Baroreflex responses to the stress of severe hemorrhage in the rat.

In two groups of anesthetized (sodium pentobarbital), mature Sprague-Dawley rats, 1) aged 2 years and weighing 300-400 grams, 2) aged 6 months weighing 200-300 grams, baroreflex-induced circulatory responses to pressor (graded doses phenylephrine) and depressor (graded doses nitroglycerine) agents were compared to those occurring during progressive hemorrhage in the same animals. Graded withdrawals of blood from the femoral artery elicited progressive hypotension accompanied by bradycardia rather than expected tachycardia. Graded doses of phenylephrine (2.5 ug to 40 ug bolus, via femoral vein) regularly induced elevations in arterial blood pressure with associated reflex bradycardia. Similarly graded doses of nitroglycerine induced a marked decline in arterial blood pressure, without expected tachycardia. As hypotension became more severe (during hemorrhage), atrioventricular conduction slowed and A-V block developed, resulting in statistically greater slowing in ventricular than in atrial excitation and contractile cycles. Heart failure during hemorrhage in the rat is characterized sequentially by severe bradycardia, depressed atrial contractile force, impaired conduction and A-V block, terminating in ventricular, atrial, and finally, in pacemaker failure. Baroreceptor reflexes were blunted or even absent in both young and old animals during induced hypotension.     

Treatment of PAT

It has been suggested that the dive reflex (elicited by face immersion in water with breath-hold) may be employed to induce vagally-mediated bradycardia in individuals with paroxysmal atrial tachycardia. However, in several cases the use of this reflex is reported to have led to exacerbation of the cardiac dysfunction. Examination of heartrate and EKG T-wave amplitude changes during the dive in healthy, college-aged individuals indicated that warming the water (10° through 20° C to 40° C) decreased the bradycardia, but did not alter theattenuation (approximately 100 μv) of the T-wave. The latter effect was taken to indicate that sympathetic activity, as indexed by T-wave amplitude, was not reduced by increases in water temperature. On the other hand, a 90° head-up to head-down body tilt produced a bradycardia response of some 30 bpm as well as a T-wave amplitudeincrease (sympathetic withdrawal) in the order of 100 μv. These data suggest that individuals who exhibit symptoms of ventricular sympathetic irritability may be adversely affected by the dive maneuver, regardless of water temperature. The body-tilt induced reflex in such individuals may thus be more appropriate given the large-magnitude bradycardia and absence of T-wave attenuation. At the present, however, the body-tilt preparation has been used only with healthy normal subjects, so this suggestion remains to be directly tested.     

An animal analogue to systematic desensitization and elimination of avoidance

Rats first acquired a two-way avoidance response to a discrete warning signal (80 db white noise.) The effects of 3 experimental and 3 control treatments on elimination of the response were evaluated on a nonshock posttreatment extinction test. Group Systematic Desensitization (SD) received graded exposure to the warning signal while they were eating. Rats in Graded Hierarchy (GH) and Extinction (Ext) groups were yoked to Ss in the SD group such that GH and Ext treatment was identical with that of SD except that neither group ate and the Ext group was exposed to the full intensity warning signal (nongraded exposure) on all trials. None of the control groups was exposed to the warning signal between acquisition and the posttreatment test. Results indicated that SD, while interfering with avoidance during treatment, did not differ in effectiveness from control treatment and was significantly less effective than GH and Ext, when avoidance was tested in extinction. It was suggested that the present analogue SD technique impaired S's reception of (exposure to) the warning signal during treatment.     

Selective autonomic blockade of conditioned and unconditioned cardiovascular changes in rhesus monkeys (Macaca mulatta).

Changes in heart rate and in systolic and diastolic blood pressures were examined in eight rhesus monkeys during six sessions of differential classical conditioning. The conditioned stimuli consisted of tones differing in frequency and the unconditioned stimuli consisted of tail shock. Both the conditioned responses (CRS) and unconditioned responses (UCRs) consisted of increases in heart rate and in systolic and diastolic pressures, but blood pressure CRs sometimes occurred in the absence of heart rate CRs. Graded doses of the selective blocking agents propranolol, phentolamine, and atropine methylnitrate were systemically administered to four of the monkeys prior to additional conditioning sessions. The results suggested that the CRs and UCRs were mediated by both sympathetic and parasympathetic influences.     

The Heteroscedastic Graded Response Model with a Skewed Latent Trait: Testing Statistical and Substantive Hypotheses Related to Skewed Item Category Functions

The Graded Response Model (GRM; Samejima, Estimation of ability using a response pattern of graded scores, Psychometric Monograph No.?17, Richmond, VA: The Psychometric Society, 1969) can be derived by assuming a linear regression of a continuous variable, Z, on the trait, ??, to underlie the ordinal item scores (Takane & de Leeuw in Psychometrika, 52:393?C408, 1987). Traditionally, a normal distribution is specified for Z implying homoscedastic error variances and a normally distributed ??. In this paper, we present the Heteroscedastic GRM with Skewed Latent Trait, which extends the traditional GRM by incorporation of heteroscedastic error variances and a skew-normal latent trait. An appealing property of the extended GRM is that it includes the traditional GRM as a special case. This enables specific tests on the normality assumption of Z. We show how violations of normality in Z can lead to asymmetrical category response functions. The ability to test this normality assumption is beneficial from both a statistical and substantive perspective. In a simulation study, we show the viability of the model and investigate the specificity of the effects. We apply the model to a dataset on affect and a dataset on alexithymia.     

Blood flow,blood pressure and heart rate changes accompanying hind leg flexion in conditional and unconditional reflexes

Results

During flexion of the hind leg to US or CS, as well as during spontaneous lifting of the leg, the blood flow in the appropriate femoral artery suddenly increases for 10–14 seconds, systemic blood pressure shows transient decrease, while heart rate and respiratory movements are accelerated. To perform one flexion and subsequent extension about 7 ml extra blood flow is necessary during UR and 5 ml during CR. During acute extinction of the CR the described vegetative changes become less and less, parallel with the gradual decrease of flexor movement of the hind leg. The sequence of extinction of the individual measured parameters was as follows: flexion, blood pressure, blood flow, heart rate, and lastly, respiration. In the mechanism of the vegetative changes accompanying the conditional hind leg flexion three main components are involved: (1) muscular-visceral reflexes originating from different receptors of the contracting muscles, (2) the emotional changes, and (3) the conditional component as a separate conditional reflex for each measured parameter. Principles underlying the formation of conditional reflexes are discussed under the headings ofschizokinesis, peripheral andcentral stimulations.Organ responsibility is the basis for the formation of the conditional reflex.     

Successive-beat analysis of cardiovascular orienting and conditional responses

We have shown that prominent changes in heart rate (HR) and blood pressure (BP) occur in dogs during classical defensive conditioning. These changes are usually analyzed as average HR and BP during control periods versus averages during conditional stimulus (CS) and unconditional stimulus (US) periods. A new method has been developed for evaluation of these functions, viz., analysis across many trials of successive beats beginning at onset of CS and working backward (control period) and forward (CS period). Nine awake dogs were continuously studied: six with HR and intra-arterial BP measurements and three with HR measurements only. A drop in HR occurs 1 to 2 beats after CS onset (often noted as a “dropped” beat on individual trials). In some dogs, on the third to fifth beat HR reaches its maximum during the CS period, thereafter falling slightly, but still above baseline; other dogs show progressively increasing HR throughout the whole CS period. At US onset (foreleg shock) HR usually rises rapidly to a peak greater than that at CS maximum. BP follows HR changes fairly closely, diastolic better than systolic. These results indicate that I) this method can reveal transients previously unsuspected, 2) a prominent initial sudden bradycardia followed by tachycardia commonly occurs in conditioning in dogs, 3) the latent period of prominent HR increase is usually quite short (1.3 to 1.6 secs.), and 4) BP follows HR directly during the early part of the CS.     

Cardiovascular generalization and differentiation: The relationship between heart rate and blood pressure

The present study was designed to study generalization and differentiation and to check the relation between heart rate and blood pressure in cardiovascular conditioning. Five naive mongrel dogs were presented with 10 sec 1000 cps tone regularly reinforced with 0.5-sec shock to a left foreleg. Four other 10-sec tones (600, 800, 1200, 1400 cps), never reinforced, were administered in a randomized and counterbalanced fashion using a differential reinforcing technique. The response measures were heart rate and three indices of blood pressure,i.e., systolic, diastolic, and pulse pressures.“Initial response” of heart rate showed rapid tachycardia to all tones, with no generalization and differentiation among five tones.“Terminal response” clearly indicated generalization gradients that tachycardia to 800 and 1200 cps tones were higher than those to 600 and 1400 cps tones, respectively. Some differences were noted among systolic, diastolic, and pulse pressures, with pulse pressure showing a trend of generalization and differentiation in the“initial response.” No statistical difference, however, was obtained in blood pressure scores. Beat-by-beat analyses of correlations between heart rate and diastolic blood pressure showed that the correlations successively decreased during the“terminal response.” Overall correlations between heart rate and three indices of blood pressure were obtained, with the highest correlation between heart rate and pulse pressure. Considering the above results in relation to the classical conditioning theory, it was tentatively concluded that“initial response” includes non-conditional factors, while“terminal response” reflects mainly a true conditional response, particularly, at a long CS-US interval. This interpretation leads to the hypothesis that conditional response with a short CS-US interval may attain better conditioning scores in terms of the summation effect between a non-conditional factor and a true conditional factor.     

Brain mechanisms in fatal cardiac arrhythmia

Intravenous injection of histamine to rabbits was used as a prototype in an investigation of the mechanism of sudden death due to anaphylaxis and other causes. The “dive” reflex, bradycardia due to activation of the ophthalmic branch of the fifth cranial nerve, was induced in thirty-seven of the animals while they inhaled a very small amount of cigarette smoke. Associated with the resulting bradycadia were lowered blood pH and increased serum content of lactic acid and potassium and increased peripheral arterial constriction with elevation of diastolic blood pressure. Intravenous injection of 1 ml of histamine in the presence of the dive reflex induced potentially fatal ventricular arrhythmia, but no cardiac disturbance when administered while the dive reflex was inactive, thereby strongly suggesting that sudden death in anaphylaxis may involve an overzealous response to a normally protective neural reflex.     

Mental and physical stress as moderators of the postural response in insulin-dependent diabetic patients

Two simple stressors, mental arithmetic and isometric handgrip, were studied as moderators of the physiological response to standing in insulin-dependent diabetic patients and in healthy controls. Continuous (beat-to-beat) measures were taken of heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and skin conductance (SC) during postural change under baseline and stressor conditions. Diabetic patients without symptoms of neuropathy and healthy controls showed generally similar responses to postural change and to the stressor conditions. SBP and DBP were more responsive to the mental and physical stressors than were HR or SC, especially after standing. Two diabetic patients with postural hypotension showed significant increases in overall BP levels and less of a fall in BP during postural change under the stressor conditions, despite minimal HR or SC responses. Results indicate that these strategies are effective in increasing BP during postural change in both diabetic and nondiabetic individuals and may be useful in the management of orthostatic hypotension.     

Potentiation of the pressor response to stress by tolbutamide in dogs

Tolbutamide has previously been shown to amplify the pressor effects of “exogenous” catecholamines in conscious dogs, possibly due to sensitization of the α₁-adrenoreceptor-mediated vasoconstriction. The objective of this study was to examine if tolbutamide also amplifies the pressor effects of “endogenous” catecholamines released during psychological stress (classical Pavlovian aversive conditioning). Experiments were conducted in β-adrenoreceptor-blocked (propranolol, 1 mg/kg, i.v.) conscious dogs (n=4) trained in classical aversive conditioning. Conditioning was accomplished by following a tone (CS+) with a 1/2 second shock; another tone (CS-) was not followed by any shock and served as control. With saline pretreatment, aversive conditioning (i.e., CS+) increased mean arterial pressure (MAP) only by approximately 4.7% when compared to CS-, whereas with tolbutamide (45 mg/kg, i.v.) pretreatment, the increase in MAP induced by CS+ beyond what was induced by the CS- (approximately 6.2%) was significantly (p<0.05) larger than that with saline pretreatment. In isolated canine femoral arterial segments (n=4), the vasoconstrictor effect of phenylephrine (an α₁-agonist) at 5×10^?6M (which was the EC₅₀ value) was amplified by 2×10^?2M of tolbutamide from 54.0±2.0% to 66.9±2.1%. In conclusion, tolbutamide amplifies the pressor effects of “endogenous” catecholamines in conscious dogs, possibly by sensitization of the α₁-adrenoreceptor-mediated vasoconstriction. This mechanism of action is novel and has not been reported with other agents.     

A mechanical method for changing heart rate and blood pressure

The investigation of afferent cardiovascular influences upon central nervous processes needs a methodology which allows for independent and systematic manipulation of circulatory processes. By mechanical manipulation of posture (tilt table, orthostasis) and compression of lower body parts (by anti-G-suit) reliable changes in heart rate and blood pressure can be induced. In fourty subjects (study 1) it could be shown that sustained (30 min.) changes in heart rate (e.g. orthostatic tachycardia, decrease of heart rate during compression) and mean arterial blood pressure (increase during orthostasis with and without compression) occur. Although changes in heart rate could be achieved irregardless of whether the venous "pooling" was suppressed by an air- or water-filled pressure suit, the pressor effect did differ quite considerably. In fourty-four subjects (study 2) it could be demonstrated that only by means of an water-filled suit further increases in mean arterial blood pressure could be evoked during orthostasis. Changes in hemodynamic also lead to changes in sympatho-vagal control of cardiac activity. In study 3 (ten subjects) it could be shown, that orthostasis mainly evokes alterations in sympathetic activity whereas lower body compression leads to additional increases of vagal activity and respiratory sinus arrhythmia during orthostasis.     

Failure to develop a conditional reflex by stimulation of the cephalad portion of the severed vagosympathetic trunk: Its significance in terms of the central connections of the vagus

Stimulation of the central stump of either vagosympathetic trunk in the dog, the contralateral nerve remaining intact, regularly provoked deep respiratory movements with forceful expiration, followed by a period of apnea, and a fall in blood pressure, systolic and diastolic, of 20–60 mm/Hg. Stimulation of the cephalad portion of the left nerve provoked brief acceleration of heart rate during the period of hyperventilation, followed by bradycardia; when the stimulus was applied to the central stump of the right nerve heart rate remained relatively unchanged. When a 12-second tone as a conditional stimulus (CS) was reinforced during its last six seconds with such stimulation of the vagosympathetic trunk as an unconditional stimulus (US), despite the striking visceromotor responses elicited by the US, no conditional reflex was established even after more than 3,400 trials in 16 dogs (34–781 trials per animal).     

Phenomenological reports diagnose accuracy of eyewitness identification decisions

This study investigated whether measuring the phenomenology of eyewitness identification decisions aids evaluation of their accuracy. Witnesses (N = 502) viewed a simulated crime and attempted to identify two targets from lineups. A divided attention manipulation during encoding reduced the rate of remember (R) correct identifications, but not the rates of R foil identifications or know (K) judgments in the absence of recollection (i.e., K/[1 − R]). Both RK judgments and recollection ratings (a novel measure of graded recollection) distinguished correct from incorrect positive identifications. However, only recollection ratings improved accuracy evaluation after identification confidence was taken into account. These results provide evidence that RK judgments for identification decisions function in a similar way as for recognition decisions; are consistent with the notion of graded recollection; and indicate that measures of phenomenology can enhance the evaluation of identification accuracy.     

On no man’s land: Subjective experiences during unresponsive and responsive sedative states induced by four different anesthetic agents

To understand how anesthetics with different molecular mechanisms affect consciousness, we explored subjective experiences recalled after responsive and unresponsive sedation induced with equisedative doses of dexmedetomidine, propofol, sevoflurane, and S-ketamine in healthy male participants (N = 140). The anesthetics were administered in experimental setting using target-controlled infusion or vapouriser for one hour. Interviews conducted after anesthetic administration revealed that 46.9% (n = 46) of arousable participants (n = 98) reported experiences, most frequently dreaming or memory incorporation of the setting. Participants receiving dexmedetomidine reported experiences most often while S-ketamine induced the most multimodal experiences. Responsiveness at the end of anesthetic administration did not affect the prevalence or content of reported experiences. These results demonstrate that subjective experiences during responsive and unresponsive sedation are common and anesthetic agents with different molecular mechanisms of action may have different effects on the prevalence and complexity of the experiences, albeit in the present sample the differences between drugs were minute.     

Isatin: role in stress and anxiety

(Indoledione 2,3) isatin is an endogenous indole found both in mammalian brain and peripheral tissues. Isatin concentration in blood can exceed 1 microM and tissue concentrations vary from < 0.1 to 10 microM. Its level in the brain and periphery is increased by stress. Isatin has a wide spectrum of behavioural and metabolic effects. It is anxiogenic at lower doses and sedative at higher doses. Its most potent known in vitro actions are as an antagonist of atrial natriuretic peptide (ANP) function and NO signaling. In this review, we discuss isatin and stress in animal models, the few human studies, and also what it is known to date about the molecular mechanisms of its action. We suggest the possibility that isatin and its analogues may be interesting new pharmacological agents; Isatin antagonists may be anxiolytic, and isatin agonists may activate the HPA axis.     

Regulation of exercise intensity using ratings of perceived exertion during passive visual distraction

The purpose of this investigation was to determine if passive visual distraction altered ability to regulate exercise intensity as, assessed by ratings of perceived exertion during a 30-min. treadmill run. 10 trained females (VO2max, 52.7 ml.kg-1.min.-1) performed a graded exercise test on a treadmill to assess maximal aerobic power and rating of perceived exertion, oxygen uptake (VO2), heart rate, and running velocity at the 2.5 mmol.L-1 blood lactate concentration. Subjects then used the target rating of perceived exertion to regulate exercise intensity during a control condition, and two treatment runs with passive visual distractions. During the treatment sessions, the subjects ran on a treadmill while viewing a high-action or a low-action video with no audio. The subjects were allowed to adjust the treadmill speed throughout the run to maintain the target rating of perceived exertion; however, subjects were not allowed to view the speed setting. There were no significant differences in blood lactate concentration among the conditions for the control, low action, high action, or graded exercise test (p < or = .05). No significant differences in VO2 or running velocity were found within or among the 30-min. treatment runs and the graded exercise test. Heart rate at 5 min. of exercise during control (158 +/- 3 b.min.-1), low action (158 +/- 3 b.min.-1), and high action (159 +/- 2 b.min.-1) was significantly lower than the graded exercise test (169 +/- 3 b.min.-1). Based on the data collected, visual passive distraction did not alter regulation of intensity using ratings of perceived exertion during a 30-min. treadmill run.     

IABP在心脏直视手术围术期低心排的应用

为了探讨主动脉内球囊反搏（IABP）治疗心脏手术围术期低心输出量综合征（LCOS）的临床疗效,对16例心脏手术围术期LCOS患者,经过股动脉放置IABP导管于降主动脉内进行左心辅助治疗,IABP治疗前、后监测患者连续有创动脉收缩压（SABP）、有创平均动脉压（MABP）、中心静脉压（CVP）、动脉血氧分压（PaO2）、心率（HR）、尿量和血管活性药物的使用。结果显示,IABP辅助治疗时间25h～116h,平均（78．5±40．5）h。行IABP治疗后,SABP、MABP、PaO2较术前明显提高（P〈0．05）,HR、CVP明显下降（P〈0．05）,尿量增加,血管活性药物使用量明显减少（P〈0．05）,12例患者心功能好转而脱离IABP,11例（69．3％）存活,4例死于心源性休克,1例死于多器官功能不全综合征（MODS）。提示正确及时地使用IABP能明显改善心脏手术围术期LCOS患者的血流动力学指标,减少血管活性药物的使用,建议对有适应证者应尽早应用,适时撤离。     

Physiological responses in blood phobics

Eighteen patients with blood phobia were shown a film of thoracic operations containing large amounts of blood. Their heart rate (HR) and blood pressure (BP) were measured continuously before, during and after the watching of the film. The group data showed a diphasic response; an increase in HR and BP from baseline to the beginning of the film, and then a sharp drop in these parameters with the lowest values 4 min after the film was turned off. Individual data from 5 patients who fainted or were on the edge of doing so, showed massive bradycardia or drop in BP or both. In all of these patients at least one (range 1–33) 5-sec period of asystole was recorded. Possible theoretical explanations for this characteristic response pattern are discussed.     

Continuous dynamics in the real-time perception of race

Although the outcomes of race categorization have been studied in detail, the temporal dynamics of real-time processing of race remain elusive. We measured participants’ hand movements en route to one of two race-category alternatives by recording the streaming x, y coordinates of the computer mouse. Study 1 showed that, when categorizing White and Black computer-generated faces that featurally overlapped with the opposite race, mouse trajectories showed a continuous spatial attraction toward the opposite category. Moreover, these race-atypical White and Black targets induced spatial attraction effects that had different temporal signatures. Study 2 showed that, when categorizing real faces that varied along a continuum of racial ambiguity, graded increases in ambiguity led to corresponding increases in trajectories’ attraction to the opposite category and trajectories’ movement complexity. These studies provide evidence for temporally dynamic competition across perceptions of race, where simultaneously and partially-active race categories continuously evolve into single categorical outcomes over time. Moreover, the findings show how different social category cues may exert different dynamic patterns of influence over the real-time processing that culminates in categorizations of others.