Risk of falls is associated with 30-day mortality among older adults in the emergency department

OBJECTIVE

Falls in older adults correlate with heightened morbidity and mortality. Assessing fall risk in the emergency department (ED) not only aids in identifying candidates for prevention interventions but may also offer insights into overall mortality risk. We sought to examine the link between fall risk and 30-day mortality in older ED adults.

METHODS

Observational cohort study of adults aged ≥ 75years who presented to an academic ED and who were assessed for fall risk using the Memorial Emergency Department Fall Risk Assessment Tool (MEDFRAT), a validated, ED-specific screening tool. The fall risk was classified as low (0-2 points), moderate (3-4 points), or high (≥5) risk. The primary outcome was 30-day mortality. Hazard ratios (HR) with 95% confidence intervals (CIs) were calculated.

RESULTS

A total of 941 patients whose fall risk was assessed in the ED were included in the study. Median age was 83.7 years; 45.6% were male, 75.6% lived in private residences, and 62.7% were admitted. Mortality at 30 days among the high fall risk group was four times that of the low fall risk group (11.8% vs 3.1%; HR 4.00, 95% CI 2.18 to 7.34, p < 0.001). Moderate fall risk individuals had nearly double the mortality rate of the low-risk group (6.0% vs 3.1%), but the difference was not statistically significant (HR 1.98, 95% CI 0.91 to 4.32, p = 0.087).

CONCLUSION

ED fall risk assessments are linked to 30-day mortality. Screening may facilitate the stratification of older adults at risk for health deterioration.

Establishing healthy longevity clinics in publicly funded hospitals

Healthy longevity medicine integrates geroscience and other disciplines into clinical settings, aiming to optimize health throughout one's lifespan. Multiple factors have led to increased consumer engagement, with private clinics currently meeting the demand for guidance to improve healthy longevity. The establishment of healthy longevity clinics in publicly funded hospitals is a significant development, making longevity-focused healthcare more accessible. These clinics rely on multidisciplinary teams of physicians and allied health professionals. Diagnostics involve comprehensive evaluations of medical history, physical examinations, and various clinical tests to detect early signs of age-related functional decline. Interventions in healthy longevity medicine encompass lifestyle modifications, supplements, repurposed drugs, and social and environmental interventions. Collaboration with research institutions and industry partners is crucial for advancing healthy longevity medicine and creating standardized protocols. In this article, we review the process of creating healthy longevity clinics in public hospitals to ensure the best possible care for individuals pursuing healthy longevity.

Biomarkers of cellular senescence and risk of death in humans

A robust and heterogenous secretory phenotype is a core feature of most senescent cells. In addition to mediators of age-related pathology, components of the senescence associated secretory phenotype (SASP) have been studied as biomarkers of senescent cell burden and, in turn, biological age. Therefore, we hypothesized that circulating concentrations of candidate senescence biomarkers, including chemokines, cytokines, matrix remodeling proteins, and growth factors, could predict mortality in older adults. We assessed associations between plasma levels of 28 SASP proteins and risk of mortality over a median follow-up of 6.3 years in 1923 patients 65 years of age or older with zero or one chronic condition at baseline. Overall, the five senescence biomarkers most strongly associated with an increased risk of death were GDF15, RAGE, VEGFA, PARC, and MMP2, after adjusting for age, sex, race, and the presence of one chronic condition. The combination of biomarkers and clinical and demographic covariates exhibited a significantly higher c-statistic for risk of death (0.79, 95% confidence interval (CI): 0.76-0.82) than the covariates alone (0.70, CI: 0.67-0.74) (p < 0.001). Collectively, these findings lend further support to biomarkers of cellular senescence as informative predictors of clinically important health outcomes in older adults, including death.

Targeting cellular senescence in metabolic disease

Cellular senescence is a cell fate involving cell cycle arrest, resistance against apoptosis, and the development of a secretome that can be pro-inflammatory. In aging and obesity, senescent cells accumulate in many tissues, including adipose tissue, brain, kidney, pancreas, and liver. These senescent cells and their downstream effects appear to perpetuate inflammation and have been implicated in the pathogenesis of metabolic dysfunction. Senescent cells are cleared in part by the immune system, a process that is diminished in obesity and aging, likely due in part to senescence of immune cells themselves. Targeting senescent cells or their products improves metabolic function in both aging and in animal models of obesity. Novel therapeutics to target senescent cells are on the horizon and are currently being investigated in clinical trials in humans for multiple diseases. Early evidence suggests that senolytic drugs, which transiently disarm the anti-apoptotic defenses of pro-inflammatory senescent cells, are effective in causing depletion of senescent cells in humans. Senescence-targeting therapeutics, including senolytic drugs and strategies to increase immune clearance of senescent cells, hold significant promise for treating metabolic dysfunction in multiple tissues and disease states.

Metabolic changes in aging humans: current evidence and therapeutic strategies

Aging and metabolism are inextricably linked, and many age-related changes in body composition, including increased central adiposity and sarcopenia, have underpinnings in fundamental aging processes. These age-related changes are further exacerbated by a sedentary lifestyle and can be in part prevented by maintenance of activity with aging. Here we explore the age-related changes seen in individual metabolic tissues - adipose, muscle, and liver - as well as globally in older adults. We also discuss the available evidence for therapeutic interventions such as caloric restriction, resistance training, and senolytic and senomorphic drugs to maintain healthy metabolism with aging, focusing on data from human studies.

Orally-active, clinically-translatable senolytics restore α-Klotho in mice and humans

BACKGROUND

α-Klotho is a geroprotective protein that can attenuate or alleviate deleterious changes with ageing and disease. Declines in α-Klotho play a role in the pathophysiology of multiple diseases and age-related phenotypes. Pre-clinical evidence suggests that boosting α-Klotho holds therapeutic potential. However, readily clinically-translatable, practical strategies for increasing α-Klotho are not at hand. Here, we report that orally-active, clinically-translatable senolytics can increase α-Klotho in mice and humans.

METHODS

We examined α-Klotho expression in three different human primary cell types co-cultured with conditioned medium (CM) from senescent or non-senescent cells with or without neutralizing antibodies. We assessed α-Klotho expression in aged, obese, and senescent cell-transplanted mice treated with vehicle or senolytics. We assayed urinary α-Klotho in patients with idiopathic pulmonary fibrosis (IPF) who were treated with the senolytic drug combination, Dasatinib plus Quercetin (D+Q).

FINDINGS

We found exposure to the senescent cell secretome reduces α-Klotho in multiple nonsenescent human cell types. This was partially prevented by neutralizing antibodies against the senescence-associated secretory phenotype (SASP) factors, activin A and Interleukin 1α (IL-1α). Consistent with senescent cells' being a cause of decreased α-Klotho, transplanting senescent cells into younger mice reduced brain and urine α-Klotho. Selectively removing senescent cells genetically or pharmacologically increased α-Klotho in urine, kidney, and brain of mice with increased senescent cell burden, including naturally-aged, diet-induced obese (DIO), or senescent cell-transplanted mice. D+Q increased α-Klotho in urine of patients with IPF, a disease linked to cellular senescence.

INTERPRETATION

Senescent cells cause reduced α-Klotho, partially due to their production of activin A and IL-1α. Targeting senescent cells boosts α-Klotho in mice and humans. Thus, clearing senescent cells restores α-Klotho, potentially opening a novel, translationally-feasible avenue for developing orally-active small molecule, α-Klotho-enhancing clinical interventions. Furthermore, urinary α-Klotho may prove to be a useful test for following treatments in senolytic clinical trials.

FUNDING

This work was supported by National Institute of Health grants AG013925 (J.L.K.), AG062413 (J.L.K., S.K.), AG044271 (N.M.), AG013319 (N.M.), and the Translational Geroscience Network (AG061456: J.L.K., T.T., N.M., S.B.K., S.K.), Robert and Arlene Kogod (J.L.K.), the Connor Group (J.L.K.), Robert J. and Theresa W. Ryan (J.L.K.), and the Noaber Foundation (J.L.K.). The previous IPF clinical trial was supported by the Claude D. Pepper Older Americans Independence Centers at WFSM (AG021332: J.N.J., S.B.K.), UTHSCA (AG044271: A.M.N.), and the Translational Geroscience Network.

Targeting p21Cip1 highly expressing cells in adipose tissue alleviates insulin resistance in obesity

Insulin resistance is a pathological state often associated with obesity, representing a major risk factor for type 2 diabetes. Limited mechanism-based strategies exist to alleviate insulin resistance. Here, using single-cell transcriptomics, we identify a small, critically important, but previously unexamined cell population, p21Cip1 highly expressing (p21high) cells, which accumulate in adipose tissue with obesity. By leveraging a p21-Cre mouse model, we demonstrate that intermittent clearance of p21high cells can both prevent and alleviate insulin resistance in obese mice. Exclusive inactivation of the NF-κB pathway within p21high cells, without killing them, attenuates insulin resistance. Moreover, fat transplantation experiments establish that p21high cells within fat are sufficient to cause insulin resistance in vivo. Importantly, a senolytic cocktail, dasatinib plus quercetin, eliminates p21high cells in human fat ex vivo and mitigates insulin resistance following xenotransplantation into immuno-deficient mice. Our findings lay the foundation for pursuing the targeting of p21high cells as a new therapy to alleviate insulin resistance.

Senolytics: Potential for Alleviating Diabetes and Its Complications

Therapeutics that target cellular senescence, including novel "senolytic" compounds, hold significant promise for treating or preventing obesity-induced metabolic dysfunction, type 2 diabetes, and the multiple complications of diabetes and obesity. Senolytics selectively clear senescent cells, which accumulate with aging and obesity and represent a fundamental mechanism of aging that contributes to metabolic dysfunction and diabetes pathogenesis. In addition to improving metabolic function, targeting senescent cells holds promise as a preventive strategy to reduce the incidence and severity of diabetes complications. The intermittent administration schedule used for senolytic therapy may confer benefits in terms of improving adherence and limiting adverse effects. It is necessary to design effective clinical trials that will safely translate discoveries from preclinical models into human studies that may pave the way for a novel therapeutic class for treating obesity, diabetes, and their complications. In this review, we outline what is known regarding the role of cellular senescence in the pathogenesis of type 2 diabetes and its complications, present evidence from preclinical models that targeting cellular senescence is beneficial, review senolytic drugs, and outline the features of clinical trials investigating the role of targeting senescent cells for diabetes.

17α-Estradiol Modulates IGF1 and Hepatic Gene Expression in a Sex-Specific Manner

Aging is the greatest risk factor for most chronic diseases. The somatotropic axis is one of the most conserved biological pathways that regulates aging across species. 17α-Estradiol (17α-E2), a diastereomer of 17β-estradiol (17β-E2), was recently found to elicit health benefits, including improved insulin sensitivity and extend longevity exclusively in male mice. Given that 17β-E2 is known to modulate somatotropic signaling in females through actions in the pituitary and liver, we hypothesized that 17α-E2 may be modulating the somatotropic axis in males, thereby contributing to health benefits. Herein, we demonstrate that 17α-E2 increases hepatic insulin-like growth factor 1 (IGF1) production in male mice without inducing any changes in pulsatile growth hormone (GH) secretion. Using growth hormone receptor knockout (GHRKO) mice, we subsequently determined that the induction of hepatic IGF1 by 17α-E2 is dependent upon GH signaling in male mice, and that 17α-E2 elicits no effects on IGF1 production in female mice. We also determined that 17α-E2 failed to feminize the hepatic transcriptional profile in normal (N) male mice, as evidenced by a clear divergence between the sexes, regardless of treatment. Conversely, significant overlap in transcriptional profiles was observed between sexes in GHRKO mice, and this was unaffected by 17α-E2 treatment. Based on these findings, we propose that 17α-E2 acts as a pleiotropic pathway modulator in male mice by uncoupling IGF1 production from insulin sensitivity. In summary, 17α-E2 treatment upregulates IGF1 production in wild-type (and N) male mice in what appears to be a GH-dependent fashion, while no effects in female IGF1 production are observed following 17α-E2 treatment.

New Horizons: Novel Approaches to Enhance Healthspan Through Targeting Cellular Senescence and Related Aging Mechanisms

The elderly population is increasing faster than other segments of the population throughout the world. Age is the leading predictor for most chronic diseases and disorders, multimorbidity, geriatric syndromes, and impaired ability to recover from accidents or illnesses. Enhancing the duration of health and independence, termed healthspan, would be more desirable than extending lifespan merely by prolonging the period of morbidity toward the end of life. The geroscience hypothesis posits that healthspan can be extended by targeting fundamental aging mechanisms, rather than attempting to address each age-related disease one at a time, only so the afflicted individual survives disabled and dies shortly afterward of another age-related disease. These fundamental aging mechanisms include, among others, chronic inflammation, fibrosis, stem cell/ progenitor dysfunction, DNA damage, epigenetic changes, metabolic shifts, destructive metabolite generation, mitochondrial dysfunction, misfolded or aggregated protein accumulation, and cellular senescence. These processes appear to be tightly interlinked, as targeting any one appears to affect many of the rest, underlying our Unitary Theory of Fundamental Aging Mechanisms. Interventions targeting many fundamental aging processes are being developed, including dietary manipulations, metformin, mTOR (mechanistic target of rapamycin) inhibitors, and senolytics, which are in early human trials. These interventions could lead to greater healthspan benefits than treating age-related diseases one at a time. To illustrate these points, we focus on cellular senescence and therapies in development to target senescent cells. Combining interventions targeting aging mechanisms with disease-specific drugs could result in more than additive benefits for currently difficult-to-treat or intractable diseases. More research attention needs to be devoted to targeting fundamental aging processes.

Cellular senescence: at the nexus between ageing and diabetes

Ageing and diabetes lead to similar organ dysfunction that is driven by parallel molecular mechanisms, one of which is cellular senescence. The abundance of senescent cells in various tissues increases with age, obesity and diabetes. Senescent cells have been directly implicated in the generation of insulin resistance. Recently, drugs that preferentially target senescent cells, known as senolytics, have been described and recently entered clinical trials. In this review, we explore the biological links between ageing and diabetes, specifically focusing on cellular senescence. We summarise the current data on cellular senescence in key target tissues associated with the development and clinical phenotypes of type 2 diabetes and discuss the therapeutic potential of targeting cellular senescence in diabetes.

Targeting senescent cells alleviates obesity-induced metabolic dysfunction

Adipose tissue inflammation and dysfunction are associated with obesity-related insulin resistance and diabetes, but mechanisms underlying this relationship are unclear. Although senescent cells accumulate in adipose tissue of obese humans and rodents, a direct pathogenic role for these cells in the development of diabetes remains to be demonstrated. Here, we show that reducing senescent cell burden in obese mice, either by activating drug-inducible "suicide" genes driven by the p16Ink4a promoter or by treatment with senolytic agents, alleviates metabolic and adipose tissue dysfunction. These senolytic interventions improved glucose tolerance, enhanced insulin sensitivity, lowered circulating inflammatory mediators, and promoted adipogenesis in obese mice. Elimination of senescent cells also prevented the migration of transplanted monocytes into intra-abdominal adipose tissue and reduced the number of macrophages in this tissue. In addition, microalbuminuria, renal podocyte function, and cardiac diastolic function improved with senolytic therapy. Our results implicate cellular senescence as a causal factor in obesity-related inflammation and metabolic derangements and show that emerging senolytic agents hold promise for treating obesity-related metabolic dysfunction and its complications.

Obesity-Induced Cellular Senescence Drives Anxiety and Impairs Neurogenesis

Cellular senescence entails a stable cell-cycle arrest and a pro-inflammatory secretory phenotype, which contributes to aging and age-related diseases. Obesity is associated with increased senescent cell burden and neuropsychiatric disorders, including anxiety and depression. To investigate the role of senescence in obesity-related neuropsychiatric dysfunction, we used the INK-ATTAC mouse model, from which p16Ink4a-expressing senescent cells can be eliminated, and senolytic drugs dasatinib and quercetin. We found that obesity results in the accumulation of senescent glial cells in proximity to the lateral ventricle, a region in which adult neurogenesis occurs. Furthermore, senescent glial cells exhibit excessive fat deposits, a phenotype we termed "accumulation of lipids in senescence." Clearing senescent cells from high fat-fed or leptin receptor-deficient obese mice restored neurogenesis and alleviated anxiety-related behavior. Our study provides proof-of-concept evidence that senescent cells are major contributors to obesity-induced anxiety and that senolytics are a potential new therapeutic avenue for treating neuropsychiatric disorders.

Senescence marker activin A is increased in human diabetic kidney disease: association with kidney function and potential implications for therapy

OBJECTIVE

Activin A, an inflammatory mediator implicated in cellular senescence-induced adipose tissue dysfunction and profibrotic kidney injury, may become a new target for the treatment of diabetic kidney disease (DKD) and chronic kidney diseases. We tested the hypothesis that human DKD-related injury leads to upregulation of activin A in blood and urine and in a human kidney cell model. We further hypothesized that circulating activin A parallels kidney injury markers in DKD.

RESEARCH DESIGN AND METHODS

In two adult diabetes cohorts and controls (Minnesota, USA; Galway, Ireland), the relationships between plasma (or urine) activin A, estimated glomerular filtration rate (eGFR) and DKD injury biomarkers were tested with logistic regression and correlation coefficients. Activin A, inflammatory, epithelial-mesenchymal-transition (EMT) and senescence markers were assayed in human kidney (HK-2) cells incubated in high glucose plus transforming growth factor-β1 or albumin.

RESULTS

Plasma activin A levels were elevated in diabetes (n=206) compared with controls (n=76; 418.1 vs 259.3 pg/mL; p<0.001) and correlated inversely with eGFR (r_s=-0.61; p<0.001; diabetes). After eGFR adjustment, only albuminuria (OR 1.56, 95% CI 1.16 to 2.09) and tumor necrosis factor receptor-1 (OR 6.40, 95% CI 1.08 to 38.00) associated with the highest activin tertile. Albuminuria also related to urinary activin (r_s=0.65; p<0.001). Following in vitro HK-2 injury, activin, inflammatory, EMT genes and supernatant activin levels were increased.

CONCLUSIONS

Circulating activin A is increased in human DKD and correlates with reduced kidney function and kidney injury markers. DKD-injured human renal tubule cells develop a profibrotic and inflammatory phenotype with activin A upregulation. These findings underscore the role of inflammation and provide a basis for further exploration of activin A as a diagnostic marker and therapeutic target in DKD.

Senolytics improve physical function and increase lifespan in old age

Physical function declines in old age, portending disability, increased health expenditures, and mortality. Cellular senescence, leading to tissue dysfunction, may contribute to these consequences of aging, but whether senescence can directly drive age-related pathology and be therapeutically targeted is still unclear. Here we demonstrate that transplanting relatively small numbers of senescent cells into young mice is sufficient to cause persistent physical dysfunction, as well as to spread cellular senescence to host tissues. Transplanting even fewer senescent cells had the same effect in older recipients and was accompanied by reduced survival, indicating the potency of senescent cells in shortening health- and lifespan. The senolytic cocktail, dasatinib plus quercetin, which causes selective elimination of senescent cells, decreased the number of naturally occurring senescent cells and their secretion of frailty-related proinflammatory cytokines in explants of human adipose tissue. Moreover, intermittent oral administration of senolytics to both senescent cell-transplanted young mice and naturally aged mice alleviated physical dysfunction and increased post-treatment survival by 36% while reducing mortality hazard to 65%. Our study provides proof-of-concept evidence that senescent cells can cause physical dysfunction and decreased survival even in young mice, while senolytics can enhance remaining health- and lifespan in old mice.

Chronic senolytic treatment alleviates established vasomotor dysfunction in aged or atherosclerotic mice

While reports suggest a single dose of senolytics may improve vasomotor function, the structural and functional impact of long‐term senolytic treatment is unknown. To determine whether long‐term senolytic treatment improves vasomotor function, vascular stiffness, and intimal plaque size and composition in aged or hypercholesterolemic mice with established disease. Senolytic treatment (intermittent treatment with Dasatinib + Quercetin via oral gavage) resulted in significant reductions in senescent cell markers (TAF⁺ cells) in the medial layer of aorta from aged and hypercholesterolemic mice, but not in intimal atherosclerotic plaques. While senolytic treatment significantly improved vasomotor function (isolated organ chamber baths) in both groups of mice, this was due to increases in nitric oxide bioavailability in aged mice and increases in sensitivity to NO donors in hypercholesterolemic mice. Genetic clearance of senescent cells in aged normocholesterolemic INK‐ATTAC mice phenocopied changes elicited by D+Q. Senolytics tended to reduce aortic calcification (alizarin red) and osteogenic signaling (qRT–PCR, immunohistochemistry) in aged mice, but both were significantly reduced by senolytic treatment in hypercholesterolemic mice. Intimal plaque fibrosis (picrosirius red) was not changed appreciably by chronic senolytic treatment. This is the first study to demonstrate that chronic clearance of senescent cells improves established vascular phenotypes associated with aging and chronic hypercholesterolemia, and may be a viable therapeutic intervention to reduce morbidity and mortality from cardiovascular diseases.

Exercise Prevents Diet-Induced Cellular Senescence in Adipose Tissue

Considerable evidence implicates cellular senescence in the biology of aging and chronic disease. Diet and exercise are determinants of healthy aging; however, the extent to which they affect the behavior and accretion of senescent cells within distinct tissues is not clear. Here we tested the hypothesis that exercise prevents premature senescent cell accumulation and systemic metabolic dysfunction induced by a fast-food diet (FFD). Using transgenic mice that express EGFP in response to activation of the senescence-associated p16(INK4a) promoter, we demonstrate that FFD consumption causes deleterious changes in body weight and composition as well as in measures of physical, cardiac, and metabolic health. The harmful effects of the FFD were associated with dramatic increases in several markers of senescence, including p16, EGFP, senescence-associated β-galactosidase, and the senescence-associated secretory phenotype (SASP) specifically in visceral adipose tissue. We show that exercise prevents the accumulation of senescent cells and the expression of the SASP while nullifying the damaging effects of the FFD on parameters of health. We also demonstrate that exercise initiated after long-term FFD feeding reduces senescent phenotype markers in visceral adipose tissue while attenuating physical impairments, suggesting that exercise may provide restorative benefit by mitigating accrued senescent burden. These findings highlight a novel mechanism by which exercise mediates its beneficial effects and reinforces the effect of modifiable lifestyle choices on health span.

17α-Estradiol Alleviates Age-related Metabolic and Inflammatory Dysfunction in Male Mice Without Inducing Feminization

Aging is associated with visceral adiposity, metabolic disorders, and chronic low-grade inflammation. 17α-estradiol (17α-E2), a naturally occurring enantiomer of 17β-estradiol (17β-E2), extends life span in male mice through unresolved mechanisms. We tested whether 17α-E2 could alleviate age-related metabolic dysfunction and inflammation. 17α-E2 reduced body mass, visceral adiposity, and ectopic lipid deposition without decreasing lean mass. These declines were associated with reductions in energy intake due to the activation of hypothalamic anorexigenic pathways and direct effects of 17α-E2 on nutrient-sensing pathways in visceral adipose tissue. 17α-E2 did not alter energy expenditure or excretion. Fasting glucose, insulin, and glycosylated hemoglobin were also reduced by 17α-E2, and hyperinsulinemic-euglycemic clamps revealed improvements in peripheral glucose disposal and hepatic glucose production. Inflammatory mediators in visceral adipose tissue and the circulation were reduced by 17α-E2. 17α-E2 increased AMPKα and reduced mTOR complex 1 activity in visceral adipose tissue but not in liver or quadriceps muscle, which is in contrast to the generalized systemic effects of caloric restriction. These beneficial phenotypic changes occurred in the absence of feminization or cardiac dysfunction, two commonly observed deleterious effects of exogenous estrogen administration. Thus, 17α-E2 holds potential as a novel therapeutic for alleviating age-related metabolic dysfunction through tissue-specific effects.

Targeting senescent cells enhances adipogenesis and metabolic function in old age

Senescent cells accumulate in fat with aging. We previously found genetic clearance of senescent cells from progeroid INK-ATTAC mice prevents lipodystrophy. Here we show that primary human senescent fat progenitors secrete activin A and directly inhibit adipogenesis in non-senescent progenitors. Blocking activin A partially restored lipid accumulation and expression of key adipogenic markers in differentiating progenitors exposed to senescent cells. Mouse fat tissue activin A increased with aging. Clearing senescent cells from 18-month-old naturally-aged INK-ATTAC mice reduced circulating activin A, blunted fat loss, and enhanced adipogenic transcription factor expression within 3 weeks. JAK inhibitor suppressed senescent cell activin A production and blunted senescent cell-mediated inhibition of adipogenesis. Eight weeks-treatment with ruxolitinib, an FDA-approved JAK1/2 inhibitor, reduced circulating activin A, preserved fat mass, reduced lipotoxicity, and increased insulin sensitivity in 22-month-old mice. Our study indicates targeting senescent cells or their products may alleviate age-related dysfunction of progenitors, adipose tissue, and metabolism.

DOI:http://dx.doi.org/10.7554/eLife.12997.001

The likelihood of developing metabolic diseases such as diabetes increases with age. This is, in part, because the cells within fat and other tissues become less sensitive to the hormone insulin as people and other animals get older. Also, the stem cells that give rise to new, insulin-responsive fat cells become dysfunctional with increasing age. This is related to the accumulation of “senescent” cells, which, unlike normal fat cell progenitors, release molecules that are toxic to nearby and distant cells.

Xu, Palmer et al. have now investigated if senescent cells interfere with the activity of stem cells from human fat tissue, and if getting rid of these senescent cells might restore the normal activity and insulin responsiveness of aged fat tissue. The experiments revealed that human senescent fat cell progenitors release a protein called activin A, which impedes the normal function of stem cells and fat tissue. Additionally, older mice had higher levels of activin A in both their blood and fat tissue than young mice.

Xu, Palmer et al. then analyzed older mice that had been engineered to have senescent fat cells that could be triggered to essentially kill themselves when the mice were treated with a drug. Eliminating the senescent cells from these mice led to lower levels of activin A and more fat tissue (due to improved stem cell capacity to become fully functional fat cells) that expressed genes required for insulin responsiveness. This showed that senescent cells are a cause of age-related fat tissue loss and metabolic disease in older mice.

Next, Xu, Palmer et al. treated older mice with drugs called JAK inhibitors, which they found reduce the production of activin A by senescent cells isolated from fat tissue. After two months of treatment, the levels of activin A in the blood and in fat tissue were indeed reduced. The fat tissue in treated mice also showed fewer features associated with the development of diabetes than the fat tissue of untreated mice. As such, these results paralleled those after selectively eliminating the senescent cells.

Together these findings suggest that JAK inhibitors or drugs (called senolytics) that selectively eliminate senescent cells may have clinical benefits in treating age-related conditions such as diabetes and stem cell dysfunction.

DOI:http://dx.doi.org/10.7554/eLife.12997.002

The Achilles' heel of senescent cells: from transcriptome to senolytic drugs

The healthspan of mice is enhanced by killing senescent cells using a transgenic suicide gene. Achieving the same using small molecules would have a tremendous impact on quality of life and the burden of age-related chronic diseases. Here, we describe the rationale for identification and validation of a new class of drugs termed senolytics, which selectively kill senescent cells. By transcript analysis, we discovered increased expression of pro-survival networks in senescent cells, consistent with their established resistance to apoptosis. Using siRNA to silence expression of key nodes of this network, including ephrins (EFNB1 or 3), PI3Kδ, p21, BCL-xL, or plasminogen-activated inhibitor-2, killed senescent cells, but not proliferating or quiescent, differentiated cells. Drugs targeting these same factors selectively killed senescent cells. Dasatinib eliminated senescent human fat cell progenitors, while quercetin was more effective against senescent human endothelial cells and mouse BM-MSCs. The combination of dasatinib and quercetin was effective in eliminating senescent MEFs. In vivo, this combination reduced senescent cell burden in chronologically aged, radiation-exposed, and progeroid Ercc1^−/Δ mice. In old mice, cardiac function and carotid vascular reactivity were improved 5 days after a single dose. Following irradiation of one limb in mice, a single dose led to improved exercise capacity for at least 7 months following drug treatment. Periodic drug administration extended healthspan in Ercc1^−/Δ mice, delaying age-related symptoms and pathology, osteoporosis, and loss of intervertebral disk proteoglycans. These results demonstrate the feasibility of selectively ablating senescent cells and the efficacy of senolytics for alleviating symptoms of frailty and extending healthspan.

Cellular Senescence in Type 2 Diabetes: A Therapeutic Opportunity

Cellular senescence is a fundamental aging mechanism that has been implicated in many age-related diseases and is a significant cause of tissue dysfunction. Accumulation of senescent cells occurs during aging and is also seen in the context of obesity and diabetes. Senescent cells may play a role in type 2 diabetes pathogenesis through direct impact on pancreatic β-cell function, senescence-associated secretory phenotype (SASP)-mediated tissue damage, and involvement in adipose tissue dysfunction. In turn, metabolic and signaling changes seen in diabetes, such as high circulating glucose, altered lipid metabolism, and growth hormone axis perturbations, can promote senescent cell formation. Thus, senescent cells might be part of a pathogenic loop in diabetes, as both a cause and consequence of metabolic changes and tissue damage. Therapeutic targeting of a basic aging mechanism such as cellular senescence may have a large impact on disease pathogenesis and could be more effective in preventing the progression of diabetes complications than currently available therapies that have limited impact on already existing tissue damage. Therefore, senescent cells and the SASP represent significant opportunities for advancement in the prevention and treatment of type 2 diabetes and its complications.

Human papillomavirus vaccination: a case study in translational science

Each year 610,000 cases of anogenital and oropharyngeal cancers caused by human papillomavirus (HPV) occur worldwide. HPV vaccination represents a promising opportunity to prevent cancer on a global scale. The vaccine's story dates back to discoveries in chickens at the beginning of the 20th century with evidence that a cell-free filtrate could transmit the propensity to grow cancers. Later, studies with similarly derived filtrates from mammalian tumors showed that hosts could develop immunity to subsequent exposures. Epidemiologic studies linked cervical cancer to members of a family of viruses that cause papillomatosis and common warts. This led to work with DNA hybridization demonstrating a causal relationship. The formation of virus-like particles from viral capsid proteins led to the development of models for safe and effective vaccines. While much work remains with the acceptance of universal vaccination, the HPV vaccines Gardasil and Cervarix thus represent a century of successful translational research.

Characters of aerated compost tea from immature compost that limit colonization of bean leaflets by Botrytis cinerea

AIMS

The aim was to produce and characterize an aerated compost tea (ACT) that suppressed growth of the plant pathogen Botrytis cinerea.

METHODS AND RESULTS

Three different open-windrow composts were sampled weekly from the early secondary mesophilic stage until maturity. Each 10kg of compost sample was extracted in 30 l of aerated water for 24, 48 or 72h. Relative to water, all batches of ACT applied to detached bean leaflets reduced lesion development following single-point inoculations of B. cinerea. There was a significant linear, inverse relationship between the internal windrow temperature of compost (≤51°C) used to prepare ACT and the extent of lesion development. Bacterial diversity in ACTs from one windrow was highest using compost sampled at 48°C. The compost weight-to-water volume ratios of 1:3, 1:10 or 1:30, using compost sampled from a fourth windrow at 50°C, also produced ACTs that reduced the growth of B. cinerea on bean leaflets. The '1 : 3' ACT, and to a lesser degree the same ACT filtered to remove micro-organisms, inhibited the germination of B. cinerea conidia.

CONCLUSIONS

ACT produced using the methods reported here suppressed the growth of B. cinerea on bean leaflets, with an abundant and diverse microbial community likely to contribute to pathogen suppression.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of the use of immature compost to produce a pathogen-suppressive ACT, suggesting that compost stage is an important production variable.

Changing the substrate specificity of creatine kinase from creatine to glycocyamine: evidence for a highly evolved active site

Eight variants of creatine kinase were created to switch the substrate specificity from creatine to glycocyamine using a rational design approach. Changes to creatine kinase involved altering several residues on the flexible loops that fold over the bound substrates including a chimeric replacement of the guanidino specificity loop from glycocyamine kinase into creatine kinase. A maximal 2,000-fold change in substrate specificity was obtained as measured by a ratio of enzymatic efficiency (k(cat)/K(M).K(d)) for creatine vs. glycocyamine. In all cases, a change in specificity was accompanied by a large drop in enzymatic efficiency. This data, combined with evidence from other studies, indicate that substrate specificity in the phosphagen kinase family is obtained by precise alignment of substrates in the active site to maximize k(cat)/K(M).K(d) as opposed to selective molecular recognition of one guanidino substrate over another. A model for the evolution of the dimeric forms of phosphagen kinases is proposed in which these enzymes radiated from a common ancestor that may have possessed a level of catalytic promiscuity. As mutational events occurred leading to greater degrees of substrate specificity, the dimeric phosphagen kinases became evolutionary separated such that the substrate specificity could not be interchanged by a small number of mutations.

Bone density comparison of selected carpal and tarsal bones: validation for their use in compression fracture fixation studies of scaphoid screws

INTRODUCTION

To determine if trabecular, total and cortical bone densities of the capitate, navicular, cuboid, and first cuneiform were equivalent to those of the scaphoid, such that these bones could be used in place of the scaphoid in evaluating new headless scaphoid compression screws.

METHODS

Fifty scaphoids, capitates, naviculars, cuboids, and first cuneiforms were harvested from fresh frozen cadavers. The trabecular, total and cortical bone densities were measured using pQCT technology and statistically compared.

RESULTS

A paired t comparison between paired scaphoids and capitates showed no difference between the trabecular bone densities. However, their total bone and cortical densities were found to be different. An independent measures ANOVA comparison of the five bones, showed no significant difference in mean trabecular density between the capitates, naviculars and first cuneiforms when compared to the scaphoids. However, the mean total and cortical densities of the first cuneiforms were less than the scaphoids and the mean trabecular, total and cortical bone densities of the cuboids were all less than the scaphoids.

DISCUSSION

Compression fracture fixation studies of headless compression screws could be conducted using the capitate, navicular, and first cuneiform as models of the scaphoid when the supply of scaphoids is limited.

An investigation of the general, reproductive and postnatal developmental toxicity of Betapol, a human milk fat equivalent

Betapol consists of triglyceride fatty acids commonly found in vegetable and animal fats. A similarity to human milk fat indicated a potential use in infant formulae as well as for food use in general. To test the potential for substantial equivalence with a related food grade oil, palm oil, Betapol was fed to rats at 15% content in the diet using an augmented two-generation study, in order to obtain information on general (6 months), reproductive and postnatal developmental toxicity in a single study rather than separate studies. For comparison there were two control groups, namely a comparative control fed a diet containing 15% of food grade oil and a negative, or laboratory standard control fed a commercial rodent breeding diet (LAD), containing 2.3-4.7% fat. It was reasoned that if Betapol fed groups showed differences from the comparative control in the direction of the negative control these would reflect differences in the nutritional value of the high fat diets. Presence of a toxicant might be indicated by differences from the comparative control group opposite to the negative control group. The group fed 15% Betapol showed occasional, statistically significant differences from the comparative control group but the direction of difference was towards the negative control group and did not indicate the presence of an unexpected toxicant.

The role of arthroscopy in the evaluation and treatment of triangular fibrocartilage complex injuries in athletes

Treating athletes with TFCC injuries can be a difficult but very rewarding undertaking. Each athlete has individual priorities and concerns, ranging from general health and fitness for the recreational athlete to earning or potentially earning a living as a professional athlete. It is crucial for the treating surgeon to understand these issues to offer the appropriate treatment options at the appropriate time. Triangular fibrocartilage complex injuries are quite common in athletes because of the high loads placed on the ulnar side of the wrist, especially with ulnar-neutral and positive variance. The goal of treatment for the competitive athlete with a TFCC lesion is to hasten maximal recovery and return the athlete to participation at the pre-injury level of performance. Early wrist arthroscopy and treatment of TFCC pathology in this population is certainly a real and valuable treatment option. As has been stated, "the TFCC is the new frontier of wrist surgery" and arthroscopy has helped blaze the trail to this frontier. Competitive and recreational athletes alike benefit from arthroscopic treatment of their TFCC injuries.

Complications of endoscopic and open carpal tunnel release

Separate questionnaires regarding surgically treated complications of endoscopic and open carpal tunnel release over a 5-year period were sent to members of the American Society for Surgery of the Hand to assess and compare major complications of the 2 procedures. Four hundred fifty-five major complications from endoscopic carpal tunnel release were treated by the 708 respondents. This included 100 median nerve lacerations, 88 ulnar nerve lacerations, 77 digital nerve lacerations, 121 vessel lacerations, and 69 tendon lacerations. There were 283 major complications from open carpal tunnel release treated by 616 respondents, including 147 median nerve lacerations, 29 ulnar nerve lacerations, 54 digital nerve lacerations, 34 vessel lacerations, and 19 tendon lacerations. Although this is a retrospective voluntary study with resultant methodologic flaws, the data support the conclusion that carpal tunnel release, be it endoscopic or open, is not a safe and simple procedure. Major, if not devastating, complications can and do occur with both procedures, of which surgeons should be ever cautious.

Tri-isobutylphosphate: a prenatal toxicity study in rats

To assess the prenatal toxicity to rats of the anti-foaming agent, tri-isobutylphosphate (CAS 126-71-6), a study was conducted in which daily dosages of 0, 100, 300 and 1000 mg/kg were administered to different treatment groups by gavage from day 6 to 15 of pregnancy. Dams were killed and foetuses examined on day 20 of pregnancy. Maternal effects during the dosing period included a dosage-related increase in the frequency, persistence and severity of post dosing salivation in all test groups and significantly increased water consumption at 1000 mg/kg. Bodyweight gain at 1000 and 300 mg/kg was lower than that of controls but the differences were not statistically significant. The lowest dosage of 100 mg/kg could be considered as the maternal 'lowest observed adverse effect level' (LOAEL) or 'no observed adverse effect level' (NOAEL) according to whether increased salivation is perceived to be a true toxic effect or simply a reaction to the taste of the test material. Neither litter values nor the prevalence of foetuses with abnormalities indicated any embryotoxic effects (including teratogenicity) at any dosage. The most notable feature of the results was the occurrence of a cluster of foetuses with the congenital abnormality referred to as 'hunched posture syndrome' or 'squat foetus syndrome'. However, the incidence of this finding was similar to that noted among background data for the same strain and, in the absence of any other embryotoxic findings, was considered likely to have arisen coincidentally.

An anatomic study of the ligamentous structure of the triangular fibrocartilage complex

An anatomic study of the ligamentous structures of the triangular fibrocartilage complex and their attachments on the ulnar styloid was performed using 27 embalmed cadaver wrists. The dorsal and palmar distal radioulnar ligaments of the triangular fibrocartilage complex in each specimen contained a superficial and a deep portion. The deep portion of both ligaments inserted on the fovea of the ulna. The superficial portion of both ligaments surrounded the articular disc uniting at the ulnar-most portion of the articular disc. The tissue that is between the ulnar aspect of the superficial ligament (and integrated on its periphery) and the ulnar capsule is defined as the meniscus homologue. Anatomic variations in the meniscus homologue and the prestyloid recess (the cavity adjacent to the ulnar styloid) were seen in 1 of 3 ways; the narrow opening type in 74% of specimens, the wide opening type in 11%, and the no opening type in 15%. The ulnotriquetral ligament inserted on the palmar-radial aspect of the base of the ulnar styloid and the ulnolunate ligament inserted on the palmar border of the articular disc.

Pressure distribution in the distal radioulnar joint

Measurement of the pressure distribution within the distal radioulnar joint was performed in fresh cadaver forearms at varying positions of forearm rotation. Axial loads of 0 N, 36 N, and 89 N were applied to the wrist flexors and extensors. At neutral forearm rotation and application of 89 N axial load, an average of 12.5% of the sigmoid notch area was in contact with the ulna. Analysis of the pressure plots reveals that in pronation, the pressure was concentrated in the dorsal portion of the sigmoid notch and that in supination the pressure was distributed in the palmar portion.

Changes in carpal tunnel pressures following endoscopic carpal tunnel release: a cadaveric study

The purpose of this experiment was to determine the amount of tissue that must be sectioned to adequately decompress the median nerve during an endoscopic carpal tunnel release procedure. In 6 fresh cadaver forearms, 2 balloons were inserted into the carpal tunnel. The first balloon was filled with saline solution to cause an initial carpal intracanal pressure of 50 mmHg. Pressure measurements were recorded, using the second balloon, at various increments of the flexor retinaculum division at 3 wrist positions (neutral, 35 degrees ; flexion, 35 degrees extension). At all increments of sectioning, carpal tunnel pressures in the neutral wrist position were consistently lowest and the values in 35 degrees extension were greatest. At each wrist flexion/extension angle, the pressure statistically decreased during incremental division of the flexor retinaculum. Incomplete release of the transverse carpal ligament resulted in incomplete decompression in the canal. Sectioning the overlying aponeurosis caused a further significant decrease in intracanal pressure.

Reconstruction of the interosseous membrane of the forearm in cadavers

The biomechanical function of the interosseous membrane of the forearm was examined in 12 fresh cadaver forearms. The strain in the central band of the interosseous membrane was found to be greatest in full pronation and was significantly increased with excision of the radial head. The proximal/distal location of the lunate fossa of the radius with respect to the ulna was measured and was found to be most distal in supination and most proximal in pronation, in both the intact specimen and after excision of the radial head. Serial sectioning of the interosseous membrane and the triangular fibrocartilage complex (TFCC) demonstrated that both the central band and the TFCC are important to the axial stability of the forearm. Reconstruction of the central band, using a graft based upon the flexor carpi radialis, was performed in all 12 specimens after the interosseous membrane and the TFCC were sectioned. It was successful in preventing complete migration of the radius to the capitellum, but it was not capable of completely restoring the longitudinal stability of the forearm. Central band reconstruction as described here has not been performed in the clinical setting and is not advocated for clinical application at this time.

The interosseous membrane of the forearm: anatomy and function

The anatomic detail of the interosseous membrane was studied by dissection of 20 preserved cadaveric specimens. The interosseous membrane was found to be a complex structure consisting of a central band, accessory bands, a proximal interosseous band, and membranous portions. The central band, a stout ligamentous structure, was found in all specimens. Fibers of the central band originate on the radius and are oriented distal and ulnar an average of 21 degrees to the longitudinal axis of the ulna. Accessory bands were of less substance than the central band but were present in all specimens. The number of accessory bands ranged from 1 to 5. The proximal interosseous band is located on the dorsal surface only, and its fibers run counter to the central band. It shares a point of origin with the central band on the radius. This structure was present in 17 of 20 specimens. Since the central band was the most dominant and consistent structure, we chose to analyze the strain in the central band in 6 preserved specimens. Maximum strain in the central band of the intact specimen occurs in neutral forearm rotation. Once the radial head is removed, the percent strain universally increases throughout the arc of forearm rotation and peak strain shifts to pronation.

The cult of culling

It is difficult to understand why culling (reduction of litter size) has become such a widely used procedure in reproductive toxicity studies since there appear to have been no prior investigations to ascertain that it would improve the efficiency of studies with respect to detecting adverse effects. Perhaps the only provable advantage of culling is with respect to economics and convenience. Post hoc rationalizations for culling lack conviction because many of the claims made for culling are erroneous, inconsistent, vague, and contradictory. Mostly, they are based on part truths derived from minimal studies, conducted for totally different purposes. That experimental animals have to be killed sooner or later is unquestioned, but for ethical and scientific reasons, it is imperative that the maximum amount of information is obtained from them. Currently, the most common practice is to cull litters to four per sex (total eight) on Day 4 postpartum. This is totally divorced from natural values for most rat strains and involves elimination, usually without adequate examination, of between 30 and 45% of offspring. Without culling most of these would survive, unless there was a treatment effect. Intuitively, it would seem that removal of such a proportion of offspring would severely limit the possibility of detecting the postnatal equivalent of fetal malformations. Culling totally nullifies litter size as an indicator of toxicity. Indirectly, it also nullifies the value of mean pup weight as an indicator of toxicity because it greatly increases the variation in mean pup weight. This is quite contrary to the claim that culling reduces variance. Further, the increased growth of offspring in culled litters can have long-term consequences of a shorter overall and reproductive life span.

The relative contribution of selected carpal bones to global wrist motion during simulated planar and out-of-plane wrist motion

The relative contribution of the scaphoid, lunate, triquetrum, and capitate to wrist motion was examined in 6 fresh cadaver forearms. A wrist-joint motion simulator was used to dynamically move each wrist through planar and nonplanar motions. During wrist flexion-extension, the motion of the capitate closely followed the motion of the third metacarpal, while the lunate motion was approximately 50% of the total motion; the triquetrum, 65%, and the scaphoid, 90%. Similar differences in motion for these carpal bones occurred during radioulnar deviation and circumduction and dart-throw motions. This suggests that the scaphoid, lunate, and triquetrum do not normally function as a single unit, but that each bone has an unique arc of motion during global wrist motion.

Terminology of developmental abnormalities in common laboratory mammals (version 1)

This paper presents the first version of an internationally-developed glossary of terms for structural developmental abnormalities in common laboratory animals. The glossary is put forward by the International Federation of Teratology Societies (IFTS) Committee on International Harmonization of Nomenclature in Developmental Toxicology, and represents considerable progress toward harmonization of terminology in this area. The purpose of this effort is to provide a common vocabulary that will reduce confusion and ambiguity in the description of developmental effects, particularly in submissions to regulatory agencies worldwide. The glossary contains a primary term or phrase, a definition of the abnormality, and notes, where appropriate. Selected synonyms or related terms, which reflect a similar or closely related concept, are noted. Nonpreferred terms are indicated where their usage may be incorrect. Modifying terms used repeatedly in the glossary (e.g., absent, branched) are listed and defined separately, instead of repeating their definitions for each observation. Syndrome names are generally excluded from the glossary, but are listed separately in an appendix. The glossary is organized into broad sections for external, visceral, and skeletal observations, then subdivided into regions, structures, or organs in a general overall head to tail sequence. Numbering is sequential, and not in any regional or hierarchical order. Uses and misuses of the glossary are discussed. Comments, questions, suggestions, and additions from practitioners in the field of developmental toxicology are welcomed on the organization of the glossary as well as on the specific terms and definitions. Updates of the glossary are planned based on the comments received.

Wrist arthrodesis using a dynamic compression plate

In order to determine the effectiveness of wrist arthrodesis using dynamic compression plating and bone grafting, we reviewed 18 consecutive procedures in 17 patients performed using a standardized technique over a 6-year period. Fourteen patients had previously undergone an average of 2.1 operations prior to arthrodesis. Mean follow-up was 48 months. All but one patient reported considerable pain relief and were satisfied with their results. Grip strength remained limited compared to the contralateral wrist. Complications were limited to one case of reflex sympathetic dystrophy and metacarpophalangeal joint contracture, and minor problems related to the bone graft donor site.

Wrist joint motion simulator

A computer controlled wrist joint motion simulator has been developed that actively moves forearms from cadavers through cyclic planar flexion-extension motions, planar radial-ulnar deviation motions, and combined motions such as circumduction. Hybrid position-force feedback control algorithms are used to determine the wrist flexor and extensor tendon forces necessary to achieve the desired motions. The simulator was used in a series of 12 fresh cadaver forearms to produce both flexion-extension and radial-ulnar deviation motions and was found to cause repeatable, physiological movements. In these experiments, the extensor tendon forces were greater than those of the flexors, typically by a factor of two.

Classification and treatment of ulnar styloid nonunion

Symptomatic nonunion of the ulnar styloid is an uncommon problem that is usually best treated by simple excision of the ulnar styloid fragment. Two types of nonunion of the ulnar styloid are described here on an anatomic basis, and their treatment differs. Type 1 is defined as a nonunion associated with a stable distal radioulnar joint. Type 2 is defined as a nonunion associated with subluxation of the distal radioulnar joint. The postoperative follow-up period for the two types ranged from 4 months to 13 years, with a mean of 5 years 2 months. Eleven type 1 wrists were treated with excision of the fragment, and all patients had satisfactory relief of pain. Nine type 2 wrists required restoration of the anatomy of the traingular fibrocartilage complex. Three of these had large fragments that were treated by open reduction and internal fixation. All three patients were completely relieved of their discomfort. Six other patients underwent excision of the fragment and repair of the triangular fibrocartilage complex to the distal ulna. This group had four excellent, one good, and one fair result. If the distal radioulnar joint is stable on presentation or if its stability is restored, then long-term relief of pain from ulnar styloid nonunion is achieved by treatment of the nonunion.

Neurobehavioral aspects of developmental toxicity testing

Tests for detection of neurobehavioral changes in the offspring have been a regulatory requirement in developmental toxicity testing of drugs for almost 20 years. Keeping their purpose of hazard identification and risk assessment for humans in mind, investigators and agency reviewers have become deeply ingrained with some stereotyped behaviors with respect to such relevant issues as choice of animal species and data evaluation. Other problematic areas of study design and conduct, selection of litter representatives for testing, what methods to combine in a testing battery, and statistical treatment of results and their interpretation, will need more research and discussion in the future.

A multicenter prospective review of 640 endoscopic carpal tunnel releases using the transbursal and extrabursal chow techniques

A prospective study involving eight institutions was performed, incorporating 640 cases of carpal tunnel release using a dual portal endoscopic technique. The original transbursal technique described by Chow was used in 110 cases (17%), and the modified extrabursal technique was used in 530 cases (83%). An overall complication rate of 11% was found in the patients in whom the transbursal technique was used, compared with 2.2% in the patients in whom the extrabursal technique was used. The return-to-work status was followed in 291 cases (199 non-worker's compensation cases and 92 worker's compensation cases). The worker's compensation patients returned to work in an average of 57 days, compared with 22 days for non-worker's compensation patients. This study suggests the extrabursal dual portal endoscopic technique is associated with fewer complications than the transbursal approach, and patients covered by worker's compensation return to work later than non-worker's compensation patients.

The effect of dorsally angulated distal radius fractures on distal radioulnar joint congruency and forearm rotation

A biomechanical cadaver study was performed to evaluate the effect of dorsally angulated distal radius fractures on the distal radioulnar joint. Frykman I distal radius fractures were simulated, and laxity measurements were taken with and without sectioning the triangular fibrocartilage complex and the interosseous membrane. The findings of this study were threefold. First, measured in terms of radial diastasis, incongruency of the distal radioulnar joint occurred with increasing dorsal tilt of the distal radius. It became most dramatic with a change of more than 20 degrees of dorsal angulation of the distal radius. This corresponds to approximately 10 degrees of dorsal tilt of the articular surface of the distal radius, as measured on an x-ray film. Second, increased dorsal angulation caused interosseous membrane tightness and limited maximum pronation and maximum supination. Third, distal radioulnar joint dislocation did not occur until both the triangular fibrocartilage complex and interosseous membrane were sectioned. These results reveal the importance of anatomic reduction of the distal radius fracture and evaluation of damaged soft tissue structures.

Prenatal toxicity studies in rats and rabbits with the calcium channel blocker diproteverine

In prenatal toxicity studies, diproteverine, a calcium channel blocker with demonstrated antianginal properties, produced an unusual pattern of digital, heart, tail, and vertebral defects in rat fetuses from mothers treated during the major period of organogenesis, but only a very low incidence of heart abnormalities was seen in the rabbit. Heart changes were rarely seen in association with digital defects. The findings were consistent with those seen with other calcium channel blockers and add weight to the suggestion of Danielsson and colleagues (5) that digital malformations are a class effect for this type of compound, the effects being related to reduced uteroplacental blood flow. In addition, it is proposed that cardiovascular malformations are also a class response with calcium channel blockers. The distribution of fetal death and hemorrhages and the varying association between cardiovascular, digital, and tail abnormalities seen in the rat with increasing doses of diproteverine fits the pattern of changes reported following hypoxia in the chick embryo. Reduced uteroplacental blood flow with resultant embryonic hypoxia secondary to pharmacologic action is considered a probable mechanism of action for the induction of abnormalities produced by calcium channel blockers.

The stabilizing mechanism of the distal radioulnar joint during pronation and supination

A biomechanical cadaver study was performed to determine the roles of the stabilizing structures of the distal radioulnar joint during pronation and supination. Subluxation and dislocation of the radius with respect to the ulna were evaluated in seven cadaver forearms placed in supination, pronation, and neutral forearm rotation. The amount of subluxation was measured with all structures intact, and after sectioning in various sequences the dorsal and palmar radioulnar ligaments, the distal portion of the interosseous membrane including the pronator quadratus, and the entire interosseous membrane. After sectioning two of any four structures, the distal radioulnar joint remained stable. When the interosseous membrane was disrupted first, the dorsal radioulnar ligament was found to be more important than the palmar radioulnar ligament in stabilizing the distal radioulnar joint in pronation, and conversely the palmar radioulnar ligament was more important than the dorsal radioulnar ligament in supination. Dislocation, and frequently diastasis, occurred only with sectioning of all four structures. This suggests that all four structures contribute to stability of the distal radioulnar joint.