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Biomedical subjects

A Ott

Publications and source records attributed to A Ott.

At least 37 records · Page 2Linked to original sources
PubMed1999

Diabetes mellitus and the risk of dementia: The Rotterdam Study.

OBJECTIVE: To determine the influence of type 2 diabetes mellitus on the risk of dementia and AD. BACKGROUND: Both dementia and diabetes are frequent disorders in elderly people. METHODS: Prospective population-based cohort study among 6,370 elderly subjects. At baseline study participants were examined for presence of diabetes mellitus. Nondemented participants were followed up, on average, for 2.1 years. Incident dementia was diagnosed using a three-step screening and comprehensive diagnostic workup. To complete the follow-up, medical files were studied of persons who could not be reexamined. We estimated relative risks with proportional hazard regression, adjusting for age, sex, and possible confounders. RESULTS: During the follow-up, 126 patients became demented, of whom 89 had AD. Diabetes mellitus almost doubled the risk of dementia (relative risk [RR] 1.9 [1.3 to 2.8]) and AD (RR 1.9 [1.2 to 3.1]). Patients treated with insulin were at highest risk of dementia (RR 4.3 [1.7 to 10.5]). CONCLUSION: The diabetes attributable risk for dementia of 8.8% suggests that diabetes may have contributed to the clinical syndrome in a substantial proportion of all dementia patients.

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PubMed1999

Head trauma and risk of dementia and Alzheimer's disease: The Rotterdam Study.

OBJECTIVE: To investigate the relation between head trauma and incidence of dementia in a prospective population-based study. BACKGROUND: Whether head trauma increases the risk of dementia and AD remains controversial. It has been suggested that the risk might be particularly increased for carriers of the APOE-epsilon4 allele. METHODS: The study population included 6645 participants of the prospective population-based Rotterdam Study, aged 55 years or older, who were free of dementia at baseline. Head trauma with loss of consciousness was measured at baseline by a self-report to a physician and detailed the number of head traumas, time since head trauma, and duration of loss of consciousness. The cohort was followed for incident dementia that was diagnosed according to international criteria. Logistic regression was used to calculate the risk of dementia after adjusting for age, gender, and education. RESULTS: No increased risk of dementia or AD was found for persons with a history of head trauma with loss of consciousness (relative risk [RR] for dementia = 1.0, 95% CI, 0.5-2.0; RR for AD = 0.8, 95% CI, 0.4-1.9). Multiple head traumas, time since head trauma, and duration of unconsciousness did not significantly influence the risk of dementia. In addition, the APOE-epsilon4 allele did not modify the relationship. CONCLUSIONS: This study suggests that mild head trauma is not a major risk factor for dementia or AD in the elderly. In addition, this study does not concur with previous cross-sectional studies suggesting an interaction with the APOE genotype.

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PubMed1999

Gender differences in the incidence of AD and vascular dementia: The EURODEM Studies. EURODEM Incidence Research Group.

OBJECTIVE: To study the difference in risk for dementing diseases between men and women. BACKGROUND: Previous studies suggest women have a higher risk for dementia than men. However, these studies include small sample sizes, particularly in the older age groups, when the incidence of dementia is highest. METHODS: Pooled analysis of four population-based prospective cohort studies was performed. The sample included persons 65 years and older, 528 incident cases of dementia, and 28,768 person-years of follow-up. Incident cases were identified in a two-stage procedure in which the total cohort was screened for cognitive impairment, and screen positives underwent detailed diagnostic assessment. Dementia and main subtypes of AD and vascular dementia were diagnosed according to internationally accepted guidelines. Sex- and age-specific incidence rates, and relative and cumulative risks for total dementia, AD, and vascular dementia were calculated using log linear analysis and Poisson regression. RESULTS: There were significant gender differences in the incidence of AD after age 85 years. At 90 years of age, the rate was 81.7 (95% CI, 63.8 to 104.7) in women and 24.0 (95% CI, 10.3 to 55.6) in men. There were no gender differences in rates or risk for vascular dementia. The cumulative risk for 65-year-old women to develop AD at the age of 95 years was 0.22 compared with 0.09 for men. The cumulative risk for developing vascular dementia at the age of 95 years was similar for men and women (0.04). CONCLUSION: Compared with men, women have an increased risk for AD. There are no gender differences in risk for vascular dementia.

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PubMed1999

Is age-related maculopathy associated with Alzheimer's Disease? The Rotterdam Study.

The authors examined the relation between age-related maculopathy and Alzheimer's disease in the Rotterdam Study, a prospective population-based study in the Netherlands. From 1990 to mid-1993, subjects aged 75 years or older (n = 1,438) were screened for the presence of age-related maculopathy and Alzheimer's disease, and follow-up examinations were conducted from mid-1 993 to the end of 1994. Subjects with advanced age-related maculopathy at baseline showed an increased risk of incident Alzheimer's disease (relative risk = 2.1, 95% confidence interval: 1.1, 4.3; adjusted for age and gender), but this risk decreased after additional adjustment for smoking and atherosclerosis (relative risk = 1.5, 95% confidence interval: 0.6, 3.5). These findings suggest that the neuronal degeneration occurring in age-related maculopathy and Alzheimer's disease may, to some extent, have a common pathogenesis.

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PubMed1999

The effect of APOE on dementia is not through atherosclerosis: the Rotterdam Study.

The APOE genotype is involved in atherosclerosis, and atherosclerosis increases the risk of dementia, in particular among carriers of the APOE-epsilon4 allele. We studied, in a population-based setting (244 dementia cases; 1,002 nondemented controls), whether APOE is associated with dementia through atherosclerosis. As neither adjusting nor stratification for atherosclerosis altered the association of APOE with dementia, our study suggests that atherosclerosis is not an intermediate factor.

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PubMed1999

Rearrangement of cortex proteins constitutes an osmoprotective mechanism in Dictyostelium.

Dictyostelium responds to hyperosmotic stress of 400 mOsm by a rapid reduction of its cell volume to 50%. The reduced cell volume is maintained as long as these osmotic conditions prevail. Dictyostelium does not accumulate compatible osmolytes to counteract the osmotic pressure applied. Using two-dimensional gel electrophoresis, we demonstrate that during the osmotic shock the protein pattern remains unaltered in whole-cell extracts. However, when cells were fractionated into membrane and cytoskeletal fractions, alterations of specific proteins could be demonstrated. In the crude membrane fraction, a 3-fold increase in the amount of protein was measured upon hyperosmotic stress. In the cytoskeletal fraction, the proteins DdLIM and the regulatory myosin light chain (RMLC) were shown to be regulated in the osmotic stress response. The elongation factors eEF1alpha (ABP50) and eEF1beta were found to increase in the cytoskeletal fraction, suggesting a translational arrest upon hyperosmotic stress. Furthermore, the two main components of the cytoskeleton, actin and myosin II, are phosphorylated as a consequence of the osmotic shock, with a tyrosine residue as the phosphorylation site on actin and three threonines in the case of the myosin II heavy chain.

Actins↗
PubMed1999

Filament assembly from profilin-actin.

Profilin plays a major role in the assembly of actin filament at the barbed ends. The thermodynamic and kinetic parameters for barbed end assembly from profilin-actin have been measured turbidimetrically. Filament growth from profilin-actin requires MgATP to be bound to actin. No assembly is observed from profilin-CaATP-actin. The rate constant for association of profilin-actin to barbed ends is 30% lower than that of actin, and the critical concentration for F-actin assembly from profilin-actin units is 0.3 microM under physiological ionic conditions. Barbed ends grow from profilin-actin with an ADP-Pi cap. Profilin does not cap the barbed ends and is not detectably incorporated into filaments. The EDC-cross-linked profilin-actin complex (PAcov) both copolymerizes with F-actin and undergoes spontaneous self-assembly, following a nucleation-growth process characterized by a critical concentration of 0.2 microM under physiological conditions. The PAcov polymer is a helical filament that displays the same diffraction pattern as F-actin, with layer lines at 6 and 36 nm. The PAcov filaments bound phalloidin with the same kinetics as F-actin, bound myosin subfragment-1, and supported actin-activated ATPase of myosin subfragment-1, but they did not translocate in vitro along myosin-coated glass surfaces. These results are discussed in light of the current models of actin structure.

Actin Cytoskeleton↗
PubMed1999

Microplates: a new tool for manipulation and mechanical perturbation of individual cells.

We present a new type of microinstrument allowing manipulation and mechanical perturbation of individual cells under an optical microscope. These instruments, which we call microplates, are pulled from rectangular glass bars. They have flat tips, typically 2 microm thick x 20 microm wide, whose specific shape and stiffness can be adjusted through the pulling protocol. After appropriate chemical treatment, microplates can support cell adhesion and/or spreading. Rigid microplates are used to hold cells, whereas more flexible ones serve as stress sensors, i.e. their deflexion is used to probe forces in the range of 1-1000 nN. The main advantages of microplates are their simple geometry and surface properties, and their ability to provide mechanical measurements. In this methodological paper, we give details about microplate preparation and adhesiveness, manipulation set-up, force calibration, and image analysis. Several manipulations have already been carried out on fibroblasts, including uniaxial deformation, micropipet aspiration of adherent cells, and cell-substrate separation. Our results to date provide new insights into the morphology, mechanical properties, and adhesive resistance of cells. Many future applications can be envisaged.

Animals↗
PubMed1999

Rates and risk factors for dementia and Alzheimer's disease: results from EURODEM pooled analyses. EURODEM Incidence Research Group and Work Groups. European Studies of Dementia.

OBJECTIVE: To investigate the risk of AD associated with a family history of dementia, female gender, low levels of education, smoking, and head trauma. BACKGROUND: These putative factors have been identified in cross-sectional studies. However, those studies are prone to bias due to systematic differences between patients and control subjects regarding survival and how risk factors are recalled. METHODS: The authors performed a pooled analysis of four European population-based prospective studies of individuals 65 years and older, with 528 incident dementia patients and 28,768 person-years of follow-up. Patients were detected by screening the total cohort with brief cognitive tests, followed by a diagnostic assessment of those who failed the screening tests. Dementia was diagnosed with the Diagnostic and Statistical Manual of Mental Disorders, 3rd ed. (revised), and AD was diagnosed according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria. Incident rates and relative risk (95% CI) express the association of a risk factor for dementia. RESULTS: Incident rates for dementia and AD were similar across studies. The incidence of AD increased with age. At 90 years of age and older the incidence was 63.5 (95% CI, 49.7 to 81.0) per 1,000 person-years. Female gender, current smoking (more strongly in men), and low levels of education (more strongly in women) increased the risk of AD significantly. A history of head trauma with unconsciousness and family history of dementia did not increase risk significantly. CONCLUSION: Contrary to previous reports, head trauma was not a risk factor for AD, and smoking did not protect against AD. The association of family history with the risk of AD is weaker than previously estimated on the basis of cross-sectional studies. Female gender may modify the risk of AD, whether it be via biological or behavioral factors.

Age Distribution↗
PubMed1999

CD44 expression in sinonasal melanomas: is loss of isoform expression associated with advanced tumour stage?

The expression of the adhesion molecule CD44 was examined in 14 primary sinonasal melanomas (SMs), aggressive neoplasms with short survival times, as CD44 overexpression has been linked to poor survival in human cancers. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded sections with CD44 isoform-specific monoclonal antibodies to the CD44 standard (s) and variant isoforms (v) v5 and v6. CD44s, v5, and v6 were strongly expressed in a membranous pattern in SM in situ, early invasive SM, and in uninvolved respiratory/squamous epithelium. In invasive SM, membranous CD44s expression was identified in a large proportion of melanoma cells. Membranous staining of CD44v5 and v6 was lost in invasive SM, independently of the histological subtype. Diffuse cytoplasmic staining was observed focally in invasive SM and loss of cytoplasmic expression of CD44v6 and v5 was associated with advanced tumour stage in the linear-by-linear association test (p = 0.042 and 0.066, respectively). CD44s may not be important for malignant transformation, as it is expressed in both benign and malignant melanocytes. Loss of membranous CD44 isoform expression in widely invasive SM suggests that loss of cellular adhesion facilitates matrix and vascular infiltration and dissemination of sinonasal melanoma cells.

Adult↗
PubMed1999

[Disseminated ischemic necrosis and livedo racemosa in a chronic dialysis patient with calciphylaxis].

Calciphylaxis occurred in a 40-year old female patient with end-stage renal failure. The patient developed livedo racemosa ("livedo reticularis") with painful skin necrosis and ulcers involving multiple areas of the hip and legs after 22 years of hemodialysis. X-ray-examinations revealed calcinosis of peripheral arteries, especially of the pelvis, thigh and hands, while histological examinations showed a fibrosis and calcinosis of small subcutaneous arteries. A generalized cutaneous microangiopathy could be demonstrated by transcutaneous oxygen pressure measurements. Laboratory data showed a moderate secondary hyperparathyroidism with mild elevation of calcium-phosphate product. In addition to the hemodialysis an attempt was made to improve the microcirculation by vasoactive drugs. The clinical course was characterized by slow healing of the ulcers and occurrence of new areas of cutaneous necrosis. Calciphylaxis is a rare late complication in patients with advanced, often end-stage renal failure. It has characteristic histopathological features and is frequently, but not always, associated with a disturbed calcium and phosphorus metabolism and mildly elevated levels of parathyroid hormone. Calciphylaxis is classified as a special type of metastatic calcinosis.

Adult↗
PubMed1999

Aroma comparisons of traditional and mild yogurts: headspace gas chromatography quantification of volatiles and origin of alpha-diketones.

A quick headspace GC method for quantification of volatiles was developed, involving only minor sample preparation. Yogurt flavor compounds could be quantified in the micrograms per kilogram to milligrams per kilogram range without any difficulty, despite the complex matrix. Volatiles of traditional acidic and mild, less acidic yogurts were compared, and important differences were found for acetaldehyde, 2,3-butanedione, and 2,3-pentanedione. Concentrations of 2,3-butanedione and 2,3-pentanedione increased 2-3-fold in mild, less acidic yogurts compared to traditional acidic ones. This is due to accumulation of the precursors of the diketones, 2-acetolactate and 2-acetohydroxybutyrate, during fermentation in mild, less acidic yogurt. These precursors are subsequently converted to the corresponding diketones during storage. On the contrary, acetaldehyde formation was reduced in the mild yogurt, due to growth differences between the lactic acid bacteria used for fermentation of the milk. The quantitative results presented in this study validate previous GC sniffing conclusions (Ott et al. J. Agric. Food Chem. 1997, 45, 850-858), showing that yogurt aroma is the superposition of impact flavor compounds generated by fermentation on milk compounds.

Animals↗
PubMed1999

D-Lactate dehydrogenase gene (ldhD) inactivation and resulting metabolic effects in the Lactobacillus johnsonii strains La1 and N312.

Lactobacillus johnsonii La1, a probiotic bacterium with demonstrated health effects, grows in milk, where it ferments lactose to D- and L-lactate in a 60:40% ratio. The D-lactate dehydrogenase (D-LDH) gene (ldhD) of this strain was isolated, and an in vitro-truncated copy of that gene was used to inactivate the genomic copy in two strains, La1 and N312, by gene replacement. For that, an 8-bp deletion was generated within the cloned ldhD gene to inactivate its function. The plasmid containing the altered ldhD was transferred to L. johnsonii via conjugative comobilization with Lactococcus lactis carrying pAMbeta1. Crossover integrations of the plasmid at the genomic ldhD site were selected, and appropriate resolution of the cointegrate structures resulted in mutants that had lost the plasmid and in which the original ldhD was replaced by the truncated copy. These mutants completely lacked D-LDH activity. Nevertheless, the lower remaining L-LDH activity of the cells was sufficient to reroute most of the accumulating pyruvate to L-lactate. Only a marginal increase in production of the secondary end products acetaldehyde, diacetyl, and acetoin was observed. It can be concluded that in L. johnsonii D- and L-LDH are present in substantial excess for their role to eliminate pyruvate and regenerate NAD(+) and that accumulated pyruvate is therefore not easily redirected in high amounts to secondary metabolic routes.

Base Sequence↗
PubMed1999

Education and the incidence of dementia in a large population-based study: the Rotterdam Study.

We assessed the risk of dementia by educational level in a prospective population-based study. In the Rotterdam Study, 6,827 nondemented participants with known education level were followed for an average of 2.1 years. During this period, 137 new cases of dementia occurred. Low education was associated with higher dementia risk in women but not in men, suggesting that the association is modified by sex. Our data indicate that cross-sectional studies may overrate the association between education and risk of dementia.

Age Distribution↗
PubMed1998

Smoking and risk of dementia and Alzheimer's disease in a population-based cohort study: the Rotterdam Study.

BACKGROUND: Previous studies suggested a protective effect of smoking on Alzheimer's disease, but most were case-control studies based on prevalent cases. The findings of prospective studies on the association between smoking and the risk of dementia are inconclusive. METHODS: We did a population-based follow-up study of elderly people who were initially free of dementia. 6870 people aged 55 years and older agreed to take part. Smoking history was taken at baseline and participants were classified as never smokers, former smokers, and current smokers. During follow-up, we recorded all incident cases of dementia. We used never smokers as the reference category to calculate relative risks of dementia and Alzheimer's disease by Cox proportional hazards regression, after adjustment for age, sex, education, and alcohol intake. We also examined modification of risk by age, sex, and the apolipoprotein E (APOE) genotype. FINDINGS: During mean follow-up of 2.1 (range 1.5-3.4) years, 146 incident cases of dementia were detected, of which 105 were Alzheimer's disease. Compared with never smokers, smokers had an increased risk of dementia (relative risk 2.2 [95% CI 1.3-3.6]) and Alzheimer's disease (2.3 [1.3-4.1]). Smoking was a strong risk factor for Alzheimer's disease in individuals without the APOEepsilon4 allele (4.6 [1.5-14.2]), but had no effect in participants with this allele (0.6 [0.1-4.8]). INTERPRETATION: Smoking was associated with a doubling of the risk of dementia and Alzheimer's disease. Our finding that carriers of the APOEepsilon4 had no increased risk of dementia suggests an interaction between smoking and the APOEepsilon4 genotype in the aetiology of Alzheimer's disease.

Age Distribution↗
PubMed1998

Incidence and risk of dementia. The Rotterdam Study.

To assess age-, sex-, and subtype-specific incidence rates of dementia and to calculate the risk of dementia, the authors performed a large, community-based, prospective cohort study on dementia as part of the Rotterdam Study. Participants were recruited among residents of a suburb of Rotterdam, aged 55 years and older. Baseline examinations took place between 1990 and 1993. The average follow-up was 2.1 years. Screening for dementia followed a three-stage protocol. Medical records of subjects who had died or could not be examined in person were evaluated. Of 7,046 subjects who were nondemented at baseline, 162 developed dementia during 15,135 person-years of follow-up, resulting in an overall incidence rate of 10.7 per 1,000 person-years. From the youngest to the oldest 5-year age category, the incidence rate increased from 0.6 to 97.2 per 1,000 person-years. Only in men did the increase level off after age 85. Overall, the incidence rate per 1,000 person-years was 7.7 for Alzheimer's disease and 1.5 for vascular dementia. Dementia incidence rates and dementia-free Kaplan-Meier survival tables were used to calculate age- and sex-specific cumulative risks of dementia. Although the incidence rates of men and women up to age 85 were similar, the lifetime risk of dementia for 55-year-old women was twice as high as for men (0.33 vs. 0.16), reflecting both the higher life expectancy of women and the higher dementia risk at very old age.

Age Distribution↗
PubMed1998

Apolipoprotein E genotype, atherosclerosis, and cognitive decline: the Rotterdam Study.

The apolipoprotein E4 allele (APOE epsilon 4) and atherosclerosis are risk factors for cognitive decline. We investigated whether the effects of APOE epsilon 4 and atherosclerosis on cognitive decline are independent. A population-based follow-up study was performed on 838 subjects who were non-demented at baseline. The Mini Mental State Examination (MMSE) score at follow-up was studied as a function of APOE epsilon 4 and atherosclerosis. Mild, non-significant effects on the MMSE score were found for atherosclerosis in the absence of APOE epsilon 4 and for APOE epsilon 4 in the absence of atherosclerosis. APOE epsilon 4 carriers with two or more indicators of atherosclerosis positive, had a significantly lower MMSE score at follow-up (mean difference -0.7 points; 95% confidence interval -1.1 to -0.2) relative to non-APOE epsilon 4 carriers with no evidence of atherosclerosis. Our findings suggest that the consequences of APOE epsilon 4 and atherosclerosis are not independent, and that particularly APOE epsilon 4 carriers with atherosclerosis are at increased risk of cognitive decline.

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