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PubMed1975

Interface unit for on-line measurements of motor unit properties with a small laboratory computer.

Some simple circuitry is described which has been successfully used in conjunction with a small laboratory computer for "on-line" measurements of the force of contraction of single motor units in cat gastrocnemius and soleus muscles. Our approach emphasizes use of a sample and hold device to allow high amplification of small forces developed during single motor unit contractions which are often superimposed on relatively large whole muscle passive forces. Two digitally controlled selectable gain amplifiers are used to ensure proper modulation of the computer's ADC and to enable automatic scaling of the measured variables. An analog peak detector is incorporated into the unit such that peak force measurements can be made with the minimum of computer software. The principles governing the present design are directly applicable to the measurement of intracellularly recorded postsynaptic potentials and a variety of other physiological variables which require accurate measurement of a small transient signal superimposed on a large "control" or "resting" signal.

Animals↗

PubMed1976

Identification of an apprehension effect on physiological indices of thermal strain.

A laboratory assessment of the thermal strain produced by wearing a protective clothing assembly, in addition to a normal flying clothing assembly, in a hot environment is described. In addition to the demonstration of an increase in thermal strain when wearing the protective clothing, two points of importance emerged. First, condition replication revealed a significant apprehension effect which confounded the physiological variables used to evaluate the thermal strain, leading to an over-estimation of the severity of that strain. Second, there was a large between-subject variation amongst the eight subjects used, which made the arithmetic mean a potentially misleading statistic for evaluating the increased physiological strain caused by the additional clothing assembly during the heat exposure. The practical implications of these observations are discussed....

Adult↗

PubMed2005

Dysfunctional baroreflex regulation of sympathetic nerve activity in remitted patients with panic disorder. A new methodological approach.

BACKGROUND: Many researchers have studied the abnormalities of autonomic nervous system (ANS) such as decreased heart rate variability, which is a risk factor for sudden cardiac death, in patients with panic disorder (PD). However, no consistent abnormality has been uncovered to date. One of the reasons for this controversy may be due to the fact that most of these conventional studies have analyzed each physiological variable independent of other indices. We examined the ANS in PD patients using a new method which can more directly investigate the function of the baroreflex by examining the relation between the blood pressure (BP) and heart rate (HR). METHODS: During rest and audiovisual stimulation (AS) as mental stress such as being exposed to video imaginary of experiences such as driving motor vehicles, cardiovascular parameters, HR and BP were consecutively measured in 13 remitted PD patients and twenty aged and gender-matched normal controls (NC). In this study, to assess the cardiovascular ANS function (baroreflex) in PD we used the power spectrum analysis as usual and the mean of lag time (tau) between the Mayer wave components, which was closely related to sympathetic nerve activity of vasomotor, of HR and BP variability as a new trial. RESULTS: The PD patients and NC did not differ with regard to the power spectrum analysis of the heart rate. We found that tau in the PD group was significantly shorter than that in the NC both before and after AS, especially before. CONCLUSIONS: These findings suggest that remitted PD patients may have a dysfunctional baroreflex regulation of sympathetic nerve activity.

Acoustic Stimulation↗

PubMed2004

Modeling epithelial cell homeostasis: assessing recovery and control mechanisms.

Critical to epithelial cell viability is prompt and direct recovery, following a perturbation of cellular conditions. Although a number of transporters are known to be activated by changes in cell volume, cell pH, or cell membrane potential, their importance to cellular homeostasis has been difficult to establish. Moreover, the coordination among such regulated transporters to enhance recovery has received no attention in mathematical models of cellular function. In this paper, a previously developed model of proximal tubule (Weinstein, 1992, Am. J. Physiol. 263, F784-F798), has been approximated by its linearization about a reference condition. This yields a system of differential equations and auxiliary linear equations, which estimate cell volume and composition and transcellular fluxes in response to changes in bath conditions or membrane transport coefficients. Using the singular value decomposition, this system is reduced to a linear dynamical system, which is stable and reproduces the full model behavior in a useful neighborhood of the reference. Cost functions on trajectories formulated in the model variables (e.g., time for cell volume recovery) are translated into cost functions for the dynamical system. When the model is extended by the inclusion of linear dependence of membrane transport coefficients on model variables, the impact of each such controller on the recovery cost can be estimated with the solution of a Lyapunov matrix equation. Alternatively, solution of an algebraic Riccati equation provides the ensemble of controllers that constitute optimal state feedback for the dynamical system. When translated back into the physiological variables, the optimal controller contains some expected components, as well as unanticipated controllers of uncertain significance. This approach provides a means of relating cellular homeostasis to optimization of a dynamical system.

Biological Transport↗

PubMed1999

Partial CO2 rebreathing cardiac output--operating principles of the NICO system.

The partial rebreathing method of cardiac output estimation is reviewed with a particular focus on its application for continuous monitoring, rebreathing and implementations and from both a historical and technical perspective. The assumptions of the method are discussed as well as the various implementations. The NICO monitor and rebreathing valve are described from a functional view. The clinical data including (a) comparisons between bolus thermodilution and continuous thermodilution in patients in the OR setting, (b) comparisons to continuous thermodilution with both the Baxter and Abbott continuous cardiac output devices and (c) comparison between different means of shunt correction are presented. Compared to conventional cardiac output methods, the partial CO2 rebreathing technique is non-invasive, can easily be automated and can provide real-time and continuous cardiac output monitoring. Taking advantage of modern sophisticated sensor and signal processing technology and integrating multiple monitored physiological variables the NICO monitor is the first commercially available cardiac output system making use of the partial rebreathing of CO2.

Carbon Dioxide↗

PubMed2003

Ratings of perceived exertion throughout an ultramarathon during carbohydrate ingestion.

Ratings of perceived exertion (RPE) and their relation to selected physiological mediators during endurance exercise have been limited to laboratory settings. The present study characterized the pattern of change in perceptual responses and examined the relation between RPE and selected physiological variables during a long competitive sporting event, i.e., an ultramarathon race (68 km). A single-group design was employed in which all of the 28 subjects provided their perceptual ratings 11.9 +/- 0.2) and heart rate (HR) (138 +/- 3) periodically (every 5 km) throughout the ultramarathon, and selected physiological responses were measured before, once during (32 km), and immediately after the race. Runners drank approximately 1,000 ml of carbohydrate beverage each hour (60 gm carbohydrate hr.(-1)) and ate 2 or 3 carbohydrate gel packs per hour (25 gm each(-1)). RPE increased significantly throughout the course of the ultramarathon. No significant correlations were found between RPE and HR at any time throughout the ultramarathon. RPE averaged 10.4 +/- 0.4 at the beginning of the race (6.4 km) and 15.4 +/- 0.4 at the conclusion of the race. Subjects maintained 76.9 +/- 1.1% of maximal heart rate; however, there was a tendency for heart rate to drop significantly after 32 km. Significant time main effects were found for serum glucose, insulin, and cortisol throughout the race. However, no significant correlations were found between RPE and any of these physiological mediators. These data indicate that during an ultramarathon race there is a progressive increase in RPE without an accompanying increase in HR or decrease in blood glucose. Therefore, during competitive self-paced exercise the perceptual responses may be mediated through other neurological and physiological mechanisms.

Adult↗

PubMed1994

Care of the adult with cyanotic congenital heart disease.

In adults with cyanotic congenital heart disease (CHD), medical considerations apply to nonsurgical survivors and to postsurgical patients. The special needs of these groups present a unique challenge for the adult care practitioner. Clinical management revolves around the physiologic consequences of a right-to-left shunt. The care of the cyanotic CHD patient must encompass not only the physiologic variables that set these patients apart from the "typical" adult with acquired cardiovascular disease but also the lifelong psychosocial impact of their congenital heart program.

Adaptation, Physiological↗

PubMed1983

Biofeedback: a possible substitute for smoking, experiment I.

Biofeedback techniques were utilized in this study to identify those physiological variables which possibly contribute to maintenance of cigarette smoking and to investigate the hypothesis that smoking frequency would decrease when individuals were trained via biofeedback procedures to increase 8-12 Hz occipital EEG activity as a substitute for smoking. Results of the study indicate that of the six smokers physiologically monitored, the following physiological changes occurred while actually smoking one cigarette: four smokers increased the percent of time they were producing 4-8 cycle per second (Hz) brain waves; five smokers increased their heart rate (beats per minute); all six smokers decreased their 8-12 Hz activity. Immediately after the smoking of one cigarette, six of the smokers demonstrated an increase in their heart rate and four of the smokers demonstrated a decrease in their skin temperature. There did not appear to be any specific consistent brain wave change across the subjects. Two smokers, who were able to continue producing high levels of 8-12 Hz activity without use of the biofeedback equipment, were able to quit completely at the end of an eight-month followup period.

Alpha Rhythm↗

PubMed1996

Detection of intraoperative incidents by electronic scanning of computerized anesthesia records. Comparison with voluntary reporting.

BACKGROUND: The use of a computerized anesthesia information management system provides an opportunity to scan case records electronically for deviations from specific limits for physiologic variables. Anesthesia department policy may define such deviations as intraoperative incidents and may require anesthesiologists to report their occurrence. The actual incidence of such events is not known. Neither is the level of compliance with voluntary reporting. METHODS: Using automated anesthesia record-keeping with long-term storage, physiologic data were recorded every 15 s from 5,454 patients undergoing noncardiothoracic surgery. Recorded measurements of blood pressure, heart rate, arterial oxygen saturation, and temperature were electronically analyzed for deviations from defined limits. The computer system also was used by anesthesiologists to report voluntarily those deviations as intraoperative incidents. For each electronically detected incident: 1) the complete automated anesthesia record was examined by two senior anesthesiologists who, by consensus, eliminated case records with artifact or in which context suggested that the incident was not clinically relevant, and 2) the anesthesia information management system database was checked for voluntary reporting. RESULTS: In 473 automated anesthesia records, 494 incidents were found by electronic scanning of 5,454 automated anesthesia records. Sixty intraoperative incidents were eliminated, 25 due to artifact and 35 due to context. When the remaining 434 intraoperative incidents were checked for voluntary reporting, 18 (4.1%) matching voluntary reports were found. All intraoperative incidents that were reported voluntarily also were detected by electronic scanning. Based on a 10% sample, the sensitivity rate of electronic scanning was 97.2% (35/36), and the specificity rate was 98.4% (427/434). Among 413 cases with electronically detected intraoperative incidents, there were 29 deaths (7.0%), whereas there were only 79 deaths (1.6%) among 5,041 cases without incidents (chi 2 = 58.5, P < 0.001). CONCLUSIONS: The use of an anesthesia information management system facilitated analysis of intraoperative physiologic data and identified certain intraoperative incidents with high sensitivity and specificity. A low level of compliance with voluntary reporting of defined intraoperative incidents was found for all anesthesiologists studied. Finally, there was a strong association between intraoperative incidents and in-hospital mortality.

Anesthesiology↗

PubMed1989

Con: regional anesthesia is not preferable to general anesthesia for the patient with heart disease.

The debate over regional anesthesia and general anesthesia with respect to relative risk in different classes of patients will probably be interminable until studies addressing the issue begin to specify the treatment protocols more carefully and to control as many variables as possible. Patients with cardiovascular disease who undergo major surgery are special cases in which either form of anesthesia may be acceptable or preferable. The benefits of lesser regional procedures do not necessarily extend to major conduction blockade in these individuals. Appropriate monitoring and goal-directed control of physiologic variables throughout the entire perioperative period may be more important than the type of anesthesia. General anesthesia that is carefully prepared, monitored, and conducted cannot be ruled out in the seriously ill.

Anesthesia, Conduction↗

PubMedDate not supplied

[Genetic factors in the onset of schizophrenia].

The importance of inheritance in the development of schizophrenia was recorded in classic papers by Kraepelin and Bleuler. These observations have been confirmed by the contemporary research. In this paper, we summarize the results of genetic-epidemiological studies that include family, twin and adoption studies, as well as the results of segregation analysis and molecular-genetic research. Family studies indicate increased morbidity risk in the relatives of patients with schizophrenia, that augments with the degree of relation. Twin studies also suggest the importance of genetic factors demonstrating higher rates of concordance for the disorder in monozygotic (MZ) than in dizygotic (DZ) twins and consistent MZ/DZ ratios across the studies. Adoption studies provide further evidence for genetic vulnerability, showing an association between biological relatives separated at birth. The concept of "schizophrenia spectrum" is based on the observation of the familial aggregation of several hierarchically defined disorders in relatives of schizophrenic probands. Schizophrenia, schizoaffective disorder, schizotypal and paranoid personality disorder, other nonaffective psychoses and psychotic affective disease, according to this concept, represent manifestations of varying severity, of the same underlying vulnerability, which is transmitted within families. The results of segregation analyses support rather polygenic than monogenic inheritance, if schizophrenia is genetically homogeneous. However, the possibility of genetic heterogeneity augments the interest for searching for vulnerability genes with linkage. The results of linkage studies, indicating association between schizophrenia and markers on chromosomes 5, 6, 8 and 22, have not yet been replicated on independent samples of probands. Recent findings indicate that schizophrenia may be caused by unstable DNA (the expansion of trinucleotide repeated sequences at the disease locus). This could explain the departure from Mendelian inheritance, highly variable phenotype and wide ranging age of onset in schizophrenia. Further research in this field could not only clarify the mode of the transmission of the liability for schizophrenia and the relationship of genetic and environmental factors in the development of the disorder, but also determine which characteristics, behavior and physiological variables schizophrenia genes code for. This would, in addition, contribute to our understanding of the biological basis of schizophrenia.

Humans↗

PubMed2006

Low hematocrit worsens cerebral injury after prolonged hypothermic circulatory arrest in rats.

PURPOSE: This study tests the hypothesis that low hematocrit (Hct) worsens cerebral injury after prolonged hypothermic circulatory arrest (HCA) in rats, and the mechanism involves variable expression of the genes C-Fos, Bcl-2 and Bax. METHODS: A rat HCA model was developed, and 40 animals were randomly assigned to four groups: Sham (sham) group, or Hct groups of Hct 10%, Hct 20% and Hct 30%. After 90 min of HCA at 18 degrees C, physiologic variables were recorded and brain morphological changes were evaluated with light and electron microscopy. Expressions of C-Fos, Bcl-2, Bax in various brain areas were measured by the reverse transcriptase polymerase chain reaction and standard immunohistochemistry techniques. RESULTS: The number of injured neurons in the hippocampus CA1 and parietal cortex in the Hct 10% group (CA1: 11.44 +/- 2.52; cortex: 13.65 +/- 2.31) exceeded the mean number of injured neurons in the Hct 20% group (CA1: 8.29 +/- 1.31; cortex: 10.68 +/- 1.24; P < 0.05) and the Hct 30% group. Mean mitochondrial injury scores were greatest at lower Hct levels, while the expression of C-Fos and Bax were highest in the Hct 10% group and lowest in the Hct30% group (P < 0.05). In contrast, the expression of the Bcl-2 mRNA was greatest in the Hct 30% group (P < 0.05). CONCLUSION: Low Hct worsens cerebral injury after prolonged HCA and CPB in rats, which may relate in part to the variable expression of the genes C-Fos, Bcl-2 and Bax.

Animals↗

PubMed1991

Smoking effect on exercise response kinetics of oxygen uptake and related variables.

The effects of smoking on the kinetics of oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (Ve) and heart rate (HR) in the transition from rest to steady-state submaximal exercise was investigated in 6 female and 4 male smokers (32 +/- 8 yrs). The subjects underwent two counter-balanced treadmill tests at 60% of their maximal VO2, lasting 10 min each: one following a 24-hr smoking abstinence, and one immediately after smoking three cigarettes without prior abstinence. Physiological variables were measured at rest and every 30 sec throughout each test. The time required for a given variable to rise from its respective resting baseline to half of its steady-state value (t1/2) was calculated for VO2, VCO2, Ve and HR. Smoking abstinence was associated with t1/2 values of 32 +/- 8, 42 +/- 12, 43 +/- 10, and 30 +/- 9 sec for VO2, VCO2, Ve, and HR, respectively. Smoking significantly (p less than 0.01) lengthened those values to 51 +/- 12, 58 +/- 11, 54 +/- 8, and 41 +/- 10 sec. Concurrently, smoking raised the baseline (resting) values of HR (p less than 0.01) and of Ve, VCO2, O2 pulse (O2P), and both systolic and diastolic blood pressures (p less than 0.05). During steady-state exercise only HR values were elevated by smoking (p less than 0.01), while O2P values were lowered (p less than 0.05). These findings indicate that smoking considerably retards physiological responses to submaximal exercise.

Adult↗

PubMed1993

The physiological stress response and the role of cognitive coping in migraine patients and non-headache controls.

Our study investigated physiological response specificity and cognitive coping in migrainous patients during an achievement task situation. Thirty-three migrainous subjects and thirty-two non-headache controls were subjected to 40 min of demanding cognitive tasks and 20 min of recovery during which cranial and peripheral vasomotor responses were registered as well as electrodermal and myographic activity. Subjects of both groups were randomly assigned to two experimental conditions, a so-called 'spontaneous processing condition' and the 'positive coping treatment'. In this treatment condition subjects received a short training in the conscious use of positive self-statements in stress situations. Though a specific pattern of cranial vasomotor responses in migraine subjects could be verified by group statistics, this pattern was only found in very few individuals. Reliable differences between groups could not be identified in other physiological variables either. The hypothesis that the predicted cranial vasomotor specificity in migraine subjects correlates with negative cognitive coping habits in migraine subjects best revealed in the 'spontaneous processing' condition, was not corroborated. The treatment variation regarding coping produced somewhat paradoxical effects, more relaxed and positive self-evaluation (subjective level) and more arousal (physiological level). Results are discussed for their impact on the psycho-biological model of migraine.

Adaptation, Psychological↗

PubMed2000

Predicting success in junior elite basketball players--the contribution of anthropometic and physiological attributes.

Talent identification programs have traditionally focused on individual sports with discrete physical and physiological characteristics. Limited attention has been directed toward predicting performance in team sports. This study measured anthropometric and physiological attributes of 125 male and 123 female junior basketball players competing at the Australian Under 16 championships in 1998. In addition, experienced coaches rated the performance of players during the championships. Performance profiles were compared across playing positions and by playing performance ('Best versus Rest'). Differences in anthropometric characteristics were present across some playing positions for both males and females. Speed and agility differences between some playing positions were also present. Best players differed to Rest players on a number of anthropometric and physiological variables for both males and females. Regression analyses indicated the test variables accounted for a significant proportion of variance in playing performance for both females (41.3%) and males (38.3%). A Z score analysis indicated good alignment between the test and coach ranking of the Best player in four out of five positions for females and two out of five positions for males. Anthropometric and physiological profiling can contribute to selection procedures in junior basketball, however determinants of success are multi-factorial.

Adolescent↗

PubMed1998

The management of postsurgical pain in the elderly population.

It is likely that the trend towards ever more aggressive surgery in elderly and possibly frail patients will continue, with the lifting of traditional age limits. Recent evidence has show that surgical trauma induces processes of nervous system sensitisation that contributes to and enhances postoperative pain and leads to chronic pain. This knowledge provides a rational basis for pro-active, pre-operative and post-operative analgesic strategies which can reduce the neuronal barrage associated with tissue damage. As well as a reduction or elimination of post-operative pain, an improvement in physiological variables, such as neuroendocrine stress responses and post-operative pulmonary function can be expected. Complete pain control cannot be achieved with a single agent or technique without significant serious adverse effects, a problem which is compounded in the elderly patient due to a combination of slower drug metabolism, decreased organ function and physiological changes in cardiovascular and respiratory reserves. A balanced analgesic regimen that includes an effective afferent block (regional analgesia) is more appropriate. By preventing postoperative pain and its associated neuroendocrine sequelae, major surgical procedures in traditionally unsuitable patients can be seriously considered.

Aged↗

PubMed1992

The physiologic mechanisms of variable decelerations.

OBJECTIVES: The purpose of this study was to determine the cause and physiologic consequences of variable decelerations. STUDY DESIGN: Previous studies of heart rate changes in human and experimental animals were critically reviewed with respect to the autonomic nervous system component, the cause of the increased vagal activity, and the role of cord compression or other stimuli in these heart rate changes. RESULTS: There is abundant evidence from experimental and human studies that variable decelerations can be reproduced by either cord compression or head compression. The vagal reflex produced is probably caused by a combination of chemoreflex (earlier in the deceleration) and baroreflex (later). The variable deceleration is accompanied by an acidosis, primarily respiratory, and probably hypoxemia. Cord compression results in decreased umbilical blood flow. CONCLUSIONS: Recent Doppler velocimetry studies suggest that even though the variable decelerations may be similar in duration and depth, the reduction of umbilical blood flow may be greater when the prime cause is cord compression than when the prime cause is vagal reflex from another source.

Amniotic Fluid↗

PubMed1981

The relationship of physiological responses to the coronary-prone behavior pattern in children.

Forty-one male and female children were tested for Type A (coronary-prone) behavior using the Bortner test and the MYTH questionnaire. Based on their classification as A or B, three physiological variables were compared: systolic blood pressure (SBP), heart rate (HR) (phasic, tonic, and variability), and skin conductance (SC) (magnitude and latency of responses, number of spontaneous responses) during a 3-min rest period, a 10-min unsignaled reaction time (RT), and a 10-min word task. When using the Bortner to classify groups, Type As showed a tendency toward higher SBP levels and greater SBP reactivity to tasks, and significantly greater HR levels, HR reactivity to tasks, HR variability during rest, and SCR magnitude to RT signals. When using the MYTH, Type A females showed larger increases in SBP and HR to tasks, a lower mean HR, and a faster RT. Type A males showed a higher mean HR. Thus, children classified as Type A resemble Type A adults when compared on physiological responses to stress; however, the results depend on the method used to determine Type A behavior.

Blood Pressure↗