bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic algorithms for geophysical parameter inversion from altimeter data
Authors: Ramillien Guillaume
Published: March 2003

A new approach for inverting several geophysical parameters at the same time from altimeter and marine data by implementing genetic algorithms (GAs) is presented. These original techniques of optimization based on non-deterministic rules simulate the evolution of a population of candidate solutions for a given objective function to minimize. They offer a robust and efficient alternative to gradient techniques for non-linear parameter inversion. Here genetic algorithms are used for solving a discrete gravity problem of data associated with an undersea relief, to retrieve seven parameters at the same time: the elastic thickness, the mean ocean depth, the seamount location (longitude/latitude), its amplitude, radius and density from its observed gravity/geoid signature. This approach was also successfully used to adjust lithosphere parameters in the real case of the Rarotonga seamount [21.2°S; 159.8°W] in the Southern Cook Islands region, where GA simulations provided robust estimates of these seven parameters. The GA found very realistic values for the mean ocean depth and the seamount amplitude and the precise geographical location of Rarotonga Island. Moreover, the values of elastic thickness (∼14–15km) and seamount density (∼2850–2870kgm−3) estimated by the GA are consistent with the ones proposed in earlier studies.
Foraging behaviour of juvenile pink salmon (Oncorhynchus gorbuscha) and size‐dependent predation risk
Authors: Willette T. M.
Published: March 2003

Two hypotheses related to effects of juvenile pink salmon (Oncorhynchus gorbuscha) foraging behaviour and size on their predation risk were evaluated using field data collected in Prince William Sound, Alaska 1995–97. My results supported the hypothesis that low macrozooplankton density leads to dispersion of juvenile salmon from shallow nearshore habitats and greater predation risk, but zooplankton type was an important factor. When the biomass of large copepods (primarily Neocalanus spp.) declined, salmon dispersed from shallow nearshore habitats, and mean daily individual predator consumption of salmon increased by a factor of 5. A concomitant five‐fold increase in the probability of occurrence of salmon in predator stomachs supported the notion that increased predation on salmon was caused by a greater overlap between predator and prey when salmon dispersed offshore, not an increase in the number of salmon consumed per feeding bout. The results also generally supported the hypothesis that the timing of predation events modifies the nature of size‐dependent predation losses of salmon to different predator groups (small and large planktivores and piscivores). Size‐dependent vulnerabilities of salmon to predators were a function of both predator and prey sizes. When simulated predation was shifted from May to June, the vulnerability of salmon became more dependent on their growth than initial size. But, the size‐ and growth‐dependent vulnerabilities of salmon differed more among predator groups than between May and June, suggesting that changes in the composition of predator fields could more strongly affect the nature of size‐dependent predation than changes in the timing of predation losses.
The Effect of Helicobacter pylori Eradication on Gastric Juice and Blood Ammonia Concentrations and on Visual Evoked Potentials in Cirrhotics
Authors: Demirtürk Levent , Yazgan Yusuf , İzci Özgür , Özel Melih , Toğrol Erdem , Gültepe Mustafa , Gürbüz Ahmet Kemal , Yıldırım Şükrü
Published: March 2003

Background.

The primary source of ammonia is the gut. Ammonia can also be generated by the urease activity of Helicobacter pylori in the gastric mucosa. The aim of this study was to investigate the effect of H. pylori eradication on blood and gastric juice ammonia levels and on visual evoked potential (VEP) recordings in cirrhotic patients.

Materials and Methods.

Male patients with cirrhosis and H. pylori infection were prospectively evaluated. All patients were given triple regimen for eradication for 10 days. Gastroscopy together with gastric juice sampling for ammonia and mucosal sampling for H. pylori status was performed before and after therapy. Gastric juice and blood ammonia levels were measured and VEP recordings were obtained before and after treatment.

Results.

Twenty‐seven patients were included in the study. Patients with overt clinical hepatic encephalopathy were excluded from the study. Twenty‐four out of twenty‐seven patients became H. pylori‐negative after the treatment. Ammonia measurements and VEP recordings were evaluated in the 24 patients in whom eradication was successful. A slight but statistically significant decrease in blood and a considerable decrease in gastric juice ammonia levels were observed after treatment [from 44.23 µmol/l to 41.6 µmol/l compared with 3234 µmol/l to 2709 µmol/l, respectively (p < .05)] in patients in whom H. pylori was eradicated. VEP recordings were abnormal in 14 out of 24 patients before the treatment. Only four of these 14 patients with abnormal recordings showed improvement. (p > .05).

Conclusions.

Helicobacter pylori eradication in cirrhotics decreases blood and gastric juice ammonia concentrations whereas it does not provide an improvement in VEP recordings.
Identification of Environmental Stress‐Regulated Genes in Helicobacter pylori by a lacZ Reporter Gene Fusion System
Authors: De Vries Nicolette , Kuipers Ernst J. , Kramer Naomi E. , Van Vliet Arnoud H. M. , Bijlsma Jetta J. E. , Kist Manfred , Bereswill Stefan , Vandenbroucke‐Grauls Christina M. J. E. , Kusters Johannes G.
Published: March 2003

abstract

Background.

Helicobacter pylori persists in the human stomach for decades. This requires an efficient adaptation of H. pylori to the gastric niche and involves the regulation of bacterial genes in response to environmental stress. Efficient molecular tools to identify regulated H. pylori genes are scarce, therefore we developed a genomic lacZ reporter gene fusion system in H. pylori to screen for stress‐regulated genes.

Materials and methods.

The integration vector pBW was constructed and used to generate random genomic lacZ fusions in H. pylori. Two‐hundred‐and‐fifty H. pylori transformants were selected from this library, replica‐plated and screened for differential lacZ expression after exposure to two environmental stress conditions: increased temperature (42°C), and iron‐limitation.

Results.

From a library of H. pylori transformants with random genomic transcriptional lacZ fusions, two stress‐regulated H. pylori loci were identified. The transcription of a gene of unknown function (designated hsp12) was increased by incubation at 42°C. The transcription of a locus, consisting of the three fumarate reductase subunit genes (frdCAB) and the HP0190 gene from H. pylori strain 26695, was decreased under iron‐limitation.

Conclusions.

This is the first time that a genomic transcriptional lacZ reporter gene H. pylori library has been used as a tool for the fast and efficient identification of environmental stress‐regulated H. pylori genes.
Relationship between serum leptin concentrations and the marbling scores in Japanese Black Cattle
Authors: YONEKURA Shinichi , OKA Akio , NODA Masanobu , UOZUMI Norio , YONEZAWA Tomo , KATOH Kazuo , OBARA Yoshiaki
Published: March 2003

The objective of this study was to investigate the relationship between marbling and serum leptin concentrations. First, we compared serum leptin concentrations between Japanese Black cattle and Holstein calves, and found that the mean serum concentration was significantly higher (P < 0.05) in Japanese Black cattle (2.67 ± 0.41 ng/mL, n = 13) than in Holstein calves (1.79 ± 0.43 ng/mL, n = 5). We then examined the effects of roughage intake or vitamin A on the serum leptin concentrations in Japanese Black cattle. Although the leptin concentrations for the high roughage group were significantly higher than those for the low roughage group at 4, 7 and 20 months old, there was no significant difference in the carcass characteristics of the two groups. In addition, although there was a significant difference in the marbling score between the high vitamin A group and low vitamin A group, there was no significant difference in serum leptin concentrations between the groups. These results suggest that although serum leptin concentrations were not significantly correlated to the marbling scores they may be related to the genetic advantage for marbling in Japanese Black cattle.
Possibility of amino acid nutrition in broiler
Authors: ISHIBASHI Teru , YONEMOCHI Chisato
Published: March 2003

The consumption of poultry meats exceeds 50% of total meat consumption. With the outbreak of bovine spongiform encephalopathy and foot and mouth disease, the consumption of poultry meat is set to increase. The use of meat bone meal derived from cattle and pigs is prohibited. Therefore, plant protein has to be used more frequently and the importance of the study of amino acid nutrition is increasing. In order to improve dietary efficiency, it is necessary to elucidate the exact amino acid requirements of poultry. The amino acid requirements are not constant and are affected by various factors. By using the plasma amino acid concentration as a parameter, it is possible to predict the amino acid requirements within a short period using a small number of animals repeatedly. By satisfying the amino acid requirements through supplementing crystalline amino acids, it is possible to reduce dietary protein and excretory nitrogen simultaneously. However, when the dietary protein is reduced, the abdominal fat tends to increase. This is solved by deciding the optimum dietary protein level, but it is difficult to control the taste of poultry meat by dietary amino acids.
Mechanism of insulin action on glucose metabolism in ruminants
Authors: SASAKI Shin‐ichi
Published: March 2003

This review presents a brief overview on the mechanism of insulin action on glucose metabolism at the molecular basis in ruminants. For ruminants, an exact mechanism of insulin on glucose metabolism is still rudimentary, but it is clear that originally, if not all, the mechanism of insulin action in ruminants was the same as in other species. Like non‐ruminants, the insulin‐sensitive glucose transporter GLUT 4 is thought to be a key‐protein in the control of glucose uptake and metabolism in ruminants, and insulin regulates glucose transport by stimulating the translocation of GLUT 4 from an intracellular membrane pool to the plasma membrane in adipocytes and muscles. Moreover, insulin‐induced GLUT 4 translocation is activated through the common intracellular signaling pathway of insulin phosphatidylinositol 3‐kinase (PI3‐kinase) signaling pathway rather than the mitogen activated protein kinase (MAP kinase)‐dependent signaling pathway. However, GLUT 4 mRNA and protein, and insulin‐induced GLUT 4 translocation on adipocytes and muscles in ruminants are lower than those in rodents and human subjects. Furthermore, insulin‐induced PI3‐kinase activation is reduced concomitantly with the lower content of insulin receptor substrate‐1 (IRS‐1) in ruminants. In spite of normal status, a resistance to the stimulatory action of insulin on glucose metabolism in ruminants as compared to non‐ruminants may be due to, at least in part, the lower content of GLUT 4 and the lower capacity of insulin signal transduction, resulting to the lower glucose transport activity.
ECG and heart rate determination in fetal cattle using a digital signal processing method
Authors: CHEN Wenxi , NEMOTO Tetsu , KOBAYASHI Toshio , SAITO Toshiyuki , KASUYA Etsuko , HONDA Yoshifumi
Published: March 2003

A method of recording the fetal electrocardiogram (ECG) and heart rate (HR) is described. An abdominal lead and a thoracic lead were used to measure the fetal ECG and maternal ECG, respectively. The maternal component in the abdominal lead measurement was estimated by a digital adaptive filter using the thoracic lead measurement as a reference. By suppressing the estimated maternal components in the abdominal lead, the fetal ECG could be detected. The beat‐by‐beat fetal QRS complex peaks were determined by a digital matched filter from the fetal ECG enhanced in this way. The method was trialed in 10 pregnant Holstein cows at gestational periods ranging from 136 to 224 days. The results show that this method can extract the fetal ECG and determine the fetal HR from the raw noisy measurement data. The results suggest that the method would have applicability in monitoring fetal ECG as well as providing a non‐invasive, continuous HR profile during gestation, which will enable better understanding of the development of cattle fetuses before delivery.
Approachability and contact behavior of commercial dairy calves to humans
Authors: UETAKE Katsuji , MORITA Shigeru , KOBAYASHI Yoshiko , HOSHIBA Shinji , TANAKA Toshio
Published: March 2003

Calves (n = 106) on four dairy farms were observed for their approachability to humans. All calves experienced similar rearing conditions: Beginning individual pen, after birth until weaning at about 2 months, where they were housed individually and fed milk and a milk replacement; Late individual pen, after weaning until grouping at about 3.5 months, where they were housed individually and fed hay, silage and concentrate feed; Beginning group pen, after grouping until 5 months, where they were housed in groups of 2–5 animals and fed hay, silage and concentrate feed; later group pen, from 5 to 7 months. The number of calves that contacted an experimenter who stood in front of their pens for 10 min was recorded on 6 separate days over 3 months. Latency to touch and time spent in activities during touching such as sucking, licking, biting and rubbing were also measured. There were no significant differences in the latency to touch and the ratio of touch to non‐touch calves between the rearing conditions and the farms. The time spent touching was significantly affected by the interaction between the rearing condition and the farm (P < 0.01). In detail, the time spent sucking (P < 0.001) and licking (P < 0.01) was different between the rearing condition × farm variables. The proportion of calves that approached and touched the experimenter tended to be higher in the farms in which a stockperson worked longer inside and outside their pens (both ρ = 0.95, P = 0.051). These results were interpreted according to the perspectives of early positive reinforcement with food and the habituation process to humans existing nearby.
Pilot testing of the ‘Haemo‐QoL’ quality of life questionnaire for haemophiliac children in six European countries
Authors: Bullinger M. , Von Mackensen S. , Fischer K. , Khair K. , Petersen C. , Ravens‐Sieberer U. , Rocino A. , Sagnier P. , Tusell J. M. , Van Den Berg M. , Vicariot M.
Published: March 2003

Summary.  In a multinational working group, an instrument (Haemo‐QoL) to assess quality of life in children/adolescents with haemophilia and their parents has been developed. In co‐operation with haemophilia treatment centres in six European countries, approximately 10 children/adolescents with haemophilia per country and their parents were asked to participate in the pilot‐testing. Both self‐reported and parent‐reported questionnaires were provided for two age‐groups of children (4–16 years). Medical data was collected from physicians from patient files. Answers to open questions from participants (58 children and 57 parents) confirmed the content of 116 of the preliminary items. Cognitive debriefing revealed that the majority of the Haemo‐QoL was rated favourably, but 29 questions were recommended to be omitted and several items to be reformulated. Preliminary psychometric testing of the revised 77 item questionnaire in the same sample showed acceptable reliability and validity, which will be examined in a subsequent study with a larger patient sample.
The H1 and H2 regions of the activation domain of herpes simplex virion protein 16 stimulate transcription through distinct molecular mechanisms
Authors: Ikeda Keiko , Stuehler Thomas , Meisterernst Michael
Published: March 2003

Abstract Background: The Herpes Simplex Virion Protein 16 (VP16) contains a strong activation domain which can be subdivided into two regions, H1 and H2, both of which independently activate transcription in vivo. Several components of the basal transcription machinery have been shown to interact with the activation domain of VP16, mostly through the H1 region.

Results: We show that the H2 region binds directly to histone acetyltransferase, CBP (CREB (cAMP Responsive Element Binding Protein) Binding Protein) both in vivo and in vitro. The sites of interaction with the H2 region were mapped to both the amino‐ and carboxy‐terminal segments of CBP. A mutation in the H2 region disrupts the interaction with CBP and abolishes the ability of VP16 to mediate in vitro transactivation from chromatin templates in an acetyl‐CoA dependent manner. In contrast, human Mediator, another co‐activator complex, binds specifically to both the H1 and H2 regions.

Conclusion: The H1 and H2 regions of the VP16 activation domain activate transcription via distinct pathways. The H2 requires CBP for activation, whereas the H1 may function through Mediator and general transcription factors.
Phosphorylation and reorganization of vimentin by p21‐activated kinase (PAK)
Authors: Goto Hidemasa , Tanabe Kazushi , Manser Edward , Lim Louis , Yasui Yoshihiro , Inagaki Masaki
Published: March 2003

Background: Intermediate filament (IF) is one of the three major cytoskeletal filaments. Vimentin is the most widely expressed IF protein component. The Rho family of small GTPases, such as Cdc42, Rac and Rho, are thought to control the organization of actin filaments as well as other cytoskeletal filaments.

Results: We determined if the vimentin filaments can be regulated by p21‐activated kinase (PAK), one of targets downstream of Cdc42 or Rac. In vitro analyses revealed that vimentin served as an excellent substrate for PAK. This phosphorylated vimentin lost the potential to form 10 nm filaments. We identified Ser25, Ser38, Ser50, Ser65 and Ser72 in the amino‐terminal head domain as the major phosphorylation sites on vimentin for PAK. The ectopic expression of constitutively active PAK in COS‐7 cells induced vimentin phosphorylation. Fibre bundles or granulates of vimentin were frequent in these transfected cells. However, the kinase‐inactive mutant induced neither vimentin phosphorylation nor filament reorganization.

Conclusion: Our observations suggest that PAK may regulate the reorganization of vimentin filaments through direct vimentin phosphorylation.
Applying extinction research and theory to cue‐exposure addiction treatments
Authors: Conklin Cynthia A. , Tiffany Stephen T.
Published: March 2003

Aims To evaluate the efficacy of cue‐exposure addiction treatment and review modern animal learning research to generate recommendations for substantially enhancing the effectiveness of this treatment.

Design Meta‐analysis of cue‐exposure addiction treatment outcome studies (N = 9), review of animal extinction research and theory, and evaluation of whether major principles from this literature are addressed adequately in cue‐exposure treatments.

Findings The meta‐analytical review showed that there is no consistent evidence for the efficacy of cue‐exposure treatment as currently implemented. Moreover, procedures derived from the animal learning literature that should maximize the potential of extinction training are rarely used in cue‐exposure treatments.

Conclusions Given what is known from animal extinction theory and research about extinguishing learned behavior, it is not surprising that cue‐exposure treatments so often fail. This paper reviews current animal research regarding the most salient threats to the development and maintenance of extinction, and suggests several major procedures for increasing the efficacy of cue‐exposure addiction treatment.
Glomerular charge selectivity for horseradish peroxidase and albumin at low and normal ionic strengths
Authors: Sörensson J. , Ohlson M. , Lindström K. , Haraldsson B.
Published: March 2003

The classical concept of a negative glomerular charge barrier has recently been questioned, mainly based on the somewhat high clearance for anionic horseradish peroxidase (HRP). The validity of using anionic HRP can be tested by changing the properties of the charge barrier. A rather unequivocal approach is to reduce the ionic composition of the perfusate and hence increase the Debye length. We determined the glomerular clearance for horseradish peroxidase and serum albumin, using isolated rat kidneys perfused at 8 °C to reduce the tubular modification of the primary urine. The perfusate contained trace amounts of the neutral 125I‐nHRP and the anionic 131I‐aHRP and were otherwise identical except for different ionic strengths, 152 mM and 34 mM, respectively. During control, the fractional clearance was 0.11 ± 0.015 for nHRP and 0.045 ± 0.010 for aHRP, with an average clearance ratio (n/a) of 2.8 ± 0.24. Low ionic strength reduced for aHRP to 0.027 ± 0.006, giving an increased clearance ratio for HRP of 4.2 ± 0.44. The existence of a negative charge barrier is supported by the experiments. The result obtained during normal perfusion is compatible with a charge density (ω) of 34 mEq L−1, using a model of homogeneously charged membrane. Low ionic strength perfusion reversibly reduced the concentration of fixed charges to 12 mEq L−1, suggesting an almost threefold increase of the glomerular membrane volume. Thus, the glomerular charge barrier should be regarded to have a dynamic gel structure rather than being a rigid membrane.
The novel non‐peptide selective endothelin A receptor antagonist LU 135 252 protects against myocardial ischaemic and reperfusion injury in the pig
Authors: GONON  , WANG  , SHIMIZU  , PERNOW
Published: March 2003

The aim of the study was to investigate the efficacy of the novel non‐peptide selective endothelin A (ETA) receptor antagonist LU 135 252 to limit the extent of myocardial ischaemic and reperfusion injury. Administration of LU 135 252 (1 and 5 mg kg–1 i.v.) to anaesthetised pigs reduced mean arterial pressure (MAP) from 91 ± 4 to 79 ± 3 mmHg (P < 0.05) and 96 ± 3–82 ± 3 mmHg (P < 0.01), respectively. Heart rate, coronary blood flow and coronary vascular resistance were not affected by LU 135 252. The infarct size induced by 45‐min ligation of the left anterior descending coronary artery (LAD) followed by 4‐h reperfusion in pigs was 81 ± 5% of the area at risk in control animals given vehicle (n = 8). In pigs receiving 1 mg kg–1 (n = 6) or 5 mg kg–1 (n = 8) of LU 135 252 i.v. 20 min before ischaemia the infarct size was reduced to 64 ± 3% (P < 0.05) and 35 ± 4% (P < 0.001), respectively, of the area at risk. During the reperfusion period there was a non‐significant trend towards a higher coronary blood flow and a lower coronary vascular resistance in the groups given LU 135 252 compared to controls. Myocardial overflow of ET‐like immunoreactivity was increased during the reperfusion period but it was not affected by administration of LU 135 252. It is concluded that administration of the selective ETA receptor antagonist LU 135 252 effectively protects the myocardium from ischaemia/reperfusion injury, indicating that the ETA receptor subtype is involved in the development of ischaemia/reperfusion injury.
Human sudomotor responses to heating and cooling upper‐body skin surfaces: cutaneous thermal sensitivity
Authors: PATTERSON M.J. , COTTER J.D. , TAYLOR N.A.S.
Published: March 2003

The influence of local skin temperature (Tskl) on the control of local and whole‐body sweating was evaluated in eight healthy males. A water‐perfusion garment (37 °C) and a climatic chamber (36.45 ± 0.78 °C; [±SD]; relative humidity 60.3 ± 1.6%) were used to raise and clamp skin and core temperatures. Warm and cool stimuli were applied to four upper‐body skin regions (face, arm, forearm, hand) using perfusion patches (249.0 ± 0.2 cm2). Heating elevated, while cooling suppressed sweat rate (m˙sw) locally, and at other skin surfaces. However, the tendency for Tskl manipulations to induce localized sweat responses was no more powerful than it was at stimulating sweating in non‐treated regions (P > 0.05). Accordingly, neither thermal stimulus produced significantly greater local sudomotor influences than were elicited contralaterally (P > 0.05). No statistical support was found for the notion of inter‐regional differences in upper‐body cutaneous thermal sensitivity for sudomotor control, and, regardless of the stimulation site, whole‐body sudomotor responses to localized thermal treatments were equivalent (P > 0.05).
Human body‐fluid distribution during exercise in hot, temperate and cool environments
Authors: MAW G.J. , MACKENZIE I.L. , TAYLOR N.A.S.
Published: March 2003

Using a simultaneous‐dilution technique, we investigated body‐fluid volume changes during exercise in seven males, during 50 min of cycling (50% maximal work rate) in hot (36.2 °C), temperate (22.0 °C) and cool conditions (14.4 °C). Total body water (TBW), extracellular fluid (ECFV), plasma (PV) and erythrocyte volumes (RCV) were measured, while blood volume (BV), interstitial fluid volume (IFV), extracellular water (ECW) and intracellular water volumes (ICW) were derived. During the initial 10 min of cycling, BV decreased in all environments (P = 0.01), primarily because of a PV reduction (P = 0.01), while IFV, ECFV and ICW were not significantly changed. By 30 min, BV recovered in the temperate and cool conditions, despite mass losses of 563 and 520 mL (respectively), but remained depleted in the hot condition (P = 0.01). The 50‐min volume changes revealed that, throughout exercise, body‐fluid losses appeared to be drawn primarily from the extracellular space, regardless of air temperature. In the hot condition, the PV change represented 63% of the TBW loss, with the ICW contributing 23%. It was concluded that, during cycling, progressive dehydration mainly affected the extracellular space, with the intravascular and intracellular spaces being defended in less stressful conditions.
Swelling‐induced decrease in spontaneous pacemaker activity of rabbit isolated sino‐atrial node cells
Authors: LEI  , KOHL
Published: March 2003

The heart responds to an increase in sino‐atrial node wall stress with an augmentation in rate of contraction. It has been suggested that swelling‐activated ion channels may play a key role in that response. This paper investigates directly the effects of cell swelling onspontaneousactivity of rabbit isolated sino‐atrial node pacemaker cells. The main finding is that sino‐atrial node cells, studied in current clamp mode using amphotericin‐permeabilized patches,decreasetheir spontaneous pacemaker rate by 24.2 ± 7.8% (P < 0.01,n = 9) during 75% hyposmotic swelling. This response is opposite to the predicted impact of volume‐activation of sarcolemmal ion conductances. Computer modelling (OXSOFT ©Heart v4.8) suggests that swelling‐induced dilution of the cytosol, reduction in intracellular potassium concentration, and decrease in the delayed rectifier potassium current,IK, are leading mechanisms in the response. This is supported by voltage‐clamp data that show a swelling‐induced positive shift in the reversal potential ofIKby between 5 and 10 mV (n = 7) and a reduction in amplitude of its rapidly activating component,IKr, (n = 6). Thus, spontaneously active sino‐atrial node cells reduce pacemaking rate during swelling. This response cannot be explained by the known volume‐activated sarcolemmal ion conductances, but appears to be dictated by other mechanisms including dilution of the cytosol and reduction inIK. The results re‐enforce the view that cardiac responses to cell volume changes may be quite different from those to longitudinal stretch.
Creatine supplementation enhances maximum voluntary isometric force and endurance capacity in resistance trained men
Authors: MAGANARIS C.N. , MAUGHAN R.J.
Published: March 2003

The present study examined the hypothesis that creatine (Cr) supplementation can increase the performance of isometric exercise in subjects engaged in a strength training program. Ten male subjects were tested in three experimental trials 7 days apart (days 1, 8 and 15). In each trial the subjects' maximum voluntary force of contraction (MVC) was measured in both legs and isometric endurance capacity at 80, 60, 40 and 20% of MVC of their stronger leg (knee extensor group) was measured with a 4‐min rest between contractions. Additionally, the subjects' isometric endurance capacity at 80% of MVC of their weaker leg was measured in 10 repeated bouts interspersed with 2‐min rest. A double‐blind cross‐over design was adopted for administering Cr or placebo. Subjects were randomized into either the Cr–placebo (Group A: days 2–6: 10 g day−1 of Cr; days 9–13: 10 g day−1 of glucose polymers) or the placebo–Cr group (Group B reverse supplementation order). The daily diet was analysed, and urine samples from 24‐h collections were subjected to Cr and creatinine analysis. In each subject, ≈18 g (35%) of Cr was eliminated in the urine during the Cr supplementation period. MVC increased by about 10% (P < 0.01 in the weaker leg, P < 0.05 in the stronger leg) and body mass increased by 1.7 ± 0.4 kg (2.3%, P < 0.01) and 1.8 ± 0.3 kg (2.1%, P < 0.01) in groups A and B, respectively, after Cr supplementation, while energy intake and diet composition remained constant throughout the study. The subjects' endurance capacity increased (P < 0.05) in all the bouts after Cr supplementation. Muscle hypertrophy in response to Cr supplementation and weight training may explain the findings of the present study.
The influence of PaO2, pH and SaO2 on maximal oxygen uptake
Authors: NIELSEN  , MADSEN  , SVENDSEN  , ROACH  , SECHER
Published: March 2003

Influence of arterial oxygen pressure (PaO2) and pH on haemoglobin saturation (SaO2) and in turn on O2 uptake (VO2) was evaluated during ergometer rowing (156, 276 and 376 W; VO2max, 5.0 L min−1; n = 11). During low intensity exercise, neither pH nor SaO2 were affected significantly. In response to the higher work intensities, ventilations (VE) of 129 ± 10 and 155 ± 8 L min−1 enhanced the end tidal PO2 (PETO2) to the same extent (117 ± 2 mmHg), but PaO2 became reduced (from 102 ± 2 to 78 ± 2 and 81 ± 3 mmHg, respectively). As pH decreased during maximal exercise (7.14 ± 0.02 vs. 7.30 ± 0.02), SaO2 also became lower (92.9 ± 0.7 vs. 95.1 ± 0.1%) and arterial O2 content (CaO2) was 202 ± 3 mL L−1. An inspired O2 fraction (FIO2) of 0.30 (n = 8) did not affect VE, but increased PETO2 and PaO2 to 175 ± 4 and 164 ± 5 mmHg and the PETO2–PaO2 difference was reduced (21 ± 4 vs. 36 ± 4 mmHg). pH did not change when compared with normoxia and SaO2 remained within 1% of the level at rest in hyperoxia (99 ± 0.1%). Thus, CaO2 and VO2max increased to 212 ± 3 mL L−1 and 5.7 ± 0.2 L min−1, respectively. The reduced PaO2 became of importance for SaO2 when a low pH inhibited the affinity of O2 to haemoglobin. An increased FIO2 reduced the gradient over the alveolar‐arterial membrane, maintained haemoglobin saturation despite the reduction in pH and resulted in increases of the arterial oxygen content and uptake.
Effects of magnesium and glucose, insulin, potassium (GIK) solution on the action potential parameters of guinea‐pig atrial muscle
Authors: INGEMANSSON  , ARLOCK  , OLSSON
Published: March 2003

The present paper aims to explore the effects of [Mg2+]o and glucose, insulin and K+ (GIK) on action potential parameters in guinea‐pig atrial muscle. Specimens of atrial appendages were taken from guinea‐pig hearts. Action potentials were recorded in isolated atrial trabeculae. Resting potential (RP) and action potential duration at 90% repolarization (APD90) were measured with conventional microelectrode techniques. [Mg2+]o at 6 and 12 mmol L−1 depolarized the RP and prolonged the APD90, whereas 4 mmol L−1 had no effect at all. Glucose alone or in combination with insulin had no effect on action potential parameters. GIK solution with supernormal [K+]o at 6 mmol L−1 depolarized the RP and decreased the APD90. Intervention with [Mg2+]o at 4 mmol L−1 in combination with GIK solution with supernormal [K+]o of 6 mmol L−1, reversibly depolarized the RP, whereas the APD90 was not significantly changed. [Mg2+]o at 12 mmol L−1 in combination with GIK solution with a physiological [K+]o of 4 mmol L−1 prolonged the APD90 whereas the RP was unaffected. [Mg2+]o at 6 and 12 mmol L−1 slightly depolarized the RP and prolonged the APD90. The action potential of normally polarized atrial muscle was not sensitive to supernormal levels of glucose alone or in combination with insulin. The effects of [Mg2+]o in combination with the GIK solutions on action potential parameters seemed to be attributable to the supernormal [Mg2+]o and [K+]o alone, while these seemed to have opposite effects on APD90.
Glucose consumption by various tissues in pregnant rats: effects of a 6‐day euglycaemic hyperinsulinaemic clamp
Authors: NIEUWENHUIZEN  , SCHUILING  , BONEN  , PAANS  , VAALBURG  , KOITER
Published: March 2003

In the course of pregnancy maternal tissues become increasingly more insensitive to insulin. As 6 days of euglycaemic hyperinsulinaemic clamping, from day 8 until 14 of gestation, ameliorates total glucose consumption, we analysed the contribution of individual tissues in this phenomenon. We measured not only glucose consumption, but also concentrations of the glucose transporter protein GLUT4 in selected tissues. On day 15 of pregnancy in saline‐infused (pregnant control) rats, 18F‐fluoro‐2‐deoxy‐
D‐glucose (FDG) consumption, as measured by positron emission tomography, as well as GLUT4 content were diminished in heart (P < 0.05), and in brown (P < 0.05) and white adipose tissues (P < 0.05) when compared with non‐pregnant controls. During clamping, on day 13 of the experiments, both in pregnant and non‐pregnant rats FDG consumption was increased in liver (P < 0.05), skeletal muscle (P < 0.05), brown (P < 0.05) and white adipose tissues (P < 0.05) when compared with saline‐infused controls. In both the reproductive conditions, only in white adipose tissue was this increased FDG consumption associated with increased GLUT4 levels (P < 0.05); GLUT4 content of m. gastrocnemius, m. soleus, heart and brown adipose tissue was unaffected by clamping. In non‐pregnant rats, 24 h after clamping ceased, FDG consumption was diminished in heart compared with control non‐pregnant rats (P < 0.05). In pregnant rats, however, 24 h after clamping (i.e. day 15 of pregnancy) both FDG consumption (P < 0.05) and GLUT4 content (P < 0.05) were still increased in white adipose tissue only, when compared with saline‐infused pregnant rats on the same day of gestation. It is suggested that hyperinsulinaemic euglycaemic clamping ameliorates insulin action halfway pregnancy, in particular by stimulation of glucose consumption and GLUT4 protein content in white adipose tissue.
Long and short axis dimensions of the left ventricle change in opposite ways during respiration
Authors: WANDT  , BOJÖ  , WRANNE
Published: March 2003

Cardiac output and stroke volume are known to vary with respiration. While right ventricular stroke volume increases on inspiration, left ventricular stroke volume decreases. This is an echocardiographic study of the changes in left ventricular dimensions in 20 healthy subjects. Our results show that the decrease in left ventricular stroke volume on inspiration is a net effect of a decrease in short axis shortening due to a decrease in diastolic diameter by 4.8% (P < 0.001) and an increased motion in the long axis direction expressed as an increase in mitral ring motion by 5.5% (P < 0.001). The findings point to the importance of the interventricular septum for the regulation of stroke volume.
Hindlimb suspension induces the expression of multiple myosin heavy chain isoforms in single fibres of the rat soleus muscle
Authors: OISHI  , ISHIHARA  , YAMAMOTO  , MIYAMOTO
Published: March 2003

To examine the expression patterns of myosin heavy chain (MHC) isoforms in single fibres of the soleus muscle following weightlessness, 10‐week‐old male Wistar rats were subjected to hindlimb suspension for 4 weeks. Hindlimb suspension resulted in reduced body weight and absolute and relative mass of the soleus muscle compared with controls (P < 0.01). A total of 975, 892 and 1098 single fibres from pre‐suspended controls, age‐matched controls and suspension groups, respectively, were subjected to MHC analyses using SDS‐PAGE. Single fibres containing only MHC I decreased (87.9 vs. 67.9%, P < 0.05) and single fibres containing only MHC IIa disappeared after hindlimb suspension. On the contrary, single fibres containing multiple type II MHC isoforms were observed as follows: 10.1% single fibres contained MHCs IIa and IId; 14.1% contained MHCs I, IIa and IId; and some (1.4%) expressed the MHC IIb isoform with MHCs IIa and IId. The relative content (%) of each MHC isoform in MHC hybrid single fibres was calculated using densitometer scanning. The MHCs IIa and IId hybrid single fibres contained the same amount of MHC IIa (51.3 ± 6.3%) and MHC IId (48.7 ± 6.3%). In the MHCs I, IIa and IId hybrid single fibres, the percentage of MHC IIa was distributed in a wide range (≈80%), whereas the percentage of MHC IId was a relatively low range (≈40%), and the relative content of MHC I was inversely correlated with that of MHC IIa and MHC IId, respectively. The fibre type composition of suspended soleus muscle, analysed by histochemical myosin ATPase staining, was changed, with a decrease in the percentage of type I fibres and an increase in that of type IIA fibres. Our results indicate that hindlimb suspension induces multiple type II MHC expression in the soleus single fibres and suggest that the single fibres containing multiple type II MHC isoforms should be classified into type IIA.
High‐intensity exercise and muscle glycogen availability in humans
Authors: Balsom  , Gaitanos  , Söderlund  , Ekblom
Published: March 2003

This study investigated the effects of muscle glycogen availability on performance and selected physiological and metabolic responses during high‐intensity intermittent exercise. Seven male subjects completed a regimen of exercise and dietary intake (48 h) to either lower and keep low (LOW‐CHO) or lower and then increase (HIGH‐CHO) muscle glycogen stores, on two separate occasions at least a week apart. On each occasion the subjects completed a short‐term (<10 min) and prolonged (>30 min) intermittent exercise (IEX) protocol, 24 h apart, which consisted of 6‐s bouts of high‐intensity exercise performed at 30‐s intervals on a cycle ergometer. Glycogen concentration (mean ± SEM) inm. vastus lateralisbefore both IExshortand IExlongwas significantly lower following LOW‐CHO [180 (14), 181 (17) mmol kg (dw)–1] compared with HIGH‐CHO [397 (35), 540 (25) mmol kg (dw)–1]. In both IExshortand IExlong, significantly less work was performed following LOW‐CHO compared with HIGH‐CHO. In IExlong, the number of exercise bouts that could be completed at a pre‐determined target exercise intensity increased by 265% from 111 (14) following LOW‐CHO to 294 (29) following HIGH‐CHO (P < 0.05). At the point of fatigue in IExlong, glycogen concentration was significantly lower with the LOW‐CHO compared with HIGH‐CHO [58 (25) vs. 181 (46) mmol kg (dw)–1, respectively]. The plasma concentrations of adrenaline and nor‐adrenaline (in IExshortand IExlong), and FFA and glycerol (in IExlong), increased several‐fold above resting values with both experimental conditions. Oxygen uptake during the exercise periods in IExlongapproached 70% ofVo2max. These results suggest that muscle glycogen availability can affect performance during both short‐term and more prolonged high‐intensity intermittent exercise and that with repeated exercise periods as short as 6 s, there can be a relatively high aerobic contribution.
Reflection coefficient for albumin and capillary fluid permeability in cat calf muscle after traumatic injury
Authors: Kongstad  , Möller  , Grände
Published: March 2003

Surgery and traumatic injury are often followed by tissue oedema and a low plasma albumin concentration, indicating leakage of fluid and proteins from the intravascular to the interstitial space. Transcapillary leakage can be referred to as an increase in capillary hydraulic conductance and/or a decrease in the reflection coefficient for plasma macromolecules. This study evaluates if time‐dependent variations in the reflection coefficient for albumin and capillary hydraulic conductance can be confirmed experimentally following a surgical trauma using a blood perfused cat skeletal muscle in vivo preparation. The hydraulic conductance was estimated by the capillary filtration coefficient, and was used to evaluate variation in capillary fluid permeability. According to the Starling fluid equilibrium, the ratio between the reflection coefficients for albumin on two occasions can be calculated from the maximum osmotic absorption rates induced by a fixed intravenous bolus infusion of albumin (0.5 g kg–1) and from the capillary filtration coefficients. We found a decrease in the reflection coefficient of about 30% up to 10 h after the preparation. The capillary filtration coefficient showed no significant change over time, but decreased by 5–10% following the albumin infusion. We conclude that: (1) the reflection coefficient for albumin is reduced after a trauma, whereas the effects on the capillary fluid permeability are small, (2) albumin in plasma contributes to preserve normal capillary fluid permeability and, (3) the model seems to be useful for evaluation of relative variations in the reflection coefficient for albumin.
Isotonic and hypertonic sodium loading in supine humans
Authors: Andersen  , Jensen  , Bestle  , Bie
Published: March 2003

The hypothesis that hypertonic saline infusion induces a greater natriuresis than infusion of the same amount of sodium as isotonic saline was tested in 8 supine subjects on fixed sodium intake of 150 mmol NaCl day–1. Sodium loads equivalent to the amount of sodium contained in 10% of measured extracellular volume were administered intravenously over 90 min either as isotonic saline or as hypertonic saline (850 mmol L–1). A third series without saline infusion served as time control. Experiments lasted 8 h. Water balance and sodium loads were maintained by replacing the excreted amounts every hour. Plasma sodium concentrations only increased following hypertonic saline infusion (by 2.7 ± 0.3 mmol L–1). Oncotic pressure decreased significantly more with isotonic saline (4.1 ± 0.3 mmHg) than with hypertonic saline (3.2 ± 0.2 mmHg), indicating that isotonic saline induced a stronger volumetric stimulus. Renal sodium excretion increased more than a factor of four with isotonic and hypertonic saline but also increased during time control (factor of three). Cumulated sodium excretions following isotonic (131 ± 13 mmol) and hypertonic saline (123 ± 10 mmol) were statistically identical exceeding that of time control (81 ± 9 mmol). Plasma angiotensin II decreased in all series but plasma ANP concentrations and urinary excretion rates of endothelin‐1 remained unchanged. In conclusion, hypertonic saline did not produce excess natriuresis. However, as the two loading procedures induced similar natriureses during different volumetric stimuli, part of the natriuresis elicited by hypertonic saline could be mediated by stimulation of osmoreceptors involved in renal sodium excretion. The supine position does not provide stable time control conditions with regard to renal excretory function.
Oestrogen attenuates post‐exercise myeloperoxidase activity in skeletal muscle of male rats
Authors: Tiidus  , Bombardier
Published: March 2003

The effects of 2 weeks of oestrogen (40 μg kg BW–1β‐estradiol 3‐benzoate) injection on 24 h post‐exercise myeloperoxidase (MPO) activities were determined in plantaris and soleus muscles and liver of sexually mature male and female rats. The treadmill running protocol (45–60 min, at 28 m min–1, 15% grade) induced significant elevations in muscle MPO activities 24 h post‐exercise in male rats, while prior oestrogen administration to male rats eliminated the post‐exercise elevations in muscle MPO activities. Female rats experienced no significant post‐exercise elevations in muscle MPO activities. Hence oestrogen administration to male rats attenuated post‐exercise muscle MPO activities to levels found in female animals. Liver MPO activities were not significantly affected by exercise, gender or oestrogen administration. Oestrogen may be a factor in diminishing 24 h post‐exercise skeletal muscle leukocyte infiltration and inflammatory response in both male and female muscle.
Multiple signalling pathways exist in the stress‐triggered regulation of gene expression for catecholamine biosynthetic enzymes and several neuropeptides in the rat adrenal medulla
Authors: Nankova  , Sabban
Published: March 2003

A critical component of the response to stress is the coincident activation of the hypothalamic–pituitary–adrenal axis and the sympathoadrenal system – comprised of sympathetic ganglia and the adrenal medullae. The sympathoadrenal system produces the catecholamines – noradrenaline and adrenaline, and several neuropeptides, involved in the homeostatic mechanisms that govern the adaptation to stress. This brief survey aims to provide a general overview of the present knowledge about the impact of stress on neurotransmitter gene expression in the adrenal medulla, with particular attention paid to the apparent heterogeneity in stress‐evoked signals and regulatory pathways.
The impact of biochemical methods for single muscle fibre analysis
Authors: Pette D. , Peuker H. , Staron R.S.
Published: March 2003

Biochemical methods for single muscle fibre analysis provide sensitive measures for elucidating muscle fibre heterogeneity. The understanding of the complexity of skeletal muscle fibres, initially based on qualitative histochemistry and immunohistochemistry, has been greatly expanded by quantitative micromethods, such as microphotometry and microbiochemical assays. Assessment of metabolic enzyme activity levels has revealed pronounced scattering within and between different fibre types and has highlighted the use of specific enzyme activity ratios as discriminative measures. With the exception of type I fibres, metabolic properties are loosely coupled with molecular properties of the myofibrillar apparatus. As such, myosin heavy chain (MHC) isoforms appear to be the best choice for fibre type delineation. Among the two available methods for MHC‐based fibre type distinction, single fibre electrophoresis appears to be superior to immunohistochemistry. The electrophoretic separation of MHC isoforms in single fibres is quantitative and, as opposed to immunohistochemistry, yields important information on MHC isoform proportions in hybrid fibres. Histochemical staining for myofibrillar ATPase activity can, thus, be correlated in most cases with specific MHC isoform profiles. Single fibre studies have demonstrated a relationship between ATP phosphorylation potential and MHC isoform complement. This relationship corresponds to different tension costs and provides an additional rationale for the MHC‐based fibre type diversity and transitions. The combination of reverse transcriptase (RT) with polymerase chain reaction (PCR) has proved to be a highly sensitive tool and has extended single fibre analysis to the level of MHC mRNA isoforms. Application of RT–PCR techniques to single fibre fragments identified by their MHC protein isoform profile, provides insights at two levels of expression and, thus, has extended our knowledge on the plasticity of muscle and the dynamical state of muscle fibres.