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Results for “physiologic variables”

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PubMed2001

Biopsychosocial mediators and moderators of stress-health relationships in patients with recently diagnosed rheumatoid arthritis.

OBJECTIVE: To investigate the mediating and moderating roles of social support, coping, and physiological variables in the relationship between life events and health status. METHODS: Psychological and biological measurements were taken in 54 patients (38 women, 16 men, mean age +/- SD 56 +/-14.4 years) with recently diagnosed rheumatoid arthritis (RA). RESULTS: Life events were correlated with psychological distress, but not with disease activity. No mediators for the relationship of life events with psychological well-being and disease activity were observed. In 40 tests, 4 moderators were found: Problem-focused coping, perceived support, diastolic blood pressure, and total number of lymphocytes were moderators of the relationship between daily hassles and health status (P < or = 0.05). CONCLUSION: Our study provides limited support for the notion that the interactions of life stress with biopsychosocial variables have an impact on health. None of these variables were found to be crucial mediators of stress-health associations in recently diagnosed patients with RA, but some provocative evidence was given that biopsychosocial variables may have a minor impact on stress-health relationships.

Adaptation, Psychological↗

PubMed1991

Positron emission tomography studies of the somatosensory system in man.

Activity in the human somatosensory system was measured by regional cerebral blood flow (rCBF) and by the binding of [11C]nimodipine to L-type Ca2+ channels. These physiological variables were considered to be indicators of neuronal and synaptic activity. In general, structures in the cerebellum, thalamus and the somatosensory cortices which increased their rCBF in response to somatosensory stimulation also showed high binding of [11C]nimodipine. Voluntary movements carried out largely independently of sensory feedback, natural somatosensory stimulation and passive stimulation of the somatosensory system all activate the somatosensory system. However, it is possible by subtraction techniques to show that differences in activations between these conditions exist in the cerebellum and the somatosensory cortices in the anterior part of the parietal lobe.

Brain Mapping↗

PubMed1979

Principles of pharmacokinetics.

A compartmental representation of the body is often used to explain the principles of pharmacokinetics, where the compartments are purely hypothetical and bear no relationship to real tissues or organs. In recent years a more physiological approach has been emphasized. Differences in derived kinetic parameters, such as elimination half-life, volume of distribution and clearance, as a function of drug, patient and route of drug administration, are more easily understood when related directly to primary physiological variables, such as blood flow, enzyme activity and drug binding. In turn this allows a convenient conceptual framework for describing and predicting both unbound and total drug concentrations in many clinical situations.

Administration, Oral↗

PubMed1995

Asbestos-induced visceral pleural fibrosis reduces pulmonary compliance.

To determine the nature of respiratory functional impairment caused by asbestos-induced visceral pleural fibrosis (VPF) and to discover which pulmonary physiological variable best reveals it, we examined 59 asbestos-exposed construction workers having asbestos-related changes on chest radiographs. Computed tomography scans of the thorax were also performed. Visceral pleural fibrosis was diagnosed in 29 subjects: seven had only VPF, 17 had VPF and pleural plaques, and five had VPF, plaques, and asbestosis. In subjects without VPF, 23 had plaques, six had plaques and asbestosis, and one had only minor fibrotic parenchymal changes insufficient for a diagnosis of asbestosis. Flow-volume spirometry, body plethysmography, static and dynamic compliance, and pulmonary diffusing capacity for carbon monoxide were measured. The subjects with VPF had significantly lower static (p = 0.005) and dynamic (p = 0.007) compliance values than those without. Other respiratory function variables failed to show any significant differences. We conclude that the measurement of static and dynamic compliance is a useful method in assessing pulmonary function impairment caused by visceral pleural fibrosis.

Adult↗

PubMed1984

In vivo phosphorus nuclear magnetic resonance spectroscopy in status epilepticus.

Bicuculline-induced status epilepticus was studied in paralyzed rabbits ventilated with an oxygen and nitrous oxide mixture. An Oxford Instruments TMR 32-200 spectrometer was used to record phosphorus 31 nuclear magnetic resonance spectra of the in vivo brain. An array of conventional physiological variables including the electroencephalogram was simultaneously recorded. Several features were consistently observed during status epilepticus: (1) Phosphocreatine levels fell to about two-thirds of their control values and remained at that level despite a gradual decline in seizure activity; (2) intracellular pH declined and then remained constant, whereas seizure discharges declined; (3) adenosine triphosphate levels remained constant at their control values. These new, lower levels of brain phosphocreatine and intracellular pH were largely unaffected by increases in seizure activity brought about by elevation of blood pressure from levels too low to support adequate cerebral perfusion, by waning of anticonvulsant drug effect, or by repeated doses of bicuculline.

Acid-Base Equilibrium↗

PubMed1979

Anatomic models of the tracheobronchial and pulmonary regions of the rat.

Models of the lung airways of a rat were developed from complete measurements of the tracheobronchial airways. A silicone rubber cast of the tracheobronchial airways of a rat lung was prepared and all individual airway segments down to and including the terminal bronchioles were measured to obtain the segment diameters, lengths, branching angles and angles of inclination to gravity. Models of the rat tracheobronchial airways were constructed based on the original measurements and the subsequent analysis. Some mathematical assumptions about acinar anatomy distal to terminal bronchioles were made to extend the models to include pulmonary regions. Emphasis was placed on the "Typical Path Lung Model" which used one typical pathway to represent either a whole lung or a lobe of the lung. The models are simple and can be applied in calculation of physiologic variables or particle deposition during inhalation in various lobes of the lung.

Animals↗

PubMed1985

Thermoregulatory adjustments in squirrel monkeys exposed to microwaves at high power densities.

The present study was undertaken to investigate the thermal adjustments of squirrel monkeys exposed in a cold environment to relatively high energy levels of microwave fields. The animals (Saimiri sciureus) were equilibrated for 90 min to a cool environment (Ta = 20 degrees C) to elevate metabolic heat production (M). They were then exposed for brief (10-min) or long (30-min) periods to 2,450-MHz continuous-wave microwaves. Power densities (MPD) were 10, 14, 19, and 25 mW/cm2 during brief exposures and 30, 35, 40, and 45 mW/cm2 during long exposures (rate of energy absorption: SAR = 0.15 [W/kg]/[mW/cm2]). Individual exposures were separated by enough time to allow physiological variables to return to baseline levels. The results confirm that each microwave exposure induced a rapid decrease in M. In a 20 degree C environment, the power density of a 10-min exposure required to lower M to approximate the resting level was 35 mW/cm2 (SAR = 5.3 W/kg). During the long exposures, 20 min was needed to decrease M to its lowest level. Cessation of irradiation was associated with persistence of low levels of M for periods that depended on the power density of the preceding microwave exposure. Vasodilation, as indexed by changes in local skin temperature, occurred at a high rate of energy absorption (SAR = 4.5 W/kg) and was sufficient to prevent a dramatic increase in storage of thermal energy by the body; vasoconstriction was reinstated after termination of irradiation. Patterns of thermophysiological responses confirm the influence both of peripheral and of internal inputs to thermoregulation in squirrel monkeys exposed to microwaves in a cool environment.

Animals↗

PubMed1979

Effect of marihuana on cardiorespiratory responses to submaximal exercise.

Six male chronic marihuana (MH) users exercised on a bicycle ergometer for 15 min at approximately 50% VO2max under 3 conditions: (1) not smoking (control), (2) after smoking MH containing 7.5 mg (-) delta-9-tetrahydrocannabinol, and (3) after smoking placebo marihuana (PL). The MH was administered double-blind in a counterbalanced repeated-measures design. Heart rates (HRs), arterial blood pressures (BPs), pulmonary ventilation (VE), and oxygen uptake (VO2) were measured during exercise and 15 min recovery. PL had no effect on any of the physiologic variables. Smoking MH had no effect on systolic blood pressure (SBP), diastolic blood pressure (DBP), VE, or VO2, but did induce a marked increase in heart rate which persisted throughout exercise and recovery periods, averaging 34% higher than control values at rest, 18% higher during exercise, and up to 50% higher during recovery. MH smoking increased the product of HR x SBP in all circumstances.

Adult↗

PubMed2001

Analysis and visualization of single-trial event-related potentials.

In this study, a linear decomposition technique, independent component analysis (ICA), is applied to single-trial multichannel EEG data from event-related potential (ERP) experiments. Spatial filters derived by ICA blindly separate the input data into a sum of temporally independent and spatially fixed components arising from distinct or overlapping brain or extra-brain sources. Both the data and their decomposition are displayed using a new visualization tool, the "ERP image," that can clearly characterize single-trial variations in the amplitudes and latencies of evoked responses, particularly when sorted by a relevant behavioral or physiological variable. These tools were used to analyze data from a visual selective attention experiment on 28 control subjects plus 22 neurological patients whose EEG records were heavily contaminated with blink and other eye-movement artifacts. Results show that ICA can separate artifactual, stimulus-locked, response-locked, and non-event-related background EEG activities into separate components, a taxonomy not obtained from conventional signal averaging approaches. This method allows: (1) removal of pervasive artifacts of all types from single-trial EEG records, (2) identification and segregation of stimulus- and response-locked EEG components, (3) examination of differences in single-trial responses, and (4) separation of temporally distinct but spatially overlapping EEG oscillatory activities with distinct relationships to task events. The proposed methods also allow the interaction between ERPs and the ongoing EEG to be investigated directly. We studied the between-subject component stability of ICA decomposition of single-trial EEG epochs by clustering components with similar scalp maps and activation power spectra. Components accounting for blinks, eye movements, temporal muscle activity, event-related potentials, and event-modulated alpha activities were largely replicated across subjects. Applying ICA and ERP image visualization to the analysis of sets of single trials from event-related EEG (or MEG) experiments can increase the information available from ERP (or ERF) data.

Alpha Rhythm↗

PubMed2006

Interneurons targeting similar layers receive synaptic inputs with similar kinetics.

GABAergic interneurons play diverse and important roles in controlling neuronal network dynamics. They are characterized by an extreme heterogeneity morphologically, neurochemically, and physiologically, but a functionally relevant classification is still lacking. Present taxonomy is essentially based on their postsynaptic targets, but a physiological counterpart to this classification has not yet been determined. Using a quantitative analysis based on multidimensional clustering of morphological and physiological variables, we now demonstrate a strong correlation between the kinetics of glutamate and GABA miniature synaptic currents received by CA1 hippocampal interneurons and the laminar distribution of their axons: neurons that project to the same layer(s) receive synaptic inputs with similar kinetics distributions. In contrast, the kinetics distributions of GABAergic and glutamatergic synaptic events received by a given interneuron do not depend upon its somatic location or dendritic arborization. Although the mechanisms responsible for this unexpected observation are still unclear, our results suggest that interneurons may be programmed to receive synaptic currents with specific temporal dynamics depending on their targets and the local networks in which they operate.

Animals↗

PubMedDate not supplied

Acute toxicity studies of alpha-ketoglutarate: a promising antidote for cyanide poisoning.

Recently we have shown that cyanide poisoning by the oral (p.o.) route could be antagonized significantly by pretreatment or simultaneous treatment of alpha-ketoglutarate (alpha-KG), administered p.o. in rodents. The protective effect of alpha-KG was dose dependent (0.125-2.0 g kg(-1)) and the effect was significant at a dose above 1.0 g kg(-1). In order to establish the safety of alpha-KG, various haematological, biochemical and histological parameters were studied following p.o. administration of 2.0 g kg(-1)alpha-KG in female rats, and various physiological parameters were studied following p.o. administration of 2.0 or 4.0 g kg(-1)alpha-KG in anaesthetized male rats. The p.o. LD(50) of alpha-KG in male and female rats was >5.0 g kg(-1) and no toxic signs were observed in the surviving animals. Except for an increase in plasma alkaline phosphatase and urea levels after 1 h and a decrease in inorganic phosphorus levels after 7 days of treatment, no significant change in haematology, biochemistry or histology of the vital organs were observed. Mean arterial pressure and neuromuscular transmission were decreased at 4.0 g kg(-1)alpha-KG but other physiological variables such as heart rate, respiratory rate, rectal temperature, left ventricular pressure (systolic), arterial pressure (systolic) and arterial pressure (diastolic) were not altered. The changes observed at 4.0 g kg(-1)alpha-KG are unlikely to be of toxicological concern. The results indicate that alpha-KG at 2.0 g kg(-1) (p.o.)-a dose offering maximum antidotal efficacy-is non-toxic and therefore can be considered suitable for cyanide poisoning.

Administration, Oral↗

PubMedDate not supplied

The physical principles of Doppler and spectral analysis.

The Doppler effect provides an ultrasonic method for the detection of echoes from moving structures, particularly flowing blood. In its most simple form, the continuous wave Doppler offers velocity information without depth resolution and is therefore used mainly for the examination of superficial structures. The pulsed Doppler, in combination with real-time imaging, provides a more flexible tool for the interrogation of selected sites in an ultrasound image for motion and flow. The recent development of Doppler flow imaging, in which limited Doppler information is displayed over an entire ultrasound image, usually in color and in real-time, promises to secure the association between Doppler and conventional ultrasound imaging techniques. Spectral analysis permits features of the Doppler signal to be identified which are associated with hemodynamic phenomena, such as flow disturbance and wave reflection. In addition, it allows the quantitative application of Doppler to the estimation of such physiological variables as velocity, flow rate, and pressure difference.

Blood Flow Velocity↗

PubMed1982

Architecture of the hind limb muscles of cats: functional significance.

Force, velocity, and displacement properties of a muscle are determined in large part by its architectural design. The relative effect of muscle architecture on these physiological variables was studied by determining muscle weight, fiber length, average sarcomere length, and approximate angle of pinnation of 24 cat hind limb muscles. Muscle lengths ranged from 28.3 to 144 mm, whereas fiber lengths ranged from 8.4 to 105.5 mm. Generally, fiber to muscle length ratios were similar throughout a muscle. Estimated angles of pinnation of muscle fibers varied from 0 to 21 degrees with most having an angle of less than 10 degrees. The cross-sectional area of the knee extensors was similar to the knee flexors (16.43 vs. 16.83 cm2) whereas the cross-sectional area of the ankle extensors was more than six times greater than the ankle flexors (18.59 vs. 2.83 cm2). There was a 6.7-fold difference in the maximal force between muscles, when normalized to a constant weight, that could be attributed to architectural features. Ratios of wet weight to predicted maximal tetanic tension for each muscle and muscle group were calculated to compare the relative priority of muscle force versus muscle length-velocity for a given mass of muscle. These ratios varied from 0.4 to 4.84. The ratios suggest that velocity and/or displacement is a priority for the hamstrings, whereas force is a priority for the quadriceps and lower leg muscles. As much as a 12.6-fold difference in maximal velocity between muscles can be attributed to differences in fiber lengths. This can be compared to approximately a 2.5-fold difference in maximal velocity reported to occur as a result of biochemical (intrinsic) differences.

Animals↗

PubMed1985

Lymphatic transport of liposome-encapsulated agents: effects of liposome size following intraperitoneal administration.

Liposomal encapsulation can limit passage of a drug from a peritoneal administration site to blood, while enhancing lymphatic transport. We evaluated the effects of liposome size on lymphatic transport after intraperitoneal administration. Liposomes tested had mean diameters of either 0.72, 0.46, 0.17, or 0.048 micron and identical compositions. [14C]Sucrose was the aqueous space marker (model drug). Doses were given to thoracic-duct-cannulated rats. The subsequent 0-5 h time-course of carbon-14 was quantified in thoracic lymph, several lymph nodes, blood, and urine. Calibration studies indicated a maximum of approximately 30% of the absorbed dose could be collected in thoracic lymph. Carbon-14 levels in the various nodes covered a 1000-fold range, and relatively high levels were observed in the left mediastinal, parathymic, cisternal, and renal lymph nodes. Liposome stability in vivo and in vitro increased with decreasing size. Absorption from the peritoneal cavity was independent of size. The smallest liposomes were collected in lymph with little lymph node retention. The largest liposomes were retained most by lymph nodes, and would be the best prototypical carrier of the group if increased therapeutic availability within both lymph and lymph nodes is desired. The results implicate other, unexplored physical and physiological variables as potentially of equal importance.

Animals↗

PubMed2002

Neurodevelopmental care in the NICU.

Neurodevelopmental care, which is any NICU intervention undertaken to improve neurodevelopmental outcome, includes NICU design, nursing routines, nursing care plans, management of pain, feeding methods and, most importantly, encouraging parental involvement with their NICU infant. Recognition that sensory stimulation can overwhelm preterm infants and increase physiologic signs of stress led to attempts to reduce sensory input. More recent approaches judiciously add back soothing sensory input (e.g., therapeutic touch, soft music). Circadian light/dark cycles and physical activity improve preterm growth. Attention to infant positioning and handling affects physiologic variables and joint mobility, if not functional motor abilities. A highly organized system of care for NICU infants is Als' NIDCAP (i.e., Neonatal Individualized Developmental Care and Assessment Program). Although NIDCAP may reduce need for respiratory support and hospital length of stay, it does not significantly influence neurodevelopmental outcome at 2-3 years. Pain management includes benign interventions (e.g., nonnutritive sucking, oral glucose), but the prolonged use of narcotics must be balanced against the consequences of sedation and dependency. The foremost challenge for NICUs remains parent disenfranchisement. Kangaroo care, which involves parent/infant skin-to-skin contact, improves preterm growth, decreases nosocomial infections and may shorten hospital length of stay. A great deal of work needs to be done to identify and demonstrate efficacy of specific interventions and changes that humanize the NICU, encourage parental involvement, support infant development and optimize preterm neurodevelopmental outcomes.

Breast Feeding↗

PubMed1991

Measurement of the blood-brain barrier permeability and leakage space using dynamic MR imaging. 1. Fundamental concepts.

Leakage of Gd-DTPA through a defective blood-brain barrier is measured quantitatively using dynamic MRI scanning, in which repeated scans are made after a bolus injection. Image registration artifacts are minimized; a dose of 0.1 mM/kg and an IR sequence enable enhancement to be measured quantitatively. The triexponential enhancement curve is fitted to a theoretical model based on compartmental analysis. The transfer constant, or permeability surface area product per unit volume of tissue (k), and leakage space per unit volume of tissue (v1) are measured. Estimates for a quickly enhancing multiple sclerosis lesion are k = 0.050 min-1, v1 = 21%; for a slow one k = 0.013 min-1, v1 = 49%. This implies permeability in the range 4-17 x 10(-6) cm s-1, in broad agreement with other physiological methods. The method is noninvasive and can be used to make serial measurements in patients and in experimental animal models. The time course of pathological aspects of diseases with blood-brain barrier breakdown, such as multiple sclerosis, tumors, and infections (e.g., HIV) can be studied, along with their response to therapy. The measurements are of physiological variables and are therefore independent of imaging equipment and field.

Adult↗

PubMed1995

Regional comparison of tumor vascularity and permeability parameters measured by albumin-Gd-DTPA and Gd-DTPA.

Sequential albumin-Gd-DTPA and Gd-DTPA dynamic enhancement studies were performed in an animal tumor model for the comparison of regional vascularity and permeability parameters measured by these two different sizes of contrast agents. The early albumin-Gd-DTPA enhancement arises from the vascular compartment, and the averaged signal enhancement derived from the first 3 to first 6 images postinjection can be reliably used to assess vascularity. The signal intensity in the images during the period of 5-10 min post-albumin-Gd-DTPA injection shows a steady linear variation. The intercept of the linear relationship is another indicator of the vascularity and the slope represents the tumor permeability to albumin-Gd-DTPA. The Gd-DTPA enhancement study was analyzed by a two-compartmental pharmacokinetic model to calculate the regional vascularity and permeability. The permeability parameters measured from albumin-Gd-DTPA and Gd-DTPA show an excellent correlation. The vascularity parameters measured from albumin-Gd-DTPA show good linear correlation with the low vascularity groups measured by Gd-DTPA, but show saturation for the high vascularity groups. The enhancement mechanisms for both contrast agents are discussed to relate the imaging parameters to the physiological variables.

Albumins↗

PubMed1988

Self-management of hypertension: predictors of success in diastolic blood pressure reduction.

The purpose of this study was to determine which borderline hypertension subjects could succeed in self-regulating blood pressure, and to distinguish the psychologic and physiologic variables that predicted success. Thirty-four white, male, unmedicated, borderline hypertensive subjects participated in a 14-session biofeedback/cognitive self-management training program. Of these, 22 exited with diastolic pressure below 90 mm Hg; 12 exited equal to or above 90 mm Hg. Both groups exited with scores markedly lower on the Symptoms Checklist-90 (SCL-90). The successful group began and ended on all cognitive/affective subscales at a lower level than the unsuccessful group. A discriminant analysis revealed that lower scores on the SCL-90, lower systolic blood pressures, and higher heart rates during a mental task at the beginning of treatment distinguished those who succeeded in self-regulation from those who could not succeed. The possible mechanisms for blood pressure control/change as a consequence of biofeedback are discussed.

Adult↗