Morning compared to afternoon school-based exercise on cognitive function in adolescents.

PURPOSE: Adolescents may be less ready to learn in the mornings due to a propensity for waking up later. High-intensity interval exercise (HIIE) has been shown to acutely improve cognitive functioning in teenagers. This within-measures study explored whether the benefit of HIIE differs when delivered in the morning or afternoon. METHODS: 37 teenagers (19 boys, 13.7 ± 0.4 years) each completed 3 trials in school; morning HIIE (MORN), afternoon HIIE (AFTER) and a no-exercise control trial (CON). The HIIE involved 10x10 second sprints, interspersed by 50 s of walking. Cognitive function was assessed using a battery of computerised tasks four times over the course of the day. RESULTS: Z scores for reaction time, but not proportion of correct responses, were improved 45 min post exercise in the MORN trial (P < 0.01, d = 0.47), and this improvement persisted until the third (P = 0.04, d = 0.34), but not final (P = 0.93, d = 0.01), time point. Global reaction time was not improved 45 min post exercise in the AFTER trial (P = 0.17, d = 0.20). Global reaction time was quicker 45 min post morning exercise compared to the same time point in CON (P = 0.02, d = 0.56) and AFTER (P = 0.01, d = 0.72). CONCLUSION: HIIE may be more effectual in improving cognitive functioning when delivered in the morning.

The acute influence of amateur boxing on dynamic cerebral autoregulation and cerebrovascular reactivity to carbon dioxide.

PURPOSE: The purpose of this study was to investigate the acute effect of head impacts, sustained over the course of three rounds of amateur boxing, on indices of cerebrovascular function. METHODS: Eighteen university amateur boxers (six female) completed three experimental trials in a randomised order; (1) three rounds of boxing (BOX), (2) an equivalent bout of pad boxing (where no blows to the head were sustained; PAD), and (3) a time-matched seated control trial (CON). Indices of cerebrovascular function were determined immediately before and 45 min after each trial. Specifically, dynamic cerebral autoregulation (dCA) was determined by considering the relationship between changes in cerebral blood velocity and mean arterial pressure during 5 min of squat-stand manoeuvres at 0.05 and 0.10 Hz. Cerebrovascular reactivity was determined using serial breath holding and hyperventilation attempts. RESULTS: Participants received an average of 40 ± 16 punches to the head during the BOX trial. Diastolic, mean and systolic dCA phase during squat stand manoeuvres at 0.05 Hz was lower after BOX compared to pre BOX (P ≤ 0.02, effect size (d) ≥ 0.74). No other alterations in dCA outcomes were observed at 0.05 or 0.10 Hz. The number of head impacts received during the BOX trial was associated with the change in systolic phase (r = 0.50, P = 0.03). No differences in cerebrovascular reactivity to breath holding or hyperventilation were observed. CONCLUSIONS: A typical bout of amateur boxing (i.e., three rounds) can subtly alter cerebral pressure-flow dynamics, and the magnitude of this change may be related to head impact exposure.

The acute influence of sucrose consumption with and without vitamin C co-ingestion on microvascular reactivity in healthy young adults.

BACKGROUND: Sugar sweetened beverages (SSB) are a major source of dietary sugar and a public health concern. Glucose consumption acutely influences microvascular reactivity in healthy adults, possibly via oxidative stress. The purpose of this study was to observe the acute influence of a more relevant dose of sucrose on microvascular reactivity, and to identify whether this response is influenced by the amount of vitamin C typically contained in SSB. METHODS: Thirteen ostensibly healthy adults (8 male, 5 female) performed three 1-day trials in a randomized order; the consumption of 300 ml water (control; CON), or 300 ml water with 50 g sucrose (SUGAR) or 50 g sucrose with 160 mg of vitamin C (VITC). Near infrared spectroscopy was used to determine peak reactive hyperaemia (PRH), the rate of desaturation (Slope 1) and reperfusion (Slope 2), and the total area under the reperfusion curve versus time (TRH) following 5 min of forearm cuff occlusion before and 30, 60, 90 and 120 min after test drink consumption. RESULTS: SUGAR and VITC significantly increased the total area under the curve versus time for plasma glucose (P < 0.05 for both). No changes in microvascular reactivity were observed between trials, although VITC increased Slope 1 compared to both SUGAR and CON 30 and 60 min post drink (P < 0.05 for both). CONCLUSION: The consumption of a sugar load representative of commercially available SSB did not influence microvascular reactivity. The co-ingestion of Vitamin C also failed to influence microvascular reactivity, but did increase the rate of oxygen extraction.

Survey of trainers on the use of swimming exercise for Standardbred racehorses in Australia.

OBJECTIVES: To determine swimming training practices in Australian harness racing horses and potential targets for future research. METHODS: An online survey of Australian Standardbred trainers and telephone interviews with 20 leading trainers were conducted. Questions relating to swimming facility and protocol, perceived benefits and contraindications were included. Descriptive data analysis was performed. RESULTS: Data were collected from 270 trainers: 250 by online survey (250/1770, response rate 14.1%) and 20 by interview. Of these, 103 trainers (38.1%), including 91 surveyed trainers (91/250, 36.4%) and 12 interviewed trainers (12/20, 60.0%), used swimming exercise. The most popular reasons for swimming were to replace trackwork for horses with limb injuries (79.4%), improve or maintain fitness (62.7%) and provide mental stimulation through variety in training (40.0%). Free swimming (78.4%) was more common than tethered, but the frequency and duration for horses in full training varied widely between trainers, with a median of four swim sessions per horse each week (range 0.5-12) for a median of 7 min (range 1.5-30 min) per session, mostly as a continuous swim, but sometimes as intervals. The main reasons given by those not swimming horses were lack of an adequate facility (60.5%) and lack of perceived benefit (16.2%). Reasons for not swimming individual horses varied widely. CONCLUSIONS: Trainer opinions and protocols varied widely with respect to swimming exercise for Standardbred race horses. The role of swimming exercise requires further study so that evidence-based recommendations can be made.

Exercise intensity and the protection from postprandial vascular dysfunction in adolescents.

Acute exercise transiently improves endothelial function and protects the vasculature from the deleterious effects of a high-fat meal (HFM). We sought to identify whether this response is dependent on exercise intensity in adolescents. Twenty adolescents (10 male, 14.3 ± 0.3 yr) completed three 1-day trials: 1) rest (CON); 2) 8 × 1 min cycling at 90% peak power with 75 s recovery [high-intensity interval exercise (HIIE)]; and 3) cycling at 90% of the gas exchange threshold [moderate-intensity exercise (MIE)] 1 h before consuming a HFM (1.50 g/kg fat). Macrovascular and microvascular endothelial function was assessed before and immediately after exercise and 3 h after the HFM by flow-mediated dilation (FMD) and laser Doppler imaging [peak reactive hyperemia (PRH)]. FMD and PRH increased 1 h after HIIE [P < 0.001, effect size (ES) = 1.20 and P = 0.048, ES = 0.56] but were unchanged after MIE. FMD and PRH were attenuated 3 h after the HFM in CON (P < 0.001, ES = 1.78 and P = 0.02, ES = 0.59). FMD remained greater 3 h after the HFM in HIIE compared with MIE (P < 0.001, ES = 1.47) and CON (P < 0.001, ES = 2.54), and in MIE compared with CON (P < 0.001, ES = 1.40). Compared with CON, PRH was greater 3 h after the HFM in HIIE (P = 0.02, ES = 0.71) and MIE (P = 0.02, ES = 0.84), with no differences between HIIE and MIE (P = 0.72, ES = 0.16). Plasma triacylglycerol concentration and total antioxidant status concentration were not different between trials. We conclude that exercise intensity plays an important role in protecting the vasculature from the deleterious effects of a HFM. Performing HIIE may provide superior vascular benefits than MIE in adolescent groups.

Applying the dual-isotope conceptual model to interpret physiological trends under uncontrolled conditions.

The inter-relationships among δ(13)C and δ(18)O in tree ring cellulose and ring width have the potential to illuminate long-term physiological and environmental information in forest stands that have not been monitored. We examine how within-stand competition and environmental gradients affect ring widths and the stable isotopes of cellulose. We utilize a natural climate gradient across a catchment dominated by Douglas-fir and temporal changes in climate over an 8-year period. We apply a dual-isotope approach to infer physiological response of trees in differing crown dominance classes to temporal and spatial changes in environmental conditions using a qualitative conceptual model of the (13)C-(18)O relationship and by normalizing the data to minimize other variance. The δ(13)C and δ(18)O of cellulose were correlated with year-to-year variation in relative humidity and consistent with current isotope theory. Using a qualitative conceptual model of the (13)C-(18)O relationship and physiological knowledge about the species, we interpreted these changes as stomatal conductance responses to evaporative demand. Spatial variance between plots was not strong and seemed related to leaf nitrogen rather than any other environmental variable. Dominant trees responded to environmental gradients more consistently with current isotope theory as compared with other classes within the same stand. We found a correlation of stable isotopes with environmental variables is useful for assessing the impacts of environmental change over short time series and where growth varies only minimally with climate.

Admission uric acid levels and length of expectant management in preterm preeclampsia.

OBJECTIVE: Uric acid is known to be elevated in preeclampsia. We sought to determine if uric acid levels on admission correlate with the length of expectant management in preterm patients with preeclampsia. STUDY DESIGN: A retrospective chart review was conducted on singleton preeclamptic pregnancies delivered between 24 0/7 and 37 0/7 weeks' gestation at Tufts Medical Center between January 2005 and December 2007. Patients with a multiple gestation and those transferred or discharged before delivery were excluded. Data regarding signs and symptoms of preeclampsia, laboratory values, pregnancy complications and outcome were abstracted from the medical records. Correlation between admission uric acid level and days of expectant management was assessed. The relative risk (RR) was used to estimate the effect of uric acid levels on expectant management length >7 days. Mantel-Haenszel χ(2) values were used to construct 95% confidence intervals (CIs) around the RR. RESULT: Four hundred seventy-one charts were reviewed. Of these, 190 met inclusion criteria. In all, 55 patients (28.9%) were managed expectantly for >1 week. Admission uric acid level correlated with days of expectant management (P<0.0001). Uric acid levels at admission were categorized as ≤4.0 mg dl(-1) (low uric acid level), 4.1 to 6.0 mg dl(-1) (medium) and ≥6.1 mg dl(-1) (high). Relative to women with high uric acid levels at admission, we observed a sevenfold higher rate of extending expectant management for >1 week among women with low uric acid level (7.0; 95% CI: 3.34 to 14.68). Women with medium uric acid levels at admission also had a higher likelihood of prolonging pregnancy relative to women with high uric acid levels (RR: 2.81; 95% CI: 1.32 to 5.96) (P-value for trend <0.0001). CONCLUSION: Admission uric acid levels correlate with the length of expectant management in preterm patients with preeclampsia. Pregnancy prolongation for >1 week is significantly more likely in patients with low and medium uric acid levels at the time of admission. Uric acid levels may be helpful in assessing disease severity and counseling preeclamptic patients regarding likelihood of extended expectant management.

Perceptions of quality of life and priorities of owners of cats with heart disease.

BACKGROUND: Owners' perceptions and priorities regarding quality of life (QoL) are important considerations given the unknown efficacy of many commonly administered medications, stress of hospital visits, difficulties providing home care, and personal choices including euthanasia. OBJECTIVE: To describe the relative importance of quality versus quantity of life to owners of cats with heart disease. ANIMALS: Two hundred and thirty-nine cats with heart disease. METHODS: Prospective questionnaire-based clinical study. Cat owners completed a questionnaire to identify important parameters when assessing their cat's QoL, the relative importance of quality versus quantity of life, and willingness to trade survival time for QoL. Variables associated with these parameters were evaluated with multivariate analyses. RESULTS: Appetite, owner interaction, sleep patterns, and litterbox habits were deemed important to QoL. Concern over pet suffering was significantly greater than concern over life expectancy. Ninety-three percent of owners were willing to trade survival time for good QoL; 57% of these were willing to trade up to 6 months. On multivariate analysis, the only factor significantly (P=.002) associated with willingness to trade 6 months was study site. Owner concern regarding stress of administering medications at home increased with number and frequency of medications. CONCLUSIONS AND CLINICAL RELEVANCE: These results indicated that QoL is more important to owners of cats with heart disease than longevity. The various priorities and concerns of cat owners should be taken into account in order to provide optimal care.

Toward using delta13C of ecosystem respiration to monitor canopy physiology in complex terrain.

In 2005 and 2006, air samples were collected at the base of a Douglas-fir watershed to monitor seasonal changes in the delta13CO2 of ecosystem respiration (delta13C(ER)). The goals of this study were to determine whether variations in delta13C(ER) correlated with environmental variables and could be used to predict expected variations in canopy-average stomatal conductance (Gs). Changes in delta13C(ER) correlated weakly with changes in vapor pressure deficit (VPD) measured 0 and 3-7 days earlier and significantly with soil matric potential (psi(m)) (P value <0.02) measured on the same day. Midday G (s) was estimated using sapflow measurements (heat-dissipation method) at four plots located at different elevations within the watershed. Values of midday Gs from 0 and 3-7 days earlier were correlated with delta13C(ER), with the 5-day lag being significant (P value <0.05). To examine direct relationships between delta13C(ER) and recent Gs, we used models relating isotope discrimination to stomatal conductance and photosynthetic capacity at the leaf level to estimate values of stomatal conductance ("Gs-I") that would be expected if respired CO2 were derived entirely from recent photosynthate. We compared these values with estimates of Gs using direct measurement of transpiration at multiple locations in the watershed. Considering that the approach based on isotopes considers only the effect of photosynthetic discrimination on delta13C(ER), the magnitude and range in the two values were surprisingly similar. We conclude that: (1) delta13C(ER) is sensitive to variations in weather, and (2) delta13C(ER) potentially could be used to directly monitor average, basin-wide variations in Gs in complex terrain if further research improves understanding of how delta13C(ER) is influenced by post-assimilation fractionation processes.

Differential expression of IEG mRNA in rat brain following acute treatment with clozapine or haloperidol: a semi-quantitative RT-PCR study.

Antipsychotic drugs have been shown to modulate immediate early gene (IEG) expression in rat brain regions that are associated with schizophrenia, which may be directly linked to their immediate therapeutic benefit. In this study, we analysed the expression profile of a series of IEGs (c-fos, c-jun, fra-1, Krox-20, Krox-24, arc, sgk-1, BDNF and NARP) in six rat brain regions (prefrontal cortex, hippocampus, striatum, nucleus accumbens, thalamus and cerebellum). Rats (n=5) were administered either clozapine (20 mg/kg i.p.), haloperidol (1 mg/kg i.p.) or the appropriate vehicle with pre-treatment times of 1, 6 and 24 h. IEG expression was analysed in these regions by Taqman RT-PCR. The spatial and temporal profile of IEG induction following antipsychotic drug treatment correlates with regions associated with the efficacy and side effect profile of each drug. In particular, sgk-1 expression levels after antipsychotic drug treatment may have predictive value when investigating the profile of a novel antipsychotic drug.

Aortic adaptation to pregnancy: elevated expression of matrix metalloproteinases-2 and -3 in rat gestation.

The maternal aorta undergoes substantial functional and structural adaptation in pregnancy. Both aortic diameter and compliance are increased and studies of animal and human gestation indicate that these changes are initiated in early pregnancy and maintained until delivery. The mechanisms underlying aortic adaptation in normal pregnancy remain largely unknown but matrix metalloproteinase enzymes (MMP) are likely to play a key role. Gene expression of candidate MMP and specific tissue inhibitors of MMP (TIMP) were investigated in non-pregnant, pregnant (days 7, 14, 21) and postpartum (day 7) rat aorta using real-time PCR. Of the gene transcripts studied (MMP-2, -3, -7, -9, -12, -13, MT1MMP, TIMP-1, -2) in rat aorta, only MMP-3 was significantly elevated with a 24-fold increase observed in late gestation compared to virgin control (P = 0.0001). MMP-2 mRNA appeared constitutively expressed and unchanged at time-points studied, but MMP-2 activity as assessed by gelatin zymography suggested further modulation after transcription and/or post-translation in rat aorta with activity increased in early pregnancy (P < 0.01, compared to virgin control). These data suggest that MMP-2 and MMP-3 may contribute to adaptive processes in the maternal rat aorta at different gestations and further support a role for this family of enzymes in physiological vascular remodelling.

Gestational profile of matrix metalloproteinases in rat uterine artery.

Mechanisms underlying structural reorganization of the uterine artery in pregnancy remain largely unknown. Matrix metalloproteinases (MMPs) which are involved in degradation of vascular wall matrix are likely to play a key role. In this investigation of rat uterine artery, key MMPs and the specific tissue inhibitors of MMPs (TIMPs) together with three housekeeping genes were studied before, during and after pregnancy, using real time PCR. Data were analysed by partial least squares analysis as well as by conventional univariate methods. Each gene studied [MMP-2, MMP-3, MMP-7, MMP-9, MMP-12, MMP-13, membrane-type 1 (MT1)-MMP, TIMP-1, TIMP-2, GAPDH, cyclophilin and beta-actin] increased in late pregnancy (day 21). MMP-2, MT1MMP, MMP-3 and TIMP-1 transcripts were also elevated at day 7. TIMP-1 and MMP-3 mRNA expression returned to virgin control values in the post-partum, whereas others remained elevated or increased further (MMP-9, MMP-13). Gelatin zymography showed maximum elevation of MMP-2 at day 21. A novel 43-45 kDa gelatinolytic doublet was observed which increased in density with gestation and may represent an active MMP-2 fragment. Together, these data strongly suggest that MMPs and TIMPs are likely to play an important role in remodelling uterine arteries in rat pregnancy and may represent means by which vasodilatation is maintained in later pregnancy. Continued elevated levels of some MMPs post-partum may contribute to vessel regression and return to a non-pregnant physiological state.

Reliance on stored water increases with tree size in three species in the Pacific Northwest.

In tall old forests, limitations to water transport may limit maximum tree height and reduce photosynthesis and carbon sequestration. We evaluated the degree to which tall trees could potentially compensate for hydraulic limitations to water transport by increased use of water stored in xylem. Using sap flux measurements in three tree species of the Pacific Northwest, we showed that reliance on stored water increases with tree size and estimated that use of stored water increases photosynthesis. For Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), water stored in xylem accounted for 20 to 25% of total daily water use in 60-m trees, whereas stored water comprised 7% of daily water use in 15-m trees. For Oregon white oak (Quercus garryana Dougl. ex Hook.), water stored in xylem accounted for 10 to 23% of total daily water use in 25-m trees, whereas stored water comprised 9 to 13% of daily water use in 10-m trees. For ponderosa pine (Pinus ponderosa Dougl. ex Laws.), water stored in xylem accounted for 4 to 20% of total daily water use in 36-m trees, whereas stored water comprised 2 to 4% of daily water use in 12-m trees. In 60-m Douglas-fir trees, we estimated that use of stored water supported 18% more photosynthesis on a daily basis than would occur if no stored water were used, whereas 15-m Douglas-fir trees gained 10% greater daily photosynthesis from use of stored water. We conclude that water storage plays a significant role in the water and carbon economy of tall trees and old forests.

The relationship between tree height and leaf area: sapwood area ratio.

The leaf area to sapwood area ratio (A l:A s) of trees has been hypothesized to decrease as trees become older and taller. Theory suggests that A l:A s must decrease to maintain leaf-specific hydraulic sufficiency as path length, gravity, and tortuosity constrain whole-plant hydraulic conductance. We tested the hypothesis that A l:A s declines with tree height. Whole-tree A l:A s was measured on 15 individuals of Douglas-fir (Pseudotsuga menziesii var. menziesii) ranging in height from 13 to 62 m (aged 20-450 years). A l:A s declined substantially as height increased (P=0.02). Our test of the hypothesis that A l:A s declines with tree height was extended using a combination of original and published data on nine species across a range of maximum heights and climates. Meta-analysis of 13 whole-tree studies revealed a consistent and significant reduction in A l:A s with increasing height (P<0.05). However, two species (Picea abies and Abies balsamea) exhibited an increase in A l:A s with height, although the reason for this is not clear. The slope of the relationship between A l:A s and tree height (ΔA l:A s/Δh) was unrelated to mean annual precipitation. Maximum potential height was positively correlated with ΔA l:A s/Δh. The decrease in A l:A s with increasing tree size that we observed in the majority of species may be a homeostatic mechanism that partially compensates for decreased hydraulic conductance as trees grow in height.

Assessment of the bone status of Nigerian women by ultrasound and biochemical markers.

Ultrasound analysis of the calcaneus and serum markers of bone turnover were used to examine the bone status of healthy Nigerian women who reside in an area of the world where dietary calcium intake is generally low and estrogen replacement therapy is not widely available. A total of 218 women (108 premenopausal and 110 postmenopausal) between the ages of 16 and 95 years were enrolled in the study. Broadband ultrasound attenuation (BUA) and speed of sound velocity (SOS) were measured and used to calculate the stiffness index (SI) of the calcaneus. In this cross-sectional study, the Nigerian women exhibited a marked age-dependent decline in SI that was defined by the regression equation SI = 105.9 - 6.62E-3 x Age2. SI was significantly correlated with age (r = -0.41, P < 0.001) and with serum NTx concentrations (r = -0.26, P < 0.001), but not with serum levels of bone-specific alkaline phosphatase (BSAP). Years since menopause was also significantly correlated with SI (r = 0.40, P < 0.001). A significant increase in serum NTx concentration occurred at least a decade before a significant decline in SI was evident. In the total study group, 24% of the women had T-scores indicative of osteopenia and 9% had T-scores indicative of osteoporosis, based on US reference data. Although the reported current incidence of fracture is low in women in sub-Saharan West Africa, these data show that after menopause Nigerian women have a decline in bone quality and increase in bone turnover similar to North American Caucasian women.

Identifying patient preferences for communicating risk estimates: a descriptive pilot study.

BACKGROUND: Patients increasingly seek more active involvement in health care decisions, but little is known about how to communicate complex risk information to patients. The objective of this study was to elicit patient preferences for the presentation and framing of complex risk information. METHOD: To accomplish this, eight focus group discussions and 15 one-on-one interviews were conducted, where women were presented with risk data in a variety of different graphical formats, metrics, and time horizons. Risk data were based on a hypothetical woman's risk for coronary heart disease, hip fracture, and breast cancer, with and without hormone replacement therapy. Participants' preferences were assessed using likert scales, ranking, and abstractions of focus group discussions. RESULTS: Forty peri- and postmenopausal women were recruited through hospital fliers (n = 25) and a community health fair (n = 15). Mean age was 51 years, 50% were non-Caucasian, and all had completed high school. Bar graphs were preferred by 83% of participants over line graphs, thermometer graphs, 100 representative faces, and survival curves. Lifetime risk estimates were preferred over 10 or 20-year horizons, and absolute risks were preferred over relative risks and number needed to treat. CONCLUSION: Although there are many different formats for presenting and framing risk information, simple bar charts depicting absolute lifetime risk were rated and ranked highest overall for patient preferences for format.

Shoot structure and photosynthetic efficiency along the light gradient in a Scots pine canopy.

We examined the effects of structural and physiological acclimation on the photosynthetic efficiency of Scots pine (Pinus sylvestris L.) shoots. We estimated daily light interception (DLI) and photosynthesis (DPHOT) of a number of sample shoots situated at different positions in the canopy. Photosynthetic efficiency (epsilon) was defined as the ratio of DPHOT to the potential daily light interception (DLI(ref)) defined as the photosynthetically active radiation (PAR) intercepted per unit area of a sphere at the shoot location. To calculate DLI(ref), DLI and DPHOT, the radiation field surrounding a shoot in the canopy was first modeled using simulated directional distributions of incoming PAR on a clear and an overcast day, and estimates of canopy gap fraction in different directions provided by hemispherical photographs. A model of shoot geometry and measured data on shoot structure and photosynthetic parameters were used to simulate the distribution of PAR irradiance on the needle surface area of the shoot. Photosynthetic efficiency (epsilon) was separated into light-interception efficiency (epsilon(I) = DLI/DLI(ref)) and conversion efficiency (epsilon(PHOT) = DPHOT/DLI). This allowed us to quantify separately the effect of structural acclimation on the efficiency of photosynthetic light capture (epsilon(l)), and the effect of physiological acclimation on conversion efficiency (epsilon(PHOT)). The value of epsilon increased from the top to the bottom of the canopy. The increase was largely explained by structural acclimation (higher epsilon(I)) of the shade shoots. The value of epsilon(PHOT) of shade foliage was similar to that of sun foliage. Given these efficiencies, the clear-day value of DPHOT for a sun shoot transferred to shade was only half that of a shade shoot at its original position. The method presented here provides a tool for quantitatively estimating the role of acclimation in total canopy photosynthesis.

Endothelin-1 during and after cardiopulmonary bypass: association to graft sensitivity and postoperative recovery.

OBJECTIVE: Our objectives are 2-fold: (1) to serially measure the release of endothelin and graft-conduit endothelin sensitivity during and after coronary artery bypass grafting and (2) to define potential relationships of changes in endothelin levels to perioperative parameters. METHODS: Endothelin plasma content was measured in patients (n = 105) undergoing bypass grafting from select vascular compartments before operations and at specific intervals up to 24 hours postoperatively. Endothelin sensitivity was determined in isolated internal thoracic artery segments. RESULTS: Systemic arterial and pulmonary arterial endothelin levels were increased by approximately 50% immediately after bypass grafting and increased by another 85% during the first 24 hours postoperatively. Endothelin levels were highest in patients with prolonged ventilatory requirements and extended stays in the intensive care unit (10.2 +/- 0.8 vs 13.2 +/- 1.1 fmol/mL, P =.02, and 9.8 +/- 0.7 vs 13.9 +/- 1.2 fmol/mL, P =.01, respectively. Endothelin sensitivity of the internal thoracic artery was increased in patients requiring prolonged vasodilator support with nitroglycerin. CONCLUSIONS: Systemic and pulmonary arterial endothelin levels remained increased for at least 24 hours postoperatively. Prolonged pharmacologic management and increased intensive care unit stay were associated with increased systemic endothelin release and heightened graft-conduit sensitivity to endothelin.

Matrix metalloproteinase expression and activity in isolated myocytes after neurohormonal stimulation.

Changes in myocardial matrix metalloproteinase (MMP) activity and expression have been associated with left ventricular (LV) remodeling. A recent study demonstrated that LV myocytes synthesize and release MMPs, which suggests that LV myocytes may participate in myocardial remodeling. However, extracellular stimuli that may potentially influence LV myocyte MMP production remains to be defined. In the present study MMP activity and expression were measured in porcine LV myocyte preparations (10(5) total cells; n = 6) following incubation (6 h) with endothelin-1 (ET-1;50 pM), angiotensin II (ANG II; 1 microM), or the beta-receptor agonist isoproterenol (Iso; 10 nM). LV myocyte-conditioned media were then subjected to gelatin zymography and an MMP-2 antibody capture assay. MMP zymographic gelatinase activity and MMP-2 content were increased by over 40% in LV myocyte-conditioned media after incubation with ET-1 or ANG II (P < 0.05). Exposure to the phorbol ester phorbol 12-myristate 13-acetate (PMA; 50 ng/ml) resulted in a 30% increase in zymographic gelatinase activity and a 63% increase in MMP-2 content (P < 0.05), suggesting that protein kinase C activation may be an intracellular mechanism for MMP induction. With the use of a confocal microscopy, membrane type-1 MMP (MT1-MMP) was localized to porcine LV myocytes, and immunoblotting for MT1-MMP using LV myocyte extracts revealed that after exposure to Iso, ET-1, ANG II, or PMA (P < 0.05), MT1-MMP abundance increased over 50%. Thus stimulation of specific neurohormonal systems that are relevant to LV remodeling influences LV myocyte MMP synthesis and release.

Determination of changes in mRNA expression in a rat model of neuropathic pain by Taqman quantitative RT-PCR.

The aim of this study was to develop a rapid and accurate high throughput method of screening multiple genes across a single sample set to detect changes in gene expression in the dorsal root ganglion (DRG) following partial sciatic nerve ligation in the rat. Using Taqman quantitative RT-PCR, we show that expression of a number of genes, including galanin, vasointestinal peptide and neuropeptide Y are rapidly increased 24 h post-operation in the DRGs on the ligated side only. Other genes tested, including vanilloid receptor-1, substance P, galanin receptor-2 and housekeeping genes did not alter. Analysis of the expression of ASIC4 showed a small difference in expression at 7 days post ligation. By applying a statistical method for analysis of multiple variables, partial least squares, we show that the expression change of ASIC4 was significantly altered on the ligated side even though the change was small. This method will allow us to rapidly identify changes in expression of candidate genes that may be involved in adaptive responses in the DRG due to nerve injury.