Bicycling over a Lifetime Is Associated with Less Symptomatic Knee Osteoarthritis: Data from the Osteoarthritis Initiative

INTRODUCTION

To evaluate the relationship between a history of bicycling and symptomatic and structural outcomes of knee osteoarthritis (OA), the most common form of arthritis.

METHODS

This was a retrospective, cross-sectional study within the Osteoarthritis Initiative (OAI), where we investigated OAI participants with complete data on bicycling, knee pain, and radiographic evidence of knee OA. We used a self-administered questionnaire at the 96-month OAI visit to identify participation in bicycling during four time periods throughout a participant's lifetime (ages 12-18, 19-34, 35-49, and > 50 years old). Using logistic regression, we evaluated the influence of prior bicycling status (any history, history for each time period, number of periods cycling) on three outcomes at the 48-month OAI visit: frequent knee pain, radiographic OA (ROA), and symptomatic radiographic OA (SOA), adjusting for age and gender.

RESULTS

2607 participants were included; 44.2% were male; mean age was 64.3 (SD 9.0) years; body mass index was 28.5 (SD 4.9) kg/m 2 . The adjusted risk ratio for the outcome of frequent knee pain, ROA, and SOA among those who reported any history of bicycling compared to non-bicyclers was 0.83 (0.73-0.92), 0.91 (0.85-0.98), and 0.79 (0.68-0.90), respectively. We observed a dose-response among those who participated in bicycling during more time periods.

CONCLUSIONS

People who participated in bicycling had a lower prevalence of frequent knee pain, ROA, and SOA. The benefit appeared cumulative. This study indicates that bicycling may be favorable to knee health and should be encouraged.

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.

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.

Quadriceps Strength and Knee-Related Symptom State 6 Months After Anterior Cruciate Ligament Reconstruction

CONTEXT

Isometric quadriceps strength metrics and patient-reported outcomes are commonly used in return-to-sport assessments in those with anterior cruciate ligament reconstruction (ACLR). Patients may experience clinical knee-related symptoms aggravating enough to seek additional medical care after ACLR. In addition to seeking additional medical care, these patient-reported clinical knee-related symptoms may also influence function after ACLR. However, whether an association exists between these common quadriceps metrics and the patient-reported clinical knee-related symptom state is unknown.

OBJECTIVE

To determine if meeting isometric quadriceps strength and symmetry criteria is associated with acceptable clinical knee-related symptoms at 5 to 7 months post-ACLR.

DESIGN

Cross-sectional study.

SETTING

Laboratories.

PATIENTS OR OTHER PARTICIPANTS

We classified individuals at 5 to 7 months post-ACLR based on their isometric ACLR and uninvolved-limb quadriceps strength or quadriceps strength symmetry. We also dichotomized participants based on the Englund et al criteria for unacceptable clinical knee-related symptoms.

MAIN OUTCOME MEASURE(S)

Quadriceps strength variables were compared between groups using analysis of covariance, and the relative risk of a participant in each quadriceps strength group reporting acceptable clinical knee-related symptoms was determined using binary logistic regression.

RESULTS

A total of 173 individuals participated. The isometric quadriceps strength and limb symmetry index were different (P < .001) between quadriceps strength groups. Those categorized as both strong and symmetric had a 1.28 (95% CI = 0.94, 1.74) and individuals categorized as symmetric only had a 1.29 (95% CI = 0.97, 1.73) times greater relative risk of reporting acceptable clinical knee-related symptoms compared with the neither strong nor symmetric group.

CONCLUSIONS

The majority of individuals (85%) recovering from ACLR failed to meet either the clinical quadriceps strength or symmetry criteria at 5 to 7 months post-ACLR. Quadriceps strength and quadriceps strength symmetry are clinically important but may not be primary determinants of the clinical knee-related symptom state within the first 6 months post-ACLR.

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.

Knee symptoms do not affect walking biomechanics among women 6 months after anterior cruciate ligament reconstruction

Women with anterior cruciate ligament reconstruction report worse pain and knee-related symptoms, and also exhibit biomechanical changes that may be related to knee osteoarthritis (OA) development. This is particularly concerning as symptom state has been previously associated with knee OA development. The purpose of this study was to compare lower extremity walking biomechanics between women (age: 21.40 ± 8.54 years) experiencing clinically significant knee-related symptoms and women with acceptable symptoms 6 months following surgery. Twenty-eight women with history of primary, unilateral anterior cruciate ligament reconstruction who completed a lower extremity walking biomechanics assessment 6 months following surgery were included in this analysis. Women were dichotomized as experiencing acceptable or clinically significant knee symptoms according to Knee injury and OA Outcomes Score cut-offs described by Englund et al. Walking biomechanics were compared between women with clinically significant and acceptable symptoms using one-way analysis of covariances for involved limb biomechanics. Biomechanical variables of interest were: peak vertical ground reaction forces (vGRFs), vGRF loading rates, knee flexion angles, knee extension moments, knee adduction angles, and knee adduction moments, and gait speed. Nearly 60% of women reported clinically significant knee symptoms 6 months postoperative. There were no statistically significant differences between symptom groups for walking biomechanics and gait speed outcomes. These findings suggest patient reported knee symptoms may not be a primary influence on walking biomechanics 6 months following anterior cruciate ligament reconstruction. Though, longitudinal assessment of changes in symptom state and walking biomechanics may be warranted as poorer walking biomechanics and symptoms are indicators of knee OA.

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.

Longitudinal Changes in Ultrasound-Assessed Femoral Cartilage Thickness in Individuals from 4 to 6 Months Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

Diagnostic ultrasound provides a valid assessment of cartilage health that has been used to observe cross-sectional cartilage thickness differences post-ACLR (anterior cruciate ligament reconstruction), but has not been used longitudinally during early recovery post-ACLR.

DESIGN

The purpose of this study was to assess longitudinal changes in femoral cartilage thickness via ultrasound in individuals at 4 to 6 months post-ACLR and compared to healthy controls. Twenty participants (50% female, age = 21.1 ± 5.7 years) completed testing sessions 4 and 6 months post-ACLR. Thirty healthy controls (57% female, age = 20.8 ± 3.8 years) without knee injury history completed 2 testing sessions (>72 hours apart). Femoral cartilage ultrasound images were captured bilaterally in ACLR participants and in the dominant limb of healthy controls during all sessions. Average cartilage thicknesses in the medial, intercondylar, and lateral femoral regions were determined using a semi-automated processing technique.

RESULTS

When comparing cartilage thickness mean differences or changes over time, individuals post-ACLR did not demonstrate between limb differences (P-range = 0.50-0.92), limb differences compared to healthy controls (P-range = 0.19-0.94), or changes over time (P-range = 0.22-0.72) for any femoral cartilage thickness region. However, participants demonstrated cartilage thickening (45%) or thinning (35%) that exceeded minimal detectable change (MDC) from 4 to 6 months post-ACLR, respectively.

CONCLUSIONS

Using MDC scores may help better identify within-subject femoral cartilage thickness changes longitudinally post-ACLR due to bidirectional cartilage thickness changes.

Quadratic Association Between Corticomotor and Spinal-Reflexive Excitability and Self-Reported Disability in Participants With Chronic Ankle Instability

CONTEXT

Spinal-reflexive and corticomotor excitability may have a critical role in altering muscle function needed to stabilize the ankle in people with chronic ankle instability (CAI).

OBJECTIVE

To determine the association between self-reported disability and both spinal-reflexive and corticomotor excitability in people with CAI.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PARTICIPANTS

30 participants with CAI.

MAIN OUTCOME MEASURES

Soleus spinal-reflexive excitability was measured with normalized Hoffmann reflexes (H:M ratio), and corticomotor excitability was measured with transcranial magnetic stimulation and quantified by normalized motor-evoked-potential (MEP) amplitudes at 120% of active motor threshold (120%MEP). Self-reported disability was quantified with the activities-of-daily-living and sport subscales of the Foot and Ankle Ability Measure (FAAM-ADL and FAAM-S). Separate linear Pearson product-moment correlations and nonlinear quadratic correlations were used to determine associations between the neural-excitability and disability variables.

RESULTS

Thirty participants were included in the spinal-reflexive-excitability analysis, while only 19 were included in the corticomotor analysis. There was a significant, weak linear association between H:M ratio and FAAM-ADL (R = .39, P = .03) and a nonsignificant, weak linear association between H:M ratio and FAAM-S (R = .36, P = .06). There were significant, moderate quadratic associations between H:M ratio and both FAAM-ADL (R = .48, P = .03) and FAAM-S (R = .50, P = .02). There was a significant, moderate linear association between 120%MEP and FAAM-ADL (R = -.48, P = .04) and a nonsignificant, moderate negative linear association between FAAM-S (R = -.42, P = .07). There was a significant, moderate quadratic association between 120%MEP and FAAM-ADL (R = .57, P = .046) and a significant, strong quadratic correlation between 120%MEP and FAAM-S (R = .71, P = .004).

CONCLUSIONS

There are significant quadratic associations between self-reported disability and both spinal-reflexive and corticomotor excitability of the soleus. CAI participants with low or high neural excitability present with lower function.

Electron microscopic exploration of human endothelium in step-serial sections of early and advanced atherosclerotic lesions

A transmission electron microscopic study of step-serial sections of numerous human early and advanced atherosclerotic lesions obtained under conditions preventing artificial endothelial loss was undertaken. It was found that (1) no endothelial denudation with platelet aggregation occurred over any early myoproliferative lesions, (2) endothelial denudation with platelet aggregation had developed only over the mostly necrotic caps of some advanced end-stage lesions, and (3) all stages of atherosclerosis showed endothelial changes that indicated increased permeability of the endothelium over plaques for plasma constituents, namely, opened interendothelial junctions and endothelial lipid inclusions. These results suggest that endothelial denudation and platelet aggregation is not an initiating event in human atherogenesis but something that happens late over the disintegrating surface of some end-stage lesions as a prelude to supra-plaque thrombosis--in agreement with our light microscopic findings of 25 years ago that thrombosis in human atherosclerotic arteries is usually triggered by a breakdown of the mostly necrotic caps of advanced plaques.

Vessel invasion by tumour cells. An ultrastructural study

The present electron microscopic investigation explored the mechanism through which the cells of an experimental fibrosarcoma implanted in the liver of syngeneic mice broke through the continuous (unperforated) endothelium of peri-tumour veins to enter the blood stream, as well as the immediate reaction of blood cells to the tumour breakthrough. It was found that at their point of contact with the endothelial tube of the peri-tumour vein, the tumour cells caused the endothelial basement membrane to disappear and they entered the vein lumen either by inducing an opening of interendothelial junctions, or by causing intensive vacuolation and disintegration of individual endothelial cells--and thus producing gaps for their passage into the lumen. Both mechanisms of entry were sometimes observed in the same tumour. At their point of breakthrough into the vein lumen, many neoplastic cells were immediately covered by a dense platelet aggregate or they were surrounded by numerous polymorph leucocytes (neutrophils more often than eosinophils) that stuck to their surfaces and sometimes caused a focal disappearance of the tumour cell plasma membrane at the site of polymorph-tumour cell contact. Occasionally polymorph lysosomal granules migrated to such contact areas, and the plasma membrane of the contacting polymorph disappeared as well. Finally, some polymorphs apparently plunged into the cytoplasm of vessel-invading tumour cells, while others were seemingly phagocytised by the latter.

The role of microvascular environment in the metastasizing ability of an experimental tumor

A rapidly growing, locally very invasive and easily transplantable fibrosarcoma that was developed through chemical carcinogenesis in Balb/c mice in this laboratory several years ago did not metastasize into the viscera of its hosts when implanted into the subcutaneous connective tissue or skeletal muscle of syngeneic mice. When, however the same tumour was implanted into the liver or the kidneys of Balb/c mice it metastasized extensively into many different organs within 2 weeks of its transplantation. Evidence is presented that because of some unknown deficiency the cells of the fibrosarcoma under study are unable to penetrate through the endothelial wall into the lumen of the particular type of vessels which surround and vascularize the tumours in the subcutaneous connective tissue and muscle, and that, in contrast, they can easily cross into the lumen of the vessels that surround and vascularize them in the liver and kidney. Thus, this in vivo study indicates that the type of microvascular environment in which certain experimental tumours are transplanted can control their ability to accomplish vascular invasion, the first step of the metastatic process.

Prevention of lipofuscin development in neurons by anti-oxidants

It was documented that ageing is associated with a progressive and highly significant proliferation of the total number of light microscopically visible lipofuscin granules in the grey substance of sections of the cervical spinal cord of Balb/c mice. The mean total numbers (+/- standard errors) of lipofuscin granules in standard sections of the glutaraldehyde-osmium fixed, epon embedded spinal cords that were examined with a phase contrast light microscope in 1 week, 1 month, 8 months and 18 months old mice were 0, 269 +/- 56, 1101 +/- 82 and 2464 +/- 318, respectively. The population densities of multiglobular lipofuscin units as seen with the electron microscope in random spinal cord neurons of the same 4 age groups corresponded well with the above quantitative, light microscopic data. Continuous treatment for 8 months with either the natural anti-oxidant Vitamin E (alpha-tocopherol) at 40 mg/mouse/week or the synthetic anti-oxidant butylated hydroxytoluene at about 100 mg/mouse/week diminished significantly the proliferation of lipofuscin granules in spinal cord neurons that developed during that period of ageing. No toxicity of any sort was caused by these two treatments. These results provide support for the peroxide theory of lipofuscin biogenesis and encourage further exploration of the possibilities of obtaining greater anti-lipofuscin effects with less molecular bulk of antioxidants.

Initiation of a transplantable fibrosarcoma by the synergism of two non-initiators, alpha-tocopherol and soya oil

When, in the course of an ageing study, alpha-tocopherol (vitamin E), dissolved in soya oil, was given to 22 Balb/c mice once a week subcutaneously for 10 months, it caused the development of vigorously growing fibrosarcomata at the site of the injections in 17 (77.3%) of the animals. The tumors produced in this manner proved eminently transplantable into syngeneic Balb/c hosts, and have been serially transplanted every 3-4 weeks for over 3 years in such recipients, having reached their 44th transplantation cycle at the present time; upon transplantation, they now exhibit a 100% "take" incidence and proliferate extremely rapidly, growing from pin-head size to up to half the weight of a whole recipient mouse within 3 weeks. All fibrosarcomata showed marked mitotic activity, invasion of adjacent tissues and extensive necrotic areas, and they became more undifferentiated after the third transplantation cycle. Neither pure alpha-tocopherol alone nor soya oil alone produced any tumors when given subcutaneously once a week, for 10 months to groups of 22 Balb/c mice each. It is concluded that the two agents alpha-tocopherol and soya oil which proved non-carcinogenic when injected alone, developed a powerful carcinogenic effect when they acted on subcutaneous connective tissue simultaneously. The possible mechanisms of this phenomenon are discussed.