Post-traumatic stress in older, community-dwelling adults with hypertension during the COVID-19 pandemic: An investigation of pre-pandemic sociodemographic, health, and vascular and inflammatory biomarker predictors

COVID-19 pandemic-related traumatic stress (PRTS) symptoms are reported in various populations, but risk factors in older adults with chronic medical conditions, remain understudied. We therefore examined correlates and pre-pandemic predictors of PRTS in older adults with hypertension during COVID-19. Participants in California, aged 61-92 years (n = 95), participated in a pre-pandemic healthy aging trial and later completed a COVID-19 assessment (May to September 2020). Those experiencing ⩾1 PRTS symptom (n = 40), and those without PRTS symptoms (n = 55), were compared. The PRTS+ group had poorer mental and general health and greater impairment in instrumental activities of daily living. Pre-pandemic biomarkers of vascular inflammation did not predict increased odds of PRTS; however, greater pre-pandemic anxiety and female gender did predict PRTS during COVID-19. Our findings highlight PRTS as a threat to healthy aging in older adults with hypertension; targeted approaches are needed to mitigate this burden, particularly for females and those with pre-existing anxiety.

Tai Chi versus health education as a frailty intervention for community-dwelling older adults with hypertension

BACKGROUND

Frailty is associated with poor outcomes among older adults with hypertension and complicates its pharmacological management. Here, we assessed whether 12-weeks of instructor-guided, group Tai Chi (TC) practice improved frailty relative to Healthy Aging Practice-centered Education (HAP-E) classes in older adults with hypertension.

METHODS

Secondary analysis of a randomized controlled trial in San Diego County, USA, of 167 community-dwelling individuals aged ≥ 60 yrs (70% female; 72.1 ± 7.5 yrs), defined as non-frail (66%) or frail (34%) based on 53-item deficit accumulation frailty index (FI). Linear mixed-effects models were used to assess pre-to-post intervention differences in FI and logistic regression to explore differential odds of clinically meaningful FI change.

RESULTS

One hundred thirty-one participants completed post-intervention assessments. Frailty decreased pre-to-post intervention in the TC (ΔFI = - 0.016, d = - 0.39, - 0.75 to - 0.03), but not the HAP-E arm (ΔFI = - 0.009, d = - 0.13, - 0.52-0.27), despite no significant group differences between the TC and HAP-E arms (d = - 0.11, - 0.46-0.23). Furthermore, greater odds of improved FI were observed for frail participants in the TC (OR = 3.84, 1.14-14.9), but not the HAP-E (OR = 1.34, 0.39-4.56) arm. Subgroup analysis indicated treatment effects in TC were attributed to frail participants (frail: ΔFI = - 0.035, d = - 0.68, -1.26 to - 0.08; non-frail: ΔFI = - 0.005, d = - 0.19, - 0.59-0.22), which was not the case in the HAP-E arm (frail: ΔFI = - 0.017, d = - 0.23, - 0.81-0.35; non-frail: ΔFI = - 0.003, d = - 0.07, - 0.47-0.33). Frail participants were no more likely to drop-out of the study than non-frail (71% vs. 69% retained).

CONCLUSIONS

Twelve weeks of twice-weekly guided TC practice was well-tolerated, associated with decreases in frailty, and increased odds of clinically meaningful FI improvement at post-intervention.

Tai chi or health education for older adults with hypertension: effects on mental health and psychological resilience to COVID-19

OBJECTIVE

To compare the effectiveness of 12 weeks of community-based, in-person, group Tai Chi (TC) and Health Education (HAP-E) in improving health and wellbeing in older adults with hypertension and in promoting psychological resilience during COVID-19.

METHODS

A 12-week randomized controlled trial (RCT) in San Diego County, USA. Self-reported depressive symptoms, anxiety, sleep disturbances, gratitude, resilience, mental and physical health were assessed in-person pre- and post-intervention, and by long-term follow-up surveys during COVID-19. Linear mixed-effects models were used to assess study arm differences over time and logistic regression to identify predictors of positive intervention response.

RESULTS

Of 182 randomized participants (72.6 ± 7.9 yrs; 72% female), 131 completed the intervention. Modest improvements in health and wellbeing occurred post-intervention in both arms (Cohen's d: TC = 0.38, 95% CI: 0.25-0.51; HAP-E = 0.24, 0.11-0.37), though positive intervention responses were more than twice as likely in TC (OR = 2.29, 1.07-4.57). Younger age, higher anxiety, and poorer mental health at baseline predicted greater odds of response. Small declines in health and wellbeing were reported at the first COVID-19 follow-up, with smaller declines in the TC arm (Cohen's d: TC = -0.15, -0.31-0.00; HAP-E = -0.34, -0.49 to -0.19). Health and wellbeing stabilized at the second COVID-19 follow-up. Most participants (>70%) reported that the interventions benefitted their health and wellbeing during COVID-19.

CONCLUSION

TC and HAP-E improved health and wellbeing, though TC conferred greater odds of an improved mental health response. Declines in health and wellbeing were observed at pandemic follow-up, with smaller declines in the TC arm, suggesting increased resilience.

Trends, heterogeneity, and correlates of mental health and psychosocial well-being in later-life: study of 590 community-dwelling adults aged 40-104 years

OBJECTIVE

The goal of this study was to examine if mental health and psychosocial well-being differed between middle-aged (MA; 40-59 years), younger-old (YO; 60-79 years), and older-old (OO; 80+ years) adults with respect to their trends, heterogeneity, and correlates.

METHODS

Eighteen mental health and psychosocial well-being instruments were administered to 590 adults over age 40. Cross-sectional data also included self-report-based measures of sociodemographics, cognitive functioning, physical health and activity, and body mass index.

RESULTS

Age trends across instruments varied in magnitude and shape, but generally supported an inverted U-shaped trend in mental health and psychosocial well-being, with small increases from MA to YO age (d = 0.29) and smaller declines from YO to OO age (d = -0.17). A U-shaped association between age and mental health heterogeneity was also observed. The strongest correlates of mental health and psychosocial well-being differed by age (MA: perceived stress; YO: successful aging; OO: compassion toward others), as did the associations of a flourishing versus languishing mental health and well-being profile.

CONCLUSIONS

Our findings support the "paradox of aging," whereby declines in physical and cognitive health co-occur with relatively preserved mental health and well-being. Our findings indicate that variance in mental and psychosocial health does not increase linearly with age and support careful consideration of heterogeneity in mental health and aging research. Our findings also suggest that mental health and psychosocial well-being decouple from stress-related dimensions in MA and become increasingly associated with positive, other-oriented emotions in OO, broadly supporting socioemotional theories of aging.

Treatment patterns and costs among biologic-naive patients initiating apremilast or biologics for psoriatic arthritis

Aim: We evaluated treatment patterns and healthcare costs of initiating psoriatic arthritis (PsA) treatment with oral apremilast versus biologics. Methods: Claims data identified biologic-naive adults with PsA who initiated either apremilast or a biologic from 2013 to 2016. Results: Medication adherence was similar at 12 months (76.9 vs 73.4%; p = 0.175) between apremilast (n = 381) and matched biologic (n = 761) patients. Apremilast users had $12,715 lower total costs per-patient-per-month (p < 0.001), largely due to outpatient pharmacy and medical costs. Conclusion: Commercially insured patients with PsA initiating apremilast had adherence similar to those initiating biologics but lower total healthcare costs.

Cost of peripheral neuropathy in patients receiving treatment for multiple myeloma: a US administrative claims analysis

Background:

Peripheral neuropathy (PN) is a common consequence of multiple myeloma (MM) among those commonly treated with older-generation proteasome inhibitors (PIs). In this study, we evaluated the economic burden attributable to PN among MM patients in real-world practice settings in the US.

Methods:

Adults diagnosed with MM and first treated (index event) between 1 July 2006 and 28 February 2017 were identified from MarketScan® Commercial and Medicare claim databases. Continuous enrollment for at least 12 months without treatment and PN diagnoses were required pre-index. Patients were followed for at least 3 months until inpatient death or end of data. The International Classification of Diseases, ninth revision, Clinical Modification (ICD-9-CM) and ICD-10-CM diagnosis codes were used to identify PN. Propensity-score matching was applied to match every patient with PN to two MM patients without a PN diagnosis (controls). Healthcare utilization and expenditures per patient per month (PPPM) in the postindex period were estimated.

Results:

Of 11,851 patients meeting the study criteria, 15.5% had PN. After matching 1387 patients with PN and 2594 controls were identified. Baseline characteristics were well balanced between cohorts; mean follow up was 23–26 months. PPPM total costs were significantly higher by $1509 for patients with PN than controls, driven by higher hospitalization (PN 77.4%, controls 67.2%; p < 0.001) and emergency department rates (PN 67.8%, controls 58.4%; p < 0.001) and more outpatient hospital-based visits PPPM (PN 13.5 ± 14.7, controls 11.5 ± 18.0; p < 0.001).

Conclusions:

PN is a prevalent MM treatment complication associated with a significant economic burden adding to the complexity and cost of MM treatment. Highly effective novel treatments such as carfilzomib may reduce the overall disease burden.

Malaria vaccines in the eradication era: current status and future perspectives

INTRODUCTION

The challenge to eradicate malaria is an enormous task that will not be achieved by current control measures, thus an efficacious and long-lasting malaria vaccine is required. The licensing of RTS, S/AS01 is a step forward in providing some protection, but a malaria vaccine that protects across multiple transmission seasons is still needed. To achieve this, inducing beneficial immune responses while minimising deleterious non-targeted effects will be essential.

AREAS COVERED

This article discusses the current challenges and advances in malaria vaccine development and reviews recent human clinical trials for each stage of infection. Pubmed and ScienceDirect were searched, focusing on cell mediated immunity and how T cell subsets might be targeted in future vaccines using novel adjuvants and emerging vaccine technologies.

EXPERT COMMENTARY

Despite decades of research there is no highly effective licensed malaria vaccine. However, there is cause for optimism as new adjuvants and vaccine systems emerge, and our understanding of correlates of protection increases, especially regarding cellular immunity. The new field of heterologous (non-specific) effects of vaccines also highlights the broader consequences of immunization. Importantly, the WHO led Malaria Vaccine Technology Roadmap illustrates that there is a political will among the global health community to make it happen.

Real-world US healthcare costs of psoriasis for biologic-naive patients initiating apremilast or biologics

AIM

Biologics and apremilast have advanced psoriasis management by adding treatment options. This study evaluated persistence, adherence and healthcare costs among biologic-naive patients receiving apremilast or biologics.

METHODS

Administrative claims data for adults starting apremilast or biologics from 1 January 2013 to 30 June 2016 were matched based on demographics.

RESULTS

Apremilast (n = 703) and biologics (n = 1378) had similar baseline characteristics. 12-month persistence and adherence rates were similar. Adjusted total healthcare costs were lower with apremilast versus biologics (p < 0.001) due to lower total outpatient pharmacy costs (p < 0.001).

CONCLUSION

Real-world apremilast users had similar adherence and lower total healthcare costs versus biologic users. Apremilast's cost advantage was evident regardless of whether the patients were persistent or nonpersistent, or switched or did not switch treatments.

Change in Sense of Nondual Awareness and Spiritual Awakening in Response to a Multidimensional Well-Being Program

OBJECTIVE

This study examined the effects of a comprehensive mind-body program on sense of nondual awareness and spiritual awakening.

DESIGN AND INTERVENTION

The study compared the effects of participation in an intensive 6-day Ayurveda-based mind-body program that addressed physical, emotional, and spiritual domains as compared with a control condition.

SETTING

Resort setting.

SUBJECTS

Participants were 69 healthy women and men (mean age 53.9 years; range 32-86).

OUTCOME MEASURE

The primary outcome was the Nondual Embodiment Thematic Inventory (NETI).

RESULTS

A significant group by time interaction (p = 0.029) indicated that after the intervention, participants in the mind-body program showed a significant increase in NETI scores (p < 0.03), which was sustained 1 month later (p < 0.01).

CONCLUSION

Findings suggest that an intensive program providing holistic instruction and experience in mind-body practices can lead to a significant and sustained shift in perception of self-awareness, one that is likely favorable to well-being.

Effect of body mass index on maternal morbidity following peripartum hysterectomy

The objective of this study was to estimate the impact of maternal body mass index (BMI) on maternal morbidity following unscheduled peripartum hysterectomy. A retrospective cohort study of consecutive peripartum hysterectomies at our institution from 1988 through 2012; scheduled hysterectomies were excluded. Medical records were reviewed and maternal, foetal and surgical data collected for each subject. Maternal BMI was categorized by the National Institute of Health classifications for overweight and obese. Statistical analyses included evaluation for trend. A total of 360,774 women delivered at Parkland Hospital during the study period with 665 (1.8 per 1000 deliveries) unscheduled peripartum hysterectomies performed. BMI was available for 635 women. Gestational diabetes, chronic hypertension and pregnancy-related hypertension were significantly higher in all three obesity categories, P = < 0.01. Post-partum complications, such as venous thrombosis and composite surgical morbidity did not differ among BMI groups. Estimated blood loss and units transfused did not differ across the BMI categories, P = 0.42 and P = 0.38, respectively. Increasing BMI was associated with longer surgical times and more wound infections, P = 0.01. These complications should be considered when approaching a peripartum hysterectomy in patients with obesity.

Ustekinumab dosing, persistence, and discontinuation patterns in patients with moderate-to-severe psoriasis

OBJECTIVES

Ustekinumab is the most recently approved biologic for the treatment of moderate-to-severe psoriasis. Real-world dosing patterns of ustekinumab are yet to be fully characterized.

METHODS

A retrospective, observational study was conducted using MarketScan Commercial and Medicare databases. A cohort of psoriasis patients treated with ustekinumab between 25 September 2009 and 31 October 2010 was evaluated. Main outcomes included ustekinumab dosing and treatment patterns. Kaplan-Meier estimates were calculated to adjust for the censoring of data. Subgroup analysis was conducted for biologic-experienced patients and biologic-naïve patients.

RESULTS

One thousand ustekinumab patients were included, of whom 60% were biologic-experienced. The average age was 49.0 and 53.9% were male. 63.3% of patients initiated ustekinumab with a 45 mg dose and 34.5% initiated with a 90 mg dose. Mean (median) days from initial dose to second dose was 31.1 (28.0). During maintenance therapy, dose intervals spanned from 80.6 to 81.2 (84.0) days. About 81.4% of patients were persistent during the variable-length follow-up period.

CONCLUSIONS

The majority of patients received the 45 mg ustekinumab dose. The mean dosing intervals were consistent with the US prescribing guidelines. Biologic-naïve and biologic-experienced patients had similar dosing patterns. Ustekinumab treatment achieved a persistency rate as high as 81.4% over an average of 186.5 (SD 114.2) days of follow-up.

The inpatient experience and predictors of length of stay for patients hospitalized with systolic heart failure: comparison by commercial, Medicaid, and Medicare payer type

OBJECTIVE

Descriptions of the inpatient experience for patients hospitalized with systolic heart failure (HF) are limited and lack a cross-sectional representation of the US population. While length of stay (LOS) is a primary determinant of resource use and post-discharge events, few models exist for estimating LOS.

RESEARCH DESIGN AND METHODS

MarketScan(®) administrative claims data from 1/1/2005-6/30/2008 were used to select hospitalized patients aged ≥18 years with discharge diagnoses for both HF (primary diagnosis) and systolic HF (any diagnostic position) without prior HF hospitalization or undergoing transplantation.

RESULTS

Among 17,597 patients with systolic HF; 4109 had commercial; 2118 had Medicaid; and 11,370 had Medicare payer type. Medicaid patients had longer mean LOS (7.1 days) than commercial (6.3 days) or Medicare (6.7 days). In-hospital mortality was highest for patients with Medicaid (2.4%), followed by Medicare (1.3%) and commercial (0.6%). Commercial patients were more likely to receive inpatient procedures. Renal failure, pressure ulcer, malnutrition, a non-circulatory index admission DRG, receipt of a coronary artery bypass procedure or cardiac catheterization, or need for mechanical ventilation during the index admission were associated with increased LOS; receipt of a pacemaker device at index was associated with shorter LOS.

LIMITATIONS

Selection of patients with systolic HF is limited by completeness and accuracy of medical coding, and results may not be generalizable to patients with diastolic HF or to international populations.

CONCLUSION

Inpatient care, LOS, and in-hospital survival differ by payer among patients hospitalized with systolic HF, although co-morbidity and inpatient procedures consistently influence LOS across payer types. These findings may refine risk stratification, allowing for targeted intensive inpatient management and/or aggressive transitional care to improve outcomes and increase the efficiency of care.

Comparative persistence and adherence to overactive bladder medications in patients with and without diabetes

AIMS

This retrospective administrative claims-based study evaluated comparative persistence and adherence to overactive bladder (OAB) medications in US patients with and without diabetes.

METHODS

Patients ≥ 18 years who initiated OAB medications between 1 January 2005 and 30 June 2008 were analysed from the Truven Health MarketScan Commercial and Medicare Supplemental databases. A 12-month baseline period prior to OAB medication initiation was used to classify patients into diabetes and non-diabetes cohorts, and measure demographic and clinical characteristics. Patients in each cohort were directly matched 1 : 1 based on index year, age, gender and geographic region. Multiple logistic regression was used to compare cohorts on outcomes of ≥ 80% adherence to OAB medications and refilling a second OAB medication prescription. Cox's proportional hazards model compared time to non-persistence with OAB medications between both cohorts.

RESULTS

In total, 36,560 patients were included in each cohort. Compared with the non-diabetes cohort, the diabetes cohort had 21.5% higher odds of ≥ 80% adherence to OAB medications, 16.6% higher odds of filling a second OAB medication prescription and 10.3% lower hazard of non-persistence with OAB medications during a 12-month evaluation period.

CONCLUSIONS

Patients with diabetes were more persistent and adherent to OAB medications and had higher odds of filling a second medication prescription than patients without diabetes. Further research is needed to identify factors responsible for these findings.

Rates and predictors of 30-day readmission among commercially insured and Medicaid-enrolled patients hospitalized with systolic heart failure

BACKGROUND

Heart failure (HF) readmission rates are primarily derived from Medicare enrollees. Given increasing public scrutiny of HF readmissions, understanding the rate and predictors in populations covered by other payers is also important, particularly among patients with systolic dysfunction, for whom most HF-specific therapies are targeted.

METHODS AND RESULTS

MarketScan Commercial and Medicaid Administrative Claims Databases were used to identify all first hospitalizations with an International Classification of Diseases-9 discharge diagnosis code for HF (primary position) and systolic HF (any position) between January 1, 2005, and June 30, 2008. Among 4584 unique systolic HF index admissions (mean age 55 years), 30-day crude readmission rates were higher for Medicaid than commercially insured patients: all-cause 17.4% versus 11.8%; HF-related 6.7% versus 4.0%, respectively. In unadjusted analysis, higher comorbidity and prior healthcare utilization predicted readmission; age, sex, and plan type did not. After adjustment for case mix, the odds of all-cause and HF-related readmission were 32% and 68% higher, respectively, among Medicaid than commercially insured patients (P<0.02 for both). No significant differences in readmission rates were seen for managed care versus fee-for-service or capitated versus noncapitated plan types.

CONCLUSIONS

Compared with commonly cited Medicare HF readmission rates of 20% to 25%, Medicaid patients with systolic HF had lower 30-day readmission rates, and commercially insured patients had even lower rates. Even after adjustment for case mix, Medicaid patients were more likely to be readmitted than commercially insured patients, suggesting that more attention should be focused on readmissions among socioeconomically disadvantaged populations.

Effects of Aerobic Fitness and Adiposity on Coagulation Biomarkers in Men vs. Women with Elevated Blood Pressure

A hypercoagulable state is a potential mechanism linking elevated blood pressure (BP), adiposity and a sedentary lifestyle to development of coronary heart disease (CHD). We examined relationships among aerobic fitness and adiposity in 76 sedentary subjects with elevated BP. Blood levels of plasminogen activator inhibitor-1 (PAI-1), D-dimer, von Willebrand factor (vWF) and thrombomodulin were assessed as biomarkers of coagulation. In individuals with elevated BP, percent body fat and fitness were associated with biomarkers indicative of a hypercoagulable state, even after demographic and metabolic factors were considered. D-dimer was positively associated with percent body fat (beta=0.37, p=0.003). PAI-1 was higher in men than in women (beta=-0.31, p=0.015) and associated with lower VO2peak (beta=-0.35, p=0.024). Thrombomodulin was positively associated with VO2peak (beta=0.56, p< 0.01). vWF was not significantly associated with fitness or adiposity. Our results emphasise that both percent body fat and physical fitness are important in the maintenance of haemostatic balance.

Incidence and cost of CAP in a large working-age population

OBJECTIVES

To estimate incidence rates and quantify excess medical and productivity cost of community-acquired pneumonia (CAP) in a commercially insured, working-age population.

METHODS

Using the Thomson Reuters MarketScan Commercial Claims and Encounters Database, we estimated the annual incidence of CAP from 2003 through 2007 and evaluated its excess direct medical and productivity costs due to short-term disability and workplace absenteeism for adult patients aged 18 to 64 years. A cohort of CAP patients was 1:3 propensity score matched to a control cohort without pneumonia. Both excess direct medical costs and excess productivity costs were estimated in multivariate ordinary least squares (OLS) and generalized linear model (GLM) adjusting for demographic and clinical characteristics.

RESULTS

A total of 402,831 patients with CAP and 1,208,231 matched controls were included. Overall annual CAP incidence was 4.89 cases per 1000 person-years. Excess annual medical cost of CAP ranged from $7220 by OLS to $11,443 by GLM. Inpatient costs, outpatient costs, and pharmacy costs explained 34%, 51%, and 15% of this excess cost of the GLM models, respectively. CAP patients had an additional productivity cost of $2391. Among adults younger than 65 years, these estimates imply an incidence of CAP of 950,000 annual cases at a cost of $10.6 billion (range: $9.04-$13.1), of which 80% are direct medical costs and 20% are productivity costs.

CONCLUSIONS

CAP is a frequent and costly event in a working-age population with a national cost of $10.6 billion. Interventions that could successfully prevent CAP could have a significant impact on healthcare costs and productivity.

Tumor necrosis factor blocker dose escalation among biologic naïve rheumatoid arthritis patients in commercial managed-care plans in the 2 years following therapy initiation

OBJECTIVE

This study uses real-world US managed-care claims data to estimate dose escalation rates over the first and second years of therapy among biologic naïve rheumatoid arthritis (RA) patients initiating tumor necrosis factor (TNF) blocker therapy with etanercept, adalimumab, or infliximab.

METHODS

Non-elderly adult (age 18-65 years) RA patients initiating etanercept, adalimumab, or infliximab from July 1, 2005 to April 30, 2009, were identified using the MarketScan Commercial Database. National and regional dose-escalation patterns were evaluated 12 and 24 months after initiation. In the single-instance method, dose escalation was defined as having one average weekly dose 115%, 130%, or 150% greater than the initial average weekly dose. By the two-instances method, dose escalation was defined as having two consecutive claims with an average weekly dose 115% or 130% greater than the initial average weekly dose.

RESULTS

A total of 2747 patients met the inclusion criteria (mean age 50 years [SD=10]; 74% female). More patients initiated etanercept (44%) than adalimumab (37%) or infliximab (20%). Using the single-instance method, dose escalation at 12 months ranges were 0.8-1.5% for etanercept, 10.8-12.5% for adalimumab, and 16.4-42.5% for infliximab; ranges at 24 months were 0.8-2.1% for etanercept, 14.3-17.5% for adalimumab, and 26.4-57.6% for infliximab. The two-instances method showed a similar relationship among the treatment cohorts at both 12 and 24 months, with lower dose-escalation rates for etanercept (0.8%, 0.8%) than adalimumab (8.7%, 13.3%) or infliximab (22.9%, 37.6%) at the 130% threshold (p<0.001). Dose-escalation rates for etanercept, adalimumab, and infliximab were consistent across US geographic regions.

CONCLUSION

Patients initiating etanercept had lower rates of dose escalation than patients initiating adalimumab or infliximab in the first and second year following therapy initiation, as well as across US geographic regions. These results may not be generalizable to the entire US RA population.

Effects on blood pressure and autonomic nervous system function of a 12-week exercise or exercise plus DASH-diet intervention in individuals with elevated blood pressure

AIM

Hypertension is related to abnormalities in autonomic nervous system (ANS) function, with increased sympathetic output and decreased parasympathetic tone. Lifestyle interventions are the first line of treatment in hypertension, and decreased blood pressure (BP) effects may be related to changes in ANS function. Using heart rate recovery (HRR) from exercise as an index of parasympathetic tone and plasma noradrenaline as an index of sympathetic tone, we investigated the effects of lifestyle interventions on ANS function in patients with elevated BP.

METHODS

Sedentary participants with elevated BP were randomly assigned to either an exercise only (N = 25), exercise plus dietary approaches to stop hypertension (DASH) diet (N = 12), or waitlist control (N = 15) 12-week intervention. Plasma noradrenaline was measured at rest and participants performed a peak exercise test before and after the intervention. HRR was calculated as peak heart rate (HR) minus HR at 1 min post-exercise.

RESULTS

Heart rate recovery showed a significant group by time interaction; both intervention groups showed increases in HRR from pre- to post-intervention, while waitlist showed no change. Similarly, both exercise plus diet and exercise groups, but not waitlist, showed significant reductions in BP from pre- to post-intervention. Linear regression revealed that BP post-intervention was significantly predicted by change in HRR when controlling for pre-BP, age, gender and BMI.

CONCLUSIONS

Lifestyle interventions induced training-reduced BP and altered autonomic tone, indexed by HRR. This study indicates the importance of behavioural modification in hypertension and that increased parasympathetic function is associated with success in reduction of BP.

Phylogeny and ecophysiology of opportunistic "snow molds" from a subalpine forest ecosystem

Mats of coenocytic "snow molds" are commonly observed covering the soil and litter of alpine and subalpine areas immediately following snow melt. Here, we describe the phylogenetic placement, growth rates, and metabolic potential of cold-adapted fungi from under-snow mats in the subalpine forests of Colorado. SSU rDNA sequencing revealed that these fungi belong to the zygomycete orders Mucorales and Mortierellales. All of the isolates could grow at temperatures observed under the snow at our sites (0 degrees C and -2 degrees C) but were unable to grow at temperatures above 25 degrees C and were unable to grow anaerobically. Growth rates for these fungi were very high at -2 degrees C, approximately an order of magnitude faster than previously studied cold-tolerant fungi from Antarctic soils. Given the rapid aerobic growth of these fungi at low temperatures, we propose that they are uniquely adapted to take advantage of the flush of nutrient that occurs at the soil-snow interface beneath late winter snow packs. In addition, extracellular enzyme production was relatively high for the Mucorales, but quite low for the Mortierellales, perhaps indicating some niche separation between these fungi beneath the late winter snow pack.

Sperm plasma membrane breakdown during Drosophila fertilization requires Sneaky, an acrosomal membrane protein

Fertilization typically involves membrane fusion between sperm and eggs. In Drosophila, however, sperm enter eggs with membranes intact. Consequently, sperm plasma membrane breakdown (PMBD) and subsequent events of sperm activation occur in the egg cytoplasm. We previously proposed that mutations in the sneaky (snky) gene result in male sterility due to failure in PMBD. Here we support this proposal by demonstrating persistence of a plasma membrane protein around the head of snkysperm after entry into the egg. We further show that snky is expressed in testes and encodes a predicted integral membrane protein with multiple transmembrane domains, a DC-STAMP-like domain, and a variant RING finger. Using a transgene that expresses an active Snky-Green fluorescent protein fusion (Snky-GFP), we show that the protein is localized to the acrosome, a membrane-bound vesicle located at the apical tip of sperm. Snky-GFP also allowed us to follow the fate of the protein and the acrosome during fertilization. In many animals, the acrosome is a secretory vesicle with exocytosis essential for sperm penetration through the egg coats. Surprisingly, we find that the Drosophila acrosome is a paternally inherited structure. We provide evidence that the acrosome induces changes in sperm plasma membrane, exclusive of exocytosis and through the action of the acrosomal membrane protein Snky. Existence of testis-expressed Snky-like genes in many animals, including humans, suggests conserved protein function. We relate the characteristics of Drosophila Snky, acrosome function and sperm PMBD to membrane fusion events that occur in other systems.

Cloned cattle derived from a novel zona-free embryo reconstruction system

As the demand for cloned embryos and offspring increases, the need arises for the development of nuclear transfer procedures that are improved in both efficiency and ease of operation. Here, we describe a novel zona-free cloning method that doubles the throughput in cloned bovine embryo production over current procedures and generates viable offspring with the same efficiency. Elements of the procedure include zona-free enucleation without a holding pipette, automated fusion of 5-10 oocyte-donor cell pairs and microdrop in vitro culture. Using this system, zona-free embryos were reconstructed from five independent primary cell lines and cultured either singularly (single-IVC) or as aggregates of three (triple-IVC). Blastocysts of transferable quality were obtained at similar rates from zona-free single-IVC, triple-IVC, and control zona-intact embryos (33%, 25%, and 29%, respectively). In a direct comparison, there was no significant difference in development to live calves at term between single-IVC, triple-IVC, and zona-intact embryos derived from the same adult fibroblast line (10%, 13%, and 15%, respectively). This zona-free cloning method could be straightforward for users of conventional cloning procedures to adopt and may prove a simple, fast, and efficient alternative for nuclear cloning of other species as well.

BAF is required for emerin assembly into the reforming nuclear envelope

Mutations in emerin cause the X-linked recessive form of Emery-Dreifuss muscular dystrophy (EDMD). Emerin localizes at the inner membrane of the nuclear envelope (NE) during interphase, and diffuses into the ER when the NE disassembles during mitosis. We analyzed the recruitment of wildtype and mutant GFP-tagged emerin proteins during nuclear envelope assembly in living HeLa cells. During telophase, emerin accumulates briefly at the ‘core’ region of telophase chromosomes, and later distributes over the entire nuclear rim. Barrier-to-autointegration factor (BAF), a protein that binds nonspecifically to double-stranded DNA in vitro, co-localized with emerin at the ‘core’ region of chromosomes during telophase. An emerin mutant defective for binding to BAF in vitro failed to localize at the ‘core’ in vivo, and subsequently failed to localize at the reformed NE. In HeLa cells that expressed BAF mutant G25E, which did not show ‘core’ localization, the endogenous emerin proteins failed to localize at the ‘core’ region during telophase, and did not assemble into the NE during the subsequent interphase. BAF mutant G25E also dominantly dislocalized LAP2β and lamin A from the NE, but had no effect on the localization of lamin B. We conclude that BAF is required for the assembly of emerin and A-type lamins at the reforming NE during telophase, and may mediate their stability in the subsequent interphase.

Distinct functional domains in emerin bind lamin A and DNA-bridging protein BAF

Loss of emerin, a lamin-binding nuclear membrane protein, causes Emery-Dreifuss muscular dystrophy. We analyzed 13 site-directed mutations, and four disease-causing mutations that do not disrupt emerin stability or localization. We show that emerin binds directly to barrier-to-autointegration factor (BAF), a DNA-bridging protein, and that this binding to BAF requires conserved residues in the LEM-motif of emerin. Emerin has two distinct functional domains: the LEM-domain at the N-terminus, which mediates binding to BAF, and a second functional domain in the central region, which mediates binding to lamin A. Disease mutation Δ95-99 mapped to the lamin-binding domain and disrupted lamin A binding in vitro. Two other disease-linked residues, Ser54 and Pro183, mapped outside the BAF and lamin-binding domains, suggesting that emerin may have additional functional domains relevant to disease. The disease-linked emerin proteins all remained active for binding to BAF, both in vitro and in vivo, suggesting that disease can result from the loss of specific molecular interactions between emerin and either lamin A or putative novel partner(s). The demonstration that emerin binds directly to BAF, coupled to similar results for LAP2, provides proof in principle that all LEM-domain nuclear proteins can interact with BAF, with interesting implications for chromatin attachment to the nuclear envelope.

Virology. HIV--breaking the rules for nuclear entry

How does human immunodeficiency virus (HIV) gain access to the carefully guarded nucleus of the host cell? In a Perspective, Segura-Totten and Wilson elaborate on new findings (de Noronha et al.) showing that the HIV protein Vpr is crucial for causing transient herniations in the host cell nuclear envelope. These ruptures are sufficient to enable the preintegration complexes of invading virions to enter the nucleus and to integrate with host cell DNA.

The nuclear envelope: emerging roles in development and disease

The chromosomes of eukaryotic cells are separated from the cytoplasm by the nuclear envelope. The nuclear envelope includes two riveted membranes, plus embedded pore complexes that mediate nuclear import and export. In this sense, the nuclear envelope is truly a border zone. However, the envelope also links directly to chromosomes, and anchors two major infrastructures--the nuclear lamina and Tpr filaments--to the nuclear perimeter. Proteins of the nuclear envelope mediate a variety of fundamental activities, including DNA replication, gene expression and silencing, chromatin organization, cell division, apoptosis, sperm nuclear remodeling, the behavior of pronuclei, cell fate determination, nuclear migration and cell polarity. Furthermore, mutations in nuclear lamins and lamin-binding proteins cause tissue-specific inherited diseases. This special issue of Cell and Molecular Life Sciences is devoted to recent major advances in the characterization of nuclear envelope proteins and their roles. We offer here an overview of the topics covered in this issue of CMLS, and also discuss the emerging recognition that the nuclear envelope is an organelle critical for a wide range of genetic and developmental activity in multicellular organisms.

Nuclear envelope organization in papillary thyroid carcinoma

Papillary thyroid carcinomas (PTCs) have characteristic nuclear shape changes compared to follicular-type thyroid epithelium. We tested the hypothesis that the altered nuclear shape results from altered distribution or expression of the major structural proteins of the nuclear envelope. Lamin A, lamin B1, lamin C, lamin B receptor (LBR), lamina-associated polypeptide 2 (LAP2), emerin, and nuclear pores were examined. PTC's with typical nuclear features by H&E were compared to non-neoplastic thyroid and follicular neoplasms using confocal microscopy, and semi-quantitative immunoblotting. Lamin A/C, lamin B1, LAP2, emerin, and nuclear pores all extend throughout the grooves and intranuclear inclusions of PTC. Their distribution and fluorescent intensity is not predictably altered relative to nuclear envelope irregularities. By immunoblotting, the abundance (per cell) and electrophoretic mobilities of lamin A, lamin B1, lamin C, emerin, and LAP2 proteins do not distinguish PTC, normal thyroid, or follicular neoplasms. These results do not support previously published predictions that lamin A/C expression is related to a loss of proliferative activity. At least three LAP2 isoforms are identified in normal and neoplastic thyroid. LBR is sparse or undetectable in all the thyroid samples. The results suggest that the irregular nuclear shape of PTC is not determined by these nuclear envelope structural proteins per se. We review the structure of the nuclear envelope, the major factors that determine nuclear shape, and the possible functional consequences of its alteration in PTC.

Transcriptional repression, apoptosis, human disease and the functional evolution of the nuclear lamina

The number and complexity of genes encoding nuclear lamina proteins has increased during metazoan evolution. Emerging evidence reveals that transcriptional repressors such as the retinoblastoma protein, and apoptotic regulators such as CED-4, have functional and dynamic interactions with the lamina. The discovery that mutations in nuclear lamina proteins cause heritable tissue-specific diseases, including Emery-Dreifuss muscular dystrophy, is prompting a fresh look at the nuclear lamina to devise models that can account for its diverse functions and dynamics, and to understand its enigmatic structure.

C. elegans nuclear envelope proteins emerin, MAN1, lamin, and nucleoporins reveal unique timing of nuclear envelope breakdown during mitosis

Emerin, MAN1, and LAP2 are integral membrane proteins of the vertebrate nuclear envelope. They share a 43-residue N-terminal motif termed the LEM domain. We found three putative LEM domain genes in Caenorhabditis elegans, designated emr-1, lem-2, and lem-3. We analyzed emr-l, which encodes Ce-emerin, and lem-2, which encodes Ce-MAN1. Ce-emerin and Ce-MAN1 migrate on SDS-PAGE as 17- and 52-kDa proteins, respectively. Based on their biochemical extraction properties and immunolocalization, both Ce-emerin and Ce-MAN1 are integral membrane proteins localized at the nuclear envelope. We used antibodies against Ce-MAN1, Ce-emerin, nucleoporins, and Ce-lamin to determine the timing of nuclear envelope breakdown during mitosis in C. elegans. The C. elegans nuclear envelope disassembles very late compared with vertebrates and Drosophila. The nuclear membranes remained intact everywhere except near spindle poles during metaphase and early anaphase, fully disassembling only during mid-late anaphase. Disassembly of pore complexes, and to a lesser extent the lamina, depended on embryo age: pore complexes were absent during metaphase in >30-cell embryos but existed until anaphase in 2- to 24-cell embryos. Intranuclear mRNA splicing factors disassembled after prophase. The timing of nuclear disassembly in C. elegans is novel and may reflect its evolutionary position between unicellular and more complex eukaryotes.

Teratogen-induced activation of ERK, JNK, and p38 MAP kinases in early postimplantation murine embryos

BACKGROUND

Although many teratogens are known to activate apoptotic pathways culminating in abnormal development, little is known about how the embryo transduces a teratogenic exposure into specific responses. Signal reception and transduction are regulated by a number of signal transduction pathways, including the extracellular signal-regulated protein kinases (ERKs), c-Jun N-terminal kinases (JNKs) and the stress-activated protein kinase, p38.

METHODS

To analyze the effects of teratogens on MAP kinases, we used whole embryo culture, Western blot analyses, and antibodies recognizing inactive or active MAP kinases, or both.

RESULTS

We show that heat shock (HS) induces a rapid, strong, but transient activation of ERK, JNK, and p38 with maximal activation occurring within 30 min of the heat shock. By contrast, cyclophosphamide (CP) and staurosporine (ST) failed to activate ERK or JNK during the time period studied (7. 5 hr). ST and CP did induce a low but reproducible activation of p38 beginning at around 3 hr and 5 hr, respectively, after the initiation of exposure. Previous work has shown that heat shock induces elevated cell death in the embryo, primarily in the developing neuroepithelium, but not in the embryonic heart. Thus, we also compared the activation of these three MAP kinase pathways in heads, hearts, and trunks isolated from day 9 embryos exposed to 43 degrees C for 15 min. The results show that ERK, JNK, and p38 are activated in heads, hearts, and trunks.

CONCLUSIONS

Our results show that day 9 embryos do activate MAP kinase signaling pathways in response to teratogenic exposures; however, activation of a particular pathway does not appear to be required for teratogen-induced apoptosis.

Review: nuclear lamins--structural proteins with fundamental functions

The nuclear lamina is located between the inner nuclear membrane and the peripheral chromatin. It is composed of both peripheral and integral membrane proteins, including lamins and lamina-associated proteins. Lamins can interact with one another, with lamina-associated proteins, with nuclear scaffold proteins, and with chromatin. Likewise, most of the lamina-associated proteins are likely to interact directly with chromatin. The nuclear lamina is required for proper cell cycle regulation, chromatin organization, DNA replication, cell differentiation, and apoptosis. Mutations in proteins of the nuclear lamina can disrupt these activities and cause genetic diseases. The structure and assembly of the nuclear lamina proteins and their roles in chromatin organization and cell cycle regulation were recently reviewed. In this review, we discuss the roles of the nuclear lamina in DNA replication and apoptosis and analyze how mutations in nuclear lamina proteins might cause genetic diseases.

The nuclear envelope, muscular dystrophy and gene expression

Lamins and other nuclear envelope proteins organize nuclear architecture through structural attachments that vary dynamically during the cell cycle and cell differentiation. Genetic studies have now shown that people with mutations in either lamins A/C or emerin, a nuclear membrane protein, develop Emery-Dreifuss muscular dystrophy. A mouse model for this rare disease has been created by knocking out the gene that encodes lamin A/C. This article discusses these and other recent results in the wider context of nuclear envelope function, as a framework for thinking about the possible ways in which defects in nuclear envelope proteins can lead to disease.

Stable five- and six-coordinated silicate anions in aqueous solution

Addition of aliphatic polyols to aqueous silicate solutions is shown to yield high concentrations of stable polyolate complexes containing five- or six-coordinated silicon. Coordinating polyols require at least four hydroxy groups, two of which must be in threo configuration, and coordinate to silicon via hydroxy oxygens at chain positions on either side of the threo pair. The remarkable ease by which these simple sugar-like molecules react to form hypervalent silicon complexes in aqueous solution supports a long-standing supposition that such species play a significant role in the biological uptake and transport of silicon and in mineral diagenesis.

Demonstration of Tritrichomonas foetus in the external genitalia and of specific antibodies in preputial secretions of naturally infected bulls

Portions of penis and prepuce were collected from 24 bulls with current or recent Tritrichomonas foetus infection. Epididymides were collected from seven of the bulls, and seminal vesicles and prostate were collected from four. Following immunohistochemical staining with two monoclonal antibodies (34.7C4.4 and TF1.15) prepared against T. foetus surface antigens, trichomonads were identified in sections from 15 of the bulls. Organisms were most often located in penile crypts in the midshaft and caudal regions and less often in preputial crypts. Trichomonads were not observed in sections from other genitalia or in subepithelial tissue. T. foetus antigen, however, was present in the cytoplasm of some epithelial cells and the cytoplasm of some mononuclear cells in subepithelial lymphoid aggregates and follicles. Preputial smegma was collected from 16 T. foetus-infected bulls and from 16 control bulls with negative T. foetus cultures. Preputial antibody levels to TF1.17, a surface antigen of T. foetus, were determined by an enzyme-linked immunosorbent assay. Preputial secretions from infected bulls contained specific antibody of each isotype and subisotype tested. IgG1 responses were the greatest, IgM and IgA responses were approximately equal, and IgG2 responses were low. Each isotype and subisotype response in infected bulls was significantly greater than that in the controls. These results confirm previous speculation concerning anatomical sites of infection and suggest that parasite antigen can be taken up and processed locally, resulting in deposition of specific IgG1, IgG2, IgA, and IgM antibodies in the preputial cavity.

Roles of LAP2 proteins in nuclear assembly and DNA replication: truncated LAP2beta proteins alter lamina assembly, envelope formation, nuclear size, and DNA replication efficiency in Xenopus laevis extracts

Humans express three major splicing isoforms of LAP2, a lamin- and chromatin-binding nuclear protein. LAP2beta and gamma are integral membrane proteins, whereas alpha is intranuclear. When truncated recombinant human LAP2beta proteins were added to cell-free Xenopus laevis nuclear assembly reactions at high concentrations, a domain common to all LAP2 isoforms (residues 1-187) inhibited membrane binding to chromatin, whereas the chromatin- and lamin-binding region (residues 1-408) inhibited chromatin expansion. At lower concentrations of the common domain, membranes attached to chromatin with a unique scalloped morphology, but these nuclei neither accumulated lamins nor replicated. At lower concentrations of the chromatin- and lamin-binding region, nuclear envelopes and lamins assembled, but nuclei failed to enlarge and replicated on average 2. 5-fold better than controls. This enhancement was not due to rereplication, as shown by density substitution experiments, suggesting the hypothesis that LAP2beta is a downstream effector of lamina assembly in promoting replication competence. Overall, our findings suggest that LAP2 proteins mediate membrane-chromatin attachment and lamina assembly, and may promote replication by influencing chromatin structure.

Heat shock protein 70 (Hsp70) protects postimplantation murine embryos from the embryolethal effects of hyperthermia

Previous work has shown that there is a positive correlation between the induction of Hsp70 and its transient nuclear localization and the acquisition and loss of induced thermotolerance in postimplantation rat embryos. To determine whether Hsp70 is sufficient to induce thermotolerance in postimplantation mammalian embryos, we used a transgenic mouse in which the normally strictly inducible Hsp70 is constitutively expressed in the embryo under the control of a beta-actin promoter. Day 8.0 mouse embryos heterozygous for the Hsp70 transgene were not protected from the embryotoxic effects of hyperthermia (43 degrees C); however, homozygous embryos, expressing approximately twice as much Hsp70 as heterozygous embryos, were partially protected (increased embryo viability) from the embryolethal effects of hyperthermia. Although the viability of transgenic embryos was significantly increased compared with that of nontransgenic embryos, this protection did not extend to embryo growth and development. To determine whether the failure to achieve a more robust protection was related to the expression of insufficient Hsp70 in transgenic embryos, we undertook experiments to determine whether the level of Hsp70 correlated with the level of thermotolerance induced by various lengths of a 41 degrees C heat shock. A 41 degrees C, 5-minute heat shock failed to induce Hsp70 or thermotolerance, a 41 degrees C, 15-minute heat shock induced Hsp70 and a significant level of thermotolerance, while a 41 degrees C, 60-minute heat shock induced an even higher level of Hsp70 as well as a higher level of thermotolerance. Quantitation of Hsp70 levels indicated that thermotolerance was associated with levels of Hsp70 of 820 pg/microg embryo protein or greater. Subsequent quantitation of the amount of Hsp70 expressed in homozygous transgenic embryos indicated a level of 577 pg/microg embryo protein, that is, a level below that associated with induced thermotolerance. Overall, results presented indicate that Hsp70 does play a direct role in the induction of thermotolerance in postimplantation mouse embryos; however, the level of thermotolerance is dependent on the level of Hsp70 expressed.

Ro 32-3555, an orally active collagenase selective inhibitor, prevents structural damage in the STR/ORT mouse model of osteoarthritis

OBJECTIVE

To determine the efficacy of a selective inhibitor of collagenases in an animal model of osteoarthritis (OA).

METHODS

Ro 32-3555, an orally active collagenase selective inhibitor, was administered to STR/ORT mice. Microfocal x-ray-generated images of the hind limbs were visually scored for joint space narrowing, osteophyte formation, and calcification of tendons. Histologic sections of the knees were scored for cartilage changes including loss of surface matrix, fibrillation, and eburnation.

RESULTS

Significant inhibition of joint space narrowing and osteophyte formation was achieved in groups of animals treated with 10-50 mg/kg(-1) of Ro 32-3555. These effects were confirmed histologically in the same groups of animals: histologic analysis revealed that Ro 32-3555 protected cartilage from degradative changes.

CONCLUSION

Ro 32-3555, a collagenase selective inhibitor, inhibits both the cartilage and bone changes in this mouse model of OA, and thus shows great potential as a treatment of OA in humans.

Growing or just getting along? Technical and adaptive competence in coping among adolescents

This study examined coping among African American adolescents with learning disabilities. Ninety-seven African American adolescents and their mother or primary caregiver participated in the study. The study centered on a new conceptual distinction between technical competence in coping and adaptive competence in coping. Technical competence referred to short-term, reactive attempts at coping based on individuals' abilities to find techniques for reducing their feelings of distress. Adaptive competence referred to longer-term, developmental processes of adaptive change that resulted in more global benefits for the individual. Past literature was reassessed on the basis of this conceptual distinction, and a new model of technical and adaptive competence in coping was proposed based on developmental theory. Perceptions of coping efficacy and the incidence of behavioral problems were regressed on measures of technical and adaptive competence in coping. Results were explored first as a general test of the model on the total sample, and second as a comparative analysis between gender subsamples. Total sample findings were consistent with hypothesized results. Technical competence was a better predictor of feelings of efficacy and adaptive competence was a better predictor of behavioral problems. Gender subsample differences were significant and supported a picture of gender-typed approaches to coping.

TPEN, a Zn2+/Fe2+ chelator with low affinity for Ca2+, inhibits lamin assembly, destabilizes nuclear architecture and may independently protect nuclei from apoptosis in vitro

We used Xenopus egg extracts to examine the effects of TPEN, a chelator with strong affinities for Zn2+, Fe2+, and Mn2+, on nuclear assembly in vitro. At concentrations above 1 mM, TPEN blocked the assembly of the nuclear lamina and produced nuclei that were profoundly sensitive to stress-induced balloon-like 'shedding' of nuclear membranes away from chromatin-associated membranes. TPEN-arrested nuclei were also defective for DNA replication, which could be explained as secondary to the lack of a lamina. Imaging of TPEN-arrested nuclei by field emission in-lens scanning electron microscopy (FEISEM) revealed clustered, structurally-perturbed nuclear pore complexes. TPEN-arrested nuclei were defective in the accumulation of fluorescent karyophilic proteins. All detectable effects caused by TPEN were downstream of the effects of BAPTA, a Ca2+/Zn2+ chelator that blocks pore complex assembly at two distinct early stages. Surprisingly, TPEN-arrested nuclei, but not control nuclei, remained active for replication in apoptotic extracts, as assayed by [32P]-dCTP incorporation into high molecular weight DNA, suggesting that TPEN blocks a metal-binding protein(s) required for nuclear destruction during programmed cell death.

Nuclear assembly

We review old and new insights into the structure of the nuclear envelope and the components responsible for its dynamic reassembly during mitosis. New information is coming to light about several of the proteins that mediate nuclear reassembly. These proteins include the lamins and their emerging relationship with proteins such as otefin and the MAN antigens: peripheral proteins that might participate in lamina structure. There are four identified proteins localized to the inner nuclear membrane: the lamina-associated proteins LAP1 and LAP2, emerin, and the lamin B receptor (LBR). LBR can interact independently with lamin B and a chromodomain protein, Hp1, and appears to be a central player in targeting nuclear membranes to chromatin. Intermediates in the assembly of nuclear pore complexes (NPCs) can now be studied biochemically and visualized by high resolution scanning electron microscopy. We discuss the possibility that the filament-forming proteins Tpr/p270, NuMA, and perhaps actin may have roles in nuclear assembly.

ARF is not required for nuclear vesicle fusion or mitotic membrane disassembly in vitro: evidence for a non-ARF GTPase in fusion

Xenopus laevis egg extracts are a well-characterized system for studying nuclear envelope dynamics in vitro. ADP-ribosylation factor (ARF), a 21 kDa GTPase involved in vesicular transport, inhibits nuclear vesicle fusion in vitro when membranes are preincubated with ARF and GTP gamma S (Boman et al., Nature 358, 512-514 (1992)). To test the hypothesis that ARF was required for nuclear envelope assembly or disassembly, we examined these events in cytosol from which ARF was depleted by size fractionation or inhibited with brefeldin A (BFA). In ARF-depleted extracts, vesicles bound chromatin and fused to enclose the chromatin, but the resulting enclosed nuclei lacked pore complexes and remained small. Further growth was not stimulated by adding ARF1, suggesting that fractionation removed other proteins required for pore complex assembly and nuclear growth. Nuclei assembled in ARF-depleted extracts, and rat liver nuclei, disassembled normally in mitotic ARF-depleted reactions. BFA, which inhibits ARF binding to membranes, had no effect on nuclear assembly or disassembly. We concluded that ARF is not essential for nuclear membrane dynamics. Nuclear vesicle fusion was still inhibited by GTP gamma S in ARF-depleted reactions and in reactions containing BFA, strongly suggesting that there is another unidentified GTPase that is either required for vesicle fusion or capable of inhibiting fusion in the presence of GTP gamma S.

Nuclear envelope assembly in Xenopus extracts visualized by scanning EM reveals a transport-dependent ‘envelope smoothing’ event

We analyzed the pathway of nuclear envelope assembly in Xenopus egg extracts using field emission in-lens scanning electron microscopy. The binding, fusion, and flattening of vesicles onto the chromatin surface were visualized in detail. The first nuclear pore complexes assembled in flattened patches of nuclear envelope, before the chromatin was fully enclosed by membranes. Confirming previous transmission electron microscope observations, two morphologically distinct types of vesicles contributed to the nuclear membranes: ribosome-carrying (‘rough’) vesicles, many of which bound directly to chromatin, and ‘smooth’ vesicles, which appeared to associate primarily with other nuclear vesicles or membrane patches. The presence of ribosomes, an outer nuclear membrane marker, on many chromatin-binding vesicles suggested that chromatin-attachment proteins integral to the inner membrane were present on vesicles that also carried markers of the outer membrane and endoplasmic reticulum. Chromatin-associated vesicles also carried pore membrane proteins, since pore complexes formed when these vesicles were incubated with cytosol. A change in nuclear envelope morphology termed ‘envelope smoothing’ occurred 5–15 minutes after enclosure. Nuclear envelopes that were assembled in extracts depleted of wheat-germ-agglutinin-binding nucleoporins, and therefore unable to form functional pore complexes, remained wrinkled, suggesting that ‘smoothing’ required active nuclear transport. Lamins accumulated with time when nuclei were enclosed and had functional pore complexes, whereas lamins were not detected on nuclei that lacked functional pore complexes. Very low levels of lamins were detected on nuclear intermediates whose surfaces were substantially covered with patches of pore-complex-containing envelope, suggesting that pore complexes might be functional before enclosure.

Dimples, pores, star-rings, and thin rings on growing nuclear envelopes: evidence for structural intermediates in nuclear pore complex assembly

We used field emission in-lens scanning electron microscopy to examine newly-assembled, growing nuclear envelopes in Xenopus egg extracts. Scattered among nuclear pore complexes were rare ‘dimples’ (outer membrane depressions, 5–35 nm diameter), more abundant holes (pores) with a variety of edge geometries (35–45 nm diameter; 3.3% of structures), pores containing one to eight triangular ‘star-ring’ subunits (2.1% of total), and more complicated structures. Neither mature complexes, nor these novel structures, formed when wheat germ agglutinin (which binds O-glycosylated nucleoporins) was added at high concentrations (&gt;500 microg/ml) directly to the assembly reaction; low concentrations (10 microg/ml) had no effect. However at intermediate concentrations (50–100 microg/ml), wheat germ agglutinin caused a dramatic, sugar-reversible accumulation of ‘empty’ pores, and other structures; this effect correlated with the lectin-induced precipitation of a variable proportion of each major Xenopus wheat-germ-agglutinin-binding nucleoporin. Another inhibitor, dibromo-BAPTA (5,5′-dibromo-1,2-bis[o-aminophenoxylethane-N,N,N′,N′-tetraacetic acid), had different effects depending on its time of addition to the assembly reaction. When 1 mM dibromo-BAPTA was added at time zero, no pore-related structures formed. However, when dibromo-BAPTA was added to growing nuclei 40–45 minutes after initiating assembly, star-rings and other structures accumulated, suggesting that dibromo-BAPTA can inhibit multiple stages in pore complex assembly. We propose that assembly begins with the formation and stabilization of a hole (pore) through the nuclear envelope, and that dimples, pores, star-rings, and thin rings are structural intermediates in nuclear pore complex assembly.

Ionophore-releasable lumenal Ca2+ stores are not required for nuclear envelope assembly or nuclear protein import in Xenopus egg extracts

The nuclear envelope of higher eukaryotes disassembles early in mitosis and reassembles later around the daughter chromosomes. Previous in vitro work supported the hypothesis that the release of lumenal Ca2+ stores via inositol 1,4,5-trisphosphate-gated Ca2+ channels is required for nuclear assembly in Xenopus egg extracts. Other work suggested that lumenal Ca2+ stores are required for nuclear protein import in mammalian cells in vivo, but not in vitro. Here, we rigorously tested the role of lumenal Ca2+ stores in nuclear assembly and nuclear protein import using Xenopus egg extracts. Lumenal Ca2+ stores were depleted by pretreating the extracts with Ca2+ ionophores (ionomycin, A23187) or inhibitors of Ca(2+)-sequestering pumps (thapsigargin, cyclopiazonic acid). Extracts depleted of lumenal Ca2+ stores assembled nuclei around demembranated sperm chromatin. These nuclei were morphologically indistinguishable from control nuclei when viewed by light or electron microscopy. Nuclei lacking lumenal Ca2+ stores excluded membrane-impermeant fluorescent dextrans, indicating the formation of a sealed nuclear envelope, and they accumulated a fluorescent nucleophilic protein, nucleoplasmin, indicating that nuclear pore complexes were functional. DNA replication occurred in the lumenal-Ca(2+)-depleted nuclei, though less efficiently than control nuclei. Our demonstration that in vitro nuclear import does not depend on lumenal Ca2+ stores confirms a previous unpublished observation by Greber and Gerace, and suggests that import defects seen in ionophore-treated living cells are not directly due to the loss of lumenal Ca2+. Finally, we concluded that, contrary to our expectations, lumenal Ca2+ stores are not required for nuclear envelope assembly in Xenopus egg extracts.

Nuclear envelope assembly after mitosis

In higher eukaryotes, the entire nucleus disassembles during prometaphase of the cell cycle and later reassembles around daughter chromosomes. Remarkably, the complex events that occur to create a functional nucleus in vivo can be duplicated in vitro by using cell-free extracts. Current experiments are aimed at understanding the molecular mechanisms of assembly and disassembly of the nuclear pore complexes and nuclear membranes, and the functional roles of four identified inner membrane proteins, two of which bind to both chromatin and the nuclear lamina.