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Biomedical subjects

A J Bos

Publications and source records attributed to A J Bos.

18 recordsLinked to original sources
PubMed2006

Widely distributed and predominant CTX-M extended-spectrum beta-lactamases in Amsterdam, The Netherlands.

Three hundred sixty Enterobacteriaceae and nonfermenting gram-negative bacilli, isolated during one week in May 2004 at five hospitals in Amsterdam, The Netherlands, were evaluated for the presence of extended-spectrum beta-lactamases (ESBLs). A prevalence of 7.8% was found, in contrast to the 1% observed in 1997. CTX-M ESBLs dominated, and four types were identified in 18 isolates.

Anti-Bacterial Agents↗
PubMed2005

Additional value of typing Noroviruses in gastroenteritis outbreaks in Amsterdam, The Netherlands.

BACKGROUND: In Amsterdam, 17 of the 55 gastroenteritis (GI) outbreaks reported from January 2002 to May 2003 were confirmed to be caused by noroviruses (NV). OBJECTIVE: In this study, we describe the molecular epidemiology of a group of nine outbreaks associated with a catering firm and two outbreaks, 5 months apart, in an Amsterdam hospital. All outbreaks were typed to confirm their linkage, and the hospital-related cases were studied to see if the two outbreaks were caused by one persisting NV strain or by a reintroduction after 5 months. RESULTS AND CONCLUSIONS: For the outbreaks associated with the catering firm one NV genogroup I strain was found which was identical in sequence among customers and employees of the caterer. This was not the strain that predominantly circulated in 2002/2003 in and around Amsterdam, which was the NV genogroup II4 "new variant" (GgII4nv) strain. In the Amsterdam hospital, the two outbreaks were caused by this predominant GgII4nv type, and we argue that NV was most likely reintroduced in the second outbreak from the Amsterdam community.

Caliciviridae Infections↗
PubMed2001

Hormone replacement therapy and longitudinal changes in blood pressure in postmenopausal women.

BACKGROUND: The incidence of hypertension in postmenopausal women exceeds that in age-matched men. Longitudinal studies relating hormone replacement therapy (HRT) to blood pressure changes are sparse. OBJECTIVE: To investigate the association between HRT and longitudinal changes in blood pressure in postmenopausal women. DESIGN: Longitudinal observational study. SETTING: Community-dwelling volunteers. PATIENTS: 226 healthy, normotensive postmenopausal women from the Baltimore Longitudinal Study of Aging with a mean (+/-SD) age of 64 +/- 10 years were followed for 5.7 +/- 5.3 years. Seventy-seven women used both estrogen and progestin, and 149 used neither. MEASUREMENTS: Lifestyle variables, blood pressure, and traditional cardiovascular risk factors were measured at baseline and approximately every 2 years thereafter. RESULTS: Systolic blood pressure at baseline was similar in HRT users and nonusers (133.9 +/- 16.0 mm Hg vs. 132.4 +/- 14.8 mm Hg). Over time, average systolic blood pressure increased less in HRT users than nonusers, independent of other cardiovascular risk factors, physical activity, and alcohol use. For example, HRT users who were 55 years of age at their first Baltimore Longitudinal Study of Aging visit experienced a 7.6-mm Hg average increase in systolic blood pressure over 10 years; in contrast, the average increase in nonusers was 18.7 mm Hg. The lesser increase in systolic blood pressure in HRT users was more evident at older age. Diastolic blood pressure, which did not change statistically over time in either group, was not associated with HRT. CONCLUSION: Postmenopausal women taking HRT have a smaller increase in systolic blood pressure over time than those not taking HRT. This difference is intensified at older ages.

Age Factors↗
PubMed2001

Effect of estrogen and progestin replacement on arterial stiffness indices in postmenopausal women.

Our objectives were to investigate whether long-term estrogen replacement therapy (ERT) is associated with a reduction in age-associated increases in arterial stiffness and blood pressure (BP), and whether the addition of progestin modifies the effects of estrogen. ERT has been found to have beneficial effects on cardiovascular risk. There are few data, however, delineating the effects of ERT on BP and arterial stiffness, and their age-associated changes. BP and aorto-femoral pulse wave velocity (PWV) were measured in 134 postmenopausal volunteers, aged 51 to 90 years, from the Baltimore Longitudinal Study of Aging, screened to exclude clinical and occult cardiovascular disease, and classified as ERT non-users (N=57) or ERT users (N=77). The latter group was further substratified according to the use of estrogen alone (N=32) or a combination of estrogen and progestins (N=45). ERT users showed similar body habitus, physical activity, and plasma lipids compared to non-ERT users. ERT was associated with an average 9.8 mmHg lower systolic BP (p<0.001), and a 6.3 mmHg lower pulse pressure (p<0.01) than in non-users. Multiple regression analysis showed that ERT was an independent predictor of lower SBP and PP (p<0.05). By analysis of covariance, ERT predicted a reduced age-associated increase in SBP, PP, and PWV (p<0.05). When systolic BP was >130 mmHg, the combination of ERT and progestins predicted a higher PWV than ERT alone. In conclusion, ERT in postmenopausal women can beneficially affect the vascular system, by reducing BP and the age-associated increase in arterial stiffness. The addition of progestins to ERT may reduce these beneficial effects.

Aged↗
PubMed2001

Is the apoE4 allele an independent predictor of coronary events?

PURPOSE: Although the apolipoprotein E genotype epsilon4 (apoE4) has been associated with high cholesterol levels, whether it is an independent predictor of coronary events is not certain. SUBJECTS AND METHODS: We measured apoE genotypes in 730 participants in the Baltimore Longitudinal Study of Aging (421 men and 309 women, mean [+/- SD] age of 52+/-17 years) who were free of preexisting coronary heart disease. A proportional hazards regression model was used to study the association between risk factors and the occurrence of coronary events, defined as angina pectoris, documented myocardial infarction by history or major Q waves on the electrocardiogram (Minnesota Code 1:1 or 1:2), or coronary death, adjusted for other risk factors, including total plasma cholesterol level. RESULTS: The apoE4 allele was observed in 200 subjects (27%), including 183 heterozygotes and 17 homozygotes. Coronary risk factor profiles were similar in those with and without apoE4. Coronary events developed in 104 (14%) of the 730 subjects, including 77 (18%) of the 421 men during a mean follow-up of 20 years and 27 (9%) of the 309 women during a mean follow-up of 13 years. Coronary events occurred significantly more frequently in subjects with apoE4 (n = 40, 20%) than in those without this allele (64, 12%, P <0.05). In a multivariate model, apoE4 was an independent predictor of coronary events in men (risk ratio [RR]= 2.9, 95% confidence interval [CI]: 1.8 to 4.5, P<0.0001) but not in women (RR = 0.9, 95% CI: 0.4 to 1.9, P = 0.62). CONCLUSION: The apoE4 genotype is a strong independent risk factor for coronary events in men, but not women. The association does not appear to be mediated by differences in total cholesterol levels.

Adult↗
PubMed2001

On the applicability of the AAPM TG-60/TG-43 dose calculation formalism to intravascular line sources: proposal for an adapted formalism.

Despite the widely recognized usefulness of the AAPM TG-43 brachytherapy dose calculation formalism, a straightforward application of this approach to describe the dose distribution about intravascular line sources as proposed by TG-60 may be difficult or even impossible, especially when these line sources emit low-energy photons or beta particles. The causes of these limitations are investigated and illustrated by means of some numerical examples. In order to solve the observed limitations an adapted formalism is proposed, intended specifically for the description of the dose rate distribution about line sources but conceptually similar to the TG-43/TG-60 formalism. Several examples are presented to illustrate the usefulness of the proposed line source dose calculation formalism.

Anisotropy↗
PubMed2000

Modelling of a 188W/188Re beta line source for coronary brachytherapy by means of EGS4 Monte Carlo simulations.

In this paper, we present results from three different simulation models that are used to determine the dose distribution around a 188W/188Re coronary brachytherapy source with EGS4 Monte Carlo simulations. The three models are found to give similar results within 10%. Agreement was found with experimental data from measurements in a PMMA phantom. It has been shown that in the therapeutically relevant region the beta line source can be characterized by the radial depth-dose distribution in water.

Angioplasty, Balloon, Coronary↗
PubMed1998

The relationship of obesity and the development of coronary heart disease to longitudinal changes in systolic blood pressure.

In an investigation of the relationship of obesity and the development of coronary heart disease (CHD) to longitudinal changes in systolic blood pressure (SBP), a sample of 1029 male participants from the Baltimore Longitudinal Study of Baltimore (BLSA), who were free of CHD at the beginning of the study, were examined with a total of 4111 examinations (mean of four examinations per person) conducted during the study period. The mean follow-up time was 8.1 years with a maximum of 16 examinations and 30.9 years of follow-up. During the follow-up period, 192 participants developed CHD, and these participants' data collected after the CHD event were excluded from the analysis. A proportional hazards regression model was used to calculate the relative risk of developing CHD for several CHD risk factors. Both simple and multiple proportional hazards regression models indicate a strong association between body mass index (BMI), cholesterol, cigarette smoking, and systolic blood pressure (SBP) with the risk of developing CHD. In addition, a linear mixed-effects model was used to examine changes in SBP measurements over time and to identify factors, including the age at first examination and time in study, that are related to that change. The results from the linear mixed-effects model analysis indicate that those in the obese group (BMI > or = 30 kg/m2) have SBP measurements that are on average 9.0 mm Hg higher than those in the normal group (20 < or = BMI < 25). Also, SPB measurements were on average 6.6 mm Hg higher in those who developed CHD during the study period than those who remained free of disease. In addition, SPB showed a quadratic relationship with time, and its patterns of change with time were different among the different age groups. Also, the relationship between changes in SBP with respect to cholesterol was dependent on time in the study as well.

Adult↗
PubMed1995

Effectiveness of lead aprons in vascular radiology: results of clinical measurements.

PURPOSE: To determine the effectiveness of 0.5-mm-thick lead-equivalent aprons in vascular radiology. MATERIALS AND METHODS: The radiation dose to radiology personnel was measured under and over lead aprons in more than 100 patient examinations. Thermoluminescent dosimeters of high and normal sensitivities (detection levels of 1 and 10 microGy, respectively) were used. Dose measurements in clinical practice were complemented with real-time measurement of generating potential, dose-area product, and fluoroscopy time. In addition, measurements of the radiation attenuation of aprons were performed in simulated exposure conditions. The generating potential in fluoroscopy--weighted for the contribution to the occupational exposure--varied between about 70 and 95 kV per examination (average, 78 kV). RESULTS: On the basis of measurements obtained under clinical conditions in vascular radiology, attenuation factors between 70 and 280 were derived. The typical radiation attenuation factor for 0.5-mm-thick lead-equivalent aprons was 200. CONCLUSION: The effectiveness of 0.5-mm-thick lead-equivalent aprons, determined with clinical measurements, agrees with estimates based on generating potential. Previously published effective doses, inferred from nonclinically determined radiation transmission factors, probably overestimate the actual dose levels.

Abdomen↗
PubMed1994

[Effects of aging on urinary secretion of 3-hydroxyproline and its importance for cancer screening in the elderly with ROC analysis].

OBJECTIVE: to observe the influence of aging on urinary secretion of 3-hydroxyproline (3-Hyp) in normal subjects and in cancer patients and study the effects of aging on the accuracy of urinary 3-Hyp as a general-purpose cancer screening test. DESIGN: We reanalyzed, from the aspect of gerontology, the amounts of 3-Hyp in the urine samples of the 211 healthy persons and 94 patients with cancer reported earlier. The two groups were divided in 3 age subgroups: adult, 30 to 44 years, middle-aged, 45 to 64 years, and aged, 65 years and older. The cancer stage was separated into 3 categories: stage 1, the early stage without any invasion, stage 2, locally invasive with no distant metastasis, and stage 3, advanced cancer. The correlation of age and urinary 3-Hyp was analyzed in normal subjects and cancer patients. Sensitivity and specificity were calculated for different cutoff points in the diverse groups to construct the receiver operating characteristic (ROC) curves. MAIN RESULTS: We observed that aging decreases the urinary secretion of 3-Hyp in normal subjects, with a correlation coefficient of -0.250 (p < 0.001). The mean levels of urinary 3-Hyp in patients with cancer were significantly higher than in the normal subjects, p = 0.005. The correlation coefficient of urinary 3-Hyp and age was not significant (0.100) in cancer patients. The cutoff points of 0.800 mg/g creatinine of urinary 3-Hyp for persons under 65 years of age and 0.600 mg/g creatinine for persons 65 years or older were the best thresholds for cancer screening. In the ROC analyses, we observed that 3-Hyp has higher accuracy for cancer screening in the aged group for all stages together and in the aged and middle-aged for early stages of cancer. CONCLUSIONS: The urinary 3-Hyp test was more effective for cancer screening in old persons (65 years or older), where cancer is more frequent and more difficult to discover. The authors stress the necessity and importance of verifying the effectiveness of urinary 3-Hyp for general cancer screening in a larger population and in a community set.

Adult↗
PubMed1991

Comparative epidemiology of oral cancer in Brazil and India.

A comparison of the risk factors and occurrence of oral cancer in Brazil and India is presented. These two countries have among the highest incidence rates for such cancer in the world. A distinct pattern of risk factors was observed for each country: in India, tobacco chewing was the predominant risk factor: in Brazil, the major risk factor was the combination of tobacco smoking and alcohol consumption. Observations by descriptive epidemiology reveal high age-standardized incidence rates of oral cancer along with some distinctive differences associated with age distribution, sex ratios, and trends in each country. The desirability of additional oral cancer prevention research is also emphasized.

Adult↗
PubMed1990

Cardiovascular diseases and alimentary comparison study: preliminary analysis from Brazil.

The Cardiovascular Diseases and Alimentary Comparison (CARDIAC) Study (1) was designed to study the relationship of dietary factors to blood pressure (BP) and other major cardiovascular disease (CVD) in widely different populations of both industralized and developing countries. The primary aim of the research was to test specific hypotheses linking the intake of certain dietary constituents, e.g., sodium (Na), potassium (K), calcium (Ca), and protein, to BP (core study). The final aim was to contribute to the scientific information base required to guide the formulation of dietary goals for the primary prevention of CVD. The results of the preliminary analysis of data from Brazil in 57 inhabitants (22 men and 35 women) suggest a nonsignificant statistical correlation of Na intake estimated by urinary Na excretion and diastolic BP (DBP) and systolic BP (SBP) (p greater than 0.05), K intake estimated by urinary K excretion for DBP and SBP (p greater than 0.05), and taurine intake estimated by taurine urinary excretion for DBP and SBP (p greater than 0.05). A positive correlation was found between body mass index (BMI) and BP (p less than 0.01), for both DBP and SBP.

Adult↗
PubMed1985

Incorporation routes of elements into human hair; implications for hair analysis used for monitoring.

A study has been made on the incorporation of some trace elements and minerals into human hair by measuring their distributions across hair diameters. For this study the Particle Induced X-ray Emission (PIXE) technique using the proton microbeam of the Vrije Universiteit of Amsterdam has been applied. Results of measurements on single hair strands at different positions in the root and outside the skin provide evidence that the elements not only can enter the cortex via the matrix but also via the hair root sheaths. Moreover, there are indications that the distribution of an endogenous element is not always homogeneously spread over a cross section of the hair. Endogenous Fe and Pb seem to be peaked on the periphery of the hair by natural means, while the elements S,Zn and Cu of the samples measured are found to be distributed homogeneously across the hair diameter. The consequences for hair analysis in use for monitoring the trace elements status of an individual are discussed.

Adult↗
PubMed1984

Discrepancies between histological and physical methods for trace element mapping in the rat brain.

This paper contains a comparison between four experimental methods for the detection of trace metals in biological tissues, e.g. autoradiography, dithizone-, Timm-staining and microPIXE (Particle Induced X-ray Emission). As research object the hippocampus of the rat was chosen and mainly the Zn-distribution in the fascia dentata has been examined. The comparison was judged on four criteria: spatial resolution, specificity, quantification and influence of the protein binding of the metal on the outcome of each method. Some additional Timm and microPIXE experiments have been performed to compare the metal concentrations for both normal and Zn-deficient rats. The Zn/Cu ratio for both kinds of rats were calculated and some striking differences in the concentrations were obtained. The Zn/Cu ratio for a normal rat was found to be about 40% higher than for a deficient one.

Animals↗
PubMed1982

Characterization of hereditary partial myeloperoxidase deficiency.

We studied a family with a partial myeloperoxidase deficiency. The myeloperoxidase in the neutrophils and monocytes of the parents and their two sons had normal spectral properties (determined optically and by EPR). Enzymic characteristics (oxidation of iodide) were indistinguishable from those of normal myeloperoxidase; moreover, immunological identity between the myeloperoxidase in the leukocytes of the family members and normal myeloperoxidase was found. No differences in heat stability were observed. The neutrophils and monocytes of the sons contained 9% to 18% of the myeloperoxidase content of normal cells; the neutrophils and monocytes of the parents contained 45% to 58%. These data suggest either that the parents are heterozygous and the sons homozygous for hereditary partial myeloperoxidase deficiency or that each parent is heterozygous for a different type of myeloperoxidase deficiency and the sons combine both deficiencies. The oxidative metabolism of the neutrophils during phagocytosis was not affected by the myeloperoxidase deficiency. The killing of Staphylococcus aureus was apparently normal. The perforation of Escherichia coli by the neutrophils of the sons, however, was retarded in comparison with normal neutrophils.

Adult↗
PubMed1981

Some enzymatic characteristics of eosinophil peroxidase from patients with eosinophilia and from healthy donors.

Some enzymatic characteristics of human eosinophil peroxidase were compared with those of human myeloperoxidase. Both enzymes catalyzed the oxidation of iodide by hydrogen peroxide. This assay proved to be very sensitive; the activity of 100 eosinophils/ml could be measured. The position of the pH optimum of this reaction was linearly dependent on the logarithm of the iodide/H2O2 ratio. At the same substrate ratio, this optimum was about 1 pH unit higher for eosinophil peroxidase than for myeloperoxidase. This difference may be related to the action of myeloperoxidase inside an acidified phagolysosome as opposed to the extracellular action of eosinophil peroxidase on the surface of certain parasites. Under defined conditions (KI, 1.4 mM; H2O2, 0.18 mM; cetyltrimethylammonium bromide, 0.008% [wt/vol]; pH 6), the activity of eosinophil peroxidase could be measured in a mixed granulocyte suspension independently of myeloperoxidase. Eosinophils from patients with eosinophilia were found to contain as much peroxidase activity as did eosinophils from healthy donors. No enzymatic differences in eosinophil peroxidase were found between the two types of donors.

Cetrimonium↗
PubMedDate not supplied

Paravertebral abscess due to nondiphtheria coryneform bacteria as a complication of ingrown toenails.

A patient developed a paravertebral abscess due to nondiphtheria coryneform bacteria following infected ingrown toenails. Both the causative role of this uncommon pathogen and the unusual origin were established by cultures of tissue from the toes, blood and an aspirate of the paravertebral abscess. The microorganism was tentatively identified as an atypical variant of Arcanobacterium haemolyticum.

Abscess↗