bluuebunny/crossref_metadata_2025 huggingface dataset:
Why does it work?
Authors: Dindorf Wojciech
Published: April 2003

Recently I was playing with two spheres, one made of hard steel, the other of hard rubber. I found that I could easily tilt my stretched palm to a large angle and the balls did not want to roll down. It worked, however, only when the steel ball was above the rubber one. In other workds, rubber first.
Solving an “unsolvable” projectile-motion problem
Authors: Montalvo David
Published: April 2003

If there were any rules about teaching physics, “Don’t assign problems to the students that you, yourself, cannot solve” would probably top the list. And yet this bias is an unfortunate one: a closer examination of some of these problems can lead to new and valuable understandings.
Physics on graphing calculators
Authors: Phillips Dennis W.
Published: April 2003

Access to graphing calculators in the physics classroom makes possible two programs and activities mentioned here pertaining to blackbody radiation curves and alpha particle scattering by a nucleus.
Weight—An official definition
Authors: Iona Mario
Published: April 2003

The opinion paper by Richard C. Morrison asks why there is such a variety of definitions of weight. The first hurdle of establishing the meaning of weight is to make it clear that we are dealing with a force and not a synonym for mass. We should also realize that the authors are trying to describe a common but rather complicated experience, and not a simple textbook concept of a fundamental nature such as force or energy.
π from a milk container
Authors: Guerra-Vela Claudio
Published: April 2003

A simple hands-on exercise to measure π is described. The exercise helps physics students at the first-year level to find the π value and understand this important idea in a way hard to forget.
Kinetic Art
Authors: Bouffard Karen
Published: April 2003

In this Physics Olympics challenge, each participant builds an artistic structure that will move in whole or in part. The piece will remain in place, be easily set in motion, will remain in motion for at least two minutes, and be able to do so repeatedly.
A website for the “misforgotten”
Authors: Stahl Frieda A.
Published: April 2003

We now have a uniquely dynamic new information device—a website, “Contributions of 20th Century Women to Physics.” This website is a student-friendly resource for courses in physics, as well as history of physics, physics and society, women in science, and other topical areas of women’s studies.
The importance of graphs in undergraduate physics
Authors: Deacon Christopher
Published: April 2003

The graph is a tool for the analysis of data, but like any tool is only as effective as a student’s ability to interpret it in a meaningful way. This article suggests ways that graphs can be plotted to extract the maximum information from an experiment.
Holt Physics
Authors: Serway Raymond A. , Faughn Jerry S. ,   Physics Textbook Review Committee
Published: April 2003

This 1999 textbook by Serway and Faughn is one of seven textbooks reviewed in this issue of The Physics Teacher.
Myths about gravity and tides
Authors: Sawicki Mikolaj
Published: April 2003

Popular misconceptions and outright myths about gravity and tides are illustrated by examples recently found in magazines and newspapers, and then discussed.
Showing forces in the terrestrial magnetic field
Authors: Bednarek Stanislaw
Published: April 2003

Two demonstrations showing emf induced in the Earth’s magnetic field are described. A long wire is shaken or twirled and the current induced can be detected by a milliammeter.
The fractal dimension of breads
Authors: Amaku Marcos , Horodynski-Matsushigue Lighia B. , Pascholati Paulo R.
Published: April 2003

In this paper, we present an alternative way of estimating the fractal dimension of breads, by means of a graphical analysis. This method of analysis can be used either in the secondary school or in a university laboratory course.
Galileo’s pendulum
Authors: Erlichson Herman
Published: April 2003

In this paper we describe the second laboratory experiment in the liberal-arts physics course with the title “Galileo to Newton and Beyond.” The experiment calls attention to Galileo’s erroneous belief in the isochrony of the pendulum no matter how large the pendulum amplitude was. This belief dates from at least as early as 1602, 36 years before his Two New Sciences was published.
Radioactivity experiments for project investigation
Authors: Mak Se-yuen
Published: April 2003

Two radioactivity experiments, using KCI as the source, are recommended for pupils’ project investigation: (1) The mass absorption coefficient of β-particles for four different substances were determined and compared with an empirical formula. (2) The half-life of 40K was determined from the count-rate. Possibilities for improvement are discussed.
Camera and telescope free-for-all!
Authors: Byrd Gene , Graham Mark
Published: April 2003

Would you believe that for practically no expense you can do a lab in which each student dissects a camera and builds a telescope?
Heating water: Rate correction due to Newtonian cooling
Authors: O’Connell James
Published: April 2003

Water temperature does not increase linearly when heated at a constant rate because of concurrent Newtonian cooling. The correction to the linear temperature vs time curve can be obtained experimentally by measuring the exponential cooling curve from high temperature to room temperature.
Electromagnetism in the movies
Authors: Everitt Lori R. , Patterson Evelyn T.
Published: April 2003

We have developed five introductory electricity and magnetism lessons composed of student activities centering on analysis of short clips from popular movies. We describe our motivation for doing this, the kinds of activities, and offer our materials to those interested.
Supernumerary rainbows
Authors: Sawicki Mikolaj , Sawicki Pawel
Published: April 2003

Late in the afternoon of July 19, 1999, we were able to photograph some very unusual rainbows in the sky over Boulder, Colorado. The picture here shows a primary rainbow, a fainter secondary bow above it, and several pastel-shaded rainbows inside the primary one. While we think we counted as many as four concurrent rainbows in that afternoon, only three of them show up in developed prints.
PSST! — Want to buy my lecture notes?
Authors: Singham Mano
Published: April 2003

A few years ago, when the Internet was really taking off and Case Western Reserve University was in the vanguard of efforts to electronically link everyone on campus, an idea came to me. I teach the large introductory physics courses having around 200 students in a lecture and I have been handing out daily homework assignment sheets to all the students in the classes. This involved a great deal of tedious photocopying and the carrying of vast quantities of paper to class each day. My thought was, why not put all this stuff on the Web so that students could access it whenever and wherever they wanted? A colleague warned me against this. “If you do that,” I was told, “students will have no reason to come to your lectures.“
Extrapolations and prognostications
Authors: Swartz Clifford E.
Published: April 2003

It’s that time of millennium again when we look to the past and prophesy about the future. My own family memories don’t go much past the 20th century, although my wife is a direct descendant of a woman convicted of witchcraft in Salem. Not recently, of course. A century ago, my mother was going to school in a one-room schoolhouse with student desks in rows and a blackboard up front for the teacher. In high school she studied physics but there were no student laboratory exercises and only a few demonstrations by the teacher. She didn’t like it.
The “holey” ball launcher
Authors: Tomac Mike
Published: April 2003

A homemade pitching machine that launches plastic holey balls can be constructed from drill motors and sanding disks. This could possibly find uses in the physics classroom.
Inexpensive demonstrator of Newton’s first law
Authors: Williams Karen
Published: April 2003

Newton’s first law can be stated as: An object will move with constant velocity (which may be zero) unless acted upon by a net external force. Student scores on the Force Concept Inventory show that students don’t understand Newton’s laws, even though they may nod their heads in understanding during classroom discussions.
The make-it-yourself drop-tower microgravity demonstrator
Authors: LaCombe Jeffrey C. , Koss Matthew B.
Published: April 2003

Modern research-scale drop towers provide scientists with brief periods of apparent low-gravity from free-fall in which a wide variety of scientific experiments can be conducted. It is shown here that affordable, classroom-scale drop towers can assist in science education by demonstrating a wide range of physical principles in a high-impact, attention-getting manner. The equipment described here can be constructed for as little as a few hundred dollars, and when combined with readily available televisions and videotape recorders, make an excellent classroom teaching aid.
Dynamic electric field maps of point charge moving with constant velocity
Authors: Jefimenko Oleg D.
Published: April 2003

Conventional electric field maps of a uniformly moving point charge depict the time-independent electric field co-moving with the charge. Much more important is, however, the time-dependent electric field of the moving charge as it is seen by a stationary observer. This field can be depicted by “dynamic field maps” whose properties and the method of construction are described in this article.
How big is the Moon?
Authors: Lo Presto Michael C.
Published: April 2003

Introductory astronomy is likely to be the only formal exposure many college students have to that specific discipline. It also may be one of the few, if not the only, course they will ever take in science. Accordingly, many instructors take it upon themselves not only to teach about astronomy, but also about the nature of scientific inquiry.
A cheap simple ammeter for batteries-and-bulbs activities
Authors: Kagan David T.
Published: April 2003

The use of batteries and bulbs to teach the fundamentals of circuit analysis has been with us for many years. Even recent innovations in pedagogy seem to rely on batteries and bulbs. In addition, the California Science Content Standards for fourth grade require that “students know how to design and build simple series and parallel circuits using components such as wires, batteries, and bulbs.” These standards go on to indicate that students should be able to use a compass to detect magnetic fields and know that electric currents produce magnetic fields.
A quick experiment on reflection from concave mirrors
Authors: Greenslade Thomas B.
Published: April 2003

I had need of an hour-long experiment illustrating the properties and use of cylindrical concave mirrors for my nonscience majors, and put together an exercise using off-the-shelf ideas and equipment. There is clearly nothing new here, but other teachers may find some combination of the ideas useful.
Blending history with physics: Acoustic refraction
Authors: Ross Charles D.
Published: April 2003

A brief overview of atmospheric acoustics is followed by a description of how acoustic refraction can provide an interesting way of blending history with a traditional physics topic.
Communities of on-line physics educators
Authors: MacIsaac Dan
Published: April 2003

I briefly describe the nature, content, scope, history, and culture of PHYS-L and related electronic mailing lists dedicated to the teaching and learning of physics (including PHYSHARE, TAP-L and PhysLrnR). I also describe etiquette and writing guidelines for contributing to discussions on mailing lists. Finally, I review technical guidelines for controlling physics list subscriptions and related archive software.
An interview with John Dewey on science education
Authors: Ansbacher Ted
Published: April 2003

Sooner or later almost all physics teachers are forced by the evidence to conclude that students do not attain understanding of concepts by listening to lectures — no matter how lucid they may be. A more fruitful alternative, which many teachers have arrived at independently, actively involves the students, starting with their own experiences and guiding them from there, through observation and reasoning, towards knowledge with understanding. There is great value in tracing the history of this educational thread: it confirms that the ideas have deep roots and have stood the test of time; it provides clues to the troubling question of why,!! if this approach is so good, it is still not widely practiced; and, more importantly, it allows new thinking to start from “the shoulders of giants” rather than at ground level. One of these giants is John Dewey.
Shapes of bubbles and drops in motion
Authors: O’Connell James
Published: April 2003

The shapes of moving fluid bubbles and drops are determined by the forces of buoyancy and viscous drag and shear. Motion through a high-viscosity fluid is seen to produce tails at the rear of the bubbles or drops.
Investigating refrigerator magnets
Authors: Schmidt Martin F.
Published: April 2003

Two articles recently carried in The Physics Teacher have included discussions of “refrigerator magnets.” These articles have been informative, and I would like to add the simple analogy of a horseshoe magnet to the discussion. After all, a horseshoe magnet is a “one-sided” magnet in that it has the effective part of its field only on the end where the poles are, whereas the end with the U-bend provides little useful magnetic force.
The old order changeth, again
Authors: Swartz Clifford E.
Published: April 2003

The journal’s history is recounted as Cliff Swartz reflects on his years as editor of The Physics Teacher in his final editorial.
An apparatus evaluation
Authors: Peterson Randolph S. , Walkiewicz Thomas A.
Published: April 2003

The first few weeks of a modern physics course usually begin with special relativity. And with that beginning comes the question,“What experiments can our students try to help bring to life the theory they are studying?” A NaI (TI) detector with a multichannel analyzer, an amplifier, and a high-voltage power supply are the only equipment necessary for the first three weeks of experiments.
Precision laboratory apparatus for the study of magnetic forces
Authors: Sinacore Joseph , Graf Erlend H.
Published: April 2003

An apparatus suitable for the study of magnetic forces by physics undergraduates is described. By using an electronic scale to determine the torque exerted on a current-carrying coil by the almost uniform magnetic field of a pair of Helmholtz coils, students can verify the Lorentz-force law for current-carrying wires to an accuracy of a few percent.
In praise of simple physics
Authors: Russell Tom
Published: April 2003

Preservice physics teachers working with batteries and bulbs made important “corrections” to their knowledge of simple circuits. Use of quite simple materials made the difference. Perhaps all physics teachers should consider the possibilities of “simple physics.”
Relativistic metersticks
Authors: Greenslade Thomas B.
Published: April 2003

Recently I made a set of relativistic metersticks that represent the apparent length of a meterstick passing the stationary observer.
Forces for Morphogenesis Investigated with Laser Microsurgery and Quantitative Modeling
Authors: Hutson M. Shane , Tokutake Yoichiro , Chang Ming-Shien , Bloor James W. , Venakides Stephanos , Kiehart Daniel P. , Edwards Glenn S.
Published: April 2003

We investigated the forces that connect the genetic program of development to morphogenesis in
Drosophila
. We focused on dorsal closure, a powerful model system for development and wound healing. We found that the bulk of progress toward closure is driven by contractility in supracellular “purse strings” and in the amnioserosa, whereas adhesion-mediated zipping coordinates the forces produced by the purse strings and is essential only for the end stages. We applied quantitative modeling to show that these forces, generated in distinct cells, are coordinated in space and synchronized in time. Modeling of wild-type and mutant phenotypes is predictive; although closure in
myospheroid
mutants ultimately fails when the cell sheets rip themselves apart, our analysis indicates that β
PS
integrin has an earlier, important role in zipping.
Samples of Stars Beyond the Solar System: Silicate Grains in Interplanetary Dust
Authors: Messenger Scott , Keller Lindsay P. , Stadermann Frank J. , Walker Robert M. , Zinner Ernst
Published: April 2003

We have identified six circumstellar silicate grains within interplanetary dust particles (IDPs). Their extrasolar origins are demonstrated by their extremely anomalous oxygen isotopic compositions. Three
17
O-rich grains appear to originate from red giant or asymptotic giant branch stars. One
16
O-rich grain may be from a metal-poor star. Two
16
O-poor grains have unknown stellar sources. One of the grains is forsterite, and two are amorphous silicate “GEMS” (glass with embedded metal and sulfides), which is consistent with astronomical identifications of crystalline and amorphous silicates in the outflows of evolved stars. These observations suggest cometary origins of these IDPs and underscore the perplexing absence of silicates among circumstellar dust grains from meteorites.
Visualizing tmRNA Entry into a Stalled Ribosome
Authors: Valle Mikel , Gillet Reynald , Kaur Sukhjit , Henne Anke , Ramakrishnan V. , Frank Joachim
Published: April 2003

Bacterial ribosomes stalled on defective messenger RNAs (mRNAs) are rescued by tmRNA, an ∼300-nucleotide-long molecule that functions as both transfer RNA (tRNA) and mRNA. Translation then switches from the defective message to a short open reading frame on tmRNA that tags the defective nascent peptide chain for degradation. However, the mechanism by which tmRNA can enter and move through the ribosome is unknown. We present a cryo–electron microscopy study at ∼13 to 15 angstroms of the entry of tmRNA into the ribosome. The structure reveals how tmRNA could move through the ribosome despite its complicated topology and also suggests roles for proteins S1 and SmpB in the function of tmRNA.
Hyperdiversity Up Close
Authors: Schultz T. R.
Published: April 2003

Pheidole
in the New World

A Dominant, Hyperdiverse Ant Genus.
By E. O. Wilson
. Harvard University Press, Cambridge, MA, 2003. 804 pp. and CD-ROM. $125, £85.95. ISBN 0-674-00293-8.

In a taxonomic monograph that caps more than 20 years of work, Wilson covers all 624 known species belonging to the most abundant and diverse genus of ants in the New World.
Molecular Epidemiology ofMycoplasma conjunctivaein Caprinae: Transmission across Species in Natural Outbreaks
Authors: Belloy Luc , Janovsky Martin , Vilei Edy M. , Pilo Paola , Giacometti Marco , Frey Joachim
Published: April 2003

Mycoplasma conjunctivaeis the etiological agent of infectious keratoconjunctivitis, a highly contagious ocular infection that affects both domestic and wild Caprinae species in the European Alps. In order to study the transmission and spread ofM. conjunctivaeacross domestic and wild Caprinae populations, we developed a molecular method for subtyping and identifying strains ofM. conjunctivae. This method is based on DNA sequence determination of a variable domain within the genelppS, a gene that encodes an antigenic lipoprotein ofM. conjunctivae. This domain oflppSshows variations among different strains but remains constant upon generations of individual strains on growth medium and thus allows identification of individual strains and estimation of their phylogenetic intercorrelations. The variable domain oflppSis amplified by PCR using primers that match conserved sequences oflppSflanking it. Sequence analysis of the amplified fragment enables fine subtyping ofM. conjunctivaestrains. The method is applicable both to isolated strains and to clinical samples directly without requiring the cultivation of the strain. Using this method, we show thatM. conjunctivaewas transmitted between domestic and wild animals that were grazing in proximate pastures. Certain animals also presented infections with two different strains simultaneously.
Effect of Temperature, pH, and Initial Cell Number on
luxCDABE
and
nah
Gene Expression during Naphthalene and Salicylate Catabolism in the Bioreporter Organism
Pseudomonas putida
RB1353
Authors: Dorn Jonathan G. , Frye Robert J. , Maier Raina M.
Published: April 2003

One limitation of employing
lux
bioreporters to monitor in situ microbial gene expression in dynamic, laboratory-scale systems is the confounding variability in the luminescent responses. For example, despite careful control of oxygen tension, growth stage, and cell number, luminescence from
Pseudomonas putida
RB1353, a naphthalene-degrading
lux
bioreporter, varied by more than sevenfold during saturated flow column experiments in our laboratory. Therefore, this study was conducted to determine what additional factors influence the luminescent response. Specifically, this study investigated the impact of temperature, pH, and initial cell number (variations within an order of magnitude) on the peak luminescence of
P. putida
RB1353 and the maximum degradation rate (
V
max
) during salicylate and naphthalene catabolism. Statistical analyses based on general linear models indicated that under constant oxygen tension, temperature and pH accounted for 98.1% of the variability in luminescence during salicylate catabolism and 94.2 and 49.5% of the variability in
V
max
during salicylate and naphthalene catabolism, respectively. Temperature, pH, and initial substrate concentration accounted for 99.9% of the variability in luminescence during naphthalene catabolism. Initial cell number, within an order of magnitude, did not have a significant influence on either peak luminescence or
V
max
during salicylate and naphthalene catabolism. Over the ranges of temperature and pH evaluated, peak luminescence varied by more than 4 orders of magnitude. The minimum parameter deviation required to alter
lux
gene expression during salicylate and naphthalene catabolism was a change in temperature of 1°C, a change in pH of 0.2, or a change in initial cell number of 1 order of magnitude. Results from this study indicate that there is a need for careful characterization of the impact of environmental conditions on both the expression of the reporter and catabolic genes and the activities of the gene products. For example, even though
lux
gene expression was occurring at ∼35°C, the luciferase enzyme was inactive. Furthermore, this study demonstrates that with careful characterization and standardization of measurement conditions, the attainment of a reproducible luminescent response and an understanding of the response are feasible.
Surface Display of the Receptor-Binding Region of the
Lactobacillus
brevis
S-Layer Protein in
Lactococcus
lactis
Provides Nonadhesive Lactococci with the Ability To Adhere to Intestinal Epithelial Cells
Authors: Åvall-Jääskeläinen Silja , Lindholm Agneta , Palva Airi
Published: April 2003

Lactobacillus
brevis
is a promising lactic acid bacterium for use as a probiotic dietary adjunct and a vaccine vector. The N-terminal region of the S-layer protein (SlpA) of
L
.
brevis
ATCC 8287 was recently shown to mediate adhesion to various human cell lines in vitro. In this study, a surface display cassette was constructed on the basis of this SlpA receptor-binding domain, a proteinase spacer, and an autolysin anchor. The cassette was expressed under control of the
nisA
promoter in
Lactococcus
lactis
NZ9000. Western blot assay of lactococcal cell wall extracts with anti-SlpA antibodies confirmed that the SlpA adhesion domain of the fusion protein was expressed and located within the cell wall layer. Whole-cell enzyme-linked immunosorbent assay and immunofluorescence microscopy verified that the SlpA adhesion-mediating region was accessible on the lactococcal cell surface. In vitro adhesion assays with the human intestinal epithelial cell line Intestine 407 indicated that the recombinant lactococcal cells had gained an ability to adhere to Intestine 407 cells significantly greater than that of wild-type
L
.
lactis
NZ9000. Serum inhibition assay further confirmed that adhesion of recombinant lactococci to Intestine 407 cells was indeed mediated by the N terminus-encoding part of the
slpA
gene. The ability of the receptor-binding region of SlpA to adhere to fibronectin was also confirmed with this lactococcal surface display system. These results show that, with the aid of the receptor-binding region of the
L
.
brevis
SlpA protein, the ability to adhere to gut epithelial cells can indeed be transferred to another, nonadhesive, lactic acid bacterium.
Functional Replacement of the
Escherichia coli
d-
(−)-Lactate Dehydrogenase Gene (
ldhA
) with the
l-
(+)-Lactate Dehydrogenase Gene (
ldhL)
from
Pediococcus acidilactici
Authors: Zhou Shengde , Shanmugam K. T. , Ingram L. O.
Published: April 2003

The microbial production of
l-
(+)-lactic acid is rapidly expanding to allow increased production of polylactic acid (PLA), a renewable, biodegradable plastic. The physical properties of PLA can be tailored for specific applications by controlling the ratio of
l-
(+) and
d
-(−) isomers. For most uses of PLA, the
l-
(+) isomer is more abundant. As an approach to reduce costs associated with biocatalysis (complex nutrients, antibiotics, aeration, product purification, and waste disposal), a recombinant derivative of
Escherichia coli
W3110 was developed that contains five chromosomal deletions (
focA-pflB frdBC adhE ackA ldhA
). This strain was constructed from a
d
-(−)-lactic acid-producing strain, SZ63 (
focA-pflB frdBC adhE ackA
), by replacing part of the chromosomal
ldhA
coding region with
Pediococcus acidilactici ldhL
encoding an
l
-lactate dehydrogenase. Although the initial strain (SZ79) grew and fermented poorly, a mutant (SZ85) was readily isolated by selecting for improved growth. SZ85 exhibited a 30-fold increase in
l
-lactate dehydrogenase activity in comparison to SZ79, functionally replacing the native
d
-lactate dehydrogenase activity. Sequencing revealed mutations in the upstream, coding, and terminator regions of
ldhL
in SZ85, which are presumed to be responsible for increased
l
-lactate dehydrogenase activity. SZ85 produced
l
-lactic acid in M9 mineral salts medium containing glucose or xylose with a yield of 93 to 95%, a purity of 98% (based on total fermentation products), and an optical purity greater than 99%. Unlike other recombinant biocatalysts for
l
-lactic acid, SZ85 remained prototrophic and is devoid of plasmids and antibiotic resistance genes.
Compatibility of Rhizobial Genotypes within Natural Populations of
Rhizobium leguminosarum
Biovar viciae for Nodulation of Host Legumes
Authors: Laguerre Gisèle , Louvrier Philippe , Allard Marie-Reine , Amarger Noëlle
Published: April 2003

Populations of
Rhizobium leguminosarum
biovar viciae were sampled from two bulk soils, rhizosphere, and nodules of host legumes, fava bean (
Vicia faba
) and pea (
Pisum sativum
) grown in the same soils. Additional populations nodulating peas, fava beans, and vetches (
Vicia sativa
) grown in other soils and fava bean-nodulating strains from various geographic sites were also analyzed. The rhizobia were characterized by repetitive extragenomic palindromic-PCR fingerprinting and/or PCR-restriction fragment length polymorphism (RFLP) of 16S-23S ribosomal DNA intergenic spacers as markers of the genomic background and PCR-RFLP of a nodulation gene region,
nodD
, as a marker of the symbiotic component of the genome. Pairwise comparisons showed differences among the genetic structures of the bulk soil, rhizosphere, and nodule populations and in the degree of host specificity within the Vicieae cross-inoculation group. With fava bean, the symbiotic genotype appeared to be the preponderant determinant of the success in nodule occupancy of rhizobial genotypes independently of the associated genomic background, the plant genotype, and the soil sampled. The interaction between one particular rhizobial symbiotic genotype and fava bean seems to be highly specific for nodulation and linked to the efficiency of nitrogen fixation. By contrast with bulk soil and fava bean-nodulating populations, the analysis of pea-nodulating populations showed preferential associations between genomic backgrounds and symbiotic genotypes. Both components of the rhizobial genome may influence competitiveness for nodulation of pea, and rhizosphere colonization may be a decisive step in competition for nodule occupancy.
Heavy Metal Resistance of Biofilm and Planktonic
Pseudomonas aeruginosa
Authors: Teitzel Gail M. , Parsek Matthew R.
Published: April 2003

A study was undertaken to examine the effects of the heavy metals copper, lead, and zinc on biofilm and planktonic
Pseudomonas aeruginosa
. A rotating-disk biofilm reactor was used to generate biofilm and free-swimming cultures to test their relative levels of resistance to heavy metals. It was determined that biofilms were anywhere from 2 to 600 times more resistant to heavy metal stress than free-swimming cells. When planktonic cells at different stages of growth were examined, it was found that logarithmically growing cells were more resistant to copper and lead stress than stationary-phase cells. However, biofilms were observed to be more resistant to heavy metals than either stationary-phase or logarithmically growing planktonic cells. Microscopy was used to evaluate the effect of copper stress on a mature
P. aeruginosa
biofilm. The exterior of the biofilm was preferentially killed after exposure to elevated concentrations of copper, and the majority of living cells were near the substratum. A potential explanation for this is that the extracellular polymeric substances that encase a biofilm may be responsible for protecting cells from heavy metal stress by binding the heavy metals and retarding their diffusion within the biofilm.
The Surface-Associated and Secreted MopE Protein of
Methylococcus capsulatus
(Bath) Responds to Changes in the Concentration of Copper in the Growth Medium
Authors: Karlsen Odd A. , Berven Frode S. , Stafford Graham P. , Larsen Øivind , Murrell J. Colin , Jensen Harald B. , Fjellbirkeland Anne
Published: April 2003

Expression of surface-associated and secreted protein MopE of the methanotrophic bacterium
Methylococcus capsulatus
(Bath) in response to the concentration of copper ions in the growth medium was investigated. The level of protein associated with the cells and secreted to the medium changed when the copper concentration in the medium varied and was highest in cells exposed to copper stress.
Wide Geographic Distribution of Bacteriophages That Lyse the Same Indigenous Freshwater Isolate (
Sphingomonas
sp. Strain B18)
Authors: Wolf Arite , Wiese Jutta , Jost Günter , Witzel Karl-Paul
Published: April 2003

An indigenous freshwater bacterium (
Sphingomonas
sp. strain B18) from Lake Pluβsee (Schleswig-Holstein, Germany) was used to isolate 44 phages from 13 very different freshwater and brackish habitats in distant geographic areas. This bacterial strain was very sensitive to a broad spectrum of phages from different aquatic environments. Phages isolated from geographically distant aquatic habitats, but also those from the same sample, were diverse with respect to morphology and restriction pattern. Some phages were widely distributed, while different types coexisted in the same sample. It was concluded that phages could be a major factor in shaping the structure of bacterial communities and maintaining a high bacterial diversity.
Comparison of the phagocytic response of rat and hamster alveolar macrophages to man-made vitreous fibers in vitro
Authors: Dörger M , Münzing S , Allmeling A-M , Krombach F
Published: April 2003

Rats and hamsters are well known for their disparate response to inhaled mineral fibers/particles. Alveolar macrophages (AM) play an important role in the pulmonary clearance and retention of mineral fibers/particles mainly through the process of phagocytosis. The aim of this study was to investigate whether there exist differences in the phagocytic response and release of reactive oxygen species (ROS) between rat and hamster AM upon exposure to man-made vitreous fibers (MMVF) in vitro. AM were obtained by bronchoalveolar lavage and macrophage-enriched cultures were exposed to MMVFlo and MMVF21 fibers for 20 h. The phagocytic response of macrophages was determined by computer-assisted video-microscopy and the superoxide anion production was evaluated by cytochrome c reduction. A significantly higher percentage of rat AM underwent frustrated phagocytosis of both types of MMVF compared to hamster AM. This was associated with a higher ROS release by rat AM compared to hamster AM. These data may help to explain the cellular mechanisms underlying the disparate pulmonary response of rat and hamster to inhaled particulate matter.
Lack of peripheral neuropathy in Beagle dogs after 53 weeks oral administration of thalidomide capsules
Authors: Teo S , Evans M , Ehrhart J , Brockman M , Allen D , Morgan M , Stirling D , Thomas S
Published: April 2003

Thalidomide (Thalomid®) is approved for use in the US to treat complications from leprosy. Peripheral neuropathy is a dose-limiting adverse event in humans. As part of a nonrodent regulatory toxicology study, Beagle dogs were fed orally via encapsulation for 53 weeks. A component of this study was to determine if the dogs developed peripheral neuropathy. Twenty-eight male and 28 female Beagle dogs approximately 8-10 months of age were used. They were dosed at 43, 200 or 1000 mg/kg for 53 weeks followed by a 4-week treatment-free recovery period. Nerve function was assessed by electrophysiological measurements of the tibial nerve prior to dosing and at weeks 13, 27, 38 and 51. Representative dogs from each group were sacrificed at 26, 53 and 58 weeks and histologic and ultrastructural evaluations were performed on the sural nerve. Thali-domide had no effect on sensory nerve conduction velocity, duration or amplitude of the action potential. At 27 weeks, mean sensory nerve action potential amplitude for females at 43 mg/kg was significantly greater than control but was not evident at 39 weeks. Mean duration of sensory nerve action potential seemed to increase with similar magnitude over time in all dose groups including controls. Histological and ultrastructural evaluation of sections of sural nerve did not identify treatment-induced differences between control and thalidomide-dosed animals after 26 and 53 weeks of treatment. Additionally, no differences were observed following a 5-week treatment-free period at week 58. In contrast to humans, Beagle dogs did not develop thalidomide-induced peripheral neuropathy under conditions of the study.
Radiation hormesis: its historical foundations as a biological hypothesis
Authors: Calabrese E J , Baldwin L A
Published: April 2003

This paper represents the first systematic effort to describe the historical foundations of radiation hormesis. Spanning the years from 1898 to the early 1940‘s the paper constructs and assesses the early history of such research and evaluates how advances in related scientific fields affected the course of hormetic related research. The present effort was designed to not only address this gap in current knowledge, but to offer a toxicological basis for how the concept of hormetic dose-response relationships may affect the nature ofthe bioassay and its role in the risk assessment process.
Applications of immunohistochemistry in the evaluation of immunosuppressive agents
Authors: Gillett N A , Chan C
Published: April 2003

Immunohistochemistry (IHC) can be a valuable endpoint to evaluate lymphocyte subpopulations in tissues following exposure to presumptive immunosuppressive agents. IHC is more sensitive than conventional histology in detecting subtle differences in lymphocyte numbers and distribution in tissue. In combination with flow cytometric analysis of peripheral lymphocyte subpopulations, IHC can determine if alterations detected in the peripheral blood are a result of trafficking or reflective of changes in tissue distribution. These techniques can be used to evaluate adult animals as well as to evaluate the effects of immunosuppressive agents on fetal tissues in reproductive toxicology studies. While IHC can enhance the detection of subtle changes in lymphocyte subpopulations in tissue, the evaluation of additional end-points of immune function must be done to further assess the biological or clinical significance ofthese changes.
Manipulation of the phenotype of immortalised rat hepatocytes by different culture configurations and by dimethyl sulphoxide
Authors: Grant M I , Anderson K , McKay G , Wills M , Henderson C , MacDonald C
Published: April 2003

The liver-specific phenotype of immortalised rat hepato-cytes is not irretrievably lost as they age in culture but can be manipulated by modifying the culture environment.

Testosterone metabolism was used to investigate the profile of cytochrome P450 isoenzymes present in two immortalised cell lines, P9 and LQC, and in primary cultures of rat hepatocytes, cultured on collagen films, gels and double gel cultures (sandwich configuration). The extent of testosterone metabolism, and the range of metabolites produced, was increased in immortalised cells by the presence of collagen as a substratum film or gel but survival was poorer and the range of metabolites was reduced in sandwich culture. In contrast, testosterone metabolism was retained in primary hepatocytes in sandwich cultures at a higher level than in collagen film or gel cultures.

Expression of alpha class glutathione-S-transferases (GSTs) increased and that of GSTP1 decreased (changes which indicate a recovery of normal liver GST phenotype) when the medium of immortalised cell cultures was supplemented with dimethyl sulph-oxide (DMSO). DMSO also improved ethoxyresorufin 0-deethylation (EROD) and testosterone metabolism in immortalised cells. It also markedly inhibited prolifera-tion, DNA, RNA and protein synthesis.

Maximal testosterone metabolism was observed in immortalised cells cultured on collagen gels in the presence of l1o (v/v) DMSO. Development of a protocol for treating immortalised liver cells cultured on collagen gels with DMSO to switch between proliferation and differentiation may provide a convenient system expres-sing the xenobiotic metabolising enzymes required for in vitro toxicity testing.
Copper toxicity affects proliferation and viability of human hepatoma cells (HepG2 line)
Authors: Aston N S , Watt N , Morton I E , Tanner M S , Evans G S
Published: April 2003

In Wilson's disease and Indian childhood cirrhosis (ICC) copper accumulates in the liver resulting in poor hepatocyte regeneration and fibrosis. An inhibition of hepatocyte proliferation and an increase in cell death could account for these outcomes. To establish how the toxicity of this metal ion impacts upon the proliferation and viability ofthe HepG2 cells they were cultured in 4-32 jiM copper(II) sulphate (CuS04)). These levels were comparable to the circulatory and tissue concentrations of copper recorded for these two diseases. Specific uptake comparable to levels of copper recorded in the livers of patients with Wilson's disease and ICC was measured in the HepG2 cells. After 48 h acid vesicle function increased from 4 to 32 jiM Cu2 + but significantly declined at 64 MM compared to the controls. Lysosomal acid phosphatase showed a concen-tration dependent decline in activity at 72 h. Introduction Copper is a potent catalyst of processes generating reactive oxygen intermediates and its cellular up-take, transport and excretion are therefore tightly controlled. Elevated hepatic copper concentrations are associated with liver damage in Wilson's disease2, in Indian childhood cirrhosis3 (ICC), and in other copper-related cirrhoses of infancy. Nevertheless, the cellular consequences of copper toxicity remain to be understood in the context of the disease pathology. In Wilson's disease, biliary excretion of copper is impaired by mutations in a trans-Golgi P-type ATPase4 resulting in intracellular hepatic copper accumulation5 with progressive dysfunction, fibrosis, and liver failure. However, clinical variability of Wilson's disease and the lack of a clear genotype/ Cellls exposed to 64 MM Cu2 + had a potential doubling time (Tpot) 21 h longer than the control cells due to a prolonged DNA synthesis phase. At 64 jiM Cu2 +, increases of necrosis up to 18% were seen whereas comparable levels ofapoptotic and necrotic cells (< 5%) were seen below this concentration. Chronic exposure over 8 weeks impaired colony-forming effi-ciency at concentrations of 16 MM Cu2 + and above. This study suggests that when liver cells sequester large amounts of copper, the toxic effects include delayed cell-cycle progression, a gradual loss of replicative capacity, and an increased incidence of cell death.
Rat alveolar and interstitial macrophages in the fibrosing stage following quartz exposure
Authors: Zetterberg G , Elmberger G , Johansson A , Lundahl J , Lundborg M , Sköld C M , Tornling G , Camner P , Eklund A
Published: April 2003

Exposure to quartz induces pulmonary inflammation and development of fibrosis. In order to study the fibrosing process, we investigated morphology function and phenotype of alveolar (AMs) and interstitial (IMs) macrophages at an early stage of fibrosis in rats.

Rats were exposed by intratracheal instillations of 10 mg quartz (n = 8) or saline (n = 8) and studied 3 months later. AMs were obtained by bronchoalveolar lavage and IMs by mechanical fragmentation, followed by enzymatic digestion of lung tissue.

Histology revealed subacute silicosis, with early focal fibrosis and alveolar lipoproteinosis. AM quartz exposure increased phagocytic activity and expression of major histocompatibility complex (MHC) Ia antigens, the latter being associated with cellular antigen presenting capacity. IM had an even more pronounced expression of MHC than AM after quartz exposure. Both macrophage fractions had a higher expression of OX-42 (complement receptor 3, CR3) than controls, but the increase in the IM fraction might be explained by the remaining AM in the IM fraction. Exposed AM adhered less to extracellular matrix components (vitronectin and fibronectin) than controls. In contrast, the adhesion of IM to vitronectin increased after exposure.

Besides increased adhesion, the effects on IM were scarce. Our results therefore do not support the hypothesis that IM has a key role in the process of inflammation, including fibrosis.
Hormesis: A stress response in cells exposed to low levels of heavy metals
Authors: Damelin L H , Vokes S , Whitcutt J M , Damelin S B , Alexander J J
Published: April 2003

Cytotoxicity studies using a 3-(4,5 dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MT)-based in vitro toxicity assay revealed that McCoy cells exposed to low concentrations of mercuric (0.7 yM),cadmium (1 1M) and cupric chloride (3 tIM) exhibited significant increases in cellular activity. This increased activity, previously termed hormesis, coincided with the production ofhigh levels ofthe stress proteins, heat shock protein 70 (Hsp 70) and metallothionein, while the high constitutive expression of these proteins in cadmium-resistant mutant (CRM) cells corresponded to constitutive hormetic activity. Hormesis was found to obey uniform kinetics allowing for a mathematical description of this increased activity. These results suggest that hormetic activity is a specific cellular response, and most likely, a stress response to low but harmful levels of toxic agents and may therefore provide a rapid test for the presence of toxicants at concentrations associated with chronic toxicity.
Short-term adverse effects in humans of ingested mineral oils, their additives and possible contaminants–A review
Authors: Hard G C
Published: April 2003

The toxicological databases for petroleum refinery products such as mineral oils, as well as for their potential contaminants and additives, were reviewed for human cases of poisoning by the oral route. The aim was to determine whether any overlooked adulterant in the oil implicated as the cause of the 1981 outbreak of Toxic Oil Syndrome (TOS) in Spain, may have been responsible for the unusual symptomatology characterizing this disease. The essential features of TOS were peripheral eosinophilia, pulmonary oedema and endothelial damage in the acute phase; myalgia, sensory neuropathy, hepatic injury, skin oedema and sicca in the intermediate phase; and peripheral neuropathy, muscle wasting, scleroderma and hepatopathy in the chronic phase. Of the more than 70 chemical entities and mixtures reviewed here, none had been reported as producing adverse toxic effects upon ingestion resembling the specific set of symptoms and progression that characterized TOS. Because of their viscosity, the most commonly recorded disease process associated with oral ingestion of petroleum refinery products was lipid pneumonia, implicating lung exposure via aspiration. The mineral oil additives and contaminants comprised a highly diverse range of chemical entities, producing a variety of symptoms in instances of poisoning. Specifically, no chemical entity amongst the refinery products, additives or contaminants was described as inducing a syndrome involving vasculitis accompanied by thrombotic events, along with immunological consequences (such as T-lymphocyte activation and cytokine release), as is considered to be the cellular basis of TOS.
Comparison of the acute hematotoxicity of 2-butoxyethanol in male and female F344 rats
Authors: Ghanayem B I , Ward S M , Chanas B , Nyska A
Published: April 2003

Administration of 2-butoxyethanol (BE) to rodents causes acute hemolytic anemia, and metabolic activation of BE to butoxyacetic acid (BAA) is required for the development of this effect. Recent studies have shown that female rats treated with BE exhibit a variety of histopathologic lesions that are absent in males and many of these lesions are attributed to the hemolytic effects of BE. Current studies were designed to compare the acute hematotoxicity of BE in male and female F344 rats. Rats were treated with 250 mg BE/kg body weight or water (control; 5 ml/kg) by gavage. At 4, 8, or 24 h after dosing, rats were anesthetized, blood was collected by cardiac puncture, and various blood parameters were measured. BE resulted in a time-dependent swelling of erythrocytes as evidenced by an early increase in hematocrit (Hct) and mean cell volume (MCV) in male rats. In contrast, increased Hct in female rats did not accompany an increase in MCV. It is likely that hemolysis was so severe at 4 h that Hct exhibited a decline in female rats at that time point. Subsequently, red blood cell (RBCs), hemoglobin concentration (Hgb), and Hct declined as hemolysis progressed. However, the onset of BE-induced hemolysis was faster in female compared to male rats. These effects were also associated with a significant increase in the spleen weight to body weight ratio. Blood smears were also prepared and morphological changes evaluated by light microscopy included stomatocytosis, spherocytosis, and schistocytosis. Furthermore, aggregation of RBCs in female rats as evidenced by increased formation of rouleaux was observed at 24 h after BE administration. These effects were observed earlier and more frequently in female rats. No differences in the sensitivity of RBCs obtained from male and female rats and exposed to butoxyacetic acid (BAA) in vitro was observed as determined by measuring the packed cell volume. In conclusion, these data suggest that female rats are more sensitive to hemolysis and morphological alterations of erythrocytes induced by BE during the first 24 h after exposure compared to males. It is likely that the greater sensitivity of female rats to BE effects on RBCs may account for the reported development of thrombosis and tissue infarction in female rats.