Tauchbeobachtungen an Plankton und an Echostreuschichten

Zusammenfassung 1. Das Tauchen als Methode zur Untersuchung von Plankton und Echostreuschichten wird durch vier Beispiele erläutert: (a) Visuelle Beobachtungen an Wasserschichtungen und Grenzschichten durch Schwimmtaucher. (b) Untersuchung von Echostreuschichten durch Freitaucher, wobei sich ergab, daß angesammeltes biogenes Material in den untersuchten Sprung- beziehungsweise Streuschichten die Schallreflektion nicht beeinflußt. (c) Beobachtung von Großplankton und Feststellung von Planktonund Sestonkonzentrationen beim Tauchen mit dem Bathyscaph. (d) Untersuchung der Tiefenstreuschicht (deep scattering layer) durch Beobachtung der Vertikalwanderung bestimmter Arten des Großplanktons mit den Tauchbooten Bathyscaph und Soucoupe Plongeante. Physonectide Siphonophoren und Myctophiden standen in deutlicher Beziehung zur Tiefenstreuschicht und wurden als Echogeber erkannt.2. Die Möglichkeiten, von Tauchbooten aus quantitative und qualitative Proben von Plankton und auch vom Benthos zu nehmen, sind zur Zeit noch unzureichend. Die Entwicklung entsprechender Geräte für den wahlweisen und mehrfachen Einsatz bei demselben Tauchgang wird empfohlen.

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Diving observations on plankton and on scattering layers

Diving techniques are employed as a research tool in plankton investigations carried out in shallow water of the western Baltic Sea. Observations and samplings were made by skin divers on scattering layers corresponding to the discontinuity layers. Biogene materials, sometimes concentrated at the thermocline, are not responsible for this special kind of scattering, but rather discontinuity of salinity and temperature (Lenz 1965). For observations in deep water the use of undersea vehicles is recommended. From the Bathyscaph and the diving saucer, single plankton organisms and plankton concentrations were observed (e. g.Bernard 1958); investigations on the deep scattering layer have shown physonectid siphonophores and myctophids to be scatterers (Barham 1966). The equipment for sampling plankton and benthos from undersea vehicles is poorly developed. We need urgently gear for quantitative and qualitative sampling and for manifold use during single dives, i. e., multiple sampling gear and magazins for storage of samples.

     

Modelling an outbreak of an emerging pathogen

To illustrate the usefulness of mathematical models to the microbiology and medical communities, we explain how to construct and apply a simple transmission model of an emerging pathogen. We chose to model, as a case study, a large (>8,000 reported cases) on-going outbreak of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) in the Los Angeles County Jail. A major risk factor for CA-MRSA infection is incarceration. Here, we show how to design a within-jail transmission model of CA-MRSA, parameterize the model and reconstruct the outbreak. The model is then used to assess the severity of the outbreak, predict the epidemiological consequences of a catastrophic outbreak and design effective interventions for outbreak control.     

On an interacting particle system modeling an epidemic

We consider an interacting particle system onZ ^dto model an epidemic. Each site ofZ ^dcan be in either one of three states: empty, healthy or infected. Healthy and infected individuals give birth at different rates to healthy individuals on empty sites. Healthy individuals get infected by infected individuals. Infected and healthy individuals die at different rates. We prove that in dimension 1 and with nearest-neighbor interactions the epidemic may persist forever if and only if the rate at which infected individuals give birth to healthy individuals is high enough. This is in sharp contrast with models analysed by Andjel and Schinazi (1994) and Sato et al. (1994) where infected individuals do not give birth. We also show that some results in the latter reference can be obtained easily and rigorously using probabilistic coupling to the contact process.     

Solvent-tolerance of fungi located on an interface between an agar plate and an organic solvent

While 6 by 20 of type culture fungi could grow on an interface between organic solvent (log P, 4.12) and agar plate, 13 by 20 of strains could form a large colony after the removal of more toxic solvent, such as styrene (log P, 2.95) and tert-butyl acetate (log P, 1.76) because of viability of spores on the interface.     

Beugungspolarisatorische Messungen an isotonisch und an isometrisch kontrahierten Insektenmuskeln

Zusammenfassung In Ergänzung zu polarisationsmikroskopischen Untersuchungen isotonisch und isometrisch kontrahierter Insektenmuskeln sind beugungspolarisatorische Messungen an jenen und an einem Muskelmodell (Myosinfäden) angestellt worden. Soweit die Befunde heute schon gedeutet werden können, sind sie als Bestätigung des polarisations- und röntgenoptisch, visko- und thermoelastisch und nach dem kolloiden Verhalten erschlossenen leptonischen Bauplans der Objekte anzusehen.     

Inheritance of an oviposition behavior by an egg parasitoid

A quantitative genetic study revealed genetic and environmental sources of variance in percentage parasitism of European corn borer egg masses and secondary sex ratios by Trichogramma nubilale. Full and half-sib groups of T. nubilale were obtained from a nested mating design, which permitted the partitioning of the variance of T. nubilale parasitism of European corn borer egg masses into additive genetic variance, maternal/dominant variance and environmental variance. A mother-daughter regression of the percentage of an egg mass parasitized allowed a determination of the direction of a potential response to selection in the event of maternal effects. No or very little additive genetic effects were associated with the percentage of eggs within a mass parasitized and secondary sex ratios, but a significant amount of the variance for both traits had a maternal and/or dominant genetic source. The relationship between mothers and daughters in egg mass parasitism was positive, and 55.4% of the progeny of a given mother had behaviors that resemble their mother. Most of the variance had an environmental and/or unknown genetic source implying potentially high phenotypic plasticity associated with all these traits. The presence of maternal effects and phenotypic plasticity could have multiple and complex effects on progeny characters and potential responses to selection.     

Adaptation of an introduced host to an indigenous parasite

Introduction of striped bass to the west coast from the east coast of the U.S.A. provided the opportunity to study a recent host-parasite association in a marine system. An indigenous species of parasite was known to induce pathological changes in the introduced population. Because the west coast population has been in association with this pathogenic parasite more than 20 generations, we predicted that the host reaction of the west coast population would be less severe compared to that of the naive east coast stock of striped bass. This prediction was tested by conducting reciprocal infection experiments with east and west coast hosts and parasites. The group of west coast striped bass had a lower intensity of infection and exhibited less tissue damage compared to the group of east coast striped bass. We suggest that selection has acted only on the host and is driven by parasite-induced host mortality. This type of 1-sided selection is in contrast to present models of the evolution of host-parasite associations.     

Pandemic bounds for an epidemic on an infinite lattice

Exact results have previously been obtained concerning the spread of infection in continuous space contact models describing a class of multi-type epidemics. Pandemic lower and upper bounds were obtained for the spatial final size. Pandemic results have also been obtained for a discrete space model on the integer lattice using an infinite matrix formulation of the final size equations. However, the proof required restrictive constraints to be placed on the model parameters which do not hold in general and will not be valid when infection modifies behaviour. The purpose of this paper is to remove these constraints and give a general proof of the pandemic results for the multi-type epidemic on the lattice Z(N).     

Solution structure of an oligonucleotide containing an abasic site: evidence for an unusual deoxyribose conformation

The antitumor antibiotic bleomycin causes two major lesions in the deoxyribose backbone of DNA: formation of 4′-keto abasic sites and formation of strand breaks with 3′-phosphoglycolate and 5′-phosphate ends. As a model for the 4′-keto abasic site, we have characterized an abasic site (X) in d(CCAAAGXACTGGG)·d(CCCAGTACTTTGG) by two-dimensional NMR spectroscopy. A total of 475 NOEs and 101 dihedral angles provided the restraints for molecular modeling. Four unusual NOEs were observed between each anomer of the abasic site and the neighboring bases. In addition, four coupling constants for adjacent protons of the deoxyribose of both the α and β anomers of the abasic site were observed. The modeling suggests that for both anomers the abasic site is extrahelical, without significant distortion of the backbone opposite the lesion. The coupling constants further allowed assignment of an unusual sugar pucker for each anomer. The unique position of the abasic site in our structural model for each anomer is discussed in terms of repair of such lesions in vivo.     

Incidence of an electron layer on an electrically insulated body with an unsteady self-consistent positive charge

Dynamics of an electron layer incident on the surface of an electrically insulated conducting body with an unsteady self-consistent positive charge is investigated. At the initial instant, the electron velocity is directed toward the body and the electron layer is not adjacent to the body surface. One-dimensional plane, cylindrical, and spherical electron motions in vacuum and against the background of motionless ions and neutral particles are considered. Exact analytical solutions to the set of nonlinear plasma hydrodynamics equations with absorbing boundary conditions for electrons are obtained. The spatial and time dependences of the electric field, electron density, and electron velocity are found. The time evolution of the surface charge density is determined.     

Oxygen consumption by mitochondria from an endotherm and an ectotherm

Comparisons of metabolic properties of mitochondria from an endothermic and an ectothermic vertebrate were performed. Oxygen (O2) consumption rates of liver mitochondria from laboratory mice and western fence lizard (Sceloporus occidentalis) were determined over a range of temperatures (10, 20, 30 and 37 degrees C) and in the presence of a variety of substrates. At 37 degrees C the O2 consumption rate of mouse mitochondria was 4-11 times higher than lizard mitochondria in the presence of five of eight substrates. This range of differences is similar to differences reported for O2 consumption of endothermic animals, tissues and cells over those of ectotherms. Thermal sensitivity of mitochondria was measured by calculation of Q10s for O2 consumption. Q10s were highest for mouse mitochondria overall. The range that showed the highest Q10s for the mouse mitochondria was 30-20 degrees C, whereas for the lizard mitochondria it was 20-10 degrees C. Thus, mitochondria from the ectotherm showed a lower degree of temperature sensitivity than did mitochondria from the endotherm. The preferred substrate for all mitochondria at all temperatures was succinate, but mouse mitochondria then showed some preference for alpha-ketoglutarate and citrate, whereas lizard mitochondria showed a preference for pyruvate and malate + pyruvate.     

Abdominal pain associated with an intra-abdominal gonad in an adult

Controversy still surrounds management of cryptorchidism in adults. Options include orchiectomy, orchiopexy, and close observation. What about fertility if orchiectomy is chosen? How is the risk of cancer affected when observation is the choice? Follow the reasoning for the management strategy for this adult presenting with abdominal pain.     

Censoring in an epidemic with an application to hemophilia-associated AIDS

In epidemiologic studies of infectious diseases, the times of infection may be known only up to an interval. A two-stage parametric regression model is proposed for the analysis of cohort studies during an epidemic in which the exact times of infection cannot be ascertained. The methods permit joint estimation of the effects of covariates both on the risk of infection and the risk of progression to clinical disease once infected. The methodology is applied to a cohort of hemophiliacs who were at risk of infection with the AIDS virus. It was found that hemophiliacs with severe Type A hemophilia were at highest risk of infection, and the risk of infection increased sharply in the early 1980s. Hemophiliacs who were over the age of 20 at infection were at higher risk of progression to AIDS than hemophiliacs who were under age 20. The estimate of the cumulative probability of developing AIDS within t years of infection (the incubation period distribution) for hemophiliacs over age 20 was 1 - exp(-.0021t2.516). Since follow-up in this cohort was restricted to about 10 years from infection, estimates of the incubation period distribution beyond 10 years depend on model extrapolation and should be interpreted cautiously.