bluuebunny/crossref_metadata_2025 huggingface dataset:
Stem cell regulation in the shoot meristem
Authors: Groß-Hardt Rita , Laux Thomas
Published: March 2003

A small group of pluripotent stem cells in the shoot meristem is the ultimate source for all aerial parts in higher plants: the shoot axis, side branches, leaves and flowers. The stem cells are maintained in an undifferentiated state by signals from an underlying cell group, the organizing center. Genetic and molecular analyses have shown that a feedback signaling loop between stem cells and the organizing center balances stem cell renewal versus differentiation, which allows the plant to maintain the organization of the shoot meristem despite a changing cellular context. Emerging common principles indicate that plant and animal stem cells are functionally equivalent.
Localization of myoinhibitory peptide immunoreactivity inManduca sextaandBombyx mori, with indications that the peptide has a role in molting and ecdysis
Authors: Davis Norman T. , Blackburn Michael B. , Golubeva Elena G. , Hildebrand John G.
Published: March 2003

For normal development of Manduca sexta larvae, the ecdysteroid titer must drop following its sudden rise at the start of the molting cycle;this sudden decline in titer may be due to myoinhibitory peptide I (MIP I),which has an inhibitory effect on the release of ecdysone by the prothoracic glands of Bombyx mori in vitro. Using an antiserum to MIP, we have demonstrated secretion of an MIP-like peptide by the epiproctodeal glands of Manduca sexta, which are located on each proctodeal nerve, just anterior to the rectum. These MIP-immunoreactive glands are also present in B. mori. In fourth-instar larvae of M. sexta, the epiproctodeal glands show a distinct cycle of synthesis and sudden release of MIP that coincides with the time of the rapid decline in ecdysteroid titer. The function of the epiproctodeal glands appears to be the timely release of MIP during the molting cycle, so as to inhibit the prothoracic glands and thus to facilitate the sudden decline in ecdysteroid titer. In addition, we have found that MIP immunoreactivity is co-localized with that of crustacean cardioactive peptide (CCAP) in the 704 interneurons; these peptides appear to be co-released at the time of ecdysis. It is known that CCAP can initiate the ecdysis motor program; our results suggest that MIP may also be involved in activating ecdysis behavior.
A second glutamine synthetase gene with expression in the gills of the gulf toadfish (Opsanus beta)
Authors: Walsh Patrick J. , Mayer Gregory D. , Medina Mónica , Bernstein Matthew L. , Barimo John F. , Mommsen Thomas P.
Published: March 2003

We characterized the expression of the nitrogen metabolism enzyme glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] in tissues of the gulf toadfish Opsanus beta subjected to unconfined(ammonotelic) and confined (ureotelic) conditions. Enzymological results demonstrate that mass-specific GSase activities rank in the order of brain> liver > stomach ≈ kidney > intestine > gill > heart/spleen> muscle. When tissue mass is used to calculate a glutamine synthetic potential, the liver has the greatest, followed by muscle > stomach and intestine, with minor contributions from the remaining tissues. Additionally,during confinement stress, GSase activity increases significantly only in liver (fivefold) and muscle (twofold), tissues that previously showed significant expression of the other enzymes of urea synthesis. Western analyses of samples on SDS gels demonstrated that GSase-specific protein content reflected enzyme activity, and all tissues except muscle had a single,similarly sized GSase subunit of 49.4 kDa; muscle showed staining of two bands of 36.8 and 98.9 kDa, which may possibly result from another gene product or post-translational modification.

RT-PCR and RACE-PCR revealed the presence of a second GSase cDNA from gill tissue that shares only 73% nucleotide and amino acid sequence similarity with the GSase cDNA previously cloned from liver, and that lacks a mitochondrial leader-targeting sequence. RT-PCR and restriction digestion experiments demonstrated that mRNA from the original `liver' GSase is expressed in all tissues examined (liver, gill, stomach, intestine, kidney, brain and muscle),whereas the new `gill' form shows expression primarily in the gill. Gill GSase activity shows apparently exclusive expression in the soluble compartment,while other tissues expressing the `liver' form show both cytoplasmic and mitochondrial activities.

Phylogenetic analysis of a number of GSases demonstrates that the toadfish gill GSase has a greater affinity for a clade that includes the Xenopus GSase genes and one of two Fugu GSase genes, than it has for a clade containing the toadfish liver GSase and other described teleost GSase genes. The results are discussed in the context of a prior hypothesis on an ammonia-trapping mechanism in the gill of the toadfish.
Factors affecting stroking patterns and body angle in diving Weddell seals under natural conditions
Authors: Sato Katsufumi , Mitani Yoko , Cameron Michael F. , Siniff Donald B. , Naito Yasuhiko
Published: March 2003

Aquatic animals use a variety of strategies to reduce the energetic cost of locomotion. Efficient locomotion is particularly important for breath-holding divers because high levels of exercise may quickly deplete oxygen reserves,leading to the termination of a dive. We investigated the swimming behavior of eight adult Weddell seals, which are proficient divers, in McMurdo Sound,Antarctica. A newly developed data logger was attached to free-ranging females at their own breeding sites to record swimming speed, depth, two-dimensional accelerations (stroke frequency and body angle) and temperature. All seals conducted multiple deep dives (the mean dive depth range for each animal was 223.3±66.5–297.9±164.7 m). Prolonged gliding while descending was observed with thinner females (N=5 seals). But the fatter females (N=3 seals) exhibited only swim-and-glide swimming,characterized by intermittent stroking and fluctuating swim speed, throughout their descent and ascent. The body angles of four of the seals were restricted to less than 30° by the location of breathing holes in the ice and the slope of local bathymetric features. Of these four, the three fatter seals adopted the stroke-and-glide method while the other thinner seal descended with prolonged periods of gliding. Prolonged gliding seems to be a more efficient method for locomotion because the surface time between dives of gliding seals was significantly less than that of stroking animals, despite their same stroke frequencies.
Heterothermy and the water economy of free-living Arabian oryx (Oryx leucoryx)
Authors: Ostrowski Stéphane , Williams Joseph B. , Ismael Khairi
Published: March 2003

To test the idea that large, free-living, desert ungulates use heterothermy to reduce water loss, we measured core body temperature(Tb) of six free-ranging, adult Arabian oryx (Oryx leucoryx) during 2 years in the arid desert of west-central Saudi Arabia. We report the first case of heterothermy in a free-living ruminant in a desert environment: Tb varied by 4.1±1.7°C day–1 during summer (June to September) and by 1.5±0.6°C day –1 during winter (November to March). Over both seasons, mean Tb was 38.4±1.3°C. During the day in both summer and winter, Tb increased continually, suggesting that oryx store heat instead of dissipating it by evaporation, whereas at night Tb decreased. The minimum Tb was lower in summer (36.5±1.16°C) than in winter (37.5±0.51°C)despite the fact that the temperature gradient between Tband air temperature (Ta) was larger and solar radiation was lower in winter. Throughout the year, daily variation in Tb appeared to reflect thermal load(Ta,max–Ta,min) rather than an endogenous rhythm. Behavioural thermoregulation was used by oryx to cope with thermal stress during summer: animals lay down in shade in the morning shortly before Ta exceeded Tb and remained there until evening when Tb–Tabecame positive. The use of heterothermy by oryx resulted in storage ofandwould672.4 kJ day–1 animal–1258.6 kJ day–1 animal–1in winter, if heat storage is based on calculations involving mean Tb. Todissipaterequirethisheatin summerby evaporation0.28 litres H2O day–1 animal–1and0.11 litres H2O day–1 animal–1 in summer and winter,respectively. Without heat storage in summer, we estimated that oryx would have to increase their water intake by 19%, a requirement that would be difficult to meet in their desert environment. If heat storage was calculated based on the daily change in Tb rather than on heat storage above mean Tb then we estimated that oryx saved 0.538 litres H2O day–1 animal–1during summer.
The energetics of the trot–gallop transition
Authors: Wickler Steven J. , Hoyt Donald F. , Cogger Edward A. , Myers Gregory
Published: March 2003

Two studies have focused on potential triggers for the trot–gallop transition in the horse. One study concluded that the transition was triggered by metabolic economy. The second study found that it was not metabolic factors but, rather, peak musculoskeletal forces that determine gait transition speeds. In theory, peak musculoskeletal forces should be the same when trotting up an incline as when trotting at the same speed on the level. Assuming this is the case, we hypothesized that if peak forces determine gait transition speeds then horses should switch from a trot to a gallop at the same speed (i.e. the same critical force) regardless of incline. The aim of the present research was to examine the effects of incline on the trot–gallop transition speed in horses and to re-examine the role of metabolism in determining the trot–gallop transition. Horses (Equus caballus) were conditioned to run on a high-speed treadmill prior to data collection. Gait changes were recorded for each horse using a standardized testing protocol on the level and when trotting up a 10% incline. Both maximum sustained trotting speeds and minimum sustained galloping speeds, representing the lower and upper limits of the trot–gallop transition, respectively,were significantly slower when trotting up an incline. After completing collection of gait transition data, the horses were trained to extend their gaits beyond the normal transition speeds, and metabolic data were collected. Maximum sustained trotting speeds were not different from the energetically optimal transition speeds, i.e. the speed at which metabolic rates are the same for both gaits.
Insights into the evolution of human bipedalism from experimental studies of humans and other primates
Authors: Schmitt Daniel
Published: March 2003

An understanding of the evolution of human bipedalism can provide valuable insights into the biomechanical and physiological characteristics of locomotion in modern humans. The walking gaits of humans, other bipeds and most quadrupedal mammals can best be described by using an inverted-pendulum model, in which there is minimal change in flexion of the limb joints during stance phase. As a result, it seems logical that the evolution of bipedalism in humans involved a simple transition from a relatively stiff-legged quadrupedalism in a terrestrial ancestor to relatively stiff-legged bipedalism in early humans. However, experimental studies of locomotion in humans and nonhuman primates have shown that the evolution of bipedalism involved a much more complex series of transitions, originating with a relatively compliant form of quadrupedalism. These studies show that relatively compliant walking gaits allow primates to achieve fast walking speeds using long strides, low stride frequencies, relatively low peak vertical forces, and relatively high impact shock attenuation ratios. A relatively compliant, ape-like bipedal walking style is consistent with the anatomy of early hominids and may have been an effective gait for a small biped with relatively small and less stabilized joints, which had not yet completely forsaken arboreal locomotion. Laboratory-based studies of primates also suggest that human bipedalism arose not from a terrestrial ancestor but rather from a climbing, arboreal forerunner. Experimental data, in conjunction with anatomical data on early human ancestors, show clearly that a relatively stiff modern human gait and associated physiological and anatomical adaptations are not primitive retentions from a primate ancestor, but are instead recently acquired characters of our genus.
Regulation of L-alanine transport systems A and ASC by cyclic AMP and calcium in a reptilian duodenal model
Authors: Gómez Tomás , Medina Virtudes , Ramírez Cristina M. , Dópido Rosa , Lorenzo Antonio , Díaz Mario
Published: March 2003

The regulation of neutral amino acid transport by cyclic AMP (cAMP) and calcium across the isolated duodenum of the lizard Gallotia gallotihas been studied under short-circuit conditions. Active L-alanine transport was stimulated by forskolin, theophylline and dibutyryl cyclic AMP (db-cAMP). All these agents increased transmural potential difference (PD) and short-circuit current (Isc) in a manner consistent with the activation of a chloride secretory pathway. Both forskolin and theophylline increased intracellular cAMP levels in the lizard duodenal mucosa. Addition of calcium ionophore A23187 rapidly reduced mucosa-to-serosa L-alanine fluxes and diminished net L-alanine transport. Despite the reduction of alanine fluxes by A23187, transepithelial PD and Iscvalues were increased by the ionophore. Analyses of the responses of isolated transport pathways indicated that the Na+-independent L-alanine transport system was unaffected by db-cAMP or calcium ionophore. By contrast,Na+-dependent transport activities were profoundly modified by these agents. Thus, while system A [α-methylamino-isobutiric acid(MeAIB)-transporting pathway] was stimulated by increased calcium, system ASC activity was nearly abolished. Calcium ionophore also potentiated the electrogenic response of system A. Forskolin strongly stimulated system ASC activity but left system A activity unchanged. Activation of system ASC by forskolin was clearly electroneutral, as pre-incubation of the tissues with the chloride channel blocker diphenylamine-2-carboxilic acid (DPC) completely prevented forskolin-induced transepithelial electrical responses. It is concluded that intracellular messengers cAMP and calcium oppositely modulate active Na+-dependent L-alanine transport in the lizard intestine. The different sensitivity exhibited by individual transport pathways may well account for the changes observed in overall alanine transport.
Evolution of glutamine synthetase in vertebrates: multiple glutamine synthetase genes expressed in rainbow trout (Oncorhynchus mykiss)
Authors: Murray Brent W. , Busby Ellen R. , Mommsen Thomas P. , Wright Patricia A.
Published: March 2003

Glutamine synthetase (GSase) is a key enzyme in nitrogen metabolism and encoded by a single gene in mammals. Using PCR cloning techniques, including RT-PCR from total RNA and PCR from a cDNA library, we find evidence of four expressed GSase mRNAs for the tetraploid rainbow trout. For two of these mRNAs(Onmy-GS01, -GS02) we characterize the full-length coding regions,and for two others (Onmy-GS03, -GS04), we describe partial sequences. Northern analysis of Onmy-GS01, -GS02, -GS03 and -GS04 indicates that (1) Onmy-GS02 is expressed at higher levels relative to the other transcripts in most adult tissues, with the exception of brain and gill, where Onmy-GS01 is at the highest level,and (2) the tissue with the highest level of expression of all four transcripts is the brain, with decreasing levels in the intestine, liver, red muscle, gill/kidney, white muscle and heart. Clearly, rainbow trout possess multiple GSase genes with differing levels of tissue expression, implying manifold potential routes of regulation for this octameric enzyme. Our data also indicate that caution should be taken when interpreting mRNA expression data of a single gene, unless multiple genes have been ruled out. Consistent with a southern blot, phylogenetic and intron sequence analyses imply that the trout genes are encoded by at least four separate loci, belonging to two distinct evolutionary branches. Our data on rainbow trout, together with those from two full-length zebrafish Danio rerio GSase genes compiled from GenBank ESTs, support the idea that fish GSases are polyphyletic and that gene duplications have occurred at multiple points and in independent lineages throughout the evolution of bony fishes.
Regulation of Na+/K+-ATPase activity by nitric oxide in the kidney and gill of the brown trout (Salmo trutta)
Authors: Tipsmark Christian K. , Madsen Steffen S.
Published: March 2003

In teleost fish, successful osmoregulation involves controlled ion transport mechanisms in kidney and gill epithelia. In this study, the effect of nitric oxide (NO) on Na+/K+-ATPase was investigated in vitro in these two tissues in brown trout (Salmo trutta)acclimated to freshwater. The NO donor sodium nitroprusside (SNP) inhibited in situ Na+/K+-ATPase activity, measured as ouabain-sensitive Rb+ uptake, in both samples of kidney and gill tissue and in isolated gill cells. The effect was dose-dependent in both tissues, with a maximal observed inhibition of approximately 40–50% (1 mmol l –1 SNP). The time-course of inhibition revealed a maximum effect with 10 min pre-incubation. The effect of SNP was reproduced with another NO donor, papa-nonoate (NOC-15; 200 μmol l–1), and was prevented by the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO; 1 mmol l–1). To further investigate the mechanism of the NO effect,whole-tissue Na+ and K+ levels were analysed. In kidney,SNP (1 mmol l–1) led to an increase in tissue Na+levels and a decrease in K+ levels in a 3:2 ratio. In gill tissue,no change in either ion was observed. These observations indicate that the effect on Na+/K+-ATPase is direct rather than due to a decrease in intracellular Na+, its rate-limiting substrate. SNP elevated the level of cyclic GMP (cGMP) in both kidney and gill tissue. Dibutyryl cyclic GMP (db-cGMP; 1 mmol l–1) also inhibited Na+/K+-ATPase activity in both tissues. Hence, a possible mechanism may involve the cGMP-activated kinase, even though other mechanisms cannot be excluded.
Regulation of promoter occupancy during activation of cryptobiotic embryos from the crustacean Artemia franciscana
Authors: Martinez-Lamparero Ana , Casero Marie-Carmen , Ortiz-Caro Javier , Sastre Leandro
Published: March 2003

Artemia franciscana embryos can suspend their development and metabolism at the gastrula stage to enter a state of cryptobiosis, forming cysts. Embryonic development and metabolism can be resumed under favorable environmental conditions to give rise to free-swimming larvae or nauplii. The mechanisms that mediate these processes are not completely known. Here, we report our studies of the mechanisms that regulate transcriptional activation upon exiting cryptobiosis. Regulatory regions of several A. franciscana gene promoters were identified. Functional analyses in mammalian cells allowed the identification of transcriptional activator regions in the Actin302 promoter and in promoter 2 of the sarco/endoplasmic reticulum Ca2+-ATPase-encoding gene. These regions were shown to specifically bind protein factors from nuclear extracts of A. franciscana nauplii by means of electrophoretic mobility shift assays. Several protein-binding regions were also detected by DNase I protection analysis in the promoters of the genes encoding the α1 subunit of Na+/K+-ATPase, actin 302 and sarco/endoplasmic reticulum Ca2+-ATPase. Specific DNA-binding proteins in nauplius nuclear extracts were detected for all the promoter regions analyzed. These proteins were either not present in cyst nuclear extracts or were present in much smaller concentrations. Three of the five regions analyzed also bound proteins present in cyst nuclear extracts. These data indicate that transcriptional activation upon exiting cryptobiosis in A. franciscana involves the expression/activation of DNA-binding transcription factors that are not present in cyst nuclei
Behavioral attraction of Leach's storm-petrels (Oceanodroma leucorhoa) to dimethyl sulfide
Authors: Nevitt Gabrielle A. , Haberman Karen
Published: March 2003

A recent model for olfactory foraging by procellariiform seabirds suggests that these birds use biogenic sulfur compounds to locate productive areas for foraging in the southern oceans. The present study refines a simple approach to test birds' responses to odors on land and extends our knowledge to a northern species, the Leach's storm-petrel (Oceanodroma leucorhoa). Rather than working at sea, we tested the behavioral response to dimethyl sulfide (DMS) at night in breeding colonies on Kent Island, New Brunswick,Canada. Birds were presented with either 5 ml DMS (100 μmol l–1 concentration) or control (water) solutions from a platform 1.5 m in height positioned in a flyway 10 m from a breeding colony. We also tested birds' responses to cod liver oil, a well-established olfactory attractant of procellariiforms foraging at sea. Leach's storm-petrels approached DMS presentations nearly twice as frequently as they approached controls. We next compared the distribution of approaches against a Poisson process to test for evidence of social cueing. We found that approaches to DMS were significantly clustered. By contrast, the distribution of approaches did not depart significantly from a Poisson distribution for either cod liver oil or control presentations. Taken together, these results suggest that Leach's storm-petrels can smell DMS and potentially use it as a foraging cue. The results are consistent with the hypothesis that the detection of biogenic sulfur compounds in combination with other cues assists birds in locating foraging hotspots.
Twilight orientation to polarised light in the crepuscular dung beetleScarabaeus zambesianus
Authors: Dacke Marie , Nordström Peter , Scholtz Clarke H.
Published: March 2003

The polarisation pattern of skylight offers many arthropods a reference for visual compass orientation. The dung beetle Scarabaeus zambesianusstarts foraging at around sunset. After locating a source of fresh droppings,it forms a ball of dung and rolls it off at high speed to escape competition at and around the dung pile. Using behavioural experiments in the field and in the laboratory, we show that the beetle is able to roll along a straight path by using the polarised light pattern of evening skylight. The receptors used to detect this skylight cue can be found in the ommatidia of the dorsal rim area of the eye, whose structures differ from the regular ommatidia in the rest of the eye. The dorsal rim ommatidia are characterised by rhabdoms with microvilli oriented at only two orthogonal orientations. Together with the finding that the receptors do not twist along the length of the rhabdom, this indicates that the photoreceptors of the dorsal rim area are polarisation sensitive. Large rhabdoms, a reflecting tracheal sheath and a lack of screening pigments make this area of the eye well adapted for polarised light detection at low light levels. The fan-shaped arrangement of receptors over the dorsal rim area was previously believed to be an adaptation to polarised light analysis, but here we argue that it is simply a consequence of the way that the eye is built.
Functional consequences of a gene duplication and fusion event in an arginine kinase
Authors: Compaan Deanne M. , Ellington W. Ross
Published: March 2003

Arginine kinase (AK) from the foot of the razor clam Ensis directus consists of two full-length AK domains, denoted D1 and D2, fused in a single polypeptide chain. The full-length cDNA for Ensis AK was obtained and its deduced amino acid sequence was analyzed in the context of the X-ray crystal structure of a typical, monomeric AK. Both domains of Ensis AK contain most of the residues currently thought to be critical in catalysis, suggesting that both AK domains are catalytically competent. The full-length Ensis AK, a D2–NusA–His-tag fusion protein and a D2-truncated AK (enterokinase cleavage product of the fusion protein) were expressed in Escherichia coli and purified. All recombinant AK constructs displayed high enzyme activity. Attempts at expressing active D1 alone, D2 alone or a D1–NusA–His-tag fusion protein were unsuccessful. The catalytic properties of the active proteins were compared with the corresponding properties of recombinant AK from the horseshoe crab Limulus polyphemus, which is a typical monomeric AK. In contrast to expectations, the kinetic results strongly suggest that Ensis AK has only one active domain, namely D2. The Kcat values for all Ensis constructs were roughly twice that of typical AKs, indicating higher overall catalytic throughput at the competent active site. Furthermore, both the full-length and truncated D2 Ensis AKs showed no synergism of substrate binding unlike typical AKs. The D2–NusA–His-tag fusion construct actually displayed negative synergism of substrate binding, which means that, in effect, the first substrate bound acts as a competitive inhibitor of the second. The conservation of the structure of the apparently inactive D1 may be related to constraints imposed by structural changes that could potentially impact substrate binding in D2 and/or possibly influence the proper folding of the enzyme during synthesis. Overall, the results from the present study indicate that the AK contiguous dimer from Ensis directus functions with activity in only the second domain. Although lacking activity in D1, D2 appears to compensate by having a higher intrinsic catalytic throughput than typical 40-kDa monomeric AKs.
Adaptation in pheromone-sensitive trichoid sensilla of the hawkmoth Manduca sexta
Authors: Dolzer Jan , Fischer Karin , Stengl Monika
Published: March 2003

In extracellular tip recordings from long trichoid sensilla of male Manduca sexta moths, we studied dose–response relationships in response to bombykal stimuli of two different durations in the adapted and the non-adapted state. Bombykal-responsive cells could be distinguished from non-bombykal-sensitive cells in each trichoid sensillum because the bombykal-responsive cell always generated the action potentials of larger initial amplitude. The bombykal cell, which was recorded at a defined location within a distal flagellar annulus, can resolve at least four log10-units of pheromone concentrations but is apparently unable to encode all stimulus durations tested. Parameters of the amplitude-modulated sensillar potential and the frequency-modulated action potential responses were examined in different states of adaptation. Evidence is presented for the existence of several mechanisms of adaptation, which affect distinct steps of the transduction cascade. After adapting pheromone stimuli, the sensillar potential rises to a lower amplitude and declines faster compared with the non-adapted response. In addition, the frequency of the adapted action potential response is reduced. Only the time of rise of the sensillar potential is differentially affected by adapting pheromone stimuli of different duration. The time of rise does not increase after short, but only after long, adapting stimuli. Both short and long adapting stimuli shift the dose–response curves of the sensillar potential amplitude, as well as the initial slope of its rising phase, to higher stimulus concentrations by approximately one log10-unit. The shift in the dose–response curve of the action potential response is larger than for the sensillar potential response, suggesting that an additional adaptation mechanism acts at the level of action potential generation. Furthermore, a faster decline of the sensillar potential after short and long adapting stimuli suggests that the resting potential of the olfactory receptor neuron is stabilized.
A mobile-bearing total knee prosthesis compared with a fixed-bearing prosthesis
Authors: Price A. J. , Rees J. L. , Beard D. , Juszczak E. , Carter S. , White S. , de Steiger R. , Dodd C. A. F. , Gibbons M. , McLardy-Smith P. , Goodfellow J. W. , Murray D. W.
Published: March 2003

Before proceeding to longer-term studies, we have studied the early clinical results of a new mobile-bearing total knee prosthesis in comparison with an established fixed-bearing device. Patients requiring bilateral knee replacement consented to have their operations under one anaesthetic using one of each prosthesis. They also agreed to accept the random choice of knee (right or left) and to remain ignorant as to which side had which implant. Outcomes were measured using the American Knee Society Score (AKSS), the Oxford Knee Score (OKS), and determination of the range of movement and pain scores before and at one year after operation.

Preoperatively, there was no systematic difference between the right and left knees. One patient died in the perioperative period and one mobile-bearing prosthesis required early revision for dislocation of the meniscal component.

At one year the mean AKSS, OKS and pain scores for the new device were slightly better (p < 0.025) than those for the fixed-bearing device. There was no difference in the range of movement.

We believe that this is the first controlled, blinded trial to compare early function of a new knee prosthesis with that of a standard implant. It demonstrates a small but significant clinical advantage for the mobile-bearing design.
Relationship between outcome and annual surgical experience for the Charnley total hip replacement
Authors: Fender D. , van der Meulen J. H. P. , Gregg P. J.
Published: March 2003

Using a regional arthroplasty register, we assessed the outcome, at five years, of 1198 primary Charnley total hip replacements (THRs) undertaken across a single health region in England in 1990. An independent clinical and radiological assessment was completed for 497 operations, carried out in 18 different hospitals, under the care of 56 consultants and by differing grades of surgeon. The overall number of failures in this group was 44 (8.9%). We found that the risk of failure in patients operated on by a consultant whose firm carried out 60 or more THRs in 1990 was 25% of that of patients under the care of a consultant whose firm undertook less than 30, adjusting for a number of patient, surgeon and hospital characteristics (16% v 4%; p < 0.001 for linear trend).

Our study shows that the early outcome of hip replacement surgery varies with the number of replacements undertaken by the consultant firm. A national arthroplasty register would be a convenient source for such data.
Quadricepsplasty for knee stiffness after femoral lengthening in congenital short femur
Authors: Hosalkar H. S. , Jones S. , Chowdhury M. , Hartley J. , Hill R. A.
Published: March 2003

We review the results of a modified quadricepsplasty in five children who developed stiffness of the knee after femoral lengthening for congenital short femur using an Ilizarov external fixator which spanned the knee.

All had a full range of movement of the knee before lengthening was undertaken. Unifocal lengthening was carried out in the distal metaphysiodiaphyseal region of the distal femur with a mean gain of 6.5 cm. The mean percentage lengthening was 24%.

At the end of one year after removal of the Ilizarov frame and despite intensive physiotherapy all patients had stiffness. Physiotherapy was continued after the quadricepsplasty and, at the latest follow-up (mean 27 months), the mean active flexion was 102° (80 to 130). The gain in movement ranged from 50° to 100°. One patient had a superficial wound infection which settled after a course of oral antibiotics. None developed an increased extension lag after surgery and all were very satisfied with the results. Quadricepsplasty is a useful procedure for stiffness of the knee after femoral lengthening which has not responded to physiotherapy.
Turn-up bone flap for lengthening the below-knee amputation stump
Authors: Pant R. , Younge D.
Published: March 2003

When amputation just below the knee becomes necessary after extensive loss of bone from the tibia and of anterior soft tissue in the treatment of tumours, fractures or infection, the remaining proximal tibia may be too short for a below-knee prosthesis, although the knee may be normal. We have included the distal tibia or foot in a long posterior flap by turning it up thus increasing the length of a very short proximal tibial stump. The knee is thereby saved, allowing satisfactory use of a below-knee prosthesis.

This technique is particularly applicable when the distal leg is normal and well vascularised. Five procedures have been undertaken. We present two illustrative cases.
Bone mineral density in long-term survivors of highly malignant osteosarcoma
Authors: Holzer G. , Krepler P. , Koschat M. A. , Grampp S. , Dominkus M. , Kotz R.
Published: March 2003

We studied the bone mineral density (BMD) of 48 long-term survivors of highly malignant osteosarcoma who had been treated according to the chemotherapy protocols of the German- Swiss-Austrian Co-operative Osteosarcoma Study Group which include high-dose methotrexate. The mean age of the patients was 31 ± 4.2 years and the mean follow-up 16 ± 2.2 years. The BMD of the lumbar spine and of the proximal femur of the non-operated side was measured by dual- energy x-ray absorptiometry. A questionnaire was given to determine life-style factors, medical history and medication. Ten patients were osteoporotic, 21 osteopenic and 17 normal according to the WHO definition.

Eighteen patients suffered fractures after receiving chemotherapy and all had significantly lower levels of BMD for all the sites measured.
Blood Lead, Blood Pressure, and Hypertension in Perimenopausal and Postmenopausal Women
Authors: Nash Denis , Magder Laurence , Lustberg Mark , Sherwin Roger W. , Rubin Robert J. , Kaufmann Rachel B. , Silbergeld Ellen K.
Published: March 2003

Context

Lead exposures have been shown to be associated with increased blood pressure and risk of hypertension in older men. In perimenopausal women, skeletal lead stores are an important source of endogenous lead exposure due to increased bone demineralization.

Objective

To examine the relationship of blood lead level with blood pressure and hypertension prevalence in a population-based sample of perimenopausal and postmenopausal women in the United States.

Design, Setting, and Participants

Cross-sectional sample of 2165 women aged 40 to 59 years, who participated in a household interview and physical examination, from the Third National Health and Nutrition Examination Survey conducted from 1988 to 1994.

Main Outcome Measures

Associations of blood lead with blood pressure and hypertension, with age, race and ethnicity, cigarette smoking status, body mass index, alcohol use, and kidney function as covariates.

Results

A change in blood lead levels from the lowest (quartile 1: range, 0.5-1.6 µg/dL) to the highest (quartile 4: range, 4.0-31.1 µg/dL) was associated with small statistically significant adjusted changes in systolic and diastolic blood pressures. Women in quartile 4 had increased risks of diastolic (>90 mm Hg) hypertension (adjusted odds ratio [OR], 3.4; 95% confidence interval [CI], 1.3-8.7), as well as moderately increased risks for general hypertension (adjusted OR, 1.4; 95% CI, 0.92-2.0) and systolic (>140 mm Hg) hypertension (adjusted OR, 1.5; 95% CI, 0.72-3.2). This association was strongest in postmenopausal women, in whom adjusted ORs for diastolic hypertension increased with increasing quartile of blood lead level compared with quartile 1 (adjusted OR, 4.6; 95% CI, 1.1-19.2 for quartile 2; adjusted OR, 5.9; 95% CI, 1.5-23.1 for quartile 3; adjusted OR, 8.1; 95% CI, 2.6-24.7 for quartile 4).

Conclusions

At levels well below the current US occupational exposure limit guidelines (40 µg/dL), blood lead level is positively associated with both systolic and diastolic blood pressure and risks of both systolic and diastolic hypertension among women aged 40 to 59 years. The relationship between blood lead level and systolic and diastolic hypertension is most pronounced in postmenopausal women. These results provide support for continued efforts to reduce lead levels in the general population, especially women.
Multiple Sclerosis and Epstein-Barr Virus
Authors: Levin Lynn I. , Munger Kassandra L. , Rubertone Mark V. , Peck Charles A. , Lennette Evelyne T. , Spiegelman Donna , Ascherio Alberto
Published: March 2003

Context

Infection with Epstein-Barr virus (EBV) has been associated with an increased risk of multiple sclerosis (MS), but the temporal relationship remains unclear.

Objective

To determine whether antibodies to EBV are elevated before the onset of MS.

Design, Setting, and Population

Nested case-control study conducted among more than 3 million US military personnel with blood samples collected between 1988 and 2000 and stored in the Department of Defense Serum Repository. Cases were identified as individuals granted temporary or permanent disability because of MS. For each case (n = 83), 2 controls matched by age, sex, race/ethnicity, and dates of blood sample collection were selected.

Main Outcome Measures

Antibodies including IgA against EBV viral capsid antigen (VCA) and IgG against VCA, nuclear antigens (EBNA complex, EBNA-1, and EBNA-2), diffuse and restricted early antigens, and cytomegalovirus.

Results

The average time between blood collection and MS onset was 4 years. The strongest predictors of MS were serum levels of IgG antibodies to VCA or EBNA complex. The risk of MS increased monotonically with these antibody titers; relative risk (RR) in persons in the highest category of VCA (≥2560) compared with those in the lowest (≤160) was 19.7 (95% confidence interval [CI], 2.2-174; P for trend = .004). For EBNA complex titers, the RR for those in the highest category (≥1280) was 33.9 (95% CI, 4.1-283; P for trend <.001) vs those in the lowest category (≤40). Similarly strong positive associations between EBV antibodies and risk of MS were already present in samples collected 5 or more years before MS onset. No association was found between cytomegalovirus antibodies and MS.

Conclusion

These results suggest a relationship between EBV infection and development of MS.
Preparation and properties of heat‐shrinkable cross‐linked low‐density polyethylene
Authors: Morshedian J. , Khonakdar H. A. , Mehrabzadeh M. , Eslami H.
Published: March 2003

In this work, heat‐shrinkable characteristics of a polyethylene compound were obtained by blending mixtures of low‐density polyethylene with varying amount of peroxide. These were then extruded and molded to the required shape and then cross‐linked by chemical means, followed by heating and stretching and then cooled to “freeze‐in” the oriented polymer structure (elastic memory). A decrease in the melting point and heat of fusion (ΔHf), as determined from the DSC melting enthalpies, was observed with an increase in the dicumyl peroxide (DCP) concentration. Tests on the heat shrinkablity of the samples showed that the stretching temperature has a large effect on the shrinkage temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. The elongation at break decreased with an increase in the DCP concentration. Increasing the temperature in lightly cross‐linked samples (low percent DCP) resulted in a reduction in the elongation at break. Increasing the cross‐linking density (DCP content) gave an opposite effect. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 112–119, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10041
Continuous production of ultrathin polymeric nanofilms using the spontaneous film formation technique
Authors: Hinrichsen Georg , Hoffmann Andreas , Schleeh Thomas , Macht Christian
Published: March 2003

The paper deals with a unique continuous laboratory process for the manufacture of ultrathin nanofilms of various thermoplastic polymers, such as polycarbonate, polyetherimide, polysulfone, and liquid crystalline polyester, based upon the recently developed spontaneous film formation technique. Continuous films with a width up to 14 cm and a thickness of 20–100 nm were produced using a prototype laboratory apparatus at a windup velocity of 1–20 m/min. The length of the film can be almost infinite, i.e. longer than 1 km. The produced films are of high quality and can be used as layer materials, as membranes, in optical devices and sensors, as well as for microlithographic purposes. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 120–125, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10042
Nanoparticles from a controlled polymerization process
Authors: Tirumala Vijaya R. , Caneba Gerard T. , Dar Yadunandan , Wang Hsien‐Hau , Mancini Derrick C.
Published: March 2003

Free‐radical retrograde precipitation polymerization process in the past has shown excellent control characteristics over reaction rate, molecular weight, and in the entrapment of live radicals for the generation of block copolymers. The same principle has now been extended to study the reaction confinement to a nanoscale region. Nanosized polymer particles have been reported to form from block copolymers, conventional precipitation polymerization methods, or through emulsion polymerization approaches. In this work, we present a new method of generating nanosized polymer particles by polymerizing the monomer in an environment that precipitates the polymer above the lower critical solution temperature. The nanoparticles have been characterized by both tapping‐mode atomic force microscopy observations and in situ synchrotron time‐resolved small‐angle X‐ray scattering analysis. The results from both the techniques showed the formation of nanoparticles in the size range of 15–30 nm, directly from the polymerization process. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 126–136, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10043
Processing characteristics of PET/PEN blends, part 1: Extrusion and transesterification reaction kinetics
Authors: Tharmapuram Sriram R. , Jabarin Saleh A.
Published: March 2003

Blends of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalene dicarboxylate) (PET/PEN) have exhibited properties that are of commercial interest to the packaging industry. Melt processing of PET with PEN results in transesterification reactions. The blend properties are controlled by the kinetics of these reactions. The chemical kinetics equations have been modified to predict theoretical processing temperatures required for different blend compositions to achieve critical levels of transesterification. These values are found to be in close agreement with the experimentally observed values obtained for blends processed in a twin‐screw extruder. The critical transesterification temperature is dependent on the equilibrium melting point of the miscible blend and the nature of the PET and PEN resins used for preparing the blend. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 137–146, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10044
Processing characteristics of PET/PEN blends, part 2: Rheology and degradation kinetics
Authors: Tharmapuram Sriram R. , Jabarin Saleh A.
Published: March 2003

Blends and copolyesters of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalene dicarboxylate), PET/PEN, have shown promise in high performance container applications. In the first part of this series on the processing characteristics of PET/PEN blends, we investigated the applicability of reaction kinetics to predict the critical transesterification temperature during processing and the influence of the equilibrium melting point of the miscible blends on the critical transesterification temperature. In the present work, we have studied both the rheology and degradation kinetics of the blends as a function of material composition. Melt viscosity loss was measured as a function of time and temperature. Activation energies for degradation were calculated from experimental data. Results show that blends containing a minimum of 10% PEN by weight are as stable as PEN in terms of thermal and thermal‐oxidative degradation. Addition of low amounts of PEN to PET causes a depression in melt viscosity. A critical composition of 10% PEN by weight is required before an increase in blend viscosity is observed. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 147–154, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10045
Processing characteristics of PET/PEN blends, part 3: Injection molding and free blow studies
Authors: Tharmapuram Sriram R. , Jabarin Saleh A.
Published: March 2003

The injection molding and orientation characteristics of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalene dicarboxylate) (PET/PEN) blends are discussed. Injection molding was carried out to produce preforms with good optical clarity. The difference between the processing temperature and the equilibrium melting point of the materials, their crystallizability, and their levels of transesterification are major factors controlling optical clarity in the preforms. Free blow experiments were conducted on the injection‐molded preforms to study changes in the blow‐up ratio (BUR) as a function of molecular weight, blend composition, level of transesterification, and the difference between the orientation temperature and the glass‐transition temperature (T – Tg). Results indicate that for a given value of intrinsic viscosity and T – Tg, the blends will require higher stretch ratios than that of PET to achieve equivalent levels of strain‐induced crystallization. The BUR for a given blend composition is independent of the degree of randomness after a critical level of transesterification has been achieved. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 155–167, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10046