Altered connectivity of the default mode network in cognitively stable adults with Down syndrome: "Accelerated aging" or a prelude to Alzheimer's disease?

INTRODUCTION

Most individuals with Down syndrome (DS) have the neuropathological changes of Alzheimer's disease (AD) by age 40 and will have developed dementia by age 60. Alterations of the intrinsic connectivity of the default mode network (DMN) are associated with AD in the neurotypical population. In this study, we sought to determine whether, and how, connectivity between the hubs of the DMN were altered in cognitively stable adults with DS who did not have evidence of either mild cognitive impairment or AD.

METHODS

Resting state functional MRI scans were collected from 26 healthy adults with DS and 26 healthy age-matched non-DS controls. Nodes comprising the DMN were generated as ROI's (regions of interest) and inter-nodal correlations estimated.

RESULTS

Analysis of intra-network connectivity of the DMN revealed anterior-posterior DMN dissociation and hyper- and hypo-connectivity, suggesting "accelerated aging" in DS.

DISCUSSION

Disruption of the DMN may serve as a prelude for AD in DS.

Malonyl coenzyme A affects insulin-stimulated glucose transport in myotubes

There seems to be an association between increased concentrations of malonyl coenzyme A (malonyl CoA) in skeletal muscle and diabetes and/or insulin resistance. The purpose of the current study was to test the hypothesis that treatments designed to manipulate malonyl CoA concentrations would affect insulin-stimulated glucose transport in cultured C2C12 myotubes. We assessed glucose transport after polyamine-mediated delivery of malonyl CoA to myotubes, after incubation with dichloroacetate (which reportedly increases malonyl CoA levels), or after exposure of myotubes to 2-bromopalmitate, a carnitine palmitoyl transferase I inhibitor. All three of these treatments prevented stimulation of glucose transport by insulin. We also assayed glucose transport after 30 min of inhibition of acetyl coenzyme A carboxylase (ACC), the enzyme which catalyzes the production of malonyl CoA. Three unrelated ACC inhibitors (diclofop, clethodim, and Pfizer CP-640186) all enhanced insulin-stimulated glucose transport. However, none of the treatments designed to manipulate malonyl CoA concentrations altered markers of proximal insulin signaling through Akt. The findings support the hypothesis that acute changes in malonyl CoA concentrations affect insulin action in muscle cells but suggest that the effects do not involve alterations in proximal insulin signaling.

Association between HLA-DQB1 and cervical dysplasia in Vietnamese women

Host genetic background seems to play a key role in cervical carcinogenesis as only a small subset of women infected with high-risk human papillomaviruses (HPVs) develop cervical cancer. The rate of cervical cancer in Vietnamese women is notably high. To explore the association of human leukocyte antigen (HLA)-DQB1 alleles, HPV infection, and cervical dysplasia in this population, cervical smears were obtained from 101 women attending the obstetrics and gynecology clinic of Da Nang General Hospital in Vietnam. Besides the Papanicolaou test, HPV and HLA-DQB1 genotyping were performed using cervical smear DNA. Additionally, a subset of 30 blood samples was used as the gold standard for HLA genotyping. HLA-DQB1 alleles showed no association with HPV infection status. However, a positive association with cervical dysplasia was found for HLA-DQB1*0302 (P= 0.0229, relative risk (RR) = 4.737) and HLA-DQB1*0601 (P= 0.0370, RR = 4.038), whereas HLA-DQB1*0301 (P= 0.0152, RR = 0.221) was found negatively associated. The low diversity of HLA-DQB1 alleles, wide spectrum of HPV genotypes, and high prevalence of HPV 16 and HPV 18 observed in the study population suggest a permissive/susceptible genetic background that deserves further research. Total concordance of HLA-DQB1 genotyping results between blood and cervical cells confirms the potential value of cervical smears as an effective tool for the development of cervical cancer biomarkers.

Transforming growth factor-beta 2 is an autocrine growth inhibitory factor for the MOSER human colon carcinoma cell line

The MOSER human colon carcinoma cell line is significantly growth inhibited by exogenous transforming growth factor-beta (TGF-beta). The secretion of TGF-beta by these cells was examined to determine if endogenous TGF-beta might also regulate MOSER cell growth. MOSER cells secreted 11 ng TGF-beta/10(6) cells, 24% of which was in the active form. Blocking antibodies specific for TGF-beta 2 stimulated growth 1.4-fold, while TGF-beta 1 specific antibodies were without effect. Treatment of MOSER cells with the differentiation agent, N,N-dimethylformamide (DMF), inhibited cell growth and resulted in an 8-fold increase in secreted TGF-beta (20% active). Only antibodies specific for TGF-beta 2 were able to reverse the growth inhibitory effect of DMF on these cells. Therefore, TGF-beta 2 acted as a negative autocrine inhibitory factor for MOSER cells and the growth inhibitory effects of DMF were mediated by the increased secretion of active TGF-beta 2.

Sodium butyrate alters the response of a human colon carcinoma cell line to transforming growth factor-beta 1

The effects of sodium butyrate (NaB) on the response of the RCA human colon carcinoma cell line to transforming growth factor-beta 1 (TGF-beta 1) were examined. NaB induced differentiation, as judged by an increase in cellular alkaline phosphatase, in the RCA cells and this differentiation was accompanied by a decreased growth rate. TGF-beta 1 did not significantly alter the growth or state of differentiation of the RCA cells. The growth rate of cells treated simultaneously with NaB and TGF-beta 1 was similar to that of control untreated cells while the alkaline phosphatase levels remained comparable to cells treated with NaB. Addition of TGF-beta 1 to cells grown in the presence of NaB resulted in a stimulation of growth. Cells pretreated with TGF-beta 1 remained sensitive to the growth inhibitory and differentiation inducing effects of NaB. These results suggest that NaB may alter the expression of proteins responsible for a stimulatory signal response to TGF-beta 1 in RCA cells.

Characterization of the synergistic effect of insulin and transferrin and the regulation of their receptors on a human colon carcinoma cell line

The human colon carcinoma cell line, HCT 116, can be grown in chemically defined media in the absence of exogenous growth factors. The addition of transferrin and insulin will significantly stimulate growth. The interaction of these growth factors with their receptors was studied to determine whether the synergistic action of insulin and transferrin on growth involved alterations in the growth-factor receptors. Redistribution of the transferrin receptor occurred in the presence of transferrin or transferrin plus insulin. The presence of insulin in the growth media resulted in occupation of cell-surface insulin receptors without a reduction in total insulin binding. Addition of transferrin with insulin resulted in a decrease in insulin binding to its receptor, with no alteration in receptor affinity. It appears that transferrin plays a role in regulating the insulin receptor and that this may contribute to the synergistic effect of insulin and transferrin on growth.

Evaluation of the ASTRA o-cresolphthalein complexone calcium method

An automated calcium method based on o-cresolphthalein complexone chemistry and designed to be used in conjunction with the Beckman ASTRA systems (Beckman Instruments, Inc., Brea, CA) was evaluated. Day-to-day reproducibility studies yielded coefficients of variation ranging from 1.2 to 3.1%. Linearity was 5.0-15.5 mg/dL, and recovery of calcium averaged 98%. Bilirubin, creatinine, hemoglobin, and turbidity did not cause significant interference while there was a positive interference due to magnesium. The throughput is 70 samples per hour, and a single stat result can be obtained in 9 minutes from the standby mode. Very little sample (12 microL) or reagent (150 microL) is required. There was excellent correlation between the ASTRA calcium method and atomic absorption spectrophotometry (Y = 1.047x - 0.39, r = 0.9941). Analytic performance was judged acceptable according to Westgard's medical usefulness criteria of the observed total analytic errors being less than the limit of allowable error.

Protection against experimental Pseudomonas aeruginosa infection in mice by active immunization with exotoxin A toxoids

The immunoprophylactic effect of chemically inactivated Pseudomonas aeruginosa exotoxin A in experimental pseudomonas infections was studied. Exotoxin A toxoids were prepared by Formalin (f-TXD) or glutaraldehyde (g-TXD) treatment. Immunization of mice with three or four doses (10 micrograms each) of f-TXD and the synthetic adjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine (50 micrograms) induced high levels of antiexotoxin A antibodies as measured by passive hemagglutination assay and enzyme-linked immunosorbent assay. Immunization with toxoid alone did not elicit antitoxin. A significant increase in survival time and survival rate (P less than 0.01) was seen in immunized (f-TXD) and in burned and infected mice (50 to 85%) as compared with control mice immunized with formalinized bovine serum albumin (6 to 20%). Virtually 100% survival was obtained when preinfection immunization weas combined with single-dose gentamicin treatment within 24 h of infection. Immunization with g-TXD increased survival time (P less than 0.01) but did not consistently increase survival rate, and the results were not as satisfactory as those with formalinized exotoxin. The data presented indicate that active immunization with formalinized exotoxin A toxoid and adjuvant induced protective immunity to various degrees against infections in mice and could be potentially useful in prophylaxis of P. aeruginosa infections.