Properties of US Standard Endotoxin (EC-5) in human male volunteers

There has been a great interest in endotoxin testing using both Limulus amebocyte lysate (LAL) and the rabbit pyrogen test. It is often difficult to relate the results to the actual biological potency of endotoxin in man. There is a need to have the US Standard Endotoxin (Lot EC-5) tested in human volunteers so that rabbit and human data can be compared.

Human male volunteers were divided randomly into 5 groups of 12. Each group was given an intravenous injection of Lot EC-5 at a level of either 0, 2, 4, 8, or 16 endotoxin units (EU) per kg of body weight. The oral temperature was taken and recorded every 15 min for 8 h. The pyrogenic properties of the US Standard Endotoxin in humans over the test period were determined. The results indicated that there is a direct correlation between EU/kg administered and temperature rise. The threshold pyrogenic dose (≥ 1.0°F rise in 50% of volunteers) in this study is approximately 4.1 EU/kg.

Fish can show emotional fever: stress-induced hyperthermia in zebrafish

Whether fishes are sentient beings remains an unresolved and controversial question. Among characteristics thought to reflect a low level of sentience in fishes is an inability to show stress-induced hyperthermia (SIH), a transient rise in body temperature shown in response to a variety of stressors. This is a real fever response, so is often referred to as ‘emotional fever’. It has been suggested that the capacity for emotional fever evolved only in amniotes (mammals, birds and reptiles), in association with the evolution of consciousness in these groups. According to this view, lack of emotional fever in fishes reflects a lack of consciousness. We report here on a study in which six zebrafish groups with access to a temperature gradient were either left as undisturbed controls or subjected to a short period of confinement. The results were striking: compared to controls, stressed zebrafish spent significantly more time at higher temperatures, achieving an estimated rise in body temperature of about 2–4°C. Thus, zebrafish clearly have the capacity to show emotional fever. While the link between emotion and consciousness is still debated, this finding removes a key argument for lack of consciousness in fishes.

A combined iron and thyroid hormone protocol suppresses ischemia–reperfusion injury in rat livers

Liver preconditioning (PC) against ischemia–reperfusion (IR) injury is attained by iron (Fe) or thyroid hormone (T₃) administration.

[Telemedicine in Bolivia: RAFT-Altiplano project, experiences, future prospects, and recommendations]

OBJECTIVE

The objective of the RAFT-Altiplano project (RAFT: Réseau en Afrique Francophone pour la Télémédecine, or African Francophone Telemedicine Network) is to evaluate the viability, potential, and risks of implementing and developing a telemedicine network in the context of a developing country-specifically, the Altiplano region of Bolivia-to improve access to medical care and continuing education in a rural area. The activities described in this report took place between 2011 and 2013.

METHODS

Digital telemedicine equipment was donated to the health centers and a Microsoft®-based platform capable of integration with other technologies (using standardized formats) was developed to manage documents and clinical content electronically. Health professionals were trained in teleconsultation and the teleconsultation workflow was designed. The tele-education system used is Dudal, which requires only a small bandwidth.

RESULTS

After three years of implementation, an organized working structure of teleconsultation and tele-education tools, adapted to the Latin American context, is now in place and connections have been established with hospitals, institutions, and health centers. The project has improved access to specialized medical care in remote health centers and third-level hospitals in urban areas, and it has become the foundation for development of the national project "TeleSalud for Bolivia" promoted by the Ministry of Health, which involves use of the new Bolivian satellite, Túpac Katari.

CONCLUSIONS

It is viable to develop and set up telemedicine tools to serve the population in remote regions of Bolivia when they are made available to government and municipal health institutions and communication between them and the health centers takes place in a coordinated manner. The sharing of experiences, challenges, and risks encountered is very useful in designing and implementing the telemedicine project "TeleSalud for Bolivia" on a national scale.

Combining animal personalities with transcriptomics resolves individual variation within a wild-type zebrafish population and identifies underpinning molecular differences in brain function

Resolving phenotype variation within a population in response to environmental perturbation is central to understanding biological adaptation. Relating meaningful adaptive changes at the level of the transcriptome requires the identification of processes that have a functional significance for the individual. This remains a major objective towards understanding the complex interactions between environmental demand and an individual's capacity to respond to such demands. The interpretation of such interactions and the significance of biological variation between individuals from the same or different populations remain a difficult and under-addressed question. Here, we provide evidence that variation in gene expression between individuals in a zebrafish population can be partially resolved by a priori screening for animal personality and accounts for >9% of observed variation in the brain transcriptome. Proactive and reactive individuals within a wild-type population exhibit consistent behavioural responses over time and context that relates to underlying differences in regulated gene networks and predicted protein-protein interactions. These differences can be mapped to distinct regions of the brain and provide a foundation towards understanding the coordination of underpinning adaptive molecular events within populations.

Thyroid hormone activates rat liver adenosine 5,-monophosphate-activated protein kinase: relation to CaMKKb, TAK1 and LKB1 expression and energy status

AMP-activated protein kinase (AMPK) is a sensor of energy status supporting cellular energy homeostasis that may represent the metabolic basis for 3,3,,5-triiodo-L-thyronine (T3) liver preconditioning. Functionally transient hyperthyroid state induced by T3 (single dose of 0.1 mg/kg) in fed rats led to upregulation of mRNA expression (RT-PCR) and protein phosphorylation (Western blot) of hepatic AMPK at 8 to 36 h after treatment. AMPK Thr 172 phosphorylation induced by T3 is associated with enhanced mRNA expression of the upstream kinases Ca2+ -calmodulin-dependent protein kinase kinase-beta (CaMKKbeta) and transforming growth-factor-beta-activated kinase-1 (TAK1), with increased protein levels of CaMKKbeta and higher TAK1 phosphorylation, without changes in those of the liver kinase B1 (LKB1) signaling pathway. Liver contents of AMP and ADP were augmented by 291 percent and 44 percent by T3 compared to control values (p less than 0.05), respectively, whereas those of ATP decreased by 64% (p less than 0.05), with no significant changes in the total content of adenine nucleotides (AMP + ADP + ATP) at 24 h after T3 administration. Consequently, hepatic ATP/ADP content ratios exhibited 64 percent diminution (p less than 0.05) and those of AMP/ATP increased by 425 percent (p less than 0.05) in T3-treated rats over controls. It is concluded that in vivoT3 administration triggers liver AMPK upregulation in association with significant enhancements in AMPK mRNA expression, AMPK phosphorylation coupled to CaMKKbeta and TAK1 activation, and in AMP/ATP ratios, which may promote enhanced AMPK activity to support T3-induced energy consuming processes such as those of liver preconditioning.

Behavioural fever is a synergic signal amplifying the innate immune response

Behavioural fever, defined as an acute change in thermal preference driven by pathogen recognition, has been reported in a variety of invertebrates and ectothermic vertebrates. It has been suggested, but so far not confirmed, that such changes in thermal regime favour the immune response and thus promote survival. Here, we show that zebrafish display behavioural fever that acts to promote extensive and highly specific temperature-dependent changes in the brain transcriptome. The observed coupling of the immune response to fever acts at the gene–environment level to promote a robust, highly specific time-dependent anti-viral response that, under viral infection, increases survival. Fish that are not offered a choice of temperatures and that therefore cannot express behavioural fever show decreased survival under viral challenge. This phenomenon provides an underlying explanation for the varied functional responses observed during systemic fever. Given the effects of behavioural fever on survival and the fact that it exists across considerable phylogenetic space, such immunity–environment interactions are likely to be under strong positive selection.

The 1918-1920 influenza pandemic in Peru

BACKGROUND

Increasing our knowledge of past influenza pandemic patterns in different regions of the world is crucial to guide preparedness plans against future influenza pandemics. Here, we undertook extensive archival collection efforts from three representative cities of Peru-Lima in the central coast, Iquitos in the northeastern Amazon region, Ica in the southern coast-to characterize the temporal, age and geographic patterns of the 1918-1920 influenza pandemic in this country.

MATERIALS AND METHODS

We analyzed historical documents describing the 1918-1920 influenza pandemic in Peru and retrieved individual mortality records from local provincial archives for quantitative analysis. We applied seasonal excess mortality models to daily and monthly respiratory mortality rates for 1917-1920 and quantified transmissibility estimates based on the daily growth rate in respiratory deaths.

RESULTS

A total of 52,739 individual mortality records were inspected from local provincial archives. We found evidence for an initial mild pandemic wave during July-September 1918 in Lima, identified a synchronized severe pandemic wave of respiratory mortality in all three locations during November 1918-February 1919, and a severe pandemic wave during January 1920-March 1920 in Lima and July-October 1920 in Ica. There was no recrudescent pandemic wave in 1920 in Iquitos. Remarkably, Lima experienced the brunt of the 1918-1920 excess mortality impact during the 1920 recrudescent wave, with all age groups experiencing an increase in all cause excess mortality from 1918-1919 to 1920. Middle age groups experienced the highest excess mortality impact, relative to baseline levels, in the 1918-1919 and 1920 pandemic waves. Cumulative excess mortality rates for the 1918-1920 pandemic period were higher in Iquitos (2.9%) than Lima (1.6%). The mean reproduction number for Lima was estimated in the range 1.3-1.5.

CONCLUSIONS

We identified synchronized pandemic waves of intense excess respiratory mortality during November 1918-February 1919 in Lima, Iquitos, Ica, followed by asynchronous recrudescent waves in 1920. Cumulative data from quantitative studies of the 1918 influenza pandemic in Latin American settings have confirmed the high mortality impact associated with this pandemic. Further historical studies in lesser studied regions of Latin America, Africa, and Asia are warranted for a full understanding of the global impact of the 1918 pandemic virus.

Spontaneous neural activity of the anterodorsal lobe and entopeduncular nucleus in adult zebrafish: a putative homologue of hippocampal sharp waves

Spontaneous neural activity is instrumental in the formation and maintenance of neural circuits that govern behavior. In mammals, spontaneous activity is observed in the spinal cord, brainstem, diencephalon, and neocortex, and has been most extensively studied in the hippocampus. Using whole-brain in vitro recordings we establish the presence of spontaneous activity in two regions of the zebrafish telenchephalon: the entopeduncular nucleus (EN) and the anterodorsal lobe (ADL). The ADL is part of the lateral telencephalic pallium, an area hypothesized to be functionally equivalent to the mammalian hippocampus. In contrast, the EN has been hypothesized to be equivalent to the mammalian basal ganglia. The observed spontaneous activity is GABA modulated, sensitive to glutamate and chloride transporter antagonists, and is abolished by sodium pump blockers; moreover, the spontaneous activity in the ADL is a slow multiband event (∼100 ms) characterized by an embedded fast ripple wave (∼150-180 Hz). Thus, the spontaneous activity in the ADL shares physiological features of hippocampal sharp waves in rodents. We suggest that this spontaneous activity is important for the formation and maintenance of neural circuits in zebrafish and argue that applying techniques unique to the fish may open novel routes to understand the function of spontaneous activity in mammals.

The zebrafish brain in research and teaching: a simple in vivo and in vitro model for the study of spontaneous neural activity

Recently, the zebrafish (Danio rerio) has been established as a key animal model in neuroscience. Behavioral, genetic, and immunohistochemical techniques have been used to describe the connectivity of diverse neural circuits. However, few studies have used zebrafish to understand the function of cerebral structures or to study neural circuits. Information about the techniques used to obtain a workable preparation is not readily available. Here, we describe a complete protocol for obtaining in vitro and in vivo zebrafish brain preparations. In addition, we performed extracellular recordings in the whole brain, brain slices, and immobilized nonanesthetized larval zebrafish to evaluate the viability of the tissue. Each type of preparation can be used to detect spontaneous activity, to determine patterns of activity in specific brain areas with unknown functions, or to assess the functional roles of different neuronal groups during brain development in zebrafish. The technique described offers a guide that will provide innovative and broad opportunities to beginner students and researchers who are interested in the functional analysis of neuronal activity, plasticity, and neural development in the zebrafish brain.

Total knee replacement in post-traumatic arthritic knees with limitation of flexion

The objective of this study is to investigate the results of total knee arthroplasty (TKA) in traumatic osteoarthritis cases with flexion restriction and to describe the technical details of their management. A multicentre series comprising 40 patients with limitation of flexion less than or equal to 90° was selected from 152 cases of post-traumatic knee arthritis with malunion. We hypothesized that the arthroplasty complication rate would be higher than in other etiologies of limitation of flexion and would require specific management strategies.

PATIENTS

In 23 cases, intra-articular malunion was present, in 15 cases extra-articular, and in two cases combined. The mean flexion was 72±23°, extension was 6±6°, and total range of motion (ROM) 66±23°. Eight cases of flexion restriction were severe (flexion<50°), six intermediate (flexion, 50-70°) and 26 moderate. In 14 cases, the anterior tibial tuberosity was osteotomized (43% intra-articular malunion and 6% extra-articular malunion). Five simultaneous realignment osteotomies were necessary. In severe cases of limitation of flexion, five extensive quadriceps releases were associated.

RESULTS

Four mobilizations under general anesthesia were performed. In the cases of severe limitation of flexion, we noted three avulsions of the patellar tendon, two cases of cutaneous necrosis, one of which was associated with deep infection, and another case of deep infection. In the cases of moderate limitation of flexion, we noted one case of nonunion of the tibial tuberosity and two cases were revised for loosening, one aseptic and the other septic. With a mean follow-up of 5±4 years, the mean flexion was 99.4°±23 for a gain of 26.7±20°. The final flexion and the gain in flexion were correlated with preoperative flexion (r=0.62 and r=-0.47, respectively). The final amplitude was 99±27° for a gain of 33±21°. The flexion gains were comparable for both types of malunion, whether they were intra- or extra-articular.

DISCUSSION

Arthroplasty provided a substantial gain in flexion. Osteotomy of the tibial tuberosity and the realignment osteotomies should be performed if necessary, with no risk of compromising the result. Superior gains can be sought in severe cases of limitation of flexion by releasing the extensor apparatus, in absence of cutaneous scar tissue retractions and recent infection.

LEVEL OF EVIDENCE

Level 4. Noncomparative retrospective study.

Soil respiration at mean annual temperature predicts annual total across vegetation types and biomes

Soil respiration (SR) constitutes the largest flux of CO(2) from terrestrial ecosystems to the atmosphere. However, there still exist considerable uncertainties as to its actual magnitude, as well as its spatial and interannual variability. Based on a reanalysis and synthesis of 80 site-years for 57 forests, plantations, savannas, shrublands and grasslands from boreal to tropical climates we present evidence that total annual SR is closely related to SR at mean annual soil temperature (SR(MAT)), irrespective of the type of ecosystem and biome. This is theoretically expected for non water-limited ecosystems within most of the globally occurring range of annual temperature variability and sensitivity (Q(10)). We further show that for seasonally dry sites where annual precipitation (P) is lower than potential evapotranspiration (PET), annual SR can be predicted from wet season SR(MAT) corrected for a factor related to P/PET. Our finding indicates that it can be sufficient to measure SR(MAT) for obtaining a well constrained estimate of its annual total. This should substantially increase our capacity for assessing the spatial distribution of soil CO(2) emissions across ecosystems, landscapes and regions, and thereby contribute to improving the spatial resolution of a major component of the global carbon cycle.

Breast Cancer Early Detection Awareness and Its Predictors in a Brazilian Nationwide Sample

Background: In contrast to developed countries, where breast cancer (BC) mortality has dropped in the past decade, BC associated deaths are still rising in Brazil. The absence of better structured screening programs and the lack of population awareness about the disease are among the factors for the high BC mortality in the country. Emphasizing the importance of mammography is a key factor in increasing the rate of early diagnosis and, therefore, the chances of cure. In this study, we aimed to quantify the population's recognition of mammography as an important exam, and evaluated factors associated with the awareness of its importance. Methods: A cross-sectional study was conducted with 1,344 women between 40 and 65 years old in 17 state capitals in Brazil. Women answered the following question: “In your opinion, what are the means that a person has to discover that she has breast cancer?” If a woman cited mammography in her answer, she was considered as aware in our analyses. Women also responded a questionnaire that included socio-economic status, educational level, healthy lifestyle behaviors, insurance plan coverage, and family history of BC, in order to identify possible predictors of greater awareness. The relationship between predictors and awareness was evaluated through univariate and multivariate modified Poisson regression. Results: Mean age was 51 ± 7 years; 53.5% of women were between 40 and 49 years old. 30% of the sample was from the higher and 18% from the lower social class. 12% had a positive BC family history, 75% used to visit their gynecologist at least once a year, 35% have a private health insurance, and 21% were current smokers (former smokers = 23%). Only 48.5% cited mammography as a tool to discover breast cancer. In the univariate analysis, younger age, higher level of physical activity, no current or past smoking habit, private health insurance, family history of BC, regular attendance to a gynecologist, and higher income, educational level and social class were all associated with higher awareness (p&lt;0.05 for all variables). In the multivariate model, which included all the former variables except for income and education (which had high collinearity with social class), the relative risks for greater awareness were the following: higher social class = 1.30 (1.05 – 1.61), BC family history = 1.11 (0.96 – 1.29), annual visit to gynecologist = 1.43 (1.18 – 1.75), no history of smoking = 1.17 (1.01 – 1.37), frequent physical activity = 1.10 (0.985 – 1.24), age &lt; 50 = 1.19 (1.06 – 1.33), private insurance = 1.20 (1.06 – 1.36). Conclusions: In this sample, with nationwide distribution, the awareness about the importance of mammography was low. Higher socio-economic status and healthy lifestyles were associated with a higher awareness of the exam's importance. The greater mammography awareness observed in younger women might reflect a higher general interest in its own health in this group, as well as its regular contact with reproductive health services.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3079.

Pretreatment serum TIMP-1 levels and survival in advanced pancreatic cancer

e15568

Background: Tissue inhibitor of metalloproteinase-1 (TIMP-1) has been shown to have diverse multifunctional roles in tumorigenesis such as inhibition of the catalytic activity of MMPs, growth promotion, inhibition of apoptosis and regulation of angiogenesis. Elevated TIMP-1 has been associated with an unfavorable prognosis in many cancers including breast, colorectal, gastric, head and neck, lung, and lymphoma. VEGF is also intimately associated with angiogenesis. Methods: This study determined serum TIMP-1 and VEGF levels in a phase III clinical trial of 157 patients with advanced pancreatic cancer. ELISAs for TIMP-1 and VEGF (Oncogene Science / Siemens HealthCare Diagnostics, Cambridge, MA) were employed to measure pretreatment serum TIMP-1 levels in 157 pancreatic cancer patients enrolled in a randomized, double-blind, placebo-controlled phase III trial. Statistical analysis was performed with TIMP-1 and VEGF on a continuous and cutpoint basis. Serum biomarker levels were then correlated with patient survival using Kaplan -Meier life table analysis. Results: Serum TIMP-1 levels in 157 pancreatic patients had a median of 409.9 ng/mL, and ranged from 144 to 1078 ng/mL. Patients with higher serum TIMP-1 had significantly shorter survival on a continuous basis (p = 0.001), on quartile analysis (p = 0.004), and on a dichotomous cutpoint analysis of upper 25 % vs lower 75 % (median survival 101 days vs. 197 days)(p< 0.001). Serum VEGF level was not associated with survival on a continuous (p = 0.57) or cutpoint analysis (p= 0.93). Conclusions: Pancreatic cancer patients with higher serum TIMP-1 levels had significantly shorter overall survival. Serum TIMP-1 level should be evaluated as a predictive factor for response to novel treatment regimens.

[Table: see text]

Differential contribution of extracellular and intracellular calcium sources to basal transmission and long-term potentiation in the sympathetic ganglion of the rat

Calcium involved in basal ganglionic transmission and long-term potentiation (LTP) can arise either by influx from the extracellular medium or release from intracellular stores. No attempts have yet been made to concurrently explore the contributions of extracellular and intracellular Ca2+ to basal ganglionic transmission or LTP. Here, we investigate this subject using the superior cervical ganglion of the rat. To explore the extracellular Ca2+ contribution, we evaluated basal transmission and LTP at different extracellular Ca2+ concentrations. To assess intracellular Ca2+ release, we explored the contribution of the calcium-induced calcium release process by overactivation or blockade of ryanodine-sensitive Ca2+ receptor channel with caffeine, and also by blocking either IP3R with Xestospongin C or the sarco(endo)plasmic reticulum Ca2+-ATPase pump with thapsigargin. Extracellular Ca2+ affected ganglionic basal transmission and LTP to different extents. While 25% of the physiological Ca2+ concentration supported 80% of basal transmission, 50% of normal Ca2+ was required to achieve 80% of LTP. Notably, disruption of intracellular Ca2+ release by all the drugs tested apparently did not affect basal ganglionic transmission but impaired LTP. We conclude that basal transmission requires only a small level of Ca2+ entry, while LTP expression not only requires more Ca2+ entry but is also dependent on Ca2+ release from intracellular stores.

Characteristics of rabbit muscle adenylate kinase inhibition by ascorbate

Earlier studies [1-3] showed that of the glycolytic enzymes, the muscle isozymes PFK-1, LDH, and AK were inhibited by ascorbic acid. These studies on the characteristics of the inhibition of RMAK by ascorbate are part of a hypothesis [3] that ascorbate facilitates the storage of skeletal muscle glycogen by inhibiting glycolysis when the muscle is at rest. These studies examine conditions for RMAK inhibition, prevention of inhibition, and reversal of ascorbate inhibition. We found that the concentration of RMAK was an important condition for inhibition. Above 200 nM RMAK, inhibition by ascorbate could not be demonstrated and below that concentration RMAK became increasingly sensitive to ascorbate inhibition. Associated with increased sensitivity to inhibition by ascorbate is a deviation from a linear to a concave relationship between low RMAK concentrations and enzyme activity. At low RMAK concentrations, the concave relationship becomes convex in the presence of muscle aldolase. In addition, aldolase reverses inhibitions by ascorbate. A comparison of inhibition of RMAK byascorbate and inhibition of LDH-m4 [3] is discussed. Other proteins prevent RMAK inhibition but do not reverse inhibition by ascorbate. The role of RMAK as a factor in the control of the rate of glycolysis is presented as is the role of compartmentalization with respect to the proposed role for ascorbate inhibition.

Revisión de las interferencias entre los medicamentos más prescritos en el servicio de atención primaria de L’Hospitalet de Llobregat (ICS) y los análisis clínicos

OBJECTIVE

To analyse the concordance of published information on probable drug interactions and the results of clinical analyses.

DESIGN

Bibliographical review of the 50 most commonly prescribed drug products at the Primary Health Centre of L'Hospitalet de Llobregat, Barcelona, Spain, in 2002 and 2003.

DATA SOURCE

Six bibliographical sources consisting of drug product catalogues and reference books.

MEASUREMENTS

Interference with the 56 drug products studied.

RESULTS

Most theoretical interference belonged to the therapeutic group of anti-inflammatory drugs. The drug products with most interference were hydrochlorothiazide (diuretic) and gliclazide (lipid lowering). The most frequent interference was in the increase of transaminases, thrombocytopaenia, leukopaenia, hyperglycaemia, and hyperuricaemia. Only in 12% of the points of interference analysed was the rate of concordance among the various bibliographical sources reviewed higher than 50%. The highest rate of concordance was found in the diuretics.

CONCLUSIONS

Consultation of a single bibliographical source does not necessarily ensure the obtaining of reliable data on possible drug interference. This study demonstrates the need to standardize information on drug interference and to include the medication that the patient follows on the analysis application form.

Health disparities and advertising content of women's magazines: a cross-sectional study

Background

Disparities in health status among ethnic groups favor the Caucasian population in the United States on almost all major indicators. Disparities in exposure to health-related mass media messages may be among the environmental factors contributing to the racial and ethnic imbalance in health outcomes. This study evaluated whether variations exist in health-related advertisements and health promotion cues among lay magazines catering to Hispanic, African American and Caucasian women.

Methods

Relative and absolute assessments of all health-related advertising in 12 women's magazines over a three-month period were compared. The four highest circulating, general interest magazines oriented to Black women and to Hispanic women were compared to the four highest-circulating magazines aimed at a mainstream, predominantly White readership. Data were collected and analyzed in 2002 and 2003.

Results

Compared to readers of mainstream magazines, readers of African American and Hispanic magazines were exposed to proportionally fewer health-promoting advertisements and more health-diminishing advertisements. Photographs of African American role models were more often used to advertise products with negative health impact than positive health impact, while the reverse was true of Caucasian role models in the mainstream magazines.

Conclusion

To the extent that individual levels of health education and awareness can be influenced by advertising, variations in the quantity and content of health-related information among magazines read by different ethnic groups may contribute to racial disparities in health behaviors and health status.

Signal intensity of MR-images of thigh muscles following acute open- and closed chain kinetic knee extensor exercise – index of muscle use

Exercise-induced shifts in signal intensity (SI) of magnetic resonance (MR) images were examined to assess indirectly muscle use in closed- and open-chain knee extensor exercises. Eight men performed five sets of 8-12 repetitions in the leg press (LP) and the seated knee extension (KE) exercises at 50, 75 and 100%, respectively of the 5 x 10 repetition maximum (RM) load. Prior to exercise and after each load setting, images of the thigh were obtained. The increase in SI (Delta SI) of the quadriceps at 100% load was greater (P < 0.05) after KE (32.1 +/- 9.0%) than after LP (21.9 +/- 9.2%). Regardless of load, the four individual muscles of the quadriceps showed similar changes in SI after LP. The three vastii muscles showed comparable increases in SI after KE. M. rectus femoris showed greater (P < 0.05) Delta SI than the vastii muscles at 100%. Neither exercise produced increase in SI of mm. semimembranosus, semitendinosus, gracilis or biceps femoris. Mm. adductor magnus and longus showed increased (13.3 +/- 6.5%; P < 0.05) SI after LP, but not after KE, at 100% load. The present data also infer greater involvement of the quadriceps muscle in the open-chain knee extension than in the closed-chain leg press exercise. The results of the current investigation also indicate similar over-all use among the three vastii muscles in LP and KE, but differential m. rectus femoris use between the two exercises. This report extends the merits of the MR imaging technique as an aid to study individual muscle involvement in a particular exercise task.