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PubMed2006

Complex adjustments of photosynthetic potentials and internal diffusion conductance to current and previous light availabilities and leaf age in Mediterranean evergreen species Quercus ilex.

Mature non-senescent leaves of evergreen species become gradually shaded as new foliage develops and canopy expands, but the interactive effects of integrated light during leaf formation (Q(int)G), current light (Q(int)C) and leaf age on foliage photosynthetic competence are poorly understood. In Quercus ilex L., we measured the responses of leaf structural and physiological variables to Q(int)C and Q(int)G for four leaf age classes. Leaf aging resulted in increases in leaf dry mass per unit area (M(A)), and leaf dry to fresh mass ratio (D(F)) and decreases in N content per dry mass (N(M)). N content per area (N(A)) was independent of age, indicating that decreases in N(M) reflected dilution of leaf N because of accumulation of dry mass (NA = N(M) M(A)). M(A), D(F) and N(A) scaled positively with irradiance, whereas these age-specific correlations were stronger with leaf growth light than with current leaf light. Area-based maximum ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylase activity (V(cmax)A), capacity for photosynthetic electron transport (J(max)A) and the rate of non-photorespiratory respiration in light (R(d)A) were also positively associated with irradiance. Differently from leaf structural characteristics, for all data pooled, these relationships were stronger with current light with little differences among leaves of different age. Acclimation to current leaf light environment was achieved by light-dependent partitioning of N in rate-limiting proteins. Mass-based physiological activities decreased with increasing leaf age, reflecting dilution of leaf N and a larger fraction of non-photosynthetic N in older leaves. This resulted in age-dependent modification of leaf photosynthetic potentials versus N relationships. Internal diffusion conductance (g(m)) per unit area (g(m)A) increased curvilinearly with increasing irradiance for two youngest leaf age classes and was independent of light for older leaves. In contrast, g(m) per dry mass (g(m)M) was negatively associated with light in current-year leaves. Greater photosynthetic potentials and moderate changes in diffusion conductance resulted in greater internal diffusion limitations of photosynthesis in higher light. Both area- and mass-based g(m) decreased with increasing leaf age. The decrease in diffusion conductance was larger than changes in photosynthetic potentials, leading to larger CO2 drawdown from leaf internal air space to chloroplasts (delta(c)) in older leaves. The increases in diffusion limitations in older leaves and at higher light scaled with age- and light-dependent increases in MA and D(F). Overall, our study demonstrates a large potential of foliage photosynthetic acclimation to changes in leaf light environment, but also highlights enhanced structural diffusion limitations in older leaves that result from leaf structural acclimation to previous rather than to current light environment and accumulation of structural compounds with leaf age.

Acclimatization↗

PubMed2002

Stabilised cellular immuno-fluorescence assay: CD45 expression as a calibration standard for human leukocytes.

We first confirmed the precision of the quantitative indirect immunofluorescence (QIFI) test by demonstrating that blood lymphocytes from different individuals expressed CD45 leucocyte antigens at a very similar level (mean: 201 x 10(3) antibody binding capacity (ABC)/lymphocyte) with only minimal variation (CV% 2.5%). These values were maintained for 4 days in blood samples when kept at 20 degrees C, and for up to 14 days in samples fixed with TransFix. Using long-term stabilisation, after an initial drop of 10-15% the CD45 ABC/lymphocyte values remained stable at an 85-90% level for >1 year. These biological standards were used to check other quantitative IF techniques. The quantum simply cellular (QSC) method showed variable results (85-240%), and the QuantiBRITE method gave values as low as 30-40% of the expected values, indicating that biological standards such as CD45 ABC/lymphocytes are absolutely essential to check the performance of methods that claim to quantify immunofluorescence (IF). Next, these standards were used to establish the stabilised cellular immuno-fluorescence assay (SCIFA) as follows. The ABC x 10(3)/cell values established by QIFI on leucocyte populations such as lympho-, mono- and granulocytes were used to create calibration curves for the CD45 antigen and its isoforms CD45RA, -R0 and -RB. The same cell populations were then stained with monoclonal antibodies (MAbs) directly conjugated to different fluorochromes in order to translate the mean fluorescence intensity (MFI) values seen with the directly labelled reagents to values of ABCx10(3)/cells. Using SCIFA with a triple-colour direct IF, the display of CD45 and its isoforms were quantitated on the 'virgin' or 'unprimed' (CD45RA+) and 'primed' (CD45R0+) subsets in both the CD4+ and CD8+ T cell lineages. We also observed that the CD4+ and CD8+ T cells in transit between the 'virgin' and 'primed' subsets frequently displayed different levels of the CD45RA and -R0 molecules, pointing to the physiological variability of the CD45RA-R0 switching process. In conclusion, internal biological standards, with known stable expression of ABC/cell, should be used to evaluate IF staining patterns in a quantitative manner during routine investigations.

Adult↗

PubMed2000

Concurrent reductions in blood pressure and metabolic rate during fasting in the unrestrained SHR.

Fasting produces multiple cardiovascular, metabolic, and behavioral responses. To examine the interrelationship between these responses, male spontaneously hypertensive rats (SHR; n = 8) implanted with cardiovascular telemetry devices were housed in metabolic chambers at 23 degrees C for 22-h daily measurements of physiological variables. The experimental apparatus was designed so that ingestive behavior was detected by photobeams and locomotion was detected by a load sensor. Cardiovascular and metabolic status were determined as both a function of the circadian cycle (12-h dark and 10-h light), as well as during periods of inactivity (no ingestion and minimal locomotion) within the dark and light phases. Data were obtained during baseline, 48-h of caloric deprivation, and 6 days of refeeding. Fasting produced significant reductions in mean arterial pressure (dark: -9.2+/-1.3 from 143.7+/-3.7 mm Hg; light: -8.6+/-1.8 from 140.1+/-3.7 mm Hg), heart rate (dark: -43.4+/-5.2 from 330.0+/-5.2 beats/min; light: -27.4+/-5.2 from 294.0+/-5.2 beats/min), and oxygen consumption (dark: -5.0+/-0.6 from 20.6+/-0.3 ml x min(-1) x kg (0.75); light: -2.7+/-0.2 from 14.9 +/-0.2 ml x min(-1) x kg(0.75)). Analysis of inactive periods during both light and dark phases revealed that these reductions were not dependent on behavioral effects. We conclude that fasting produces concurrent and interrelated reductions in cardiovascular and metabolic function in the SHR. The merging of cardiovascular telemetry, indirect calorimetry, and behavioral monitoring provides a powerful approach for investigation of the integrative physiological responses to energetic challenges.

Animals↗

PubMed1998

Mutual information discloses relationship between hemodynamic variables in artificial heart-implanted dogs.

A mutual information (MI) method for assessment of the relationship between hemodynamic variables was proposed and applied to the analysis of heart rate (HR), arterial blood pressure (BP), and renal sympathetic nerve activity (RSNA) in artificial heart-implanted dogs to quantify correlation between these parameters. MI measures the nonlinear as well as linear dependence of two variables. Simulation studies revealed that this MI technique furnishes mathematical features well suited to the investigation of nonlinear dynamics such as the cardiovascular system and can quantify a relationship between two parameters. To constitute a model free of the natural heart, two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses in acute canine experiments. RSNA was detected with the use of bipolar electrodes attached to the renal sympathetic nerve. Analysis of data during control revealed that correlation between HR and RSNA was higher than that between HR and BP and that between RSNA and BP (P < 0.05). Although RSNA seemed to fluctuate noncorrelatedly with BP in higher pacing rates, the MI values between them disclosed their strong correlation. Surprisingly, correlation between RSNA and BP was stronger during a pacing rate of 60 beats/min than during higher pacing rates and control (P < 0. 05). It is suggested that the baroreflex system may be susceptible to pacing rates during the total artificial heart state. We calculated the time delay between HR and RSNA, between RSNA and BP, and between HR and BP by regarding a time delay at which the maximum MI value between each pair of parameters was given as a physiological delay. Our results indicate that RSNA leads BP, BP leads HR, and RSNA leads HR during control (P < 0.05). We conclude that this method could provide a powerful means for measuring correlation of physiological variables.

Algorithms↗

PubMed2004

Peak power output predicts rowing ergometer performance in elite male rowers.

The aim of the present study was to test the hypothesis that peak power output (Ppeak) sustained during maximal incremental testing would be an overall index of rowing ergometer performance over 2000 m (P2000), and to study the influence of selected physiological variables on Ppeak. A group of 54 highly trained rowers (31 heavyweight [HW] and 23 lightweight [LW] rowers) was studied. Body mass, maximal oxygen uptake ((.-)VO(2max)), oxygen consumption corresponding to a blood lactate of 4 mmol. l (-1) expressed in percentage of (.-)VO(2max) (V.O (2)La4 %), and rowing gross efficiency (RGE) were also determined during the incremental test. In the whole group Ppeak was the best predictor of P2000 (r = 0.92, p < 0.0001). Body mass (r = 0.65, p < 0.0001), V.O (2max) (r = 0.84, p < 0.0001), (.-)VO 2)La4 % (r = 0.49, p < 0.0001) and RGE (r = 0.35, p < 0.01) were significantly correlated with P2000 as well. To take the influence of body mass into account, (.-)VO(2max) was related to kg (0.57). Ppeak was significantly related to body mass (r = 0.56, p < 0.0001), (.-)VO(2max) x kg (-0.57) (r = 0.63, p < 0.0001), (.-)VO(2)La4 % (r = 0.45, p < 0.001) and RGE (r = 0.34, p < 0.05). Multiple regression analysis indicated that the above parameters taken together explained 82.8 % of Ppeak variation in the whole group. It was also demonstrated that Ppeak was the best predictor of P2000 when LW and HW groups were considered separately. It was concluded that, by integrating the main physiological factors of performance, Ppeak is an overall index of physiological rowing capacity and rowing efficiency in heterogeneous as well as in homogeneous groups. It presents the further advantage of being easily measured in the field.

Adult↗

PubMed1994

Data quality of bedside monitoring in an intensive care unit.

Computerized record keeping promises complete, accurate and legible documentation. Reliable measurements are a prerequisite to fulfill these expectations. We analyzed the physiological variables provided by bedside monitoring devices in 657 bedside visits performed by an experienced Intensive Care nurse during 75 Intensive Care rounds. We registered which variables were displayed. If a variable was displayed, we assessed whether it could be used for documentation or should be rejected. If a value was rejected the reason was registered as: the measurement was not intended (superfluous display), the current clinical situation did not allow proper measurement, or other reasons. Basic variables (vital signs and respiration related variables) were displayed in more then 90%, specific variables (e.g. intracranial pressure) were displayed in less than 50% of the situations. Displayed variables were superfluous on an average of 11% because measurement was not intended. Variables like heart rate, temperature, airway pressure, minute volume of ventilation, arrhythmia, pulmonary arterial pressure, non-invasive blood pressure, and intracranial pressure provide high quality measured values (acceptance of more than 90%). Invasive arterial pressure, central venous pressure, respiration rate and oxygen saturation (via pulse oximetry) provided lower quality values with a rejection rate higher than 10%. Inappropriate sensor technology to match the clinical environment seems to be the root cause. In future the request for automatic documentation will increase. In order to avoid additional staff workload and to ensure reliable documentation, sensor technology especially related to respiration rate, blood pressure measurements, and pulse oximetry should be improved.

Data Collection↗

PubMed1994

Reproducibility and intraindividual variability of the pattern electroretinogram.

The human pattern electroretinogram (PERG) is a contrast-specific potential presumedly reflecting the functional integrity of ganglion cells. Many studies have devised criteria that enable PERG measurements to distinguish established glaucomatous (hypertonic) eyes from normal controls. As there are relatively few reports concerning the reproducibility and reliability of the PERG, we studied the intraindividual variability of the PERG in 20 healthy subjects. Both transient and steady-state responses were recorded using a high-contrast (98%), black-and-white, counterphasing checkerboard pattern (average luminance, 80 cd/m2) generated by a television monitor (subtending angle, 13.8 degrees x 10.8 degrees) using three different check sizes (15', 30', and 60'). Recordings were performed in both eyes simultaneously at a 7-day interval under test-retest conditions. Responses of 30' spatial frequency were most consistent and resulted in a mean amplitude (+/- SD) of 2.18 +/- 0.95 microV (P50) and 4.00 +/- 1.69 microV (N95) for transient patterns and 1.84 +/- 1.25 microV for steady-state patterns. No statistically significant difference was observed between either right and left eyes, test and retest conditions or 1st- and 7th-day recording sessions for PERG parameters. In linear correlation analysis there was an adequate, positive correlation between the right and left eyes (r = 0.78); a weak correlation between test and retest conditions (r = 0.58); and no correlation between measurements made at a 7-day interval. As a consequence, we conclude that the follow-up of patients (e.g., glaucoma, ocular hypertension) by means of PERG is critical, especially when therapeutic consequences may be based on the physiological variability of a weak retinal signal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2003

Effects on breathing in awake and sleeping goats of focal acidosis in the medullary raphe.

Our aim was to determine the effects of focal acidification in the raphe obscurus (RO) and raphe pallidus (RP) on ventilation and other physiological variables in both the awake and sleep states in adult goats. Through chronically implanted microtubules, 1) a focal acidosis was created by microdialysis of mock cerebrospinal fluid (mCSF), equilibrated with various levels of CO2, and 2) medullary extracellular fluid (ECF) pH was measured by using a custom-made pH electrode. Focal acidosis in the RO or RP, by dialyzing either 25 or 80% CO2 (mCSF pH approximately 6.8 or 6.3), increased (P < 0.05) inspiratory flow by 8 and 12%, respectively, while the animals were awake during the day, but not at night while they were awake or in non-rapid eye movement sleep. While the animals were awake during the day, there were also increases in heart rate and blood pressure (P < 0.05) but no significant change in metabolic rate or arterial Pco2. Dialysis with mCSF equilibrated with 25 or 80% CO2 reduced ECF pH by the same amount (25%) or three times more (80%) than when inspired CO2 was increased to 7%. During CO2 inhalation, the reduction in ECF pH was only 50% of the reduction in arterial pH. Finally, dialysis in vivo only decreased ECF pH by 19.1% of the change during dialysis in an in vitro system. We conclude that 1) the physiological responses to focal acidosis in the RO and RP are consistent with the existence of chemoreceptors in these nuclei, and 2) local pH buffering mechanisms act to minimize changes in brain pH during systemic induced acidosis and microdialysis focal acidosis and that these mechanisms could be as or more important to pH regulation than the small changes in inspiratory flow during a focal acidosis.

Acidosis↗

PubMed1995

Quantitative coronary angiography in predicting functional significance of stenoses in an unselected patient cohort.

OBJECTIVES: This study investigated the value of quantitative coronary angiography for predicting coronary flow reserve, as calculated from the transstenotic pressure gradient in a large, unselected patient cohort. BACKGROUND: In patients with extensive coronary artery disease, quantitative coronary angiographic findings fail to correlate with functional variables of coronary stenoses. New developments in pressure-monitoring wire technology permitted validation in humans of the concept of myocardial fractional flow reserve as assessed from coronary pressure measurements. METHODS: One hundred ten patients with normal left ventricular function were studied in the setting of coronary angioplasty. Quantitative coronary angiography was performed on-line using the ACA system. Myocardial and coronary fractional flow reserve were calculated from aortic and distal coronary pressures during maximal coronary hyperemia. RESULTS: When data before and after angioplasty were pooled, a curvilinear relation was found between myocardial fractional flow reserve and both diameter stenosis (r = 0.79) and minimal lumen diameter (r = 0.82), and a linear relation was found between myocardial fractional flow reserve and angiographic stenosis flow reserve (r = 0.78). Correlations between quantitative angiographic and pressure-derived indexes, although significant, were characterized by a large dispersion of the values of myocardial fractional flow reserve for a similar angiographic degree of stenosis. Nevertheless, the sensitivity and specificity of a minimal lumen diameter < 1.5 mm to predict myocardial fractional flow reserve < 0.72 were 96% and 89%, respectively. The corresponding values for a diameter stenosis > 50% were 93% and 85%, respectively. CONCLUSIONS: 1) In an unselected patient cohort, geometric indexes of stenosis severity derived from quantitative coronary angiography correlate significantly with physiologic variables, although these relations are imprecise in individual patients. 2) Nevertheless, the diagnostic accuracy of quantitative coronary angiography in predicting myocardial fractional flow reserve < 0.72 is high and allows its use for clinical decision making in the individual patient during diagnostic or interventional procedures.

Aged↗

PubMed1986

Understanding and selecting monitoring equipment in anaesthesia and intensive care.

Techniques for sensing, acquiring, processing and displaying physiological variables used to assist the process of monitoring in anaesthesia and intensive care have been reviewed. The role of instrumental monitoring in clinical practice and the comparative effectiveness of Man versus Machine has been outlined. Future developments in monitoring in clinical practice have been identified. It is important that physicians stay abreast of developments in the technology of measurement and monitoring instrumentation so that they not only assist in the development of standards but also have a complete understanding of the precision and real usefulness of any given item of equipment. To this end, guidelines have been tabulated which may permit those who have the responsibility for acquiring updating or using monitoring equipment, to more completely examine the features of any apparatus which is being considered for purchase.

Anesthesiology↗

PubMed2006

Classification of metabolic and respiratory demands in fire fighting activity with extreme workloads.

Fire fighting work comprises work tasks requiring an energy yield at maximal or close to maximal levels of the individual. Due to the very nature of fire fighting more complex physiological variables are difficult to measure. We measured metabolic and respiratory responses in 15 male, professional fire fighters during simulated work tasks on a test ground. Work time was on the average 22 min with individual components of work tasks lasting 2-4 min. The mean oxygen consumption for the whole exercise (22 min) was 2.75+/-0.29 l/min. The most demanding work task demanded an oxygen uptake of 3.55+/-0.27 l/min. Corresponding values for respiratory minute volumes were 82+/-14 and 102+/-14l/min, respectively. Heart rates averaged 168+/-12 for the whole test and 179+/-13 beats/min for the heaviest work task. Two new classes for classification of intensive and exhausting, short term physical work are proposed for inclusion in ISO8996 and values for relevant parameters are proposed.

Adult↗

PubMed2002

Theory and applications of biotelemetry.

In this study, biotelemetry and its evolution is explained in detail. Bioelectric and physiological variables could be measured by biotelemetry systems. The development of a biotelemetry system and its principal operation are presented. The components of a biotelemetry system are explained. Biomedical data has been telemetered through every medium between two sites by using a variety of modulated energy forms. Designing of the link between transmitter and receiver is described. Important factors in designing a backpack or implanted telemeter are explained. The main features of implanted biotelemetry units are determined. Single-channel and multichannel biotelemetry systems are defined. The types of telemetry, and a comparison thereof, are given. The power sources of biotelemetry systems and features of different power sources are explained. A survey of biotelemetry applications on humans and animals is presented and advantages of using biotelemetry systems are determined.

Animals↗

PubMed2002

The scientific basis for high-intensity interval training: optimising training programmes and maximising performance in highly trained endurance athletes.

While the physiological adaptations that occur following endurance training in previously sedentary and recreationally active individuals are relatively well understood, the adaptations to training in already highly trained endurance athletes remain unclear. While significant improvements in endurance performance and corresponding physiological markers are evident following submaximal endurance training in sedentary and recreationally active groups, an additional increase in submaximal training (i.e. volume) in highly trained individuals does not appear to further enhance either endurance performance or associated physiological variables [e.g. peak oxygen uptake (VO2peak), oxidative enzyme activity]. It seems that, for athletes who are already trained, improvements in endurance performance can be achieved only through high-intensity interval training (HIT). The limited research which has examined changes in muscle enzyme activity in highly trained athletes, following HIT, has revealed no change in oxidative or glycolytic enzyme activity, despite significant improvements in endurance performance (p < 0.05). Instead, an increase in skeletal muscle buffering capacity may be one mechanism responsible for an improvement in endurance performance. Changes in plasma volume, stroke volume, as well as muscle cation pumps, myoglobin, capillary density and fibre type characteristics have yet to be investigated in response to HIT with the highly trained athlete. Information relating to HIT programme optimisation in endurance athletes is also very sparse. Preliminary work using the velocity at which VO2max is achieved (V(max)) as the interval intensity, and fractions (50 to 75%) of the time to exhaustion at V(max) (T(max)) as the interval duration has been successful in eliciting improvements in performance in long-distance runners. However, V(max) and T(max) have not been used with cyclists. Instead, HIT programme optimisation research in cyclists has revealed that repeated supramaximal sprinting may be equally effective as more traditional HIT programmes for eliciting improvements in endurance performance. Further examination of the biochemical and physiological adaptations which accompany different HIT programmes, as well as investigation into the optimal HIT programme for eliciting performance enhancements in highly trained athletes is required.

Adaptation, Physiological↗

PubMed1992

Control of intracranial pressure in patients with severe head injury.

Raised intracranial pressure (ICP) occurs at some time in 50-75% of severely head injured patients. Measurement of ICP alone is not sufficient. Arterial pressure must also be monitored: the important physiological variable is cerebral perfusion pressure. Detailed analysis of the ICP recording yields valuable information on the nature and cause of ICP, with implications for appropriate therapy. Additional measurements of importance include brain electrical activity, arterial and jugular venous oxygen saturation, and blood flow velocity in major intracranial arteries measured by transcranial Doppler sonography. These assessments not only add information about the cause of intracranial hypertension (vascular vs. nonvascular) but also help to regulate therapy, providing early warning that a treatment for reducing the ICP is actually producing global brain ischemia. In the management of raised ICP, all correctable factors must first of all be dealt with, then a choice made between hypnotic drugs and osmotic therapy according to whether the cause of raised ICP is, respectively, vascular or nonvascular.

Blood Volume↗

PubMed1994

A comparison of two methods to ascertain dietary intake: the CARDIA Study.

Data on dietary intake were collected in the Coronary Artery Risk Development in Young Adults (CARDIA) Study at the baseline examination in 1985-86 and again at the second examination 2 years later. At baseline, a diet history questionnaire developed for the CARDIA study was used; at the second exam the NCI (Block) food frequency questionnaire was used. The purpose of the present report is to compare the estimated nutrient intakes obtained with the two instruments; to compare correlations of nutrient intakes obtained at the two exams with those observed for other lifestyle and physiological variables also measured 2 years apart; and to assess ability to test hypotheses relating 2-year changes in risk factors to between-exam differences in reported nutrient intakes. Mean levels of reported intake were generally greater for both blacks and whites on the CARDIA diet history than on the Block food frequency. Rank order correlations of reported nutrient intakes between the two questionnaires indicated greater consistency between instruments for whites (r's ranging between 0.35 and 0.52) than for blacks (r's ranging between 0.29 and 0.45). Correlations over time for nutrients were smaller than those observed for body size measures and lipid levels but were similar in magnitude to those for blood pressure, physical activity, and life events. At both exams, total caloric intake was positively associated with physical activity (range of r's for CARDIA were 0.07 for white women to 0.23 for black men, the range of r's for Block were 0.06 for women to 0.11 for white men). Using data from the two examinations, 2-year changes in total plasma cholesterol were significantly related to 2 year changes in Keys scores. The results of this comparison are useful in that they show similarities and differences between two instruments developed to gather dietary intake data. The study also illustrates the need to monitor young adults during a time when rapid changes occur in many lifestyle and physiologic factors.

Adult↗

PubMed2000

Dynamic assessment of abnormalities in central pain transmission and modulation in tension-type headache sufferers.

OBJECTIVE: To examine and compare central pain processing and modulation in young tension-type headache sufferers with that of matched healthy controls using an induced headache "challenge" paradigm. BACKGROUND: Recent research has suggested that abnormalities in central pain processing and descending pain modulation may contribute to chronic tension-type headache. These abnormalities, if they contribute to headache pathogenesis, should be present in young adult tension-type headache sufferers. Recent research using static measures of physiological variables, such as muscle tenderness and exteroceptive suppression, has identified chronic muscle tenderness as a characteristic of young tension-type headache sufferers, but other central nervous system functional abnormalities may require a dynamic "challenge" to be observed. METHODS: Twenty-four young women meeting the International Headache Society diagnostic criteria for tension-type headache (headache-prone) and a matched group of 24 healthy women who reported fewer than 10 problem headaches per year (control) participated in a double-blind, placebo-controlled, crossover study. Subjects completed jaw clenching and a placebo condition on different days in counterbalanced order. Pericranial muscle tenderness, pressure-pain thresholds on the temporalis, and exteroceptive suppression periods were assessed before and after each procedure. Head pain was recorded for 12 to16 hours following each condition. RESULTS: Headache-prone subjects were more likely than controls to experience headaches after both the jaw clenching and placebo procedures, but neither group was significantly more likely to experience headaches following jaw clenching than placebo. In pretreatment measurements, headache-prone subjects exhibited greater muscle tenderness than controls, but pressure-pain detection thresholds and exteroceptive suppression periods did not differ in the two groups. Control subjects showed increases in muscle tenderness and exteroceptive suppression periods following both the clenching and placebo procedures, whereas headache-prone subjects exhibited no significant changes in any of the physiological measures following either experimental manipulation. CONCLUSIONS: These results confirm previous findings indicating abnormally high pericranial muscle tenderness in young tension headache sufferers even in the headache-free state. In addition, the results suggest that the development of headaches following noxious stimulation is more strongly related to headache proneness and associated abnormalities in central pain transmission or modulation (indexed by pericranial muscle tenderness and exteroceptive suppression responses) than muscle strain induced by jaw clenching.

Adult↗

PubMed2004

Cardiac-specific norepinephrine mass transport and its relationship to left ventricular size and systolic performance.

Objectives of this study were to develop a technique for quantifying cardiac-specific norepinephrine (NE) mass transport and determine whether cardiac NE kinetic modeling parameters were related to physiological variables of left ventricular (LV) size and systolic performance in nine patients with chronic mitral regurgitation. Biplane contrast cineventriculograms were used to determine LV size and ejection fraction (EF), micromanometer LV pressures and radionuclide LV volumes from a range of loading conditions to calculate LV end-systolic elastance, and [(3)H]NE infusions with LV and coronary sinus sampling for [(3)H]NE and endogenous NE during and after termination of infusions to model NE mass transport. Total NE release rate into cardiac interstitial fluid (M(IF)(R)) averaged 859 +/- 214 and NE released de novo into cardiac interstitial fluid (M(IF)(u,r,en)) averaged 546 +/- 174 pmol/min. Both M(IF)(R) and M(IF)(u,r,en)correlated directly with LV end-systolic volume (r = 0.84, P = 0.005; r = 0.86, P = 0.003); inversely with LV EFs (r = -0.75, P = 0.02; r = -0.81, P = 0.008); and inversely with LV end-systolic elastance values, optimally fit by a nonlinear function (r = 0.89, P = 0.04; r = 0.96, P = 0.01). We conclude that total and newly released NE into interstitial fluid of the heart, determined by regional mass transport kinetic model, are specific measures of regional cardiac-specific sympathetic nervous system activity and are strongly related to measures of LV size and systolic performance. These data support the concept that this new model of organ-specific NE kinetics has physiological relevance.

Aged↗

PubMed1999

The beaver pond analogy of blood glucose control.

The concentration of glucose is tightly regulated in the blood by a complicated set of physiological variables. To provide students with a means to more readily understand these complex mechanisms, the control of the water level in a beaver pond is presented as an analogy. A beaver must maintain a constant water level in the pond for the proper functioning of the lodge, just as blood glucose is maintained for, among other reasons, brain function. The beaver controls the water level by changing outflow over the dam and inflow from stream beds. Water flow over the dam is analogous to glucose leaving the blood for tissues, which is controlled by insulin. Inflow of water from streams is analogous to glucose absorption from the gastrointestinal tract and glucose release from the liver, the latter being controlled by glucagon and other counterregulatory hormones. The analogy is extended by considering the effects of exercise in normal and diabetic individuals on blood glucose levels.

Animals↗