Biomedical subjects

S Gao

Publications and source records attributed to S Gao.

206 records · Page 12Linked to original sources

PubMedDate not supplied

Estimating the incidence of dementia from two-phase sampling with non-ignorable missing data.

Two-phase sampling designs have been used in the field of psychiatry to estimate prevalence and incidence of a rare disease such as dementia and Alzheimer's disease. In a longitudinal study on dementia, since the repeated two-phase sampling is conducted several years after the baseline wave, some subjects may die before the follow-up wave, thus their disease status prior to death is missing. There are reasons to suggest that the missing due to death is non-ignorable. Estimation of disease incidence from longitudinal dementia study has to appropriately adjust for data missing by death as well as the sampling design used at each study wave. In this paper we adopt a selection model approach to model the missing data by death and use a likelihood approach to derive incidence estimates. A modified EM algorithm is used to deal with data from sampling selection. The non-parametric jack-knife variance estimator is used to derive variance estimates for the model parameters and the incidence estimates. The proposed approaches are applied to data from the Indianapolis-Ibadan Dementia Study.

Black or African American↗

PubMedDate not supplied

Spacing of follow-up waves in incidence studies.

Longitudinal studies of dementia are often undertaken to estimate the incidence of dementia and to identify incident cases for the study of risk factors measured on the entire cohort at baseline. The power of these analyses is determined primarily by the number of demented cases identified. Increasing the number of waves of evaluation of the cohort in a given time period increases the yield of demented cases but it also increases the cost of the study. This paper provides a method for estimating dementia incidence in the presence of mortality and loss to follow-up. It also assesses the trade-off between the cost (as measured by the number of re-evaluations) and the yield of incident dementia cases so that longitudinal studies of dementia can be designed optimally in the future.

Aged↗

PubMedDate not supplied

Oxidative stress and the ovary.

Superoxide (O(2)(-)), hydrogen peroxide (H(2)O(2)), and lipid peroxides are generated in luteal tissue during natural and prostaglandin-induced regression in the rat, and this response is associated with reversible depletion of ascorbic acid. Reactive oxygen species immediately uncouple the luteinizing hormone receptor from adenylate cyclase and inhibit steroidogenesis by interrupting transmitochondrial cholesterol transport. The cellular origin of oxygen radicals in regressing corpora lutea is predominantly from resident and infiltrated leukocytes, notably neutrophils. Reactive oxygen species are also produced within the follicle at ovulation and, like the corpus luteum, leukocytes are the major source of these products. Antioxidants block the resumption of meiosis, whereas the generation of reactive oxygen induces oocyte maturation in the follicle. Although oxygen radicals may serve important physiologic roles within the ovary, the cyclic production of these damaging agents over years may lead to an increased cumulative risk of ovarian pathology that would probably be exacerbated under conditions of reduced antioxidant status.

Animals↗

PubMedDate not supplied

Nanostructured dna-protein aggregates consisting of covalent oligonucleotide-streptavidin conjugates.

Covalent conjugates consisting of streptavidin and a 24-mer single-stranded DNA oligonucleotide have been oligomerized by cross-linking with a 5',5'-bis-biotinylated 169-base-pair double-stranded DNA (dsDNA) fragment. The oligomeric conjugates formed have been analyzed by nondenaturing gel electrophoresis and scanning-force microscopy (SFM). The comparison of analogous oligomers, prepared from native STV and the bis-biotinylated dsDNA fragment, revealed that the covalent STV-oligonucleotide hybrid conjugates self-assemble to generate oligomeric aggregates of significant smaller size, containing on average only about 2.5 times less dsDNA fragments per aggregate. Likely, this is a consequence of electrostatic or steric repulsion between the dsDNA and the single-stranded oligomer covalently attached to the hybrid, as indicated from control experiments. Nevertheless, the single-stranded oligonucleotide moiety within the oligomeric conjugates can be used as a selective molecular handle for further functionalization and manipulation. For instance, it was used for specific DNA-directed immobilization at a surface, previously functionalized with complementary capture oligonucleotides. Moreover, we demonstrate that macromolecules, such as STV and antibody molecules, which are tagged with the complementary oligonucleotide, specifically bind to the supramolecular DNA-STV oligomeric conjugates. This leads to a novel class of functional DNA-protein conjugates, suitable, for instance, as reagents in immuno-PCR or as building blocks in molecular nanotechnology.

Animals↗

PubMedDate not supplied

A factor in lymph node and spleen induced by restraint stress in mice and rats suppresses lymphocyte proliferation.

Extracts from lymph node and spleen in mice and rats subjected to restraint stress significantly suppressed lymphocyte proliferation, but extracts from brain, skeletal muscle, and thymus gland had no effect on lymphocyte proliferation, suggesting that a suppressive factor for lymphocyte proliferation might selectively be induced in lymph node and spleen. Further experiments showed that biochemical properties, molecular weight, correlation between suppressive factors in serum and in extract of the lymph tissue from stressed animals, and control of the generation, all indicated that under the conditions of restraint stress and under the control of central nervous system a suppressive factor was generated in peripheral lymph tissue and then released into the blood-stream, which acted as a strong suppressor of lymphocyte proliferation.

Animals↗

PubMedDate not supplied

Selenium removal and mass balance in a constructed flow-through wetland system.

A field study on the removal of Se from agricultural subsurface drainage was conducted from May 1997 to February 2001 in the Tulare Lake Drainage District (TLDD) of San Joaquin Valley, California. A flow-through wetland system was constructed consisting of ten 15- x 76-m unlined cells that were continuously flooded and planted with either a monotype or combination of plants, including sturdy bulrush [Schoenoplectus robustus (Pursh) M.T. Strong], baltic rush (Juncus balticus Willd.), smooth cordgrass (Spartina alterniflora Loisel.), rabbitsfoot grass [Polypogon monspeliensis (L.) Desf.], salt-grass lDistichlis spicata (L.) Greene], cattail (Typha latifolia L.), tule [Schoenoplectus acutus (Muhl. ex Bigelow) A. Löve & D. Löve], and widgeon grass (Ruppia maritima L.). One cell had no vegetation planted. The objectives of this research were to evaluate Se removal efficiency of each wetland cell and to carry out a mass balance on Se. The inflow drainage water to the cells had average annual Se concentrations of 19 to 22 microg L(-1) dominated by selenate [Se(VI), 95%]. Average weekly water residence time varied from about 3 to 15 d for Cells 1 through 7 (target 7 d), 19 to 33 d for Cells 8 and 9 (target 21 d), and 13 to 18 d for Cell 10 (target 14 d). Average weekly Se concentration ratios of outflow to inflow ranged from 0.45 to 0.79 and mass ratio (concentration x water volume) from 0.24 to 0.52 for year 2000, that is, 21 to 55% reduction in Se concentration and 48 to 76% Se removal in mass by the wetland, respectively. The nonvegetated cell showed the least Se removal both in concentration and in mass. The global mass balance showed that on the average about 59% of the total inflow Se was retained within the cells and Se outputs were outflow (35%), seepage (4%), and volatilization (2%). Independent measurements of the Se retained in the cells totaled 53% of the total Se inflow: 33% in the surface (0-20 cm) sediment, 18% in the organic detrital layer above the sediment, 2% in the fallen litter, < 1% in the standing plants, and < 1% in the surface water. Thus, about 6% of the total Se inflow was unaccounted for in the internal compartments.

Agriculture↗

PubMedDate not supplied

Caring for individuals with dementia: the Nigerian experience.

Recent epidemiological data, mainly from cross-cultural studies, have revealed that the burden of dementia and Alzheimer's disease (AD) the most common type, is significantly lower in developing than in the industrialized countries. Caring for individuals with dementia is a major consideration because most developing countries do not have the resources to provide comprehensive care in institutions. Home care that is practiced is ideal given the cultural scenario especially with the extended family support. Public policies on the care of the elderly however need to be well articulated and implemented. Hypertension was the most frequent medical co-morbidity of the demented subjects and about a third of subjects with AD were hypertensive, which may support vascular hypothesis in AD pathogenesis. The important behavioural disturbances experienced by caregivers and the associated stress levels were highlighted. The model used on the Indianapolis-Ibadan Dementia Study which involves periodic home visits, and empowerment of caregivers through regular meetings is envisaged to make caring for these individuals easier and adaptable in other African communities.

Aged↗

PubMedDate not supplied

P2P-R deficiency modifies nocodazole-induced mitotic arrest and UV-induced apoptosis.

BACKGROUND: Cell cycle progression from G1 through S to mitosis can be influenced by microtubule-dependent mechanisms that involve AP1 factors and c-Jun N-terminal kinase (JNK) activity. UV irradiation-induced apoptosis also involves AP1 factors and JNK activity. The current studies evaluated the outcome of P2P-R deficiency on these mechanisms because P2P-R expression is repressed in association with a decrease in AP1 inducibility and cell cycle progression during differentiation, and P2P-R overexpression promotes apoptosis. MATERIALS AND METHODS: The ability of the microtubule disruption drug nocodazole to induce mitotic arrest and the ability of UV irradiation to induce apoptosis was evaluated in native versus cells made P2P-R deficient by P2P-R antisense treatment. RESULTS: P2P-R deficiency restricts cell cycle progression from G1 through S to mitosis in a microtubule-dependent manner and P2P-R deficiency represses UV irradiation-induced apoptosis. CONCLUSION: P2P-R may influence AP1 and/or JNK signaling pathways.

3T3 Cells↗