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PubMed1988

Facilitating effect of cold shock on recovery from anoxia-induced contractile depression in isolated rat heart and heart muscle.

The effect of rapid cooling on the recovery process from anoxia-induced hypodynamic state was studied in isolated rat ventricular muscle and ventricle. Following 10-15 minutes' perfusion of N2-saturated Krebs solution, the muscle was reoxygenated. When the muscle was rapidly cooled for 10-30 seconds during the early phase of reoxygenation, the rate of recovery from contracture significantly increased (p less than 0.01). Rapid cooling was also effective on the recovery from contracture induced by superfusion of Krebs solution with lowered sodium chloride concentration, but it did not affect the recovery from rigor induced by CN-. In the recovery from sustained anoxia (60 minutes), cooling facilitated reattainment of tension development and reduction in contracture tension. Similarly, in whole heart, 2-3 episodes of rapid cooling for about 60 seconds significantly accelerated the recovery of pressure development after 30 minutes of anoxia. At 60 minutes after reoxygenation, pressure development in hearts that were reoxygenated without rapid cooling was 29.8 +/- 26.9% (mean +/- SD) of pressure developed before anoxia. This value increased to 93.8 +/- 27.5% following recurrent rapid cooling (p less than 0.001). At the same time, rapid cooling prevented any significant elevation in resting tension (development of oxygen paradox). These results indicate that excess intracellular calcium ions were removed by rapid cooling. This relief of the myocardium from calcium overload is believed to improve mitochondrial function and result in facilitated recovery of contractile activity.

Adenosine Triphosphate↗

PubMed1989

Estimating cardiac transmembrane activation and recovery times from unipolar and bipolar extracellular electrograms: a simulation study.

A model of one-dimensional action potential propagation was used to compare activation times and recovery times measured from simulated unipolar and bipolar electrograms with the activation and recovery times measured from simulated transmembrane action potentials. Theory predicts that the intrinsic deflection--the time of the maximum negative slope of the unipolar electrogram QRS complex--corresponds to the time of maximum positive slope of action potential depolarization. Similarly, the time of the maximum positive slope of the unipolar electrogram T wave corresponds to the time of maximum negative slope of action potential repolarization. This study showed that the difference between the unipolar electrogram activation time and the action potential activation time and the difference between the unipolar electrogram recovery time and the action potential recovery time were small during ideal conditions of uniform propagation in a long cable. Nonideal conditions, however, were associated with activation time differences in excess of 1.8 msec and recovery time differences in excess of 30 msec (243 msec in certain conditions). Nonideal conditions that had a major influence were changes in activation sequence, propagation in a short cable, and propagation through regions of nonuniform coupling resistance and/or nonuniform membrane properties. Nonideal conditions that had a smaller influence were variations in distance from the measurement site to the simulated tissue surface, nonzero reference potentials, and the addition of distant events. Recovery time differences were more sensitive to the nonideal conditions than were activation time differences, and both depended on the action potential shape. When distant events significantly contributed to the unipolar electrogram waveform, the time differences when bipolar electrograms were used were less than those when unipolar electrograms were used; however, under other conditions, the time differences were comparable. Results showed that activation times and especially recovery times measured from electrograms can be greatly affected by conditions independent of changes in the underlying action potential waveforms.

Action Potentials↗

PubMed1998

Prognostic value of motor evoked potential obtained by transcranial magnetic brain stimulation in motor function recovery in patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: The early prognostic application of transcranial magnetic brain stimulation (TMS) for assessing motor and functional recovery in ischemic stroke patients has yielded contradictory results. We performed a prospective study of patients with acute ischemic stroke and motor deficit to evaluate the early prognostic value of TMS in motor and functional recovery. METHODS: Fifty patients with different degrees of hemiparesis were studied in the first week after ischemic stroke and evaluated by clinical scales (Medical Research Council Scale, Canadian Neurological Scale, Barthel Index), with clinical follow-up over 6 months. TMS (Magstim 200) was performed at the same time, recording the motor evoked potential (MEP) in the thenar eminence muscles, with facilitation by voluntary contraction. RESULTS: Of the total group of 50 patients, MEP was absent in 20 and present in 30 (17 with normal and 13 with delayed central conduction time [CCT]). The patients with MEP showed better motor and functional recovery than those without. The MEP provided information on patient recovery, regardless of the initial strength and/or Barthel values. The degree of recovery was better in those patients with normal CCT than in those with delayed CCT. CONCLUSIONS: MEP obtained by TMS in patients with hemiparesis after acute ischemic stroke is useful as an early prognostic indicator of motor and functional recovery. This technique would allow the early identification of those patients who will have a good recovery, particularly among those with severe initial paresis.

Activities of Daily Living↗

PubMed1999

The role of diaschisis in stroke recovery.

BACKGROUND AND PURPOSE: Recovery from hemiparesis after stroke has been shown to involve reorganization in motor and premotor cortical areas. However, whether poststroke recovery also depends on changes in remote brain structures, ie, diaschisis, is as yet unresolved. To address this question, we studied regional cerebral blood flow in 7 patients (mean+/-SD age, 54+/-8 years) after their first hemiparetic stroke. METHODS: We analyzed imaging data voxel by voxel using a principal component analysis by which coherent changes in functional networks could be disclosed. Performance was assessed by a motor score and by the finger movement rate during the regional cerebral blood flow measurements. RESULTS: The patients had recovered (P<0. 001) from severe hemiparesis after on average 6 months and were able to perform sequential finger movements with the recovered hand. Regional cerebral blood flow at rest differentiated patients and controls (P<0.05) by a network that was affected by the stroke lesion. During blindfolded performance of sequential finger movements, patients were differentiated from controls (P<0.05) by a recovery-related network and a movement-control network. These networks were spatially incongruent, involving motor, sensory, and visual cortex of both cerebral hemispheres, the basal ganglia, thalamus, and cerebellum. The lesion-affected and recovery-related networks overlapped in the contralesional thalamus and extrastriate occipital cortex. CONCLUSIONS: Motor recovery after hemiparetic brain infarction is subserved by brain structures in locations remote from the stroke lesion. The topographic overlap of the lesion-affected and recovery-related networks suggests that diaschisis may play a critical role in stroke recovery.

Adult↗

PubMed2000

Time course and recovery of exacerbations in patients with chronic obstructive pulmonary disease.

Although exacerbations of chronic obstructive pulmonary disease (COPD) are associated with symptomatic and physiological deterioration, little is known of the time course and duration of these changes. We have studied symptoms and lung function changes associated with COPD exacerbations to determine factors affecting recovery from exacerbation. A cohort of 101 patients with moderate to severe COPD (mean FEV(1) 41.9% predicted) were studied over a period of 2.5 yr and regularly followed when stable and during 504 exacerbations. Patients recorded daily morning peak expiratory flow rate (PEFR) and changes in respiratory symptoms on diary cards. A subgroup of 34 patients also recorded daily spirometry. Exacerbations were defined by major symptoms (increased dyspnea, increased sputum purulence, increased sputum volume) and minor symptoms. Before onset of exacerbation there was deterioration in the symptoms of dyspnea, sore throat, cough, and symptoms of a common cold (all p < 0.05), but not lung function. Larger falls in PEFR were associated with symptoms of increased dyspnea (p = 0.014), colds (p = 0.047), or increased wheeze (p = 0.009) at exacerbation. Median recovery times were 6 (interquartile range [IQR] 1 to 14) d for PEFR and 7 (IQR 4 to 14) d for daily total symptom score. Recovery of PEFR to baseline values was complete in only 75.2% of exacerbations at 35 d, whereas in 7.1% of exacerbations at 91 d PEFR recovery had not occurred. In the 404 exacerbations where recovery of PEFR to baseline values was complete at 91 d, increased dyspnea and colds at onset of exacerbation were associated with prolonged recovery times (p < 0.001 in both cases). Symptom changes during exacerbation do not closely reflect those of lung function, but their increase may predict exacerbation, with dyspnea or colds characterizing the more severe. Recovery is incomplete in a significant proportion of COPD exacerbations.

Aged↗

PubMed1970

Micropuncture studies of the recovery phase of myohemoglobinuric acute renal failure in the rat.

Micropuncture studies of the recovery phase of glycerol-induced myohemoglobinuric acute renal failure were performed in rats whose blood urea nitrogen (BUN) had fallen at least 20% below its peak value. The glomerular filtration rate (GFR) of individual nephrons in a single kidney in the recovery period generally either was in the normal range or minimal. Each animal's BUN concentration at the time of the study was inversely related to the proportion of functioning surface nephrons, but did not correlate with individual nephron GFR values. Proximal tubule fractional water absorption was significantly depressed as manifested by both depressed inulin (TF/P) values and supernormal volumes of collections, a finding which, in the absence of a urea-induced osmotic diuresis, suggests impaired sodium transport by the damaged nephron. The mean proximal tubule hydrostatic pressure in recovery was normal and there was little variation in pressure among functioning nephrons. It is concluded that recovery from this model of acute renal failure reflects the progressive recruitment of increasing numbers of functioning nephrons. The recovery of individual nephron glomerular filtration, once begun, was rapid and complete. No evidence could be adduced that the gradual return of renal function towards normal reflects a slow release of tubular obstruction or repair of disrupted tubular epithelium. Rather, recovery appeared to be directly attributable to the return of an adequate effective glomerular filtration pressure. Significant limitation in proximal tubule water absorption persisted after individual nephron GFR had returned to normal or supernormal values in this model of experimental acute renal failure in the rat, a finding which readily accounts for the diuresis associated with the recovery phase of this syndrome.

Acute Kidney Injury↗

PubMed2005

Influence of psychiatric comorbidity on recovery and recurrence in generalized anxiety disorder, social phobia, and panic disorder: a 12-year prospective study.

OBJECTIVE: The authors sought to observe the long-term clinical course of anxiety disorders over 12 years and to examine the influence of comorbid psychiatric disorders on recovery from or recurrence of panic disorder, generalized anxiety disorder, and social phobia. METHOD: Data were drawn from the Harvard/Brown Anxiety Disorders Research Program, a prospective, naturalistic, longitudinal, multicenter study of adults with a current or past history of anxiety disorders. Probabilities of recovery and recurrence were calculated by using standard survival analysis methods. Proportional hazards regression analyses with time-varying covariates were conducted to determine risk ratios for possible comorbid psychiatric predictors of recovery and recurrence. RESULTS: Survival analyses revealed an overall chronic course for the majority of the anxiety disorders. Social phobia had the smallest probability of recovery after 12 years of follow-up. Moreover, patients who had prospectively observed recovery from their intake anxiety disorder had a high probability of recurrence over the follow-up period. The overall clinical course was worsened by several comorbid psychiatric conditions, including major depression and alcohol and other substance use disorders, and by comorbidity of generalized anxiety disorder and panic disorder with agoraphobia. CONCLUSIONS: These data depict the anxiety disorders as insidious, with a chronic clinical course, low rates of recovery, and relatively high probabilities of recurrence. The presence of particular comorbid psychiatric disorders significantly lowered the likelihood of recovery from anxiety disorders and increased the likelihood of their recurrence. The findings add to the understanding of the nosology and treatment of these disorders.

Adult↗

PubMed2006

Natural recovery and treatment-seeking in pathological gambling: results of two U.S. national surveys.

OBJECTIVE: Pathological gambling is described in DSM-IV as a chronic and persisting disorder, but recent community-based longitudinal studies that have highlighted the transitory nature of gambling-related problems have called into question whether this is an accurate characterization. This emerging evidence of high rates of recovery coupled with low rates of treatment-seeking for pathological gambling suggests that natural recovery might be common. The purpose of the present study was to document the rates of recovery, treatment-seeking, and natural recovery among individuals with DSM-IV pathological gambling disorder in two large and representative U.S. national surveys. METHOD: Prevalences of recovery, treatment-seeking, and natural recovery were estimated among individuals from the Gambling Impact and Behavior Study (N=2,417) and the National Epidemiologic Survey on Alcohol and Related Conditions (N=43,093) who reported a lifetime history of DSM-IV pathological gambling disorder (N=21 and N=185, respectively). RESULTS: Among individuals with a lifetime history of DSM-IV pathological gambling, 36%-39% did not experience any gambling-related problems in the past year, even though only 7%-12% had ever sought either formal treatment or attended meetings of Gamblers Anonymous. About one-third of the individuals with pathological gambling disorder in these two nationally representative U.S. samples were characterized by natural recovery. CONCLUSIONS: Pathological gambling may not always follow a chronic and persisting course. A substantial portion of individuals with a history of pathological gambling eventually recover, most without formal treatment. The results of large epidemiological surveys of pathological gambling may eventually overturn the established wisdom about pathological gambling disorder.

Adult↗

PubMedDate not supplied

The relationship between beta-receptor sensitivity and nocturnal blood pressure and heart rate recovery in normotensive people.

This study examined the relationship between nocturnal blood pressure (BP) dipping and chronotropic dose25 (CD25) as an indicator of beta-adrenergic receptor functioning in normotensive people. In addition, the authors evaluated the influence of beta-receptor functioning on heart rate recovery after exercise. The sample consisted of 41 participants (18 men, 23 women). Ambulatory BP monitoring took place in each patient's home. On a separate occasion, beta-adrenergic receptor sensitivity was determined by response to isoproterenol infusion. Heart rate (HR) recovery was defined as the change from peak HR to that measured after 1 and 2 minutes of recovery. Relationships between dipping and CD25 were found such that participants with higher CD25 values had less nocturnal decline in systolic BP, diastolic BP, and mean arterial pressure (r = -0.445, -0.533, -0.510, respectively; p < 0.004, 0.001, 0.001, respectively). Heart rate recovery at 1 and 2 minutes after exercise was 28.8 +/- 5 and 49.9 +/- 6 beats/minute, respectively. Participants with higher CD25 values had more heart rate decline during the first 2 minutes of recovery (r = 0.407, p < 0.008). In addition, heart rate recovery was inversely related to systolic, diastolic, and mean nocturnal blood pressure dipping (r = -0.348, -0.432, -0.408, respectively, p<0.028, 0.005, 0.009, respectively). Normotensive people with an abnormal circadian pattern of blood pressure may have desensitized beta-adrenergic receptors. This desensitization may contribute to blunted nocturnal blood pressure and increased heart rate recovery as measured at 2 minutes following exercise testing.

Adrenergic beta-Agonists↗

PubMed2005

Bronchoalveolar lavage in COPD: fluid recovery correlates with the degree of emphysema.

Bronchoscopy with bronchoalveolar lavage (BAL) is an important research tool for assessing airway inflammation in a variety of inflammatory lung diseases. In chronic obstructive pulmonary disease (COPD), BAL recovery is often low, making analysis of the recovered fluid difficult to interpret. The present authors hypothesised that the degree of emphysema may predict BAL recovery. A total of 20 COPD patients (mean age 57 yrs, range 49-69) with a median (interquartile range) forced expiratory volume in one second (FEV1) of 51 (33-69)% predicted underwent BAL. Matched "healthy" smokers and nonsmokers served as controls. Emphysema index in COPD patients was calculated on computed tomography scan as the percentage of the right lung with pixels <-950 Hounsfield units. The carbon monoxide diffusing capacity of the lung (DL,CO) was determined by the single-breath method. COPD patients had lower BAL recovery than controls. COPD patients with an emphysema index <1 had higher BAL recovery than patients with an emphysema index >1. BAL recovery correlated negatively to emphysema index and positively to DL,CO. However, no correlation was found between recovery and FEV1. In conclusion, the extent of emphysema evaluated by computed tomography-scan index and carbon monoxide diffusing capacity of the lung may predict a low bronchoalveolar lavage recovery in chronic obstructive pulmonary disease patients. These parameters may, therefore, be useful when chronic obstructive pulmonary disease patients are selected for bronchoscopy with bronchoalveloar lavage. The present study underlines the importance of careful phenotyping of chronic obstructive pulmonary disease patients.

Aged↗

PubMed1985

Gastrointestinal blood flow and O2 uptake in piglets: recovery from hypoxemia.

Gastrointestinal (GI) blood flow, O2 transport, and O2 uptake were measured during recovery from severe hypoxemia in newborn piglets. Hypoxemia was induced by lowering the inspired O2 concentration to 0.05 for 15 min. This resulted in an 82% decrease in GI O2 uptake. Recovery measurements were obtained 5 and 65 min after restoration of normoxia. During early recovery (5 min), GI O2 uptake increased above prehypoxemia baseline, presumably to "repay" the O2 deficit incurred during hypoxemia. This was mediated by an increase in the arteriovenous O2 content difference, as GI blood flow did not increase above prehypoxemia baseline. During late recovery (65 min), GI blood flow, O2 delivery, and arteriovenous O2 content difference decreased below prehypoxemia baseline. This resulted in a 52% decrease in GI O2 uptake below prehypoxemia baseline. Therefore, early recovery was characterized by an appropriate increase in GI O2 uptake; however, late recovery was characterized by a significant reduction in GI O2 transport and uptake. Circulatory homeostasis was not reestablished during the late recovery period.

Animals↗

PubMed1998

L-glutamine and transforming growth factor-alpha enhance recovery of monoacylglycerol acyltransferase and diacylglycerol acyltransferase activity in porcine postischemic ileum.

Recovery of the ability to digest and absorb lipids is essential to the maintenance of normal nutrition in infants with bowel damage. Two intrinsic microsomal enzymes, monoacylglycerol acyltransferase (MGAT) and diacylglycerol acyltransferase (DGAT), catalyze the major pathway for intestinal triacylglycerol biosynthesis. This study describes the effects of intestinal ischemia on epithelial DGAT and MGAT activities and their recovery in response to two luminal treatments: L-glutamine (Gln), the primary intestinal fuel, and transforming growth factor-alpha (TGF-alpha), a mitogenic hormone similar to epidermal growth factor present in breast milk. Ischemic damage and recovery were analyzed in mucosa from Thiry-Vella loops in the mid-ileum of 7-wk-old pigs. Loops were subjected to 2-h occlusion of local mesenteric arteries, followed by 6 or 72 h of recovery in the presence of luminal glucose (control), Gln, or TGF-alpha. Ischemic tissue followed by 6-h recovery exhibited an approximate 50% decrease in both MGAT and DGAT activities compared with nonischemic loop tissue. At 72 h, MGAT and DGAT recovery in Gln plus TGF-alpha-treated loops was significantly greater than their corresponding 6-h peak damage levels (p < 0.05). From 6 to 72 h, MGAT increased 4-fold and DGAT increased 3.6-fold after Gln plus TGF-alpha treatment. With other treatments, MGAT and DGAT activities increased <2.5-fold from 6 to 72 h. This study shows that intestinal MGAT and DGAT activities decrease after ischemic damage, yet recover rapidly in bowel exposed to Gln and/or TGF-alpha. By stimulating the rate of recovery of the villi and lipid synthesizing enzymes, these treatments could improve the efficacy of enteral feeding in infants recovering from bowel damage.

Acyltransferases↗

PubMed2005

Freeze-drying of proteins from a sucrose-glycine excipient system: effect of formulation composition on the initial recovery of protein activity.

The purpose of this study was to investigate the effect of sucrose-glycine excipient systems on the stability of selected model proteins during lyophilization. Recovery of protein activity after freeze-drying was examined for the model proteins lactate dehydrogenase and glucose 6-phosphate dehydrogenase in a sucrose-glycine-based excipient system in which the formulation composition was systematically varied. In a sucrose-only excipient system, activity recovery of both model proteins is about 80% and is independent of sucrose concentration over a range from 1 to 40 mg/mL. When both sucrose and glycine are used and the ratio of the 2 excipients is varied, however, activity recovery decreases in a pattern that is consistent with the inhibition of activity recovery by glycine crystals, despite the presence of an adequate amount of sucrose to afford protection. Annealing of sucrose-glycine formulations causes a small but significant decrease in activity recovery relative to unannealed controls, whereas no annealing effect is observed with sucrose-only formulations. Addition of 0.01% polysorbate 80 to the formulation resulted in complete recovery of activity, irrespective of the sucrose-glycine ratio or annealing. Addition of the same concentration of polysorbate 80 to the reconstitution medium caused an increase in activity recovery for each formulation, but the overall pattern remained unchanged. The data are consistent with an interfacial model for lyophilization-associated loss of protein activity involving denaturation at a solid/freeze-concentrate interface.

Animals↗

PubMed1994

Time course of recovery of spermatogenesis and Leydig cell function after cessation of gonadotropin-releasing hormone antagonist treatment in the adult rat.

This study examined the time course of recovery of spermatogenesis and its relationship to the temporal changes in circulating levels of gonadotropin and testosterone (T) and intratesticular T levels after cessation of treatment with a potent GnRH antagonist (GnRH-A). Adult male rats were given a daily sc injection of Nal-Glu-GnRH antagonist (1250 micrograms/kg BW) for 4 weeks and killed in groups of five 0, 1, 2, 3, 4, and 6 weeks after discontinuation of treatment. After cessation of treatment, plasma FSH levels returned to control values by 6 weeks, whereas LH levels returned to control values within 1 week. Both circulating as well as intratesticular levels of T returned to normal levels by 3 and 4 weeks, respectively. Interestingly, a rebound in both FSH and intratesticular T, but not in plasma T, beyond control levels occurred early in the recovery phase. The total volume of Leydig cells, which was only 15% of control values, increased 4.3-fold within 1 week and was not significantly different from control values (92% recovery) by 2 weeks posttreatment. Enumeration of earlier phases of germ cells as well as homogenization-resistant advanced (steps 17-19) spermatids revealed a progressive increase in germ cell numbers with time. Complete restoration of the numbers of preleptotene spermatocytes, pachytene spermatocytes, step 7 spermatids, and advanced spermatids occurred 1, 3, 4, and 6 weeks, respectively, after termination of GnRH-A treatment. There was also a complete reversal of GnRH-A-induced changes in testicular weight, tubule diameter, and volume of seminiferous tubules and their lumens by 6 weeks posttreatment, paralleling the recovery of spermatogenesis. These results suggest that 1) complete recovery of spermatogenesis and various other testicular parameters can be achieved in GnRH-A-treated rats after cessation of treatment; 2) the progression of various germ cells during the recovery period follows the normal time schedule of germ cell development; and 3) the recovery of spermatogenesis is preceded by supranormal levels of FSH and intratesticular T. These findings further emphasize the suitability of antagonistic analogs of GnRH for male fertility control.

Animals↗

PubMed1985

Adrenocorticotropin-stimulated adrenal androgen secretion in anorexia nervosa: impaired secretion at low weight with normalization after long-term weight recovery.

Adrenal androgen secretion is decreased in patients with anorexia nervosa. To assess the reversibility of the decreased secretion with recovery of body weight, we measured ACTH-stimulated adrenal androgen levels at different stages of recovery. Basal plasma GH and somatomedin-C levels also were measured, because both have been proposed as potential stimuli for adrenal androgen secretion. When studied at low body weight [58 +/- 3% (+/- SEM) ideal BW], women with anorexia nervosa had decreased ACTH-stimulated levels of dehydroepiandrosterone (DHA), DHA sulfate (DHAS), and androstenedione and decreased DHA to cortisol, DHAS to cortisol, and androstenedione to cortisol ratios compared to normal women. Women who had recently completed a refeeding program (within 2-4 weeks, 81 +/- 2% ideal BW) had an increased somatomedin-C level compared to low weight patients, but similar ACTH-stimulated adrenal androgen levels. Long term weight-recovered women (86 +/- 4% ideal BW, recovery for more than 6 months, with resumption of menses), however, had significant increases in ACTH-stimulated DHA and DHAS levels and DHA to cortisol and DHAS to cortisol ratios, and their hormone levels and ratios were not different from those in normal women. GH levels fell during weight recovery, although the values in the three patient groups did not differ significantly. We conclude that the recovery of adrenal androgen secretion while GH levels were falling provides evidence against a direct effect of GH as a stimulus for adrenal androgen secretion. The recovery of somatomedin-C before the recovery of adrenal androgens, however, and the positive correlation between plasma somatomedin-C and the integrated level of plasma DHAS (r = 0.50; P less than 0.02) are consistent with the hypothesis that somatomedin-C is a stimulus for adrenal androgen secretion.

Adrenal Glands↗

PubMed1983

Recovery of behavioral abnormalities after right hemisphere stroke.

We studied recovery of function in 41 patients with right hemisphere stroke. Recovery was rapid for left neglect, prosopagnosia, anosognosia, and unilateral spatial neglect on drawing (USN). Recovery was slower for h mianopia, hemiparesis, motor impersistence, and extinction. Rates of recovery were intermediate for constructional apraxia and dressing apraxia. Sex had no influence on the rate of recovery. Younger patients recovered from prosopagnosia more rapidly than older patients. Patients with smaller lesions recovered more quickly from anosognosia, USN, and hemiparesis than patients with larger lesions. Patients with hemorrhages recovered more rapidly from constructional apraxia, neglect, and motor impersistence than patients with infarcts. Recovery of function and the factors influencing recovery can by studied systematically by life table methods.

Age Factors↗

PubMed1999

Does behavioural hypothermia promote post-exercise recovery in cold-submerged frogs?

At the low temperatures of the overwintering environment of the frog Rana temporaria, small changes in ambient temperature have large effects on metabolism and behaviour, especially since Q10 values are often greatly elevated in the cold. How the overwintering aquatic frog copes with variable thermal environments in terms of its overall activity metabolism and recovery from pursuit by predators is poorly understood, as is the role of behavioural thermoregulation in furthering recovery from intense activity. Exhaustive exercise was chosen as the method of evaluating activity capacity (defined by time to exhaustion, total distance swum and number of leg contractions before exhaustion) and was determined at 1.5 and 7 degreesC. Other cohorts of frogs were examined at both temperatures to determine the metabolic (acid-base, lactate, glucose, ATP and creatine phosphate) and respiratory responses to exercise in cold-submerged frogs. Finally, temperature preference before and after exercise was determined in a thermal gradient to define the importance of behavioural thermoregulation on the recovery rates of relevant metabolic and respiratory processes. Activity capacity was significantly reduced in frogs exercised at 1.5 versus 7 degreesC, although similar levels of tissue acid-base metabolites and lactate were reached. Blood pH, plasma PCO2 and lactate levels recovered more rapidly at 1.5 degreesC than at 7 degreesC; however, intracellular pH and the recovery of tissue metabolite levels were independent of temperature. Resting aerobic metabolic rates were strongly affected by temperature (Q10=3.82); however, rates determined immediately after exercise showed a reduced temperature sensitivity (Q10=1.67) and, therefore, a reduced factorial aerobic scope. Excess oxygen consumption recovered to resting values after 5-6.25 h, and 67 % recovery times tended to be slightly faster at the lower temperatures. Exercise in the cold, therefore, provided an immediately higher factorial scope, which could be involved in the faster rate of recovery of blood lactate levels in the colder frogs. In addition, exercise significantly lowered the preferred temperature of the frogs from 6.7 to 3.6 degreesC for nearly 7 h, after which they returned to their normal, unstressed preferred temperatures. Thus, a transient behavioural hypothermia in the skin-breathing, overwintering frog may be an important strategy for minimising post-exercise stress and maintaining aerobic metabolism during recovery from intense activity.

Journal Article↗

PubMed1999

Mechanism of overshoot in cardiac function during recovery from submaximal exercise in man.

BACKGROUND: A sudden increase (overshoot) in the left ventricular ejection fraction during the recovery from maximal exercise has been reported in patients with coronary artery disease, but its mechanism has not been fully clarified. We investigated whether this phenomenon may occur in normal subjects, and whether it depends on the intensity of exercise. METHODS: Thirteen normal subjects (mean [+/- SD] age, 59 +/- 8 years old) performed two levels (25 W and 50 W) of mild-intensity, constant-work-rate exercise for 6 min on a cycle ergometer. Left ventricular function was monitored continuously during the recovery from exercise using a computerized cadmium telluride detector. RESULTS: An overshoot was observed in the ejection fraction during the first minute of recovery compared with the end-exercise value. The overshoot in the ejection fraction during recovery after the 50-W exercise was greater than that seen after the 25-W exercise. An overshoot phenomenon in stroke volume was also observed during the recovery from 50-W exercise. CONCLUSIONS: The overshoot in cardiac function observed during the early phase of recovery, which was caused mainly by an immediate decrease in end-systolic volume, occurred even after exercise of mild intensity. This phenomenon appears to suggest the existence of a transient mismatch between cardiac contractility and afterload reduction during the recovery from mild-intensity exercise, even in normal subjects.

Aged↗