No Association Between Injury-Related Fear and Isokinetic Quadriceps Strength in Individuals With a History of Anterior Cruciate Ligament Reconstruction

CONTEXT

Injury-related fear and quadriceps strength are independently associated with secondary anterior cruciate ligament (ACL) injury risk. It is not known whether injury-related fear and quadriceps strength are associated, despite their individual predictive capabilities of secondary ACL injury. The purpose of this study was to examine the association between injury-related fear and quadriceps strength in individuals at least 1 year after ACL reconstruction (ACLR).

DESIGN

Cross-sectional study.

METHODS

Forty participants between the ages of 18 and 35 years at least 1 year post unilateral primary ACLR. Participants completed the Tampa Scale of Kinesiophobia-11 (TSK-11) and a standard isokinetic quadriceps strength assessment using the Biodex Isokinetic Dynamometer. Pearson Product-Moment correlations were used to examine the linear association between the TSK-11 scores and peak torque (in nanometers per kilogram) for each limb and between the TSK-11 scores and limb symmetry indices for each limb. Pearson Product-Moment correlation coefficients (r) were interpreted as very high (.90-1.00), high (.70-.90), moderate (.50-.70), low (.30-.50), and no correlation (.00-.30).

RESULTS

The average TSK-11 score was 18.2 (5.3), average ACLR peak quadriceps torque was 1.9 (0.50) N·m/kg, average contralateral peak quadriceps torque was 2.3 (0.48) N·m/kg, and average limb symmetry index was 85.3% (12.6%). There was no statistically significant correlation between the TSK-11 and peak quadriceps torque on the ACLR limb (r = .12, P = .46), the TSK-11 and contralateral limb (r = .29, P = .07), or the TSK-11 and limb symmetry index (r = -.18, P = .27).

CONCLUSIONS

There was no association between kinesiophobia and peak isokinetic quadriceps strength in individuals at least 1 year post-ACLR. Both factors, independently, have been shown to influence risk of secondary injury in patients after ACLR.

Lower Extremity Reaction Time in Individuals With Contact Versus Noncontact Anterior Cruciate Ligament Injuries After Reconstruction

CONTEXT

Deficits in perceptual-motor function, like visuomotor reaction time (VMRT), are risk factors for primary and secondary anterior cruciate ligament (ACL) injury. Noncontact ACL injuries have been associated with slower reaction time, but whether this association exists for patients with contact ACL injuries is unknown. Exploring differences in VMRT among individuals with contact versus noncontact ACL injuries may provide a more comprehensive understanding of modifiable risk factors.

OBJECTIVE

To compare lower extremity VMRT (LEVMRT) in individuals with contact or noncontact ACL injuries after ACL reconstruction (ACLR).

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 36 participants with primary, unilateral ACLR completed an LEVMRT assessment (contact ACL injury = 20 [56%], noncontact ACL injury = 16 [44%]).

MAIN OUTCOME MEASURE(S)

The LEVMRT was assessed bilaterally and collected using a series of wireless light discs deactivated by individuals with their feet. The ACLR-active LEVMRT (ie, ACLR limb is deactivating lights) and ACLR-stable LEVMRT were compared using separate analyses of covariance to determine the association with contact or noncontact injury using time since surgery as a covariate.

RESULTS

After controlling for time since surgery, a difference and large effect size between groups was found for the ACLR-stable LEVMRT (P = .010; η2 = 0.250) but not for the ACLR-active (P = .340; η2 = 0.065) condition. The contact group exhibited slower ACLR-stable LEVMRT (521.7 ± 59.3 milliseconds) than the noncontact group (483.4 ± 83.9 milliseconds).

CONCLUSIONS

Individuals with contact ACL injury demonstrated a slower LEVMRT while their ACLR limb was stabilizing. The group differences during the ACLR-stable LEVMRT task might indicate deficits in perceptual-motor function when the surgical limb maintains postural control during a reaction time task. After ACLR, individuals with contact injuries may need additional motor learning interventions to enhance perceptual-motor functioning.

Social support and the stress-buffering hypothesis: Effects on stress and mental health in adolescent football athletes

CONTEXT

Football sports participation has been linked to both positive and negative effects on overall health. Social support, a network which provides individuals with resources to effectively cope, may positively influences one's stress and mental health. However, little research has been conducted in this population.

OBJECTIVE

To examine the relationships between social support, psychological stress, and mental health in adolescent football athletes.

DESIGN

Cross-Sectional.

SETTING

High school athletes, pre-and-post-competitive football season in XXX.

PARTICIPANTS

Black/African American adolescent athletes (N=93) competing for a school-sponsored football team.

MAIN OUTCOME MEASURES

Participants completed a battery of social support, psychological stress, and mental health symptom measures using the National Institutes of Health Toolbox Application and Patient-Reported Outcomes Measurement Information System following a competitive season. T-score means, Pearson correlations, and multiple regression analyses were conducted.

RESULTS

Social support was negatively correlated with psychological stress (Emotional support r=-.386, Family relationships r=-.412, Peer relationships r=-.265) and mental health (Depression r=-.367 and r=-.323 for Emotional support and Family relationships, respectively), whereas psychological stress and mental health (Depression r=.751 and Anxiety r=.732) were positively correlated with one another. In regression analyses, social support measures (i.e., Emotional Support, Family Relationships, and Peer Relationships) were used to predict psychological stress (F=7.094, p<.001, R2=0.191), depression symptoms (F=5.323, p<.001, R2=0.151), and anxiety symptoms (F=1.644, p=.190, R2=0.052).

CONCLUSIONS

In line with the stress buffering hypothesis, social support in the form of family relationships and overall emotional support garnered through sport participation may reduce psychological stress and help to preserve mental health of football athletes. Findings indicate perceived social support may act as a positive resource for the coping of Black/African American adolescent athletes. Further research is warranted to understand the effects of stress and social support on the mental health of adolescents, particularly racial and ethnic minorities who are underrepresented in athletic training literature.

Psychological Readiness, Injury-Related Fear, and Persistent Knee Symptoms After Anterior Cruciate Ligament Reconstruction

CONTEXT

Poor psychological responses after anterior cruciate ligament reconstruction (ACLR) have been associated with a failure to return to sport and increased secondary injury risk. However, we do not know whether poor psychological responses after ACLR influence patient-reported knee function and knee symptoms.

OBJECTIVE

To examine the association between psychological factors (ie, psychological readiness and injury-related fear) and the presence of persistent knee symptoms in individuals 6 to 12 months after ACLR.

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

In total, 101 participants, aged 13 to 25 years old, between 6 and 12 months after primary unilateral ACLR were enrolled in the study.

MAIN OUTCOME MEASURE(S)

Persistent knee symptoms were identified using an established criterion based on the subscales of the Knee injury and Osteoarthritis Outcome Score. Participants also completed the Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) and the Tampa Scale of Kinesiophobia-11 (TSK-11) to assess psychological readiness and injury-related fear, respectively. Higher ACL-RSI scores indicate higher psychological readiness, and higher TSK-11 scores indicate higher injury-related fear.

RESULTS

Twenty-nine participants (29%) met the criteria for persistent knee symptoms. For every 1 SD lower in the ACL-RSI score, participants had 2.1 times greater odds of persistent knee symptoms after ACLR (95% CI = 1.3, 3.6). For every 1 SD higher in the TSK-11 score, participants had 1.9 times greater odds of persistent knee symptoms after ACLR (95% CI = 1.1, 3.3). Both the ACL-RSI and TSK-11 were considered good at classifying persistent knee symptoms, as the areas under the curve were 0.78 and 0.73, respectively.

CONCLUSIONS

Individuals with a lower level of psychological readiness and more injury-related fear after ACLR had greater odds of persistent knee symptoms. Overall, these results highlight the potential clinical benefit of a comprehensive, biopsychosocial approach to managing health and wellness for individuals after ACLR.

Validation of a Survey to Characterize Barriers to Physical Activity After Anterior Cruciate Ligament Reconstruction

CONTEXT

Although 84% of patients expected to return to activity within 1 year of anterior cruciate ligament (ACL) reconstruction (ACLR), as few as 24% will return to their preinjury level of activity. By considering a patient's perceptions of reengagement in activity after ACLR, clinicians and researchers may be better equipped to implement interventions that are patient centered.

OBJECTIVE

To describe the validation of the ACL Reasons survey, a tool to aid clinicians and researchers in understanding patient perceptions of barriers to physical activity (PA) engagement after ACLR.

DESIGN

Cross-sectional study.

PATIENTS OR OTHER PARTICIPANTS

The ACL Reasons survey was administered via Qualtrics to 78 patients 6 to 24 months after primary, unilateral ACLR. Patients were categorized as active, more challenging, or less active based on their responses to the ACL Reasons.

MAIN OUTCOME MEASURE(S)

Development of the ACL Reasons survey occurred via an iterative process of drafting and revising based on feedback from a team of external expert reviewers. Tegner activity level, Marx activity score, the Knee injury and Osteoarthritis Outcomes Score (KOOS), ACL Return to Sport after Injury score, and Tampa Scale of Kinesiophobia score were compared among groups using analysis-of-variance and Kruskal Wallis tests.

RESULTS

Groups differed based on Tegner activity level (P < .001), Marx activity score (P = .01), KOOS pain score (P = .02), KOOS symptom score (P = .04), KOOS sports and recreation score (P < .001), KOOS quality of life score (P < .001), ACL Return to Sport after Injury score (P < .001), and Tampa Scale of Kinesiophobia score (P < .001), with the less active group performing worse on each. Knee symptoms, fear of knee symptoms or movement, and fear of injury were the most common reasons for the change in PA engagement.

CONCLUSIONS

These results support the validity of the ACL Reasons survey as a tool for identifying barriers to PA engagement after ACLR. This tool may help facilitate communication between patients with ACLR and their health care providers to enhance patient-centered care.

Current Clinical Concepts: Integration of Psychologically Informed Practice for Management of Patients With Sport-Related Injuries

Psychologically informed practice is an approach to patient management that encourages clinicians to treat patients from a biopsychosocial perspective and can be adopted by athletic trainers to manage sport-related injuries. As described in the domains of athletic training clinical practice, athletic trainers are expected to identify, address, and make appropriate referrals regarding psychosocial responses to injuries and mental health symptoms. Psychologically informed practice suggests addressing physical impairments in addition to screening and intervening for psychosocial responses with patients. In this Current Clinical Concepts paper, we discuss appropriate patient-reported outcome measures used to screen for mental health symptoms and psychosocial responses, provide recommendations on psychological interventions that can be integrated to enhance patient outcomes, and describe how to effectively refer a patient to an appropriate mental health professional.

Application of Theory for Those With Sport-Related Concussion: Understanding the Effect of Athletic Identity on Health Outcomes

Athletic identity is a psychological factor of concern for athletes after sport-related concussion (SRC). The integrated model of response to sport injury includes athletic identity as a psychological factor within its model, but it has often been overlooked as a consideration affecting outcomes of SRC. In this review, we applied the integrated model of response to sport injury to the current available evidence about the negative consequences of a stronger athletic identity on health outcomes after SRC. Theory-based research recommendations will be provided to facilitate research in this area. Recommendations for athletic training clinical practice to assess and consider athletic identity as part of routine clinical care for those after SRC will also be discussed.

Preventing Osteoarthritis After an Anterior Cruciate Ligament Injury: An Osteoarthritis Action Alliance Consensus Statement

After an anterior cruciate ligament (ACL) injury, people need secondary prevention strategies to identify osteoarthritis at its earliest stages so that interventions can be implemented to halt or slow the progression toward its long-term burden. The Osteoarthritis Action Alliance formed an interdisciplinary Secondary Prevention Task Group to develop a consensus on recommendations to provide clinicians with secondary prevention strategies that are intended to reduce the risk of osteoarthritis after a person has an ACL injury. The group achieved consensus on 15 out of 16 recommendations that address patient education, exercise and rehabilitation, psychological skills training, graded-exposure therapy, cognitive-behavioral counseling (lacked consensus), outcomes to monitor, secondary injury prevention, system-level social support, leveraging technology, and coordinated care models. We hope this statement raises awareness among clinicians and researchers on the importance of taking steps to mitigate the risk of osteoarthritis after an ACL injury.

Evidence Review for Preventing Osteoarthritis After an Anterior Cruciate Ligament Injury: An Osteoarthritis Action Alliance Consensus Statement

CONTEXT

The Osteoarthritis Action Alliance formed a secondary prevention task group to develop a consensus on secondary prevention recommendations to reduce the risk of osteoarthritis after a knee injury.

OBJECTIVE

Our goal was to provide clinicians with secondary prevention recommendations that are intended to reduce the risk of osteoarthritis after a person has sustained an anterior cruciate ligament injury. Specifically, this manuscript describes our methods, literature reviews, and dissenting opinions to elaborate on the rationale for our recommendations and to identify critical gaps.

DESIGN

Consensus process.

SETTING

Virtual video conference calls and online voting.

PATIENTS OR OTHER PARTICIPANTS

The Secondary Prevention Task Group consisted of 29 members from various clinical backgrounds.

MAIN OUTCOME MEASURE(S)

The group initially convened online in August 2020 to discuss the target population, goals, and key topics. After a second call, the task group divided into 9 subgroups to draft the recommendations and supportive text for crucial content areas. Twenty-one members completed 2 rounds of voting and revising the recommendations and supportive text between February and April 2021. A virtual meeting was held to review the wording of the recommendations and obtain final votes. We defined consensus as >80% of voting members supporting a proposed recommendation.

RESULTS

The group achieved consensus on 15 of 16 recommendations. The recommendations address patient education, exercise and rehabilitation, psychological skills training, graded-exposure therapy, cognitive-behavioral counseling (lacked consensus), outcomes to monitor, secondary injury prevention, system-level social support, leveraging technology, and coordinated care models.

CONCLUSIONS

This consensus statement reflects information synthesized from an interdisciplinary group of experts based on the best available evidence from the literature or personal experience. We hope this document raises awareness among clinicians and researchers to take steps to mitigate the risk of osteoarthritis after an anterior cruciate ligament injury.

Kinesiophobia Is Associated with Peak Knee Abduction Angle during Jump Landing after ACL Reconstruction

INTRODUCTION

This study aimed to investigate the associations between kinesiophobia, knee abduction angle (KAA) during the first 100 ms of landing, and knee flexion excursion (KFE) in individuals 5-12 months after anterior cruciate ligament reconstruction (ACLR). We hypothesized that greater kinesiophobia would be associated with greater peak KAA and lesser KFE during landing on the ACLR limb, but not on the contralateral limb.

METHODS

Thirty-six participants between 14 and 35 yr old (females = 19, age = 19.9 ± 5.1 yr, height = 172.5 ± 9.4 cm, weight = 76.7 ± 20.0 kg, time since surgery =7.2 ± 1.7 months) were recruited from a sports medicine clinic at 5-12 months after primary unilateral ACLR. Participants completed the Tampa Scale of Kinesiophobia-11 (TSK-11) to measure kinesiophobia and three successful trials of a standard drop vertical jump task. A 10-camera three-dimensional motion capture system synchronized with two embedded force plate platforms was used to capture jump-landing kinematics. Separate stepwise linear regression models were used to examine the associations between kinesiophobia, peak KAA, and KFE on the ACLR and contralateral limbs after accounting for time since surgery and biological sex.

RESULTS

When accounting for time since surgery and biological sex, every 1-point increase on the TSK-11 (i.e., increase in kinesiophobia) associated with a 0.37° increase (i.e., a 7.1% increase) in ACLR limb KAA ( P = 0.02). Kinesiophobia was not associated with contralateral limb KAA, ACLR limb KFE, or contralateral limb KFE.

CONCLUSIONS

Higher kinesiophobia was related to greater amounts of peak KAA during landing in individuals 5-12 months post-ACLR. Modifying kinesiophobia may help to decrease KAA and lead to reduced secondary ACL injury risk. Future research should investigate feasible psychological interventions to reduce kinesiophobia and improve KAA in patients post-ACLR.

Prevalence of Early Knee Osteoarthritis Illness Among Various Patient-Reported Classification Criteria After Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To compare the prevalence of participants meeting different patient-reported criteria for early osteoarthritis (OA) illness after anterior cruciate ligament reconstruction (ACLR).

METHODS

Participants completed the Knee Injury and Osteoarthritis Outcomes Score (KOOS) at a single time point 5.0-7.9 months post-ACLR. We used established KOOS subscale criteria (i.e., Luyten original and Englund original) to define patient-reported early OA illness. A two-by-two contingency table and McNemar's test were used to compare the prevalence of participants who met the Luyten original versus Englund original KOOS criteria for early OA illness. These analyses were repeated using KOOS subscale thresholds based on established population-specific patient acceptable symptom state (PASS) within the Luyten and Englund KOOS criteria (i.e., Luyten PASS and Englund PASS).

RESULTS

A greater prevalence of participants with ACLR met the Luyten original criteria (n = 165 [54%]) compared to those who met the Englund original criteria (n = 128 [42%]; χ2  = 19.3, P < 0.001). When using the KOOS subscale PASS as thresholds, a significantly greater prevalence of participants with ACLR met the Luyten PASS criteria (n = 133 [43%]) compared to those who met the Englund PASS criteria (n = 85 [28%]; χ2  = 48.0, P < 0.001). When combining the Luyten and Englund KOOS criteria and using the original/PASS subscale thresholds, respectively, 40%/57% of participants met neither, 24%/15% met only 1, and 36%/28% met both KOOS criteria.

CONCLUSION

Regardless of the classification criteria used to define early OA illness, it is concerning that 28-54% of patients report considerable symptoms ~6 months post-ACLR. Our findings will improve the classification criteria to define early OA illness, which may raise awareness for the need of population-specific criteria.

Adolescents Are Less Physically Active Than Adults After Anterior Cruciate Ligament Reconstruction

Background:

Sources of physical activity (PA) and motivation for return to sport after anterior cruciate ligament reconstruction (ACLR) differ between adolescents and adults. It is unclear whether these differences influence participation in PA during the first year after ACLR when individuals are transitioning from rehabilitative care to unrestricted activity.

Purpose:

To compare device-assessed measures of PA between adolescents and adults at 6 to 12 months after ACLR.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Included were 22 adolescents (age, 15.9 ± 1.2 years; time since surgery = 8.0 ± 2.1 months) and 23 adults (age, 22.5 ± 5.0 years; time since surgery = 8.2 ± 2.1 months) who were cleared for unrestricted PA after primary unilateral ACLR. Participants were considered physically active if they met their age-specific United States Department of Health and Human Services PA guidelines. Participants wore an accelerometer-based PA monitor for at least 7 days. Daily minutes of moderate to vigorous–PA (MVPA) and daily step counts were reported and compared between age groups using analysis of covariance, with monitor wear time and sex included as covariates. The association between age group and meeting age-specific PA guidelines was assessed using binary logistic regression and reported as an odds ratio.

Results:

Adults with ACLR participated in 16 minutes more MVPA per day (49 ± 22 vs 33 ± 16 minutes per day; P < .001) and took 2212 more steps per day (8365 ± 2294 vs 6153 ± 1765 steps per day; P < .001) when compared with adolescent participants. In addition, 83% of adults were physically active, compared with 9% of adolescents (odds ratio = 60.2; 95% CI, 7.6-493.4).

Conclusion:

Adolescents with ACLR were less physically active than adults with ACLR, and only 9% of adolescents met aerobic PA guidelines. This is concerning because PA patterns adopted early in life are predictive of PA patterns in adulthood. Our findings indicate a need to better understand underlying causes of reduced PA among adolescents with ACLR and to develop intervention strategies that promote engagement in adequate PA after rehabilitation.

Implementation of In vivo exposure therapy to decrease injury-related fear in females with a history of ACL-Reconstruction: A pilot study

OBJECTIVE

The objective of this pilot study was to examine the preliminary feasibility and efficacy of in vivo exposure therapy (IVET) to decrease injury-related fear in females with history of ACLR.

DESIGN

Pilot Study.

SETTING

Sports Medicine Research Laboratory.

PARTICIPANTS

12 female participants with history of ACLR (≥ 1 year post-operative) were randomized into a 5-week IVET group (n = 6) or 5-week sham physical activity (PA) monitoring group (n = 6).

MAIN OUTCOME MEASURES

The independent variables were Group and Time. The dependent variables were the Photographic Series of Sports Activities for ACLR (PHOSA-ACLR) and the Tampa Scale of Kinesiophobia-11 (TSK-11) scores. A Group x Time repeated measures two-way analysis of variance was completed for the PHOSA-ACLR and the TSK-11. Partial η² effect sizes were used to examine clinically meaningful differences.

RESULTS

High retention and adherence rates were observed in the intervention group. The PHOSA-ACLR exhibited a significant main effect for Time (F_1,10 = 9.92, p = 0.01, partial η² = 0.50), but not for Group. No statistically significant or clinically meaningful differences were observed for the TSK-11.

CONCLUSION

Both groups exhibited decreased injury-related fear for specific functional tasks. Future research should further examine the efficacy of IVET and PA monitoring to decrease injury-related fear in patients after ACLR.

Relationship Between Cognitive Performance and Lower Extremity Biomechanics: Implications for Sports-Related Concussion

Background

Collegiate athletes with prior sports-related concussion (SRC) are at increased risk for lower extremity (LE) injuries; however, the biomechanical and cognitive mechanisms underlying the SRC-LE injury relationship are not well understood.

Purpose

To examine the association between cognitive performance and LE land-and-cut biomechanics among collegiate athletes with and without a history of SRC and to determine the association among multiple cognitive testing batteries in the same athlete cohort.

Study Design

Controlled laboratory study.

Methods

A cohort of 20 collegiate athletes with prior SRC (9 men, 11 women; mean ± standard deviation [SD] age, 20.5 ± 1.3 years; mean ± SD time since last SRC, 461 ± 263 days) and 20 matched controls (9 men, 11 women; mean ± SD age, 19.8 ± 1.3 years) completed land-and-cut tasks using the dominant and nondominant limbs. LE biomechanical variables and a functional visuomotor reaction time (FVMRT) were collected during each trial. Athletes also completed the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) and Senaptec Sensory Station assessments.

Results

In the SRC cohort, Pearson correlation coefficients indicated slower FVMRT was moderately correlated with decreased dominant limb (r = -0.512) and nondominant limb (r = -0.500) knee flexion, while increased dominant limb knee abduction moment was moderately correlated with decreased ImPACT Visual Memory score (r = -0.539) and slower ImPACT Reaction Time (r = 0.515). Most computerized cognitive measures were not associated with FVMRT in either cohort (P > .05).

Conclusion

Decreased reaction time and working memory performance were moderately correlated with decreased sagittal plane knee motion and increased frontal plane knee loading in collegiate athletes with a history of SRC. The present findings suggest a potential unique relationship between cognitive performance and LE neuromuscular control in athletes with a history of SRC injury. Last, we determined that computerized measures of cognitive performance often utilized for SRC management are dissimilar to sport-specific cognitive processes.

Clinical Relevance

Understanding the relationship between cognitive performance and LE biomechanics in athletes with prior SRC may inform future clinical management strategies. Future research should prospectively assess cognitive and biomechanical measures, along with LE injury incidence, to identify mechanisms underlying the SRC-LE injury relationship.

Neuroplasticity in Corticolimbic Brain Regions in Patients After Anterior Cruciate Ligament Reconstruction

CONTEXT

Fear has been cited as the primary barrier to return to sport (RTS) by athletes after anterior cruciate ligament reconstruction (ACLR). Understanding the neural factors that contribute to fear after ACLR may help us to identify interventions for this population.

OBJECTIVE

To characterize the underlying neural substrate of injury-related fear in patients after ACLR versus healthy matched control individuals during a picture imagination task (PIT) consisting of sport-specific images and images of activities of daily living (ADL).

DESIGN

Case-control study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 24 right-hand-dominant participants (12 with left-sided ACLR and 12 control individuals) were enrolled. Participants underwent full-brain functional magnetic resonance imaging.

MAIN OUTCOME MEASURE(S)

Functional data were acquired using blood oxygen level-dependent (BOLD) echoplanar imaging. Independent t tests were conducted to identify between-groups differences in BOLD signal changes during all images of the PIT. Paired t tests were computed to examine differences in BOLD signal change between sport-specific and ADL images in the ACLR group.

RESULTS

Increased activation in the inferior parietal lobule and the mediodorsal thalamus was observed during PIT in the ACLR group. An inability to suppress the default mode network in the ACLR group was noted. The ACLR group exhibited increased activation in the cerebellum and inferior occipital regions during the sport-specific images versus the ADL images, but no other regions of interest demonstrated differences.

CONCLUSION

After ACLR, patients may be more predisposed to fear, anxiety, and pain during sport-specific activities and ADLs. Psychosocial interventions may be warranted after ACLR to reduce injury-related fear and mitigate potentially maladaptive neuroplasticity.

Enhancement of noradrenergic neural transmission: an effective therapy of myasthenia gravis: a report on 52 consecutive patients

Neurochemical, neuroautonomic and neuropharmacological assessments carried out on all our myasthenia gravis (MG) patients showed that they presented a neural sympathetic deficit plus excessive adrenal-sympathetic activity. These abnormalities were registered during the basal (supine-resting) state, as well as after several stress tests (orthostasis, exercise, oral glucose and buspirone). In addition, MG patients showed increased levels of free-serotonin (f5HT) in the plasma, supposedly associated with the increased platelet aggregability which we found in all MG patients. As the above trio of neurochemical disorders (low noradrenergic-activity + high adrenergic-activity + increased f-5HT plasma levels) is known to favor Th-1 immunosuppression + Th-2 predominance, we outlined a neuropharmacological strategy for reverting the above neurochemical disorder. This treatment provoked sudden (acute), and late sustained improvements. Acute effects have been attributed to the increase of alpha-1 activity at the spinal motoneuron level. Late improvements always paralleled a significant normalization of immunological disorders. Complete normalization was registered only in non-thymectomized MG patients.

The possible role of one-electron reduction of aminochrome in the neurodegenerative process of the dopaminergic system

We present for discussion a possible molecular mechanism explaining the formation of reactive oxygen species involved in the neurodegenerative process of dopaminergic system in Parkinson's disease. This new hypothesis involves one-electron reduction of aminochrome to o-semiquinone radical, which seems to be the reaction responsible for neurodegenerative process of dopaminergic system. Leukoaminochrome o-semiquinone is extremely reactive with oxygen, which reoxidizes by reducing oxygen to superoxide radicals. Superoxide radicals enzymatically or spontaneously dismutate to dioxygen and hydrogen peroxide which is a precursor of hydroxyl radicals. ESR-experiments have showed that aminochrome o-semiquinone is extremely reactive in the presence of oxygen compared to dopamine o-semiquinone. In addition, the antioxidant enzymes superoxide dismutase and catalase play a prooxidant role by increasing the autoxidation rate and formation of superoxide radicals. One electron reduction of aminochrome to o-semiquinone can be performed by flavoenzymes which use NADPH and NADH as electron donator. The ability of aminochrome o-semiquinone to autoxidize in the presence of oxygen gives rise to a redox cycling process which will continue until oxygen, NADH and/or NADPH are depleted. Depletion of NADPH will prevent glutathione reductase from reducing glutathione, which is one of the main antioxidants in the cell. In addition depletion of NADH will prevent the formation of ATP in the electron transport chain in the mitochondria. Two antioxidants, probably, neuroprotective reactions are also discussed.

Glutathione transferase M2-2 catalyzes conjugation of dopamine and dopa o-quinones

Human glutathione transferase M2-2 prevents the formation of neurotoxic aminochrome and dopachrome by catalyzing the conjugation of dopamine and dopa o-quinone with glutathione. NMR analysis of dopamine and dopa o-quinone-glutathione conjugates revealed that the addition of glutathione was at C-5 to form 5-S-glutathionyl-dopamine and 5-S-glutathionyl-dopa, respectively. Both conjugates were found to be resistant to oxidation by biological oxidizing agents such as O(2), H(2)O(2), and O(*-)(2), and the glutathione transferase-catalyzed reaction can therefore serve a neuroprotective antioxidant function.

Effects of buspirone on plasma neurotransmitters in healthy subjects

Buspirone is an anxiolytic drug which exerts several central effects. It antagonizes presynaptic inhibitory DA2 autoreceptors at dopaminergic neurons and acts as an agonist for 5-HT1A inhibitor autoreceptors at serotonergic cells. Thus, buspirone respectively enhances and depresses the firing rates of both type of neurons. At doses which correlate with dopaminergic stimulation, but not 5-HT inhibition, buspirone also increases the firing rates of the central noradrenergic cells. We measured levels of circulating neurotransmitters before and up to 240 minutes after the oral administration of 20 mg of buspirone in 32 healthy volunteers. Buspirone significantly increased levels of noradrenaline, dopamine, and free serotonin but did not affect levels of adrenaline, tryptophane, or platelet serotonin. Small but significant drops in systolic blood pressure and heart rate were observed after buspirone ingestion. Atropine administration before buspirone ingestion annulled the free serotonin increase as well as systolic blood pressure-heart rate decrease. We found significant positive correlations between noradrenaline and dopamine levels. The strength and significance of these correlations were increased by using the noradrenaline/adrenaline ratio instead of noradrenaline absolute values. This finding indicates that increases in both noradrenaline and dopamine arise from sympathetic nerves rather than the adrenal glands. We also found significant negative correlations between free serotonin increases and systolic blood pressure-heart rate decreases. Our results indicate that buspirone stimulates central sympathetic activity. These acute effects of buspirone are reflected in an increased peripheral neural sympathetic activity, but not adrenal sympathetic activity in healthy individuals. In addition, buspirone increases free serotonin plasma concentrations and decreases systolic blood pressure plus heart rate levels through mechanisms associated with parasympathetic activation.

Glutathione transferases catalyse the detoxication of oxidized metabolites (o-quinones) of catecholamines and may serve as an antioxidant system preventing degenerative cellular processes

o-Quinones are physiological oxidation products of catecholamines that contribute to redox cycling, toxicity and apoptosis, i.e. the neurodegenerative processes underlying Parkinson's disease and schizophrenia. The present study shows that the cyclized o-quinones aminochrome, dopachrome, adrenochrome and noradrenochrome, derived from dopamine, dopa, adrenaline and noradrenaline respectively, are efficiently conjugated with glutathione in the presence of human glutathione transferase (GST) M2-2. The oxidation product of adrenaline, adrenochrome, is less active as a substrate for GST M2-2, and more efficiently conjugated by GST M1-1. Evidence for expression of GST M2-2 in substantia nigra of human brain was obtained by identification of the corresponding PCR product in a cDNA library. Glutathione conjugation of these quinones is a detoxication reaction that prevents redox cycling, thus indicating that GSTs have a cytoprotective role involving elimination of reactive chemical species originating from the oxidative metabolism of catecholamines. In particular, GST M2-2 has the capacity to provide protection relevant to the prevention of neurodegenerative diseases.

Human class Mu glutathione transferases, in particular isoenzyme M2-2, catalyze detoxication of the dopamine metabolite aminochrome

Human glutathione transferases (GSTs) were shown to catalyze the reductive glutathione conjugation of aminochrome (2, 3-dihydroindole-5,6-dione). The class Mu enzyme GST M2-2 displayed the highest specific activity (148 micromol/min/mg), whereas GSTs A1-1, A2-2, M1-1, M3-3, and P1-1 had markedly lower activities (<1 micromol/min/mg). The product of the conjugation, with a UV spectrum exhibiting absorption peaks at 277 and 295 nm, was 4-S-glutathionyl-5,6-dihydroxyindoline as determined by NMR spectroscopy. In contrast to reduced forms of aminochrome (leucoaminochrome and o-semiquinone), 4-S-glutathionyl-5, 6-dihydroxyindoline was stable in the presence of molecular oxygen, superoxide radicals, and hydrogen peroxide. However, the strongly oxidizing complex of Mn3+ and pyrophosphate oxidizes 4-S-glutathionyl-5,6-dihydroxyindoline to 4-S-glutathionylaminochrome, a new quinone derivative with an absorption peak at 620 nm. GST M2-2 (and to a lower degree, GST M1-1) prevents the formation of reactive oxygen species linked to one-electron reduction of aminochrome catalyzed by NADPH-cytochrome P450 reductase. The results suggest that the reductive conjugation of aminochrome catalyzed by GSTs, in particular GST M2-2, is an important cellular antioxidant activity preventing the formation of o-semiquinone and thereby the generation of reactive oxygen species.

[Risk factors for gallbladder cancer in Chilean females]

A case-control study of gallbladder cancer was conducted with 90 Chilean cases registered at one hospital in Santiago city, Chile from January, 1992 to August, 1994. Controls were selected among outpatients of the hospital who received abdominal echography. Each case was assigned 2 age- and sex-matched controls; either with or without gallstone(s). Study subjects were all directly interviewed by well-trained medical students. The present study focused on 74 female pairs and the following findings were obtained: 1) Odds Ratio(OR)s were significantly high for education years less than or equal to 6, body mass index greater than or equal to 24.0, constipation, and consumption of egg, fried meals, green and red chili. Chili pepper consumption of both types in cases showed significantly elevated risks with higher frequency. 2) While high ORs were observed, biliary symptoms such as dyspepsia and past history of cholelithiasis were strongly involved with present gallstone(s) and may not be independent factors for gallbladder cancer. 3) Significantly low ORs were seen for past history of intestinal parasitosis and surgical operation, hormone therapy, all industrial workers and workers in clothes & textile industry. However results may be influenced by more years of education or recall bias. 4) When a conditional logistic model was applied and controls with gallstone(s) were taken as reference, those with the habit of constipation showed a significantly high risk of 2.10 (95% CI: 1.01-4.38), and the consumers of red chili with a frequency > or = 1 time/day had elevated risks of 2.16 (1.27-3.66) vs those < 1 time/day and 4.66 (1.63-13.40) vs non-consumers, respectively. From the above results, the occurrence of gallbladder cancer in Chilean females may be related to constipation and chili pepper consumption, based on the presence of gallstone(s). Further investigations are needed to elucidate whether these are actual risk factors or whether only a false association was detected.

Plasma neurotransmitters, blood pressure and heart rate during supine resting, orthostasis and moderate exercise in severely ill patients: a model of failing to cope with stress

BACKGROUND

Previous clinical research has shown that severely ill (somatic) as well as many psychosomatic patients show raised noradrenaline (NA), adrenaline (AD), cortisol, free serotonin (f5HT) and platelet aggregability. Conversely, they show reduced NA/AD plasma ratio and platelet serotonin (p5HT). They also show adrenal hyperresponsiveness to an oral glucose load. These findings are opposed to those observed in depressed patients who show adrenal gland sympathetic hyporesponsiveness and neural sympathetic hyperactivity.

OBJECTIVE

To investigate adrenal gland and neural sympathetic systems as well as the other parameters in nondrepressed severely ill patients through the orthostasis exercise stress test which in normals triggers NA but no AD rise.

METHODS

We investigated 35 severely ill patients and their age- and sex-paired controls. Systolic, diastolic pulse pressure (PP), heart rate and neuroendocrine parameters were measured supine (0 min), at orthostasis (1 min) and exercise (5 min). A second test was performed 2 weeks later, after atropine injection. Multivariate analysis of variance, paired t test and Pearson product-moment test were employed.

RESULTS

The normal PP orthostasis fall was not observed in patients. At this period, an abnormal AD peak substituted the normal NA peak. The normal p5HT-f5HT orthostasis-exercise peaks were absent in patients. Cortisol and platelet aggregability were raised in patients.

CONCLUSIONS

Severely ill (somatic) patients responded to the orthostasis-exercise stress test with adrenal and corticosuprarenal but not neural sympathetic activity. They did not show the normal parasympathetic activity at orthostasis. This adrenal gland sympathetic hyperactivity registered in somatic patients is similar to that observed in mammals which fail to cope with stress and contrary to the profile registered in depressed subjects who show NA but not AD rise.

Effects of superoxide dismutase and catalase during reduction of adrenochrome by DT-diaphorase and NADPH-cytochrome P450 reductase

NADPH-cytochrome1 P450 reductase and DT-diaphorase catalyze and one- and two-electron reduction of adrenochrome to its o-semiquinone and o-hydroquinone, respectively. Under aerobic conditions both adrenochrome o-semiquinone and o-hydroquinone proved to be unstable, undergoing autoxidation with concomitant oxygen consumption and continuous NADPH and NADH oxidation. Molecular oxygen was found to play a predominant role in autoxidation of o-semiquinone during reduction of adrenochrome catalyzed by NADPH-cytochrome P450 reductase. In addition, molecular oxygen, in the presence of manganese, was found to be responsible for the majority of autoxidation of o-semiquinone. However, the role of superoxide radicals in the autoxidation of leucoadrenochrome during the reduction of adrenochrome by DT-diaphorase was found to be predominant. Catalase different significantly with respect to NADPH and NADH oxidation during reduction of adrenochrome catalyzed by NADPH-cytochrome P450 reductase and DT-diaphorase. Catalase increased NADPH oxidation slightly, while NADH oxidation was inhibited during reduction of adrenochrome by NADPH cytochrome P450 reductase and DT-diaphorase, respectively. The presence of manganese in the incubation mixture was found to increase the prooxidant role of catalase on autoxidation during one-electron reduction of aminochrome catalyzed by NADPH cytochrome P450 reductase. A marked difference in the inhibitory effect of superoxide dismutase on oxygen consumption during adrenochrome reduction catalyzed by NADPH-cytochrome P450 reductase and DT-diaphorase was also observed. A possible mechanism for reduction of adrenochrome by NADPH-cytochrome P450 reductase and DT-diaphorase and a role for superoxide dismutase and catalase are proposed.

Superoxide dismutase and catalase enhance autoxidation during one-electron reduction of aminochrome by NADPH-cytochrome P-450 reductase

NADPH-cytochrome P-450 reductase catalyzes one-electron reduction of aminochrome to the corresponding ortho-semiquinone, which was found to be unstable as indicated by the occurrence of NADPH oxidation and oxygen consumption. The addition of superoxide dismutase and catalase, alone or together, to the incubation mixture, during reduction of aminochrome catalyzed by NADPH-cytochrome P-450 reductase, did not prevent the autoxidation of ortho-semiquinone, but instead they increased NADPH oxidation. These results contrast with the almost complete inhibition of autoxidation (NADH oxidation) of ortho-hydroquinone during reduction of aminochrome catalyzed by DT-diaphorase in the presence of both superoxide dismutase and catalase. However, the effect of superoxide dismutase and catalase on oxygen consumption was found to differ from the effect on NADH or NADPH oxidation, since these enzymes, alone or together, inhibited the oxygen consumption during the reduction of aminochrome catalyzed by both NADPH-cytochrome P-450 reductase and DT-diaphorase. These results support the proposed role of NADPH-cytochrome P-450 reductase in neurodegeneration as a consequence of activation of aminochrome to reactive oxygen species. In addition, they also support the protective and antioxidant role of DT-diaphorase, together with superoxide dismutase and catalase, by competing with NADPH-cytochrome P-450 reductase to reduce aminochrome to ortho-hydroquinone and prevent the formation of reactive oxygen species. A possible mechanism is proposed.

Superoxide dismutase and catalase prevent the formation of reactive oxygen species during reduction of cyclized dopa ortho-quinone by DT-diaphorase

Dopa was oxidized by Mn(3+)-pyrophosphate complex to the corresponding o-quinone, accompanied by the cyclization of the amino chain to form cyclized dopa ortho-quinone (cDoQ) with absorption maxima at wavelengths of 305 and 475 nm. The cyclization was found to proceed in a single step from DoQ to cDoQ without formation of cDoQH2 and oxygen consumption. DT-diaphorase catalyzes the reduction of cDoQ to the corresponding hydroquinone (cDoQH2), which was found to be unstable in the presence of oxygen. The autoxidation of the cDoQH2 was followed by recording the constant oxidation of NADH and oxygen consumption and reduction of cDoQ at a wavelength of 475 nm. It was found that three different oxidizing agents were involved in autoxidation of cDoQH2. The addition of DETAPAC resulted in a strong inhibition of NADH oxidation (65% inhibition) during the reduction of cDoQ by DT-diaphorase, suggesting that manganese was responsible for 65% of the autoxidation of cDoQH2. The addition of SOD to the incubation mixture resulted in the inhibition of NADH oxidation (79%) during the reduction of cDoQ by DT-diaphorase. In the presence of DETAPAC, the addition of SOD inhibited NADH oxidation during cDoQH2 autoxidation 75%, suggesting that superoxide radicals are responsible for 75% of the oxygen-dependent autoxidation. The remaining NADH oxidation, which was not inhibited by DETAPAC and SOD, was accompanied by a constant oxygen consumption, suggesting that this autoxidation of cDoQH2 proceeds by reducing oxygen to superoxide radical. The effect of SOD and catalase in the presence of DETAPAC was also studied. A nearly complete inhibition (90%) of oxygen consumption during the reduction of cDoQ by DT-diaphorase was observed when SOD alone or SOD and catalase were added to the incubation mixture containing DETAPAC. We conclude that SOD and catalase constitute a protective cellular system against formation of reactive oxygen species during reduction of cDoQ by DT-diaphorase.

The protective effect of superoxide dismutase and catalase against formation of reactive oxygen species during reduction of cyclized norepinephrine ortho-quinone by DT-diaphorase

Norepinephrine was oxidized by the Mn(3+)-pyrophosphate complex to the corresponding o-quinone at pH 6.5. Cyclized norepinephrine ortho-quinone showed an absorption maximum at 289 and 483 nm. No oxygen consumption was observed during oxidation of norepinephrine to o-quinone by Mn3+ and subsequent cyclization. The reduction of cyclized norepinephrine ortho-quinone to the corresponding hydroquinone was catalyzed by DT-diaphorase. However, the hydroquinone formed proved to be unstable in the presence of oxygen, since reduction of cyclized norepinephrine o-quinone by DT-diaphorase was accompanied by continuous oxidation of NADH and oxygen consumption. Addition of the chelator DETAPAC or SOD to the incubation mixture during reduction of cyclized norepinephrine ortho-quinone by DT-diaphorase strongly inhibited NADPH oxidation and oxygen consumption, suggesting that manganese and superoxide radicals were involved in hydroquinone autoxidation. Elimination of the effects of superoxide radicals, manganese and H2O2 on autoxidation of hydroquinone by addition of SOD, catalase and DETAPAC to the incubation mixture resulted in a 79% inhibition of NADH oxidation, suggesting that 21% of the autoxidation is oxygen-dependent. However, the effect of these additions on oxygen consumption was even more pronounced (93% inhibition).

Sodium nitroprusside (SNP) hypotension: intracranial pressure (ICP) and hemodynamics in pial arteriole in the rat

A detailed description is made of an acute closed cranial window method. The method is used for the study of cerebral pial microcirculation by intravital microscopy in the rat. Using these methods and techniques, the effects of systemic hypotension by SNP, i.v., on pial microvessel hemodynamics and on ICP were simultaneously measured and characterized under normophysiological conditions. The pH, PO2, PCO2 and temperature of the artificial cerebrospinal fluid (CSF) in the closed cranial window, intermittently measured, remained relatively constant, 30 to 60 min following the period of stabilization of the preparation. The infusion of SNP (6.2-35.0 micrograms/kg/min, 0.02% sol., i.v.) significantly decreased BP (52.1 +/- 13.4 mm Hg, mean +/- SD). From measurement of microvessels internal diameter (I. D.) and microhemodynamics, significant increases in pial arteriolar I.D. (from 35.4 +/- 10.1, microns, to 47.1 +/- 5.7, microns, mean and S.D., 33.0%) and estimated bulk flow (51.2%), occurred during the hypotension. The changes in hemodynamic parameter were predominantly in the arteriolar system. Only minimal changes in the venular diameter occurred during the SNP hypotension. The observed moderate (22.0%) increase in ICP during SNP hypotension in pentobarbital anesthetized rat correlates well with the microhemodynamic changes of the cerebral microcirculatory system.

Microvascular reactivity of the myopathic Syrian hamster cremaster muscle

The myopathic Syrian hamster is a genetic model of congestive heart failure that exhibits focal myocytolytic necrosis in both heart and skeletal muscle. Previous investigations of microvascular morphology in heart and skeletal muscle have shown severe arteriolar constrictions without fixed anatomical vessel lesions. This study tested the hypothesis that these constrictions indicate a hyperreactivity of the myopathic microvasculature in vivo and that the reactivity corresponds to the developmental course of myocyte pathology. The microcirculation of the cremaster muscle was studied in eight myopathic and six control hamsters in the active stage of necrosis (39-81 days of age) and five myopathic and six control hamsters in the later stage of muscle healing (150-213 days of age). The internal diameter of second order arterioles was measured during topically applied noradrenaline. The myopathic arterioles of the younger group constricted at significantly lower concentrations of noradrenaline (p less than 0.01) and constricted to 35-50% of their resting internal diameter over a narrower range of noradrenaline (p less than 0.01). This indicated both a reduced threshold to noradrenaline and an enhanced response to the agonist. Active myocytolytic necrosis was found in the contralateral cremaster muscle of each myopathic hamster. The older myopathic and control hamsters showed no significant differences in arteriolar responsiveness to applied noradrenaline and no active necrosis. These results indicate a relation between a hyperreactive microvasculature and active necrosis and a normal reacting microvasculature and diminished necrosis in the two phases of the disease. Thus a general correspondence between vascular responsiveness and myocyte pathology exists in this model of heart failure and muscular dystrophy.

Pressure effects on the flow behavior of sickle (HbSS) red cells in isolated (ex-vivo) microvascular system

The effect of varying arterial perfusion pressure (Pa) on flow behavior of human normal (HbAA) and sickle (HbSS) erythrocytes was evaluated in isolated rat mesoappendix vasculature. Red cell velocity (Vrbc) and wall shear rate in single arterioles (i.d. 20.4 +/- 4.5 Microns means and SD) were determined and total peripheral vascular resistance (PRU) calculated. The vasculature initially perfused with Ringer's solution was then perfused with red cells suspended (HCT 2%) in the same medium. At Pa of 100 mm Hg, oxy HbSS cells resulted in higher (50%) PRU and lower Vrbc (7.1 +/- 2.2 mm/sec) and wall shear rates (1800 +/- 490 sec-1) than those recorded with HbAA cells which show a more rapid microvascular passage, i.e., Vrbc (14.4 +/- 2.8 mm/sec) and wall shear rates (3810 +/- 360 sec-1). At the same Pa, partial deoxygenation (PO2 40 mm Hg) of HbSS cells caused marked (300%) increase in PRU, and decrease in Vrbc (3.2 +/- 0.9 mm/sec), and wall shear rates (820 +/- 440 sec-1). During stepwise decrement of Pa (100-30 mm Hg), PRU for oxy HbSS cells remains elevated but the overall trend is similar to that for HbAA cells and Ringer's perfusion. At Pa of 30 mm Hg, oxy HbSS cells caused some microvascular obstruction. In contrast, with decrement in Pa below 80 mm Hg partially deoxy HbSS cells resulted in progressive increase in PRU and drastic decrease in Vrbc, coupled with progressive capillary obstruction and stasis. An increased propensity of these cells to cause irreversible vasoocclusion is demonstrated when low-pressure conditions prevail.

Erythrocytes in sickle cell anemia are heterogeneous in their rheological and hemodynamic characteristics

To understand the contribution to the pathophysiology of sickle cell anemia of the different erythrocyte density types present in the blood of these patients, we have studied the viscosimetric and hemodynamic characteristics of four major classes of hemoglobin SS erythrocytes. We have isolated reticulocytes, discocytes, dense discocytes, and irreversibly sickled cells (fractions I-IV) on Percoll-Renografin density gradients. Bulk viscosity was studied in a coneplate viscosimeter and the hemodynamic studies were performed on the isolated, artificially perfused mesoappendix vasculature of the rat (Baez preparation). Bulk viscosity measurements at shear rates of 230 S-1 demonstrate that when the cells are oxygenated, fraction I (reticulocyte rich) has a higher viscosity than expected from its low intracellular hemoglobin concentration. The rest of the fractions exhibit moderate increases in bulk viscosity pari-passu with the corresponding increases in density (mean corpuscular hemoglobin concentration). When deoxygenated, all cell fractions nearly doubled their bulk viscosity and the deoxy-oxy differences remained constant. The Baez preparation renders a different picture: oxygenated fractions behave as predicted by the viscosimetric data, but, when deoxygenated, cell fractions exhibit dramatically increased peripheral resistance and the deoxy-oxy difference are directly proportional to cell density, thus, the largest increases were observed for fractions III and IV. The differences between the rheological and the hemodynamic measurements are most probably due to the different sensitivity of the two methods to the extent of intracellular polymerization. These results also demonstrate that the hitherto unrecognized fraction III cells (very dense discocytes that change shape very little on deoxygenation) are as detrimental to the microcirculation as the irreversibly sickled cell-rich fraction IV. They may, however, induce obstruction by a different mechanism. As the extent to which these fractions are populated by erythrocytes varies considerably from patient to patient, the distribution function of cell densities in each sickle cell anemia patient might have consequences for the type of pathophysiological events occurring in their microcirculation.

Some aspects of the pathophysiology of homozygous Hb CC erythrocytes

We have studied erythrocytes from homozygous CC patients in vitro and in perfused rat mesoappendix vasculature to answer some long-standing questions. By examination of wet whole blood preparations, and by comparing the cell distribution on isopycnic continuous density gradients of whole blood samples from a splenectomized CC patient with those from three intact CC patients, we have demonstrated the presence of a distinct crystal-containing band of cells that is present in the former, but totally absent from the latter. We conclude that Hb CC cells containing crystals circulate in Hb CC individuals, but in intact patients they are effectively removed by the spleen. By use of 31P nuclear magnetic resonance and viscosity measurements on cells, we have demonstrated that intracellular aggregation of hemoglobin C occurs on deoxygenation even when no crystal formation is detectable by morphological methods. These two observations are in apparent contradiction with the absence of clinical microcirculatory impairment found in both intact and splenectomized CC patients. The contradiction was resolved by rheological studies on isolated rat mesoappendix preparations and erythrocyte diameter measurements that lead to the conclusion that the hemorheological properties of CC cells in the microcirculation are nearly normal because their increased viscosity is offset by their smaller diameter and size.

Microvascular responses to norepinephrine and vasopressin during halothane anesthesia in the rat

This experiment was designed to determine the microvascular responses to the two known naturally occurring vasoconstrictors, norepinephrine (NE) and vasopressin, at known levels of central vasomotor activity before, during and after halothane anesthesia. The responses to topical application of NE and vasopressin were studied in the microvasculature of the mesentery and cremaster muscle, using microscopic methods. Neural (CNS) stimulation was accomplished through electrodes chronically implanted in vasoactive sites of the forebrain and midbrain. The increase in blood pressure in response to CNS stimulation was decreased during halothane anesthesia (32.4 +/- 5.4 per cent before and 24.7 +/- 6.1 per cent during; P less than 0.001). There was no significant change in the steady-state diameter of the microvasculature under study during or after halothane anesthesia. Marked abatement of arteriolar vasoconstriction in response to CNS stimulation was seen prior to halothane. However, the same target vessel showed increased constriction in response to topically applied NE (from 32.3 +/- 4.7 to 53.2 +/- 7.8 per cent; P less than 0.01) during halothane anesthesia. By contrast, the response to vasopressin decreased (from 42.4 +/- 5.7 to 1.0 +/- 6 per cent; P less than 0.001) with halothane. The precise mechanism(s) underlying the described hypersensitivity to NE and hyposensitivity to vasopressin in the same vascular structure during halothane anesthesia remains undetermined.

Central neural influence on precapillary microvessels and sphincter

The responses to central nervous system (CNS) stimulation of consecutive segments of arterioles down to the precapillary sphincter were measured in the mesoappendix and/or cremaster of nine male rats with indwelling electrodes. Under pentobarbital sodium anesthesia, vasoactive sites were stimulated at threshold for maximal constriction or lumen closure of the precapillary sphincter and/or immediately preceding precapillary arteriole (metarteriole). In all experiments, CNS stimulation induced blood pressure elevation and constriction of three consecutive segments of precapillary vessels and of the sphincter. A threefold increase in rate of vasomotion of precapillary sphincter and metarteriole was the rule, but this was noted infrequently in larger arterioles. In addition to an overall influence of the CNS on microcirculation, the data show a gradient of responses to stimulation, the slope of which is negatively related to the size of the vessels and sphincter, in both tissues studied. A complete lumen closure of the metarteriole and precapillary sphincter (when present) in response to CNS stimulation implies active participation in the regulation of local blood flow. No evidence was foun for central neural regulation of the precapillary sphincter independent of arteriolar control.

Pial microcirculation in subarachnoid hemorrhage

Microsurgical and microscopic methods were employed in guinea pigs to expose, observe, and measure response characteristics of cerebral cortical pial microvessels and microcirculation to traumatic and nontraumatic experimental subarachnoid hemorrhage. Bleeding produced by vascular micropuncture was associated with a 44.3% arteriolar constriction. Topical application of homologous blood alone produced a 33.2% vasoconstriction. Observed microcirculatory flow characteristics subsequent to such microvascular changes were consistent with those known to be associated with cerebral cortical infarction. These changes could be prevented or reversed by topical application of the alpha adrenergic blocker, phenoxybenzamine. Topical pretreatment with the beta adrenergic blocker, propranolol, prevented blood-induced spasm, but did not reverse such spasm once it had been established. A chemo-mechanical mechanism is suggested as underlying the vasoconstriction association with rupture of pial microvessels. It is thought that consideration of such microvascular characteristics, in conjunction with those known to be associated with larger intracranial vessels, adds to current knowledge of the pathophysiology of subarachnoid hemorrhage and may be extrapolated to bear future clinical import.

On the relationship of brain vasculature to production of neurological deficit and morphological changes following acute unilateral common carotid artery ligation in gerbils

The known susceptibility of the Mongolian gerbil to cerebral infarction following unilateral carotid artery ligation has been attributed in the past to the demonstrated absences of an anastomotic supply between the anterior and posterior cerebral circulations. In a study of 34 adult gerbils exposed to such a procedure, 11, or 33%, developed severe neurological sequelae and succumbed to the procedure in less than 30 hr, whereas 23 animals survived with only minor or transient neurological signs. All animals displayed the expected lack of an anastomosis between the anterior and posterior circulations, but in addition the animals which survived the procedure were found to have a prominent early cross-connection between the anterior cerebral arteries, whereas the animals which succumbed had no such connection. Neuropathological changes in susceptible animals were apparent as early as 3 and one-half hr after ligation and consisted of edema, initially perivascular and then intraneuronal, slowed by acute necrosis. A variety of other vascular anomalies was encountered. We conclude that the peculiar susceptibility of Mongolian gerbils to cerebral infarction following acute unilateral common carotid artery ligation is not related primarily to lack o adequate collaterals between the anterior and the anterior cerebral arteries, but to the degree of adequate adequacy of communication between the anterior cerebral arteries. The critical difference may be more one of degree, i.e. the point at which the medial branches of the anterior cerebral artery fust to become anazygos vessel, rather than an actual difference in the pattern of distribution of the anterior cerebral arteries. The presence of other variation in vascular supply in a relatively small series suggests that results of similar studies of infarction and response to treatment be interpreted with caution.

Reactivity of aorta and portal vein in germfree rats

The responsiveness of conventional and germfree rat aortas and portal veins to vasoactive agents were compared in vitro. The results indicate: (1) aortas and portal veins from germfree rats exhibit an attenuated reactivity to angiotensin, vasopressin and epinephrine but not to KC1; (2) the dose-response curves for epinephrine and the peptides were shifted to the right concomitant with a decrease in maximum contractile tension, and (3) CaC12 dose-response curves obtained on potassium-depolarized aorta were not different from one another, whereas those obtained on portal veins from germfree animals were shifted to the right with a concomitant decrease in maximum response. In addition, aortas and portal veins from germfree rats were found to exhibit a higher total Ca content (but not Mg or water) when compared to conventional animals.

Localization and measurement of microvascular and microcirculatory responses to venous pressure elevation in the rat

The effect of increase in regional draining venous pressure on the response of mesoappendix microvasculature and microcirculation was studied by direct microscopic methods <i>in vivo</i>. In 9 out of 21 experiments in pentobarbital anesthetized rats, elevation of ileo-colic vein pressure (13.0 ± 1.3 mm Hg; mean and SE) above resting levels (9.9 ± 2.2 mm Hg) resulted in persistent lumen expansion of small venular microvessels (18-68 <i>µ</i>m<i>, </i>i.d.) and evoked a vasoconstrictor response of consecutive segments of pre-capillary vessels and the sphincter. The vasoconstricor response was stimulus-dependent and reversible. The lumen reductions in percent for 9 arterioles (21.0 ± 4.37 <i>µ</i>m<i>, </i>i.d.) 9 metarterioles (9.3 ± 1.57 <i>µ</i>m<i>, </i>i.d.), and 5 precapillary sphincters (5.7 ± 1.23 <i>µ</i>m<i>, </i>i.d.) were: 17.9 ± 6.60, 43.6 ± 4.20, and 96.0 ± 3.81, respectively. In none of the experiments did the response propagate to larger arteriolar segments ( > 35–38 <i>µ</i>m, i.d.) in the tissue under observation. These microscopic studies confirmed the presence of a venous-pre-capillary and sphincter constrictor response in splanchnic vasculature in the rat.