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M X Tang

Publications and source records attributed to M X Tang.

64 records · Page 4Linked to original sources
PubMed1993

Genetic susceptibility and head injury as risk factors for Alzheimer's disease among community-dwelling elderly persons and their first-degree relatives.

We performed a community-based study to investigate the relationship of genetic susceptibility and head injury to Alzheimer's disease (AD) in 138 patients with AD and 193 healthy elderly control subjects. Data concerning presence or absence of dementia and certain exposures were also obtained from 799 first-degree relatives of the patients and 1,238 first-degree relatives of the control subjects. Adjusting for age, gender, and other risk factors, the odds ratio for AD associated with head injury was 3.7 (95% confidence interval [CI], 1.4-9.7). The association was highest for head injuries that occurred after age 70. The risk of AD was higher in first-degree relatives of patients with onset prior to age 70 than in relatives of control subjects (risk ratio [RR] = 2.5; 95% CI, 1.1-5.6). The risk was not increased for relatives of patients with onset of AD at age 70 or older. Compared with relatives without head injury, the risk of AD was increased among both head-injured relatives of patients (RR = 5.9; 95% CI, 2.3-14.8) and head-injured relatives of control subjects (RR = 6.9; 95% CI, 2.5-18.9). Our results are consistent with the hypothesis that severe head injury and genetic susceptibility are associated with AD. Both associations concur with current concepts regarding the role of amyloid in AD. Although we regard head injury, like genetic susceptibility, to be a putative risk factor for AD, the temporal relationship between head injury and AD warrants further investigation.

Age Factors↗
PubMed1993

The apolipoprotein epsilon 4 allele in patients with Alzheimer's disease.

Apolipoprotein E (APO-E) binds to the beta-amyloid peptide and is present in senile neuritic plaques in Alzheimer's disease (AD). The epsilon 4 isoform of APO-E has been associated with both sporadic and familial late-onset AD, implying a causal role. Among patients and control subjects similar in age, gender, and ethnic group from the New York City community of Washington Heights-Inwood, we found that the odds ratio (OR) for AD associated with homozygosity for APO-epsilon 4 was 17.9 (95% confidence interval [CI], 4.6-69.8) and that associated with heterozygosity for APO-epsilon 4 was 4.2 (95% CI, 1.8-9.5) compared with persons with other APO-E genotypes. The association was stronger among patients with sporadic disease (OR = 10.3; 95% CI, 3.4-31.1) than among those with a family history of dementia in a first-degree relative (OR = 0.9; 95% CI, 0.1-13.5). The association between APO-epsilon 4 and AD did not differ according to age at onset (< 65 vs > or = 65), but appeared to vary across the 3 ethnic groups investigated (black, Hispanic, and white). Our data confirm the association between AD and APO-epsilon 4 and support the hypothesis that the APO-epsilon 4 allele either confers genetic susceptibility to AD or may be in linkage disequilibrium with another susceptibility locus. Ethnic variability in the allelic frequency of APO-epsilon 4 in the elderly warrants further investigation.

Aged↗
PubMed1993

Mortality risks in gay men with human immunodeficiency virus infection and cognitive impairment.

We obtained data from 111 gay men who entered a longitudinal study of the natural history of human immunodeficiency virus (HIV) without clinical evidence of acquired immunodeficiency syndrome (AIDS), and examined them regularly over a 36-month period. Using a Cox proportional-hazard regression model to compare cumulative risk of mortality in subjects with and without cognitive impairment and several putative risk factors present at baseline, we found that the mortality risk ratio (RR) associated with poor neuropsychologic test performance was significantly increased (RR = 2.9; 95% confidence interval [CI], 1.1 to 7.8), and increased further (RR = 4.1; 95% CI, 1.3 to 12.5) when adjusted for other factors associated with mortality (a history of a disturbance in movement or gait, CD4-lymphocyte and red blood-cell counts, and age). A significant increase in symptoms related to cognitive impairment and gait, a decline in neuropsychologic test performance, and declines in CD4-lymphocyte and red-cell counts occurred over the study period. A second model was constructed to adjust for changes in CD4-lymphocyte and red-cell counts, age, medical stage, and motor symptoms over the study period, but the mortality RR for poor neuropsychologic test performance at baseline changed very little (RR = 4.7; 95% CI, 1.5 to 14.9). We conclude that the presence of cognitive impairment, manifest by poor neuropsychologic test performance in both asymptomatic and symptomatic gay men with HIV infection, is associated with a significantly increased risk of death. This effect progresses in parallel with the immunologic and systemic effects of HIV.

Adult↗
PubMed1993

Antecedent clinical features associated with dementia in Parkinson's disease.

In a prospective cohort study, we examined clinical features in 250 nondemented patients with idiopathic Parkinson's disease (PD) and then evaluated their association with incident dementia during 5 years of follow-up. Seventy-four of the patients became demented. Odds ratios for incident dementia with PD were increased for the following: being older than 70 years of age (2.7; 1.4 to 5.5), having a PD rating scale score greater than 25 (3.0; 1.5 to 6.2), being depressed (2.7; 1.5 to 6.6), being confused or psychotic on levodopa (3.3; 1.3 to 8.7), or having facial masking as a presenting sign (6.1; 1.4 to 26.9).

Aged↗
PubMed1992

A population-based investigation of Parkinson's disease with and without dementia. Relationship to age and gender.

Because the prevalence of idiopathic Parkinson's disease (PD) with or without dementia remains controversial, we initiated a population-based investigation in the Washington Heights-Inwood section of New York, NY, so that nearly complete case ascertainment could be achieved. A "registry" was developed for the study, and we advertised in periodicals and on radio and television. Subjects, or their records, were examined by experienced neurologists, and most underwent a battery of neuropsychological tests specifically designed for assessment in this community. All data were reviewed by a team of clinicians to achieve a consensus diagnosis. The crude prevalence of idiopathic PD, with and without dementia, was 99.4 per 100,000, increasing from 2.3 per 100,000 for those younger than 50 years to 1144.9 per 100,000 for those aged 80 years and older. The crude prevalence for PD with dementia alone was 41.1 per 100,000 and also increased with age from zero for those younger than 50 years to 787.1 per 100,000 for those aged 80 years and older. Prevalence ratios were comparable with those of other published population-based studies in similar settings. After standardization, men had PD with and without dementia more frequently than did women. The major difference between patients with and without dementia was a later estimated age at onset of motor manifestations. We conclude that PD is a frequent disorder in the elderly population that affects men and whites more frequently than women and nonwhites. Moreover, dementia in patients with PD is more frequent than previously recognized and is strongly related to the age at onset of motor manifestations.

Aged↗
PubMed1992

Neurologic and neuropsychological manifestations of human immunodeficiency virus infection in intravenous drug users without acquired immunodeficiency syndrome. Relationship to head injury.

We examined 99 human immunodeficiency virus (HIV)-negative and 122 HIV-positive intravenous drug users (IVDUs) without acquired immunodeficiency syndrome (AIDS) to determine whether HIV-positive IVDUs had more neurologic and neuropsychological impairment than their HIV-negative counterparts. Controlling for age, education, drug use, history of head injury, and interactions between head injury and HIV status and drug use, HIV-positive subjects had more extrapyramidal signs and frontal release signs. These findings persisted when asymptomatic HIV-positive subjects without systemic signs of infection and HIV-negative subjects were compared. Neurologic findings were more severe in those with more systemic illness. Among those reporting a history of head injury with loss of consciousness, neuropsychological performance was significantly worse in the HIV-positive subjects, and this increased with severity of illness. This was not true in the group without head injury, suggesting an interaction between history of head injury and the seropositive state. No relationship was noted between head injury and either drug use or HIV state. Therefore, subtle neurologic and neuropsychological abnormalities may precede clinical evidence of AIDS in IVDUs and may be more evident in those with head injury.

Adult↗
PubMed1990

Protein binding, sister chromatid exchange and expression of oncogene proteins in patients treated with cisplatinum (cisDDP)-based chemotherapy.

The aim of this pilot was to evaluate the feasibility of incorporating several complementary biologic markers into a molecular epidemiologic study of chemotherapy patients. Thirty-two cancer patients being treated with cis-DDP-based chemotherapy for the first time were enrolled in the study and donated a baseline sample and at least one post-treatment sample of blood. Sister Chromatid Exchange (SCEs) and plasma protein and hemoglobin binding by cisDDP were significantly increased in samples drawn at various timepoints following treatment. The pattern of nine different oncogene protein products (including those of ras, fes, and myc) remained unchanged in sera of six patients followed over the course of their treatment. However, the levels of ras P21 product were significantly elevated above normal, control levels in all six cancer patients--both prior to and throughout the course of chemotherapy. These results suggest the usefulness of utilizing a battery of markers to evaluate biologic response to cisplatinum-based chemotherapy.

Aged↗
PubMed1989

Comparison of DNA adducts and sister chromatid exchange in lung cancer cases and controls.

In a molecular epidemiological study of lung cancer cases (n = 81) and noncancer controls (n = 67), polycyclic aromatic hydrocarbon (PAH)-DNA adducts were evaluated in peripheral blood leukocytes from all subjects and in a smaller number of lung tissue specimens collected prior to or at surgery. Sister chromatid exchanges (SCE) in lymphocytes were also studied in a subset of cases and controls. Questionnaire, medical record, or tumor registry data provided a family history of cancer, as well as information on cigarette smoking, dietary and occupational exposure to PAHs, and other factors related to SCEs. In both cases and controls PAH-DNA adducts in leukocytes measured by an enzyme-linked immunosorbent assay were not significantly related to age, sex, ethnicity, amount of cigarette smoking, passive smoking, dietary charcoal, or caffeine consumption. Nor did family history of cancer or histological type of cancer significantly affect adduct levels. However, when subjects were stratified by smoking status (current, former, and nonsmoker), lung cancer cases who were current smokers had significantly higher levels of covalent adducts than current smoker controls. A seasonal variation was observed in PAH-DNA binding, with a peak in adduct levels during July-October. This peak corresponds to that seen in a prior study of aryl hydrocarbon hydroxylase inducibility by other investigators. The finding of significant levels of PAH-DNA adducts in former smokers and non-smokers supports an earlier observation that this marker is not smoking specific but reflects a pervasive and variable "background" exposure to PAH. These results are consistent with a genetically determined enhancement of PAH-DNA adduct formation in leukocytes of lung cancer cases which is evident in current smokers. The results in lung tissue are limited by the small number of samples. Adduct levels were not significantly increased in lung tissue of smokers compared with nonsmokers. An inverse linear correlation was seen between adduct values in lung tissue and age of the donors. SCEs were significantly related to pack years of smoking. However, there was no difference in the frequency of SCE between cases and controls; nor were SCE and DNA adducts significantly correlated in this small sample.

DNA, Neoplasm↗
PubMedDate not supplied

In vitro gene delivery by degraded polyamidoamine dendrimers.

Transfection of cultured cells has been reported using complexes between DNA and spherical cationic polyamidoamine polymers (Starburst dendrimers) that consist of primary amines on the surface and tertiary amines in the interior. The transfection activity of the dendrimers is dramatically enhanced (> 50-fold) by heat treatment in a variety of solvolytic solvents, e.g., water or butanol. Such treatment induces significant degradation of the dendrimer at the amide linkage, resulting in a heterodisperse population of compounds with molecular weights ranging from the very low (< 1500 Da) to several tens of kilodaltons. The compound facilitating transfection is the high molecular weight component of the degraded product and is denoted as a "fractured" dendrimer. Transfection activity is related both to the initial size of the dendrimer and its degree of degradation. Fractured dendrimers exhibit an increased apparent volume change as measured by an increase in the reduced viscosity upon protonation of the terminal amines as pH is reduced from 10.5 to 7.2 whereas intact dendrimers do not. Dendrimers with defective branching have been synthesized and also have improved transfection activity compared to that of the intact dendrimers. For a series of heat-treated dendrimers we observe a correlation between transfection activity and the degree of flexibility, computed with a random cleavage simulation of the degradation process. We suggest that the increased transfection after the heating process is principally due to the increase in flexibility that enables the fractured dendrimer to be compact when complexed with DNA and swell when released from DNA.

DNA↗