1,024 research outputs found
Possible role of fungi in negatively affecting fruit-set in avocados
Poor fruit set continues to be a major problem in the avocado industry in South Africa. In the past this was estimated to have caused a loss of income of millions of rands. In this investigation the role of fungi on the pistils of avocado cultivars after pollination was examined. Pollinated pistils of avocado cultivars ‘Pinkerton’, ‘Ryan’, ‘Hass’, ‘Fuerte’ and ‘Nabal’ were removed twenty-four hours after the first anthesis (female stage), for detection and isolation of fungi. Germinating conidia were seen on the surface of stigma adjacent to the germinated pollen grains. A number of dematiaceous fungi were isolated from the pistils and the most important species were identified.When a drop of the spore suspension of the most frequently isolated fungi was inoculated on the stigmas of emasculated flowers after hand pollination, a high rate of abscission was observed. Thus some of these fungi appear to have played a significant role which resulted in greater abscission of flowers
Common carotid intima-media thickness and risk of stroke and myocardial infarction: the Rotterdam Study
BACKGROUND: Noninvasive assessment of intima-media thickness (IMT) is widely used in observational studies and trials as an intermediate or proxy end point for cardiovascular disease. However, data showing that IMT predicts cardiovascular disease are limited. We studied whether common carotid IMT is related to future stroke and myocardial infarction.
METHODS AND RESULTS: We used a nested case-control approach among 7983 subjects aged > or =55 years participating in the Rotterdam Study. At baseline (March 1990 through July 1993), ultrasound images of the common carotid artery were stored on videotape. Determination of incident myocardial infarction and stroke was predominantly based on hospital discharge records. Analysis (logistic regression) was based on 98 myocardial infarctions and 95 strokes that were registered before December 31, 1994. IMT was measured from videotape for all case subjects and a sample of 1373 subjects who remained free from myocardial infarction and stroke during follow-up. The mean duration of follow-up was 2.7 years. Results were adjusted for age and sex. Stroke risk increased gradually with increasing IMT. The odds ratio for stroke per standard deviation increase (0.163 mm) was 1.41 (95% CI, 1.25 to 1.82). For myocardial infarction, an odds ratio of 1.43 (95% CI, 1.16 to 1.78) was found. When subjects with a previous myocardial infarction or stroke were excluded, odds ratios were 1.57 (95% CI, 1.27 to 1.94) for stroke and 1.51 (95% CI, 1.18 to 1.92) for myocardial infarction. Additional adjustment for several cardiovascular risk factors attenuated these associations: 1.34 (95% CI, 1.08 to 1.67) and 1.25 (95% CI, 0.98 to 1.58), respectively.
CONCLUSIONS: The present study, based on a short follow-up period, provides evidence that an increased common carotid IMT is associated with future cerebrovascular and cardiovascular events
Trends in stroke incidence rates and stroke risk factors in Rotterdam, the Netherlands from 1990 to 2008
Stroke incidence rates have decreased in developed countries over the past 40 years, but trends vary across populations. We investigated whether age-and-sexspecific stroke incidence rates and associated risk factors as well as preventive medication use have changed in Rotterdam in the Netherlands during the last two decades. The study was part of the Rotterdam Study, a large populationbased cohort study among elderly people. Participants were 10,994 men and women aged 55-94 years who were stroke-free at baseline. Trends were calculated by comparing the 1990 subcohort (n = 7516; baseline 1990-1993) with the 2000 subcohort (n = 2883; baseline 2000-2001). Poisson regression was used to calculate incidence rates and incidence rate ratios in age-and-sex-specific strata. We further compared the prevalence of stroke risk factors and preventive medication use in the two subcohorts. In the 1990 subcohort 467 strokes occurred during 45,428 person years; in the 2000 subcohort 115 strokes occurred in 18,356 person years. Comparing the subcohorts, incidence rates decreased by 34% in men, but remained unchanged in women. Blood pressure levels increased between 1990 and 2000, whereas the proportion of current cigarette smokers decreased in men, but not in women. There was a strong increase in medication use for treatment of stroke risk factors across all age categories in both sexes. Our findings suggest that in Rotterdam between 1990 and 2008 stroke incidence rates have decreased in men but not in women
Orthostatic Hypotension and the Long-Term Risk of Dementia: A Population-Based Study
Background: Orthostatic hypotension (OH) is a common cause of transient cerebral hypoperfusion in the population. Cerebral hypoperfusion is widely implicated in cognitive impairment, but whether OH contributes to cognitive decline and dementia is uncertain. We aimed to determine the association between OH and the risk of developing dementia in the general population. Methods and Findings: Between 4 October 1989 and 17 June 1993, we assessed OH in non-demented, stroke-free participants of the population-based Rotterdam Study. OH was defined as a ≥20 mm Hg drop in systolic blood pressure (SBP) or ≥10 mm Hg drop in diastolic blood pressure (DBP) within 3 min from postural change. We furthermore calculated within participant variability in SBP related to postural change, expressed as coefficient of variation. Follow-up for dementia was conducted until 1 January 2014. We determined the risk of dementia in relation to OH and SBP variability, using a Cox regression model, adjusted for age; sex; smoking status; alcohol intake; SBP; DBP; cholesterol:high-density lipoprotein ratio; diabetes; body mass index; use of antihypertensive, lipid-lowering, or anticholinergic medication; and apolipoprotein E genotype. Finally, we explored whether associations varied according to compensatory increase in heart rate. Among 6,204 participants (mean ± standard deviation [SD] age 68.5 ± 8.6 y, 59.7% female) with a median follow-up of 15.3 y, 1,176 developed dementia, of whom 935 (79.5%) had Alzheimer disease and 95 (8.1%) had vascular dementia. OH was associated with an increased risk of dementia (adjusted hazard ratio [aHR] 1.15, 95% CI 1.00–1.34, p = 0.05), which was similar for Alzheimer disease and vascular dementia. Similarly, greater SBP variability with postural change was associated with an increased risk of dementia (aHR per SD increase 1.08, 95% CI 1.01–1.16, p = 0.02), which was similar when excluding those who fulfilled the formal criteria for OH (aHR 1.08, 95% CI 1.00–1.17, p = 0.06). The risk of dementia was particularly increased in those with OH who lacked a compensatory increase in heart rate (within lowest quartile of heart rate response: aHR 1.39, 95% CI 1.04–1.85, p-interaction = 0.05). Limitations of this study include potential residual confounding despite rigorous adjustments, and potentially limited generalisability to populations not of European descent. Conclusions: In this population predominantly of European descent, OH was associated with an increase in long-term risk of dementia
Transient neurological attacks in the general population. Prevalence, risk factors, and clinical relevance
BACKGROUND AND PURPOSE: Patients with typical transient ischemic attacks (TIAs) have a higher risk of stroke but a lower risk of cardiac events than patients with nonspecific transient neurological symptoms. We assessed the prevalences of typical TIAs and nonspecific transient neurological attacks (TNAs) and their determinants in the general population because such data are virtually absent.
METHODS: The Rotterdam Study is a population-based cohort study of 7983 subjects, aged 55 years and over, conducted in a district of Rotterdam, the Netherlands. At baseline examination, a history of episodes of disturbances in sensibility, strength, speech, and vision that lasted less than 24 hours and occurred within the preceding 3 years was determined by a trained physician. When such a history was present, information on time of onset, duration, and disappearance of symptoms and a detailed description of the symptoms (in ordinary language) were obtained. Subjects were classified by a neurologist as typical TIA or nonspecific TNA.
RESULTS: Prevalence of TNAs was 1.9% in subjects aged 55 to 64 years, 3.5% in subjects aged 65 to 74 years, 4.3% in subjects aged 75 to 84 years, and 5.1% in subjects aged 85 years or over. Prevalence figures for typical TIA were 0.9%, 1.7%, 2.3%, and 2.2% and for nonspecific TNA 1.0%, 1.8%, 2.0%, and 2.9%, respectively. Clinical parameters such as number of attacks, onset, duration, and disappearance of symptoms were similar for typical TIA and nonspecific TNA. Increased age, male sex, diabetes mellitus, low HDL cholesterol, Q-wave myocardial infarction on electrocardiogram, and carotid atherosclerosis were related to typical TIA, whereas increased age, hypertension, low HDL cholesterol, smoking, and angina pectoris were associated with nonspecific TNA.
CONCLUSIONS: About half of the subjects with a TNA had symptoms that were not entirely typical for a TIA. Differences in associations with risk factors between typical TIA and nonspecific TNA point toward different underlying mechanisms of symptoms and may lead to different ancillary investigations and possibly treatment
Predicting Parkinson disease in the community using a nonmotor risk score
At present, there are no validated methods to identify persons who are at increased risk for Parkinson Disease (PD) from the general population. We investigated the clinical usefulness of a recently proposed non-motor risk score for PD (the PREDICT-PD risk score) in the population-based Rotterdam Study. At baseline (1990), we constructed a weighted risk score based on 10 early nonmotor features and risk factors in 6492 persons free of parkinsonism and dementia. We followed these persons for up to 20 years (median 16.1 years) for the onset of PD until 2011. We studied the association between the PREDICT-PD risk score and incident PD using competing risk regression models with adjustment for age and sex. In addition, we assessed whether the PREDICT-PD risk score improved discrimination (C-statistics) and risk classification (net reclassification improvement) of incident PD beyond age and sex. During follow-up, 110 persons were diagnosed with incident PD. The PREDICT-PD risk score was associated with incident PD (hazard ratio [HR] = 1.30; 95 % confidence interval [1.06; 1.59]) and yielded a small, non-significant improvement in overall discrimination (ΔC-statistic = 0.018[−0.005; 0.041]) and risk classification (net reclassification improvement = 0.172[−0.017; 0.360]) of incident PD. In conclusion, the PREDICT-PD risk score only slightly improves long-term prediction of PD in the community
Insulin resistance and the risk of stroke and stroke subtypes in the nondiabetic elderly
Insulin resistance, which plays a key role in the development of diabetes mellitus, is a putative modifiable risk factor for stroke. The aim of this study was to investigate if markers of insulin resistance were associated with risk of stroke in the general elderly population. This study was part of the large population-based Rotterdam Study and included 5,234 participants who were aged 55 years or older and stroke free and diabetes free at baseline (1997-2001). Fasting insulin levels and homeostasis model assessment for insulin resistance were used as markers for insulin resistance. Cox regression was used to determine associations between insulin resistance markers and stroke risk, adjusted for age, sex, and potential confounders. During 42,806 person-years of follow-up (median: 8.6 years), 366 first-ever strokes occurred, of which 225 were cerebral infarctions, 42 were intracerebral hemorrhages, and 99 were unspecified strokes. Fasting insulin levels were not associated with risk of any stroke, cerebral infarction, or intracerebral hemorrhage. Homeostasis model assessment for insulin resistance, which almost perfectly correlated with fasting insulin levels, was also not associated with risk of stroke or stroke subtypes. In conclusion, in this population-based cohort study among nondiabetic elderly, insulin resistance markers were not associated with risk of stroke or any of its subtypes
J-shaped relation between blood pressure and stroke in treated hypertensives
The objective of this study was to investigate the relationship between
hypertension and risk of stroke in the elderly. The study was performed
within the framework of the Rotterdam Study, a prospective
population-based cohort study. The risk of first-ever stroke was
associated with hypertension (relative risk, 1.6; 95% CI, 1.2 t
The efficacy of recombinant thrombopoietin in murine and nonhuman primate models for radiation-induced myelosuppression and stem cell transplantation
Radiation-induced pancytopenia proved to be a suitable model system in
mice and rhesus monkeys for studying thrombopoietin (TPO) target cell
range and efficacy. TPO was highly effective in rhesus monkeys exposed to
the mid-lethal dose of 5 Gy (300 kV x-rays) TBI, a model in which it
alleviated thrombocytopenia, promoted red cell reconstitution, accelerated
reconstitution of immature CD34+ bone marrow cells, and potentiated the
response to growth factors such as GM-CSF and G-CSF. In contrast to the
results in the 5 Gy TBI model, TPO was ineffective following
transplantation of limited numbers of autologous bone marrow or highly
purified stem cells in monkeys conditioned with 8 Gy TBI. In the 5 Gy
model, a single dose of TPO augmented by GM-CSF 24 h after TBI was
effective in preventing thrombocytopenia. The strong erythropoietic
stimulation may result in iron depletion, and TPO treatment should be
accompanied by monitoring of iron status. This preclinical evaluation thus
identified TPO as a potential major therapeutic agent for counteracting
radiation-induced pancytopenia and demonstrated pronounced stimulatory
effects on the reconstitution of immature CD34+ hemopoietic cells with
multilineage potential. The latter observation explains the potentiation
of the hematopoietic responses to G-CSF and GM-CSF when administered
concomitantly. It also predicts the effective use of TPO to accelerate
reconstitution of immature hematopoietic cells as well as possible
synergistic effects in vivo with various other growth factors acting on
immature stem cells and their direct lineage-committed progeny. The
finding that a single dose of TPO might be sufficient for a clinically
significant response emphasizes its potency and is of practical relevance.
The heterogeneity of the TPO response encountered in the various models
used for evaluation points to multiple mechanisms operating on the TPO
response and heterogeneity of its target cells. Mechanistic mouse studies
made apparent that the response of multilineage cells shortly after TBI to
a single administration of TPO is quantitatively more important for
optimal efficacy than the lineage-restricted response obtained at later
intervals after TBI and emphasized the importance of a relatively high
dose of TPO to overcome initial c-mpl-mediated clearance. Further
elucidation of mechanisms determining efficacy might very well result in a
further improvement, e.g., following transplantation of limited numbers of
stem cells. Adverse effects of TPO administration to myelosuppressed or
stem cell transplanted experimental animals were not observed
Incidence, risk, and case fatality of first ever stroke in the elderly population. The Rotterdam Study
OBJECTIVE: To estimate the incidence, survival, and lifetime risk of
stroke in the elderly population. METHODS: The authors conducted a study
in 7,721 participants from the population based Rotterdam Study who were
free from stroke at baseline (1990-1993) and were followed up for stroke
until 1 January 1999. Age and sex specific incidence, case fatality rates,
and lifetime risks of stroke were calculated. RESULTS: Mean follow up was
6.0 years and 432 strokes occurred. The incidence rate of stroke per 1,000
person years increased with age and ranged from 1.7 (95% CI 0.4 to 6.6) in
men aged 55 to 59 years to 69.8 (95% CI 22.5 to 216.6) in men aged 95
years or over. Corresponding figures for women were 1.2 (95% CI 0.3 to
4.7) and 33.1 (95% CI 17.8 to 61.6). Men and women had similar absolute
lifetime risks of stroke (21% for those aged 55 years). The survival after
stroke did not differ according to sex. CONCLUSIONS: Stroke incidence
increases with age, also in the very old. Although the incidence rate is
higher in men than in women over the entire age range, the lifetime risks
were similar for both sexes
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