3-Nitropropionic acid-exogenous animal neurotoxin and possible human striatal toxin

3-Nitropropionic acid (3-NPA)--a suicide inhibitor of succinate dehydrogenase--is a widely distributed plant and fungal neurotoxin known to induce a damage to basal ganglia, hippocampus, spinal tracts and peripheral nerves in animals. Recent reports from Northern China indicate that 3-NPA is also likely to be responsible for the development of putaminal necrosis with delayed dystonia in children after ingestion of mildewed sugar cane. This article discusses the role of 3-NPA in the causation of the disease in China, its neurotoxic effects in animals and the potential role for this compound as a probe of selective neuronal vulnerability.

Stabilization and ribosome association of unspliced pre-mRNAs in a yeast upf1- mutant

Nonsense-mediated mRNA decay, the accelerated turnover of mRNAs transcribed from genes containing early nonsense mutations, is dependent on the product of the UPF1 gene in yeast. Mutations that inactivate UPF1 lead to the selective stabilization of mRNAs containing early nonsense mutations but have no effect on the half-lives of almost all other mRNAs. Since the transcripts of nonsense alleles are not typical cellular constituents, we sought to identify those RNAs that comprise normal substrates of the nonsense-mediated mRNA decay pathway. Many yeast pre-mRNAs contain early in-frame nonsense codons and we consider it possible that a role of this pathway is to accelerate the degradation of pre-mRNAs present in the cytoplasm. Consistent with this hypothesis, we find that, in a strain lacking UPF1 function, the CYH2, RP51B, and MER2 pre-mRNAs are stabilized 2- to 5-fold and are associated with ribosomes. We conclude that a major source of early nonsense codon-containing cytoplasmic transcripts in yeast is pre-mRNAs and that the UPF1 protein may be part of a cellular system that ensures that potentially deleterious nonsense fragments of polypeptides do not accumulate.

Identification of a novel component of the nonsense-mediated mRNA decay pathway by use of an interacting protein screen

Rapid turnover of nonsense-containing mRNAs in yeast in dependent on the product of the UPF1 gene (Upf1p). Mutations in UPF1 lead to the selective stabilization of mRNAs containing early nonsense mutations without affecting the decay rates of most other mRNAs. To identify other integral components of this decay pathway, we have employed a two-hybrid screen, seeking those cellular factors that specifically interact with Upf1p. Screening of yeast genomic libraries identified six genes encoding potential Upf1p-interacting proteins. These include four previously uncharacterized genes, NMD1-4 (nonsense-mediated mRNA decay), DBP2, a gene encoding a putative RNA helicase with homology to mammalian p68 RNA helicase, and SNP1, a gene encoding a U1 snRNP 70-kD protein homolog. In this paper we report the identification and characterization of NMD2, a yeast gene that encodes a specific Upf1p-interacting protein. Disruption of NMD2 yields a nonsense-mediated mRNA decay phenotype identical to that obtained in UPF1-deletion strains, indicating that the NMD2 gene product (Nmd2p) is a new factor in the nonsense-mediated mRNA decay pathway. Deletion analysis demonstrated that the acidic carboxyl terminus of Nmd2p constituted the Upf1p-interacting domain. High-level expression of a fragment of Nmd2p containing this domain had a dominant-negative effect on nonsense-mediated mRNA decay when the protein was localized the cytoplasm but not when it was localized to the nucleus, indicating that this decay pathway has a cytoplasmic component. The association of a dominant-negative phenotype with a gene fragment identified in a two-hybrid screen suggests a generalized approach to confirming the function of genes identified in such screens.

Transient simulation of last deglaciation with a new mechanism for Bolling-Allerod warming

We conducted the first synchronously coupled atmosphere-ocean general circulation model simulation from the Last Glacial Maximum to the Bølling-Allerød (BA) warming. Our model reproduces several major features of the deglacial climate evolution, suggesting a good agreement in climate sensitivity between the model and observations. In particular, our model simulates the abrupt BA warming as a transient response of the Atlantic meridional overturning circulation (AMOC) to a sudden termination of freshwater discharge to the North Atlantic before the BA. In contrast to previous mechanisms that invoke AMOC multiple equilibrium and Southern Hemisphere climate forcing, we propose that the BA transition is caused by the superposition of climatic responses to the transient CO(2) forcing, the AMOC recovery from Heinrich Event 1, and an AMOC overshoot.

Upf1p, Nmd2p, and Upf3p are interacting components of the yeast nonsense-mediated mRNA decay pathway

Rapid turnover of nonsense-containing mRNAs in Saccharomyces cerevisiae is dependent on Upf1p, Nmd2p, and Upf3p, the products of the UPF1, NMD2/UPF2, and UPF3 genes, respectively. We showed previously that Upf1p and Nmd2p interact and that this interaction is required for nonsense-mediated mRNA decay (F. He and A. Jacobson, Genes Dev. 9:437-454, 1995; F. He, A. H. Brown, and A. Jacobson, RNA 2:153-170, 1996). In this study we have used the yeast two-hybrid system to define other protein-protein interactions among the essential components of this decay pathway. Nmd2p-Upf3p and Upf1p-Upf3p interactions were identified, and the respective domains involved in these interactions were delineated by deletion analysis. The domains of Upf1p and Upf3p putatively involved in their mutual interaction were found to correspond to the domains on the two proteins which interact with Nmd2p, suggesting that Nmd2p bridges Upf1p and Upf3p. This conclusion was reinforced by experiments showing that: (i) deletion of NMD2 completely abolishes interactions between Upf1p and Upf3p and (ii) overexpression of full-length Nmd2p or Nmd2p fragments that retain Upf1p- and Upf3p-interacting domains promotes 10- to 200-fold enhancement of Upf1p-Nmd2p-Upf3p complex formation. These results; the observation that cells harboring either single or multiple deletions of UPF1, NMD2, and UPF3 inhibit nonsense-mediated mRNA decay to the same extent; and an analysis of the possible targets of a dominant-negative NMD2 allele indicate that Upf1p, Nmd2p, Upf3p, and at least one other factor are functionally dependent, interacting components of the yeast nonsense-mediated mRNA decay pathway.

A tyrosine kinase profile of prostate carcinoma

Tyrosine kinases play central roles in the growth and differentiation of normal and tumor cells. In this study, we have analyzed the general tyrosine kinase expression profile of a prostate carcinoma (PCA) xenograft, CWR22. We describe here an improved reverse transcriptase-PCR approach that permits identification of nearly 40 different kinases in a single screening; several of these kinases are newly cloned kinases and some are novel. According to this, there are 11 receptor kinases, 9 nonreceptor kinases, and at least 7 dual kinases expressed in the xenograft tissue. The receptor kinases include erbB2, erbB3, Ret, platelet-derived growth factor receptor, sky, nyk, eph, htk, sek (eph), ddr, and tkt. The nonreceptor kinases are lck, yes, abl, arg, JakI, tyk2, and etk/bmx. Most of the dual kinases are in the mitogen-activating protein (MAP) kinase-kinase (MKK) family, which includes MKK3, MKK4, MEK5, and a novel one. As a complementary approach, we also analyzed by specific reverse transcriptase-PCR primers the expression profile of erbB/epidermal growth factor receptor family receptors in a variety of PCA specimens, cell lines, and benign prostatic hyperplasia. We found that erbB1, -2, and -3 are often coexpressed in prostate tissues, but not in erbB4. The information established here should provide a base line to study the possible growth and oncogenic signals of PCA.

A natural BH3 mimetic induces autophagy in apoptosis-resistant prostate cancer via modulating Bcl-2-Beclin1 interaction at endoplasmic reticulum

A natural BH3-mimetic, small-molecule inhibitor of Bcl-2, (-)-gossypol, shows promise in ongoing phase II and III clinical trials for human prostate cancer. In this study we show that (-)-gossypol preferentially induces autophagy in androgen-independent (AI) prostate cancer cells that have high levels of Bcl-2 and are resistant to apoptosis, both in vitro and in vivo, but not in androgen-dependent (AD) cells with low Bcl-2 and sensitive to apoptosis. The Bcl-2 inhibitor induces autophagy through blocking Bcl-2-Beclin1 interaction, together with downregulating Bcl-2, upregulating Beclin1, and activating the autophagic pathway. The (-)-gossypol-induced autophagy is dependent on Beclin1 and Atg5. Our results show for the first time that (-)-gossypol can also interrupt the interactions between Beclin1 and Bcl-2/Bcl-xL at endoplasmic reticulum, thus releasing the BH3-only pro-autophagic protein Beclin1, which in turn triggers the autophagic cascade. Oral administration of (-)-gossypol significantly inhibited the growth of AI prostate cancer xenografts, representing a promising new regimen for the treatment of human hormone-refractory prostate cancer with Bcl-2 overexpression. Our data provide new insights into the mode of cell death induced by Bcl-2 inhibitors, which will facilitate the rational design of clinical trials by selecting patients who are most likely to benefit from the Bcl-2-targeted molecular therapy.

Charge order driven by Fermi-arc instability in Bi2Sr(2-x)La(x)CuO(6+δ)

The understanding of the origin of superconductivity in cuprates has been hindered by the apparent diversity of intertwining electronic orders in these materials. We combined resonant x-ray scattering (REXS), scanning-tunneling microscopy (STM), and angle-resolved photoemission spectroscopy (ARPES) to observe a charge order that appears consistently in surface and bulk, and in momentum and real space within one cuprate family, Bi2Sr(2-x)La(x)CuO(6+δ). The observed wave vectors rule out simple antinodal nesting in the single-particle limit but match well with a phenomenological model of a many-body instability of the Fermi arcs. Combined with earlier observations of electronic order in other cuprate families, these findings suggest the existence of a generic charge-ordered state in underdoped cuprates and uncover its intimate connection to the pseudogap regime.

Diabetic retinopathy in predicting diabetic nephropathy in patients with type 2 diabetes and renal disease: a meta-analysis

AIMS/HYPOTHESIS

The aim of this meta-analysis is to determine the predictive value of diabetic retinopathy in differentiating diabetic nephropathy from non-diabetic renal diseases in patients with type 2 diabetes and renal disease.

METHODS

Medline and Embase databases were searched from inception to February 2012. Renal biopsy studies of participants with type 2 diabetes were included if they contained data with measurements of diabetic retinopathy. Pooled sensitivity, specificity, positive predictive value, negative predictive value and other diagnostic indices were evaluated using a random-effects model.

RESULTS

The meta-analysis investigated 26 papers with 2012 patients. The pooled sensitivity and specificity of diabetic retinopathy to predict diabetic nephropathy were 0.65 (95% CI 0.62, 0.68) and 0.75 (95% CI 0.73, 0.78), respectively. The pooled positive and negative predictive value of diabetic retinopathy to predict diabetic nephropathy were 0.72 (95% CI 0.68, 0.75) and 0.69 (95% CI 0.67, 0.72), respectively. The area under the summary receiver operating characteristic curve was 0.75, and the diagnostic odds ratio was 5.67 (95% CI 3.45, 9.34). For proliferative diabetic retinopathy, the pooled sensitivity was 0.25 (95% CI 0.16, 0.35), while the specificity was 0.98 (95% CI 0.92, 1.00). There was heterogeneity among studies (p < 0.001), and no publishing bias was identified.

CONCLUSIONS/INTERPRETATION

Diabetic retinopathy is useful in diagnosing or screening for diabetic nephropathy in patients with type 2 diabetes and renal disease. Proliferative diabetic retinopathy may be a highly specific indicator for diabetic nephropathy.

Clinical manifestations and diagnosis of acute pyrethroid poisoning

This article reviews 573 cases of acute pyrethroid poisoning reported in the Chinese medical literatures during 1983-1988. There were 325 cases of acute deltamethrin poisoning (occupational 158, accidental 167), 196 patients of acute fenvalerate poisoning (occupational 63, accidental 133, including 2 cases of ingestive fenvalerate-organophosphate mixture poisoning), 45 cases of acute cypermethrin poisoning (occupational 6, accidental 39) and 7 cases of other pyrethroid poisoning (occupational 2, accidental 5). The clinical manifestations have been reviewed and analysed. The diagnosis, gradation and differential diagnosis of occupational acute pyrethroid poisoning have been discussed.

Characterization of the biochemical properties of the human Upf1 gene product that is involved in nonsense-mediated mRNA decay

The Upf1 protein in yeast has been implicated in the modulation of efficient translation termination as well as in the accelerated turnover of mRNAs containing premature stop codons, a phenomenon called nonsense-mediated mRNA decay (NMD). A human homolog of the yeast UPF1, termed HUpf1/RENT1, has also been identified. The HUpf1 has also been shown to play a role in NMD in mammalian cells. Comparison of the yeast and human UPF1 proteins demonstrated that the amino terminal cysteine/histidine-rich region and the region comprising the domains that define this protein as a superfamily group I helicase have been conserved. The yeast Upf1p demonstrates RNA-dependent ATPase and 5' --> 3' helicase activities. In this paper, we report the expression, purification, and characterization of the activities of the human Upf1 protein. We demonstrate that human Upf1 protein displays a nucleic-acid-dependent ATPase activity and a 5'--> 3' helicase activity. Furthermore, human Upf1 is an RNA-binding protein whose RNA-binding activity is modulated by ATP. Taken together, these results indicate that the activities of the Upf1 protein are conserved across species, reflecting the conservation of function of this protein throughout evolution.

Determination of hemoglobin adducts in humans occupationally exposed to acrylamide

Hemoglobin (Hb) adduct determinations were used to monitor occupational exposure to acrylamide (AA) and acrylonitrile (AN). Forty-one workers in a factory in the People's Republic of China who were involved in the synthesis of AA by catalytic hydration of AN and the manufacturing of polyacrylamides were studied. Ten nonexposed workers in the same city served as controls. AA and AN exposures were monitored using the modified Edman degradation procedure for the determination of their respective Hb adducts to N-terminal valine. The adduct levels in the exposed workers were 0.3-34 nmol/g Hb for AA and 0.02-66 nmol/g Hb for AN, as determined by gas chromatography-mass spectrometry (GC-MS). The formation of glycidamide (GA), the epoxide metabolite of AA, in humans was demonstrated by GC-MS analysis of its Hb adduct to N-terminal valine following acid hydrolysis, ion-exchange chromatography, and derivatization. The GA adduct was detected in samples from the exposed persons with levels of 1.6-32 nmol/g Hb. There was a linear relationship between the AA and GA adduct levels (r = 0.96) and the ratio of the in vivo doses of GA and AA was 3:10. These results suggest that AA is metabolized to GA in humans, as had previously been shown in the rat. The high AA adduct levels in the exposed workers, as compared to those expected from air concentrations, indicate that dermal exposure may contribute significantly to the total uptake of AA. The average daily in vivo doses of AA and GA in the highest exposed workers were comparable to the in vivo doses in rats injected with 3 mg/kg AA. Since a regimen of 2 mg/kg/day is known to cause a significant increase of tumors in rats, preventive measures may be necessary for humans exposed to high levels of AA in industrial settings.

Comparison of mucosal adhesion and species identification of bifidobacteria isolated from healthy and allergic infants

Fifty bifidobacteria strains were isolated from fecal samples of allergic and age matched healthy infants. Allergic infants were found to have an adult type Bifidobacterium flora with high levels of Bifidobacterium adolescentis. Healthy infants had a typical infant Bifidobacterium flora with high levels of Bifidobacterium bifidum. These isolates were tested for their adhesive properties to human intestinal mucus. The adhesion of the fecal bifidobacteria from healthy infants was significantly higher (P<0.0001) than for allergic infants. This suggests a correlation between allergic disease and the composition of the intestinal bifidobacteria flora which has reduced adhesive abilities to the intestinal mucus. Therefore, dietary supplementation of bifidobacteria typical for healthy infants, may be beneficial in the treatment of allergic disorders.

Intranasal administration of Lactobacillus rhamnosus GG protects mice from H1N1 influenza virus infection by regulating respiratory immune responses

AIMS

To investigate whether intranasal Lactobacillus administration protects host animals from influenza virus (IFV) infection by enhancing respiratory immune responses in a mouse model.

METHODS AND RESULTS

After 3 days of intranasal exposure to Lactobacillus rhamnosus GG (LGG), BALB/c mice were infected with IFV A/PR/8/34 (H1N1). Mice treated with LGG showed a lower frequency of accumulated symptoms and a higher survival rate than control mice (P < 0.05). The YAC-1 cell-killing activity of lung cells isolated from mice treated with LGG was significantly greater than those isolated from control mice (P < 0.01). Intranasal administration of LGG significantly increased mRNA expression of interleukin (IL)-1 beta, tumour necrosis factor (TNF) and monocyte chemotactic protein (MCP)-1 (P < 0.01).

CONCLUSIONS

These results suggest that intranasal administration of LGG protects the host animal from IFV infection by enhancing respiratory cell-mediated immune responses following up-regulation of lung natural killer (NK) cell activation.

SIGNIFICANCE AND IMPACT OF STUDY

We have demonstrated that probiotics might protect host animals from viral infection by stimulating immune responses in the respiratory tract.

Repair of full-thickness femoral condyle cartilage defects using allogeneic synovial cell-engineered tissue constructs

OBJECTIVE

Synovium-derived stem cells (SDSCs) have proven to be superior in cartilage regeneration compared with other sources of mesenchymal stem cells. We hypothesized that conventionally passaged SDSCs can be engineered in vitro into cartilage tissue constructs and the engineered premature tissue can be implanted to repair allogeneic full-thickness femoral condyle cartilage defects without immune rejection.

METHODS

Synovial tissue was harvested from rabbit knee joints. Passage 3 SDSCs were mixed with fibrin glue and seeded into non-woven polyglycolic acid (PGA) mesh. After 1-month incubation with growth factor cocktails, the premature tissue was implanted into rabbit knees to repair osteochondral defects with Collagraft as a bone substitute in the Construct group. Fibrin glue-saturated PGA/Collagraft composites were used as a Scaffold group. The defect was left untreated as an Empty group.

RESULTS

SDSCs were engineered in rotating bioreactor systems into premature cartilage, which displayed the expression of sulfated glycosaminoglycan (GAG), collagen II, collagen I, and macrophages. Six months after implantation with premature tissue, cartilage defects were full of smooth hyaline-like cartilage with no detectable collagen I and macrophages but a high expression of collagen II and GAG, which were also integrated with the surrounding native cartilage. The Scaffold and Empty groups were resurfaced with fibrous-like and fibrocartilage tissue, respectively.

CONCLUSION

Allogeneic SDSC-based premature tissue constructs are a promising stem cell-based approach for cartilage defects. Although in vitro data suggest that contaminated macrophages affected the quality of SDSC-based premature cartilage, effects of macrophages on in vivo tissue regeneration and integration necessitate further investigation.

Relationships between biomarkers of exposure and neurological effects in a group of workers exposed to acrylamide

A study was performed among 41 workers heavily exposed to a mixture of acrylamide and acrylonitrile in the city of Xinxiang, Henan province, People's Republic of China. The workers underwent a complete medical and neurological examination and provided blood and urine for the determination of several biomarkers of exposure. Among the exposed workers, signs and symptoms indicating peripheral neuropathy were found with statistically significant increased frequencies compared to a group of controls from the same city. Based on neuropathic signs and symptoms and quantifiable indicators of peripheral nervous dysfunction, such as vibration thresholds and electroneuromyography measurements, a neurotoxicity index (NIn) specific for acrylamide-induced peripheral neuropathy was designed. The NIn, which adequately predicted the clinical diagnosis of peripheral neuropathy, was significantly correlated with the levels of mercapturic acids in 24-hr urine, hemoglobin adducts of acrylamide, accumulated in vivo doses of acrylamide, employment time, and vibration sensitivity. The NIn was correlated also with hemoglobin adducts of acrylonitrile, which was explained primarily by a correlation between acrylamide and acrylonitrile exposure in this workshop. However, it was not significantly correlated with momentary measures of exposure such as concentrations of acrylamide in the air or in the plasma of exposed workers. This study is the first in which adduct monitoring has been applied to the same group of individuals in which adverse health effects have been observed. The results seem to indicate that hemoglobin adducts are useful as predictors of acrylamide-induced peripheral neuropathy and that measurements of vibration thresholds are useful for identifying early neurotoxic effects in workplaces with hazardous exposures to acrylamide.

Upf1p control of nonsense mRNA translation is regulated by Nmd2p and Upf3p

Upf1p, Nmd2p, and Upf3p regulate the degradation of yeast mRNAs that contain premature translation termination codons. These proteins also appear to regulate the fidelity of termination, allowing translational suppression in their absence. Here, we have devised a novel quantitative assay for translational suppression, based on a nonsense allele of the CAN1 gene (can1-100), and used it to determine the regulatory roles of the UPF/NMD gene products. Deletion of UPF1, NMD2, or UPF3 stabilized the can1-100 transcript and promoted can1-100 nonsense suppression. Changes in mRNA levels were not the basis of suppression, however, since deletion of DCP1 or XRN1 or high-copy-number can1-100 expression in wild-type cells caused an increase in mRNA abundance similar to that obtained in upf/nmd cells but did not result in comparable suppression. can1-100 suppression was highest in cells harboring a deletion of UPF1, and overexpression of UPF1 in cells with individual or multiple upf/nmd mutations lowered the level of nonsense suppression without affecting the abundance of the can1-100 mRNA. Our findings indicate that Nmd2p and Upf3p regulate Upf1p activity and that Upf1p plays a critical role in promoting termination fidelity that is independent of its role in regulating mRNA decay. Consistent with these relationships, Upf1p, Nmd2p, and Upf3p were shown to be present at 1, 600, 160, and 80 molecules per cell, levels that underscored the importance of Upf1p but minimized the likelihood that these proteins were associated with all ribosomes or that they functioned as a stoichiometric complex.

A novel T-77C polymorphism in DNA repair gene XRCC1 contributes to diminished promoter activity and increased risk of non-small cell lung cancer

X-ray repair cross-complementing 1 (XRCC1) plays a key role in DNA base excision repair and cells lacking its activity are hypersensitive to DNA damage. Recently, we reported a SNP (rs3213245, -77T>C) in the XRCC1 gene 5' untranslated region (UTR) was significantly associated with the risk of developing esophageal squamous-cell carcinoma. Computer analysis predicted that this SNP was in the core of Sp1-binding motif, which suggested its functional significance. Gel shift and super shift assays confirmed that -77T>C polymorphic site in the XRCC1 promoter was within the Sp1-binding motif and the T>C substitution greatly enhanced the binding affinity of Sp1 to this region. Luciferase assays indicated that the Sp1-high-affinity C-allelic XRCC1 promoter was associated with a reduced transcriptional activity. The association between -77T>C and three other amino-acid substitution-causing polymorphisms in XRCC1 and risk of lung cancer was examined in 1024 patients and 1118 controls and the results showed that only the -77T>C polymorphism was significantly associated with an increased risk of developing lung cancer. Multivariate logistic regression analysis found that an increased risk of lung cancer was associated with the variant XRCC1 -77 genotypes (TC and CC) compared with the TT genotype (OR=1.46, 95% CI=1.18-1.82; P=0.001) and the increased risk was more pronounced in smokers (OR=1.63, 95% CI=1.20-2.21) than in non-smokers (OR=1.28, 95% CI=0.94-1.76). Taken together, these results showed that the functional SNP -77T>C in XRCC1 5'UTR was associated with cancer development owing to the decreased transcriptional activity of C-allele-containing promoter with higher affinity to Sp1 binding.

Baseline mass resolution of peptide isobars: a record for molecular mass resolution

Baseline resolution of two peptides, RVMRGMR and RSHRGHR, of neutral monoisotopic mass, approximately 904 Da, has been achieved by microelectrospray ionization Fourier transform ion cyclotron resonance mass spectrometry at a mass resolving power of approximately 3 300 000. The elemental compositions of these molecules differ by N40 vs. S2H8 (0.000 45 Da), which is less than one electron's mass (0.000 55 Da)! This result establishes a new record for the smallest resolved mass difference between any two molecules. This achievement is made possible by a combination of high magnetic field (9.4 T), large-diameter (4-in.) Penning trap, and low ion density. The implications for proteomics based on accurate mass measurements are discussed briefly.

Differences in composition and mucosal adhesion of bifidobacteria isolated from healthy adults and healthy seniors

Fifty-one Bifidobacterium strains were isolated from the feces of healthy adults (30-40 years old) and seniors (older than 70 years of age). B. adolescentis, B. breve, B. infantis, and B. longum were isolated from the healthy adults and B. adolescentis and B. longum from elderly subjects. The tested bacteria bound, in vitro, to intestinal mucus in a strain dependent manner. The strains isolated from healthy adults, and especially B. adolescentis, bound better to intestinal mucus than those isolated from seniors. These results indicate that the mucosal adhesive properties of the human Bifidobacterium flora were reduced with the aging of the host. This shift to a Bifidobacterium flora with reduced adhesive abilities may explain the decrease in bifidobacteria levels in the intestinal microflora of aging people.