Simvastatin exerts favourable effects on neointimal formation in a mouse model of vein graft

BACKGROUND

Simvastatin inhibits human saphenous vein neointima formation in human saphenous vein organ cultures. However, it is not known if simvastatin actually inhibits vein graft intima hyperplasia in vivo, and the underlying mechanisms behind that. In this study, we used a murine vein graft model to address these issues.

METHODS AND RESULTS

Vein grafting was performed among C57BL/6 J mice treated with low-dose (2 mg kg(-1)) or high-dose (20 mg kg(-1)) simvastatin or vehicle subcutaneously 72 h before and then daily after surgery. As compared to the vehicle, simvastatin dose-dependently significantly inhibited vein graft intima hyperplasia 4 weeks after surgeries. Immunohistochemistry studies suggested that vein graft neointima was mainly composed of vascular smooth muscle cells (VSMCs), and the rate of proliferating cell nuclear antigen (PCNA)-positive cells in the intima of vein grafts was significantly lower in simvastatin-treated groups than in control group. We isolated VSMC from mouse vena cava, simvastatin significantly reduced VSMC proliferation, and platelet-derived growth factor (PDGF)-induced VSMC migration in a dose-dependent manner.

CONCLUSION

Simvastatin inhibits neointima formation of mouse vein graft under normocholesterolaemic condition in vivo, the mechanisms might be associated with inhibitory effects of simvastatin on VSMC proliferation and migration.

Minimum effective plasma concentration of efavirenz in treatment-naïve Chinese HIV-infected patients

To assess the relationship between mean efavirenz (EFV) plasma concentration and clinical effect during the first 48 weeks of combination antiretroviral therapy (cART), the baseline CD4 cell count was recorded and plasma EFV concentration and CD4 cell count were measured every 12 weeks. HIV-RNA viral load was determined in the 48th week of cART. In total, 42 subjects were recruited and grouped according to their mean concentration of EFV during the study period: groups A, B and C with EFV concentrations (mean) <2 mg/L (1.8 mg/L), 2-4 mg/L (2.9 mg/L) and >4 mg/L (5.5 mg/L), respectively. The CD4 cell counts in group C increased more quickly than in groups B and A, although this was not statistically significant (211 ± 176/μL versus 151 ± 145/μL and 172 ± 105/μL, respectively; P = 0.799). Groups B and C had higher rates of HIV viral load suppression than group A (P = 0.017). For treatment-naïve Chinese HIV-infected patients, EFV plasma concentrations above 2 mg/L appear to suppress HIV replication more effectively than concentrations below 2 mg/L.

Does bladder urothelial cancer behave differently in young patients?

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Background: From 2000 to 2008, the incidence of bladder urothelial cancer in the young adults was diagnosed at an increasing trend at the Tongji Hospital, China. To investigate whether bladder urothelial cancer in patients under the age of 40 years behaves significantly differently from the bladder urothelial cancer in elder patients.

Methods: From 1994 to 2008, the records of 4,568 patients with pathological diagnosis of bladder urothelial cancer presented to the Tongji Hospital were retrospectively reviewed. 82 patients were younger than 40 at the time of diagnosis. The clinicopathologic parameters were compared between this group and a serial of 164 older patients during the same time period. The Kaplan-Meier and Cox regression analyses were performed for the survival analysis.

Results: 2.05% of patients with pathological diagnosis of bladder urothelial cancer presented to the Tongji Hospital were younger than 40 years (median age 32.93). Compared to the older group, young adults group had a lower sex ratio (male-to-female ratio, 3.4:1vs.6.5:1, p<0.05); much less likely with advanced stages (the percentage of invasive tumor, i.e., T1 or above, 28.1% vs. 52.4%, p<0.01); less with a high grade (the percentage of high grade tumor, 14.6% vs. 22.6%, p<0.05); lower recurrence rate (23.2% vs. 39.6%, p<0.05); less with big tumor size (the percent of tumor size greater than 3 cm, 18.3% vs. 22.0%, p<0.05); and less with multifocal (12.2% vs. 50.6%, p<0.01). Kaplan-Meier method and the log-rank test showed a significantly better cancer specific and overall survival for the group of young patients (p<0.01). The multivariate Cox regression analyses showed the following criteria were independent prognostic factors of overall survival: bladder tumor multiplicity, size greater than 3 cm, T2 or above stage, and high grade.

Conclusions: Despite an increasing trend of diagnosis, both the pathologic features and clinical outcomes were significantly better in the young patients with bladder urothelial cancer when compared to their elderly counterparts. These findings suggested that more consevertive management approaches may be warranted for this group of patients even under the circumstances of extensive bladder involvement.

No significant financial relationships to disclose.

Adjuvant radiation therapy for early-stage seminoma: Proton-photon comparison and second cancer risk

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Background: Seminoma constitutes the majority of testicular cancers and 75% percent of patients present with localized disease. Given that seminoma remains the most curable solid tumor, concerns of toxicity including late sequelae such as excess malignancies have given pause to the use of conventional adjuvant radiation therapy (RT) following orchiectomy for early-stage seminoma. As a result of the unique physical dose deposition characteristics of protons to avoid normal tissue, we evaluated both photon and proton beam therapy (PBT) treatment plans for para-aortic irradiation to assess dose distributions to organs at-risk and model rates of second cancers.

Methods: Ten patients with stage I seminoma treated with conventional adjuvant para-aortic AP-PA photon RT to 25.5 Gy between 2004-2009 at Massachusetts General Hospital had PBT plans generated (AP-PA and PA alone). The dose differences to critical organs, as modeled by Equivalent Uniform Dose (EUD), were examined. The risks of second primary malignancies were calculated using validated methods and compared both to each other and to baseline population risks.

Results: PBT plans were superior to photons in limiting dose to organs at-risk. The volume of whole body normal tissue spared 0.1 Gy was 9.0L and 7.8L for PA and AP-PA protons, respectively, compared to photons. The volume spared 1Gy was 5.0L and 3.8L for PA and AP-PA protons, respectively; while the volume spared 10Gy was 1.3L and 0.85L, respectively. PBT decreased the EUD by 46% (8.2 Gy) and 64% (10.2 Gy) to the stomach and large bowel, respectively (p<0.01), presumably translating into lower levels of nausea and fatigue. Notably, PBT was found to avert 612 excess second cancers among a population of 10,000 men diagnosed at age 35 and surviving to age 75 (p<0.01).

Conclusions: In this comparative dosimetric and modeling study, the use of protons provided a favorable dose distribution with an ability to limit unnecessary exposure to critical normal structures in the treatment of stage I seminoma patients. It is expected that this will translate into decreased acute toxicity and reduced risk of second cancers, for which prospective studies are warranted.

No significant financial relationships to disclose.

Short message service reminder intervention doubles sexually transmitted infection/HIV re-testing rates among men who have sex with men

OBJECTIVES

To evaluate the impact of a short message service (SMS) reminder system on HIV/sexually transmitted infection (STI) re-testing rates among men who have sex with men (MSM).

METHODS

The SMS reminder programme started in late 2008 at a large Australian sexual health clinic. SMS reminders were recommended 3-6 monthly for MSM considered high-risk based on self-reported sexual behaviour. The evaluation compared HIV negative MSM who had a HIV/STI test between 1 January and 31 August 2010 and received a SMS reminder (SMS group) with those tested in the same time period (comparison group) and pre-SMS period (pre-SMS group, 1 January 2008 and 31 August 2008) who did not receive the SMS. HIV/STI re-testing rates were measured within 9 months for each group. Baseline characteristics were compared between study groups and multivariate logistic regression used to assess the association between SMS and re-testing and control for any imbalances in the study groups.

RESULTS

There were 714 HIV negative MSM in the SMS group, 1084 in the comparison group and 1753 in the pre-SMS group. In the SMS group, 64% were re-tested within 9 months compared to 30% in the comparison group (p<0.001) and 31% in the pre-SMS group (p<0.001). After adjusting for baseline differences, re-testing was 4.4 times more likely (95% CI 3.5 to 5.5) in the SMS group than the comparison group and 3.1 times more likely (95% CI 2.5 to 3.8) than the pre-SMS group.

CONCLUSION

SMS reminders increased HIV/STI re-testing among HIV negative MSM. SMS offers a cheap, efficient system to increase HIV/STI re-testing in a busy clinical setting.

Associations of fat mass and fat distribution with bone mineral density in pre- and postmenopausal Chinese women

Fat mass (FM) is closely related to bone mineral density (BMD). However, the associations of FM and fat distribution with BMD in pre- and postmenopausal women are still poorly understood. The present study showed android fat mass accumulation after menopause had a negative association with BMD.

INTRODUCTION

FM is closely related to BMD. However, it is unknown whether FM and central fat distribution have different associations with BMD in pre- and postmenopausal women. The study aims to investigate the associations of FM and fat distribution with BMD in pre- and postmenopausal Chinese women.

METHODS

Two hundred sixty premenopausal and 267 postmenopausal women aged 18 to 79 years were analyzed. Lean mass (LM), FM, percent body fat (%BF), android FM, gynoid FM, and total and regional BMD were measured using dual-energy X-ray absorptiometry. Fat distribution was assessed by android to gynoid FM ratio (AOI). Multiple regression analysis was performed to examine the associations of BMD with FM, LM, and AOI.

RESULTS

FM, %BF, android FM, and AOI were significantly higher, whereas total and regional BMD were significantly lower in postmenopausal women (all р < 0.01). In premenopausal women, FM was positively associated with total and regional BMD (all р < 0.05). AOI had no significant association with BMD. In postmenopausal women, FM was significantly associated with total and regional BMD even additionally adjusting for LM (all р < 0.01). AOI had significantly negative association with total, head, arm, and leg BMD (all р < 0.05). The results remained unchanged when replacing FM with %BF.

CONCLUSIONS

There were different associations of FM and fat distribution with BMD in pre- and postmenopausal Chinese women. Increased central body fat had a negative association with BMD. Our findings may have significant implications in the prevention of menopause-related osteoporosis through reducing centralized fat deposition.

Abstract P4-06-24: KLF8 Induction of Mammary Epithelial Stem Cell Formation and Tumorigenesis by Regulating EMT-Associated MicroRNAs

Although it is well established that the epithelial-mesenchymal transition (EMT) generates cells with properties of stem cells, the molecularmechanisms responsible for this change remain largely undefined. We set out to identify the mechanisms by examining the expression of stem cell markers as well as microRNAs in MCF-10A cells during EMT induction. By immunostaining and FACS analysis, we found that during EMT induction by either TGF-β treatment or overexpression of KLF8, both the expression of CD44high/CD24low and the activity of aldehyde dehydrogenase (ALDH) were dramatically increased. Using microRNA PCR array, we identified a microRNA signature associated with the EMT. Using microRNA inhibitor, We further demonstrated that one of the microRNAs, miR-146a, is upregulated and plays an important role in keeping the stem cell percentage during EMT induced by both TGF-β and KLF8, as revealed by manipulation of miR-146a expression, analysis of the stem cell markers and mammosphere growth. Taken together, these results highlight a novel role for miR-146a in regulating the stem-like cell induction from MCF-10A cells by EMT. Experiments are in progress to investigate the contribution of KLF8-regulated expression of miR146a and its targets to the stem cell induction and transformation. Supported by: NIH, ACS, Komen and NYSTEM grants to J.Z.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-06-24.

Abstract P4-06-23: KLF8 Is Regulated by Its Novel Interacting Protein PARP-1

Krüppel-like factor 8 (KLF8) plays an important role in the progression of breast cancer invasion and metastasis. Using mass spectrometry and co-immunoprecipitation, we identified PARP-1, a chromatin-associated enzyme that catalyzes protein poly(ADP-ribosyl)ation (PARylation), as a novel KLF8 interacting protein. Co-IP and western blotting indicated that KLF8 is a PARylation substrate. Mutation of the cystein residues in the first and second zinc-finger motifs of KLF8 abolishes its interaction with PARP-1. Luciferase assays showed KLF8 activation on the cyclin D1 promoter was significantly reduced when PARP-1 was physically deleted or functionally inhibited or when KLF8-PARP-1 interaction was disrupted. Surprisingly, immunofluorescent staining demonstrated that KLF8 was localized in the nuclei of wide type MEFs, but was mislocalized in the perinuclear cytoplasm of the PARP-1-/- cells, which could be rescued by re-expression of PARP-1. The detection of γH2A.X, comet assay and clonogenic assay indicated KLF8 play a DNA repair role in a PARP-1- dependent matter. Cychloheximade-chase assay revealed the stability of KLF8 dramatically reduced by loss of PARP-1 or when KLF8-PARP-1 interaction was disrupted, meanwhile ubiquitination assay showed heavier ubiquitin chains of KLF8. This work has identified PARP-1 as a novel binding partner and post-translational modifier of KLF8 and a critical regulator of KLF8 localization, functions and stability in the cells and suggested a critical role of the interaction between KLF8 and PARP1 during metastatic progression of breast cancer. Support by: NIH, ACS and Komen grants to J.Z.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-06-23.

Abstract PD08-05: Longitudinal Change of Pain and Other Symptoms in Breast Cancer Patients with Anastrozole Treatment

Background About one in three breast cancer patients undergoing treated with aromatase inhibitors report problems with joint pain, some times interfering with work and other activities. We conducted a longitudinal study to characterize the course and impact of arthralgia and other symptoms during anastozole therapy by following how pain and other symptoms change during anastrozole treatment, and the impact of symptoms on patient's functioning, health-related quality of life (HRQoL), and work productivity.

Methods Two cohorts of patients were included: Cohort I recruited patients at the start of anastrozole therapy: Cohort II recruited patients at the beginning of their third year of treatment. Brief Pain Inventory and MD Anderson Symptom Inventory were used to monthly assess patients’ pain, multiple symptoms, and functioning. A single item of quality of life question and the Work Productivity and Activity Impairment Questionnaire: General Health V2.0 were used to measure patient's HRQoL and impairment of working productivity every 6 months. A joint pain self-assessment kit was used to locate the affected joints. Statistical analyses were based on the one-year follow-up data and t-test, mixed effects models, linear regression models, and correlation coefficients were used.

Results At this point in the study, thirty-eight patients have finished the one year assessment in cohort I and 37 patients in cohort II. Cohort I patients reported no or mild pain and symptoms before they started therapy. Compared to baseline, pain ratings on 0 to 10 scales significantly increased at the 5th month (4.17±3.66 vs. 1.52±2.38, p=.015) and then decreased to baseline levels at the 9th month. Similarly, patients reported higher level of distress (3.5±3.63 vs. 1.00±2.07, p=.014) and hot flashes (4.0±4.57 vs. 1.45±2.36, p=.039) at month 5 and decreased to baselines levels at month 9. Mixed effects model with the total symptom interference as the dependent variable identified that among all symptoms, pain had the greatest impact on patient functioning (p&lt;.0001). Patients with 4 or greater pain at month 5 reported poorer HRQoL at month 6 than those reported 3 or lower pain level (5.40±1.82 vs. 8.25±2.14, p=.020). Severity of pain at month 5 was positively correlated with working productivity: impairment at work (r=.80, p=.010), overall work productivity loss (r=.81, p=.014), and activity impairment (r=.84, p=.005). During the third year of anastrozole treatment, no symptom reaches the peak level at month 5 and no significant change was found over time, as well their HRQoL and working productivity. For cohort I patients, right knee was the most affected joint and right wrist as the most affected one for cohort II patients.

Conclusion Breast cancer patients beginning analstrozole therapy reported increased pain, distress, and hot flashes at the first year of treatment, worsening around the 5th month. Increased pain negatively impacted functioning, HRQoL, and work productivity. This study indicates that symptoms related to starting anastrozole develop over the first several months of therapy and have a functional impact on patients. Symptoms emerge when patients may be less actively followed clinically. Methods of managing these symptoms need to be investigated.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD08-05.

Quantum coherence in a one-electron semiconductor charge qubit

We study quantum coherence in a semiconductor charge qubit formed from a GaAs double quantum dot containing a single electron. Voltage pulses are applied to depletion gates to drive qubit rotations and noninvasive state readout is achieved using a quantum point contact charge detector. We measure a maximum coherence time of ∼7 ns at the charge degeneracy point, where the qubit level splitting is first-order insensitive to gate voltage fluctuations. We compare measurements of the coherence time as a function of detuning with numerical simulations and predictions from a 1/f noise model.

Raman spectroscopic investigations on natural samples from the Integrated Ocean Drilling Program (IODP) Expedition 311: indications for heterogeneous compositions in hydrate crystals

Natural gas hydrates usually are found in the form of structure I, encasing predominantly methane in the hydrate lattices as guest molecules, sometimes also minor amount of higher hydrocarbons, CO2 or H2S. Raman spectroscopy is an approved tool to determine the composition of the hydrate phase. Thus, in this study Raman spectroscopic analyses have been applied to hydrate samples obtained from Integrated Ocean Drilling Program (IODP) Expedition 311 in two different approaches: studying the samples randomly taken from the hydrate core, and--as a new application--mapping small areas on the surface of clear hydrate crystals. The results obtained imply that the gas composition of hydrate, in terms of relative concentrations of CH4 and H2S, is not homogeneous over a core or even within a crystal. The mapping method yielded results with very high lateral resolution, indicating the coexistence of different phases with the same structure but different compositions within a hydrate crystal.

Diagnosis of latent tuberculosis infection in bacille Calmette-Guérin vaccinated subjects in China by interferon-gamma ELISpot assay

OBJECTIVE

To evaluate the performance of an in-house interferon-gamma (IFN-γ) enzyme-linked immunospot (ELISpot) assay for the detection of latent tuberculosis infection (LTBI) in bacille Calmette-Guérin (BCG) vaccinated individuals with or without human immunodeficiency virus (HIV) infection.

METHODS

A total of 202 participants (93 HIV-infected and 109 non-infected) who received BCG vaccination at birth underwent tuberculin skin testing (TST) and T cell-based ELISpot assays. The performance of an in-house IFN-γ ELISpot assay (ELISpot) was evaluated by parallel comparison with the commercial IFN-γ release assay (IGRA) kit, T-SPOT®.TB, in 127 subjects. The effect of BCG vaccination on the ELISpot assay was prospectively determined by comparing the responses of IGRAs before and 3 months after BCG vaccination in 27 individuals.

RESULTS

High agreement between ELISpot and T-SPOT.TB was observed in both HIV-infected (92.47%, κ = 0.754) and non-HIV-infected subjects (97.06%, κ = 0.653). CD4(+) T-cell count does not affect Mycobacterium tuberculosis IFN-γ response as measured by both ELISpot and T-SPOT.TB. BCG vaccination resulted in 100% conversion of TST, but did not change responses to IGRAs.

CONCLUSION

The performance of this in-house ELISpot assay is comparable to commercial T-SPOT.TB in diagnosing LTBI. Both assays are useful for diagnosing LTBI in BCG-vaccinated subjects with or without HIV infection in a setting with a high prevalence of tuberculosis.

Nano-hydroxyapatite/poly(L-lactic acid) composite synthesized by a modified in situ precipitation: preparation and properties

Nano-hydroxyapatite/poly(L-lactic acid) (nano-HA/PLLA) composites with uniform HA distribution and good mechanical performance were fabricated by a modified in situ precipitation method, using Ca(OH)(2) and H(3)PO(4) as precursors for the synthesis of HA phase. This method has solved the aggregation problem of the nano-sized particles in the polymer matrix. The X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy were used to characterize the phase composition, chemical interactions and morphology of the composites, while the mechanical properties were determined by compressive measurements. The results show that the rod-like nano-HA particles synthesized by this method were uniformly distributed in the PLLA matrix. The compressive strength and Young's modulus of the composites were greatly enhanced and reached the values of 155 MPa and 3.6 GPa at 20 wt% HA content, respectively, which are much higher than those of the reference samples fabricated by direct mixing of PLLA with nano-HA particles. This supports the potential of these composites for applications in bone tissue engineering and load bearing bone defects repair.

An epidemiologic study of irritable bowel syndrome in adolescents and children in South China: a school-based study

BACKGROUND

To explore the prevalence of irritable bowel syndrome (IBS) among school-aged children in South China, and identify distribution characteristics and contributing factors.

METHODS

Primary, middle and high school students (n= 2013) were recruited from schools in Shanghai. Students completed two questionnaires, one for IBS in adolescents and children and the Screen for Child Anxiety Related Emotional Disorders (SCARED).

RESULTS

(1) The prevalence of IBS among students was 20.72% and the incidence increased with age. (2) Several physical factors and overuse of analgesics were significantly associated with IBS. (3) The prevalence of anxiety disorder was higher in older students, and in females vs. males. Students with IBS tended towards anxiety-related emotional disorders (38.14% vs. 18.96%). (4) IBS students scored higher in all SCARED categories. Within IBS students, those who frequently sought medical care reported higher scores in the somatization/panic category.

CONCLUSION

(1) Irritable bowel syndrome is a common disorder among adolescents in South China and prevalence increases with age. (2) Gastrointestinal infection, abuse of analgesics and psychological factors might be related to the incidence of IBS. (3) The tendency towards anxiety-related emotional disorders also increases with age, suggesting a possible correlation with IBS and underlining the importance of positive family and school environments. Although the prevalence of anxiety-related emotional disorders was higher in females than males, this trend was not correlated with the occurrence of IBS.

Over-expression of talin 1 and integrin-linked kinase in PBMCs of patients with ankylosing spondylitis: a proteomic study

OBJECTIVES

Ankylosing spondylitis (AS) is difficult to diagnose in its early stage due to the lack of simple and specific diagnostic indicators. This study was performed to screen candidate AS-associated proteins from peripheral blood mononuclear cells (PBMCs) of AS patients by combining a two-dimensional electrophoresis (2-DE) technique with mass spectrometry (MS) analysis.

METHODS

Twelve subjects consisting of 6 AS patients and 6 healthy volunteers (HVs) were enrolled in the 2-DE experiments. The protein expression patterns of PBMCs from different groups were analysed by PDQuest software, and the protein spots over/under-expressed by more than 2-fold between the two groups were identified by MS analysis. Western blot analyses were used to verify the differentially expressed proteins in 32 AS patients and 32 HVs.

RESULTS

Six proteins including pyruvate kinase (PK), profilin 1 (PFN1), talin 1 (TLN1), Chain A of cyclophilin A (CyPA), unknown protein (gi|16306948) and integrin-linked kinase (ILK) were identified from 10 over-expressed protein spots found by 2-DE in the AS group. Western blot experiments confirmed a higher expression of both TLN1 and ILK in AS group compared to the HV group (p<0.05).

CONCLUSIONS

TLN1 and ILK expressed higher in PBMCs of AS patients compared to healthy controls, which were involved in the integrin signalling pathway. The two proteins are likely novel disease-associated proteins and potential disease markers of AS.

YAP dysregulation by phosphorylation or ΔNp63-mediated gene repression promotes proliferation, survival and migration in head and neck cancer subsets

Over-expression of Yes-associated protein (YAP), and TP53 family members ΔNp63 and p73 with which YAP may serve as a nuclear co-factor, have been independently detected in subsets of head and neck squamous cell carcinomas (HNSCC). Their potential relationship and functional role of YAP in HNSCC are unknown. Here we reveal that in a subset of HNSCC lines and tumors, YAP expression is increased but localized in the cytoplasm in association with increased AKT and YAP phosphorylation, and decreased expression of ΔNp63 and p73. Conversely, YAP expression is decreased but detectable in the nucleus in association with lower AKT and YAP phosphorylation, and increased ΔNp63 and p73 expression, in another subset. Inhibiting AKT decreased Serine-127 phosphorylation and enhanced nuclear translocation of YAP. ΔNp63 repressed YAP expression and bound its promoter. Transfection of a YAP-Serine-127-Alanine phosphoacceptor-site mutant or ΔNp63 knockdown significantly increased nuclear YAP and cell death. Conversely, YAP knockdown enhanced cell proliferation, survival, migration, and cisplatin chemoresistance. Thus, YAP function as a tumor suppressor may alternatively be dysregulated by AKT phosphorylation at Serine-127 and cytoplasmic sequestration, or by transcriptional repression by ΔNp63, in different subsets of HNSCC. AKT and/orΔNp63 are potential targets for enhancing YAP-mediated apoptosis and chemosensitivity in HNSCC.

Radiometric dating of the late Quaternary summer monsoon on the Loess Plateau, China

Recent advances in radiometric dating have enabled independent investigation into monsoon variations. In this study, summer monsoon pedogenesis proxies (CaCO3 and magnetic susceptibility) have been analysed by optically stimulated luminescence (OSL) age for five loess-palaeosol sections over the Chinese Loess Plateau. The use of CaCO3 is complicated by the multiple influences on its variation. However, changes in magnetic susceptibility can be used as a proxy for summer monsoon induced pedogenesis. The data suggest that the summer monsoon in north-central China is not prone to high frequency shifts, although abrupt transitions occur. The overall patterns show general decreasing trends from c. 50 to 18 ka. However, between 9 and 6 ka, magnetic susceptibility increases abruptly and dramatically at the sites. These findings suggest that the Holocene ‘optimum’ in the region may be a more recent phenomenon than previously suggested, and that this summer monsoon intensity increase significantly post-dates the insolation peak occurring at 11.5 ka. An apparent close correspondence to ice volume is suggested to be a consequence of forcing via atmospheric circulation. Independently dated records that employ high sampling resolution can be used to test this hypothesis, together with suggestions over the apparent lag between insolation forcing and monsoon response.

Aeolian sediment evidence that global cooling has driven late Cenozoic stepwise aridification in central Asia

It has been a long held view that uplift of the Tibetan Plateau dominated stepwise climatic drying in central Asia during the late Cenozoic. On the other hand, global cooling may also have forced Asian drying and the subsequent formation of aeolian deposits in north China. Until now, whether the Tibetan uplift or the global cooling has been the first-order driver controlling stepwise Asian drying has remained a contentious issue. In this study, we examine the thick aeolian silt deposit, which is regarded as a good archive of palaeoclimatic changes in central Asia and north China, in order to qualitatively reconstruct the drying process in Asia during the late Cenozoic. On the basis of our long-term field surveys, laboratory analyses and previous investigations, we have obtained time sequences of Asian drying from the early Miocene to late Pleistocene; we compare this newly reconstructed time series of Asian aridification with the time series of global cooling and Tibetan uplift to identify the first-order driver of stepwise Asian aridification. A good match between the drying and global cooling might indicate that global cooling was the most likely driver of stepwise drying in interior Asia. On the other hand, controversy regarding timing and amplitude of Tibetan uplift during the late Cenozoic suggests that the prevailing conclusion that Tibetan uplift forces Asian drying should be regarded as immature. A mechanism that global cooling drove the Asian drying is tentatively suggested.