinsic toxicity levels and field application rates. This approach is extended here to a consideration of buffer zones downwind of sprayed areas by estimating the distance at which bees would encounter an LD(50) dose from spray drift. 'LD(50) distances' are determined for both ground and aerial spraying of ground crops in Britain using published data on spray deposition under various weather conditions. For ground spraying at low wind speeds (< or =3 m s(-1)), this zone of risk is up to 5 m for the great majority of compounds. Aerial spraying in unstable atmospheric conditions appears to produce drift deposits of about the same order of magnitude as from ground spraying at wind speeds of about 4 m s(-1), with maximum LD(50) distances of < or =40 m for chlorpyrifos, fenitrothion and triazophos. For aerial spraying in stable atmospheric conditions these distances would be much greater. Pieris brassicae larvae are contrasted with honeybees in their relative sensitivities to insecticides and consequent LD(50) distances.

Ethical considerations surrounding first time procedures: a study and analysis of patient attitudes toward spinal taps by students.

A patient is not always told when a student is performing a procedure for the first time. Withholding this information is a form of deception. It is justified on paternalistic grounds (it is in the patient's interest not to know), or on public policy grounds (given the choice, patients would refuse, thus compromising the training of future physicians). Using the spinal tap procedure (lumbar puncture) as a paradigm, 173 patients were surveyed to determine how they felt about first time procedures by medical students, interns, and residents. The patients indicated that they would be willing to be the subject for a student's (52%), intern's (62%), or resident's (66%) first spinal tap. This paper reassesses the ethics of consent for first time procedures based on responses to this survey.

Assessment of the effects of herbicide spray drift on a range of plant species of conservation interest.

With increasing use of herbicides there has been growing concern that spray drift from treated land will affect vegetation on adjacent nature reserves and other areas of high conservation interest. A preliminary attempt was made to assess this risk by placing a range of native plant species at different distances downwind from standardised drift events and assessing lethal effects and sublethal damage. Five herbicides were tested: asulam, 'Finesse' (chlorsulfuron + metsulfuron-methyl), glyphosate, MCPA and mecoprop. Applications were made at the appropriate time of years for each herbicide (autumn, spring and summer), and at both low and high wind speeds. The maximum safe distance at which no lethal effects were found was 6 m from the sprayer, but for most herbicides the distance was 2 m or less. Generally, damage symptoms were found at greater distances than lethal effects, but in most cases there was rapid recovery by the end of the growing season. These observations are consistent with drift-deposition models, in which the fallout of herbicide droplets has been measured. It is suggested that buffer zones surrounding nature reserves should be in the order of 5-10 m for ground sprayers to minimise the risk of herbicide impacts on these habitats.

Thermal decomposition of generation-4 polyamidoamine dendrimer films: decomposition catalyzed by dendrimer-encapsulated Pt particles.

The thermal decomposition of hydroxyl-terminated generation-4 polyamidoamine dendrimer (G4OH) films deposited on Au surfaces has been compared with decomposition of the same dendrimer encapsulating an approximately 40-atom Pt particle (Pt-G4OH). Infrared absorption reflection spectroscopy studies showed that, when the films were heated in air to various temperatures up to 275 degrees C, the disappearance of the amide vibrational modes occurred at lower temperature for the Pt-G4OH film. Dendrimer decomposition was also investigated by thermogravimetric analysis (TGA) in both air and argon atmospheres. For the G4OH dendrimer, complete decomposition was achieved in air at 500 degrees C, while decomposition of the Pt-G4OH dendrimer was completed at 400 degrees C, leaving only platinum metal behind. In a nonoxidizing argon atmosphere, a greater fraction of the G4OH decomposed below 300 degrees C, but all of the dendrimer fragments were not removed until heating above 550 degrees C. In contrast, Pt-G4OH decomposition in argon was similar to that in air, except that decomposition occurred at temperatures approximately 15 degrees C higher. Thermal decomposition of the dendrimer films on Au surfaces was also studied by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) under ultrahigh vacuum conditions. Heating the G4OH films to 250 degrees C during the TPD experiment induced the desorption of large dendrimer fragments at 55, 72, 84, 97, 127, 146, and 261 amu. For the Pt-G4OH films, mass fragments above 98 amu were not observed at any temperature, but much greater intensities for H(2) desorption were detected compared to that of the G4OH film. XPS studies of the G4OH films demonstrated that significant bond breaking in the dendrimer did not occur until temperatures above 250 degrees C and heating to 450 degrees C caused dissociation of C=O, C-O, and C-N bonds. For the Pt-G4OH dendrimer films, carbon-oxygen and carbon-nitrogen bond scission was observed at room temperature, and further decomposition to atomic species occurred after heating to 450 degrees C. All of these results are consistent with the fact that the Pt particles inside the G4OH dendrimer catalyze thermal decomposition, allowing dendrimer decomposition to occur at lower temperatures. However, the Pt particles also catalyze bond scission within the dendrimer fragments so that decomposition of the dendrimer to gaseous hydrogen is the dominant reaction pathway compared to desorption of the larger dendrimer fragments observed in the absence of Pt particles.

Implementation of an automated medication/supply distribution system.

In the summer of 1992, Carraway Methodist Medical Center implemented a computerized medication and supply distribution system from the pharmacy and central supply to the patient care units. Improved efficiency was achieved in the form of automatic billing, inventory control, decreased worked hours per patient day, and improved documentation. Regulatory requirements relating to narcotic distribution were simplified through technology eliminating manual counting, handwritten signatures, and manual record keeping. The impact from this change was cost effective, allowed more time at the bedside, provided easier access to pharmacy and central supply items, facilitated inventory control, and increased nursing productivity as well as increasing nursing satisfaction.

Single donor platelets: can we afford to use them? Can we afford not to use them?

One of the strategies to reduce the risk of harming a patient by transfusion therapy is to limit the overall risk of transfusion-transmitted disease. Central to this approach is minimizing the number of allogeneic blood products with which a patient is transfused. The usual dose of platelets for an adult patient is either six to 10 random donor platelets vs. one unit of platelets, pheresis (so-called single donor apheresis platelets). Consequently, the transfusion services at the University of Southern California Health Sciences Campus (USC University Hospital, the Norris Cancer Hospital, and Los Angeles County + USC Medical Center) routinely use single donor apheresis platelets (SDPs) rather than random donor platelets (RDPs) in an effort to minimize allogeneic platelet transfusions, and thereby reduce risk of transfusion-transmitted infection. Although there are other compelling medical, technical, and medical-legal reasons to use SDPs instead of RDPs, the authors believe that a decrease in allogeneic donor exposures alone is sufficient reason to make SDPs the platelet component of choice at their institutions.