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Biomedical subjects

A J Smits

Publications and source records attributed to A J Smits.

At least 19 recordsLinked to original sources
PubMed2002

Reynolds number dependence of streamwise velocity spectra in turbulent pipe flow.

Spectra of the streamwise velocity component in fully developed turbulent pipe flow are presented for Reynolds numbers up to 5.7x10(6). Even at the highest Reynolds number, streamwise velocity spectra exhibit incomplete similarity only: while spectra collapse with both classical inner and outer scaling for limited ranges of wave number, these ranges do not overlap. Thus similarity may not be described as complete, and a region varying with the inverse of the streamwise wave number, k(1), is not expected, and any apparent k(-1)(1) range does not attract any special significance and does not involve a universal constant. Reasons for this are suggested.

Journal Article↗
PubMed2002

Clinical effectiveness of conventional influenza vaccination in asthmatic children.

Influenza immunization rates among young asthmatics remain unsatisfactory due to persistent concern about the impact of influenza and the benefits of the vaccine. We assessed the effectiveness of the conventional inactivated trivalent sub-unit influenza vaccine in reducing acute respiratory disease in asthmatic children. We conducted a two-season retrospective cohort study covering the 1995-6 and 1996-7 influenza outbreaks in 22 computerized primary care practices in The Netherlands. In total, 349 patients aged between 0 and 12 years meeting clinical asthma-criteria were included; 14 children were lost to follow-up in the second season. The occurrence of physician-diagnosed acute respiratory disease episodes including influenza-like illness, pneumonia. bronchitis, bronchiolitis, asthma exacerbation and acute otitis media in vaccinated and unvaccinated children were compared after adjustments for age, prior health care and medication use. The occurrence of acute respiratory disease in unvaccinated children was 28% and 24% in the 1995-6 and 1996-7 season, respectively, and was highest in children under 6 years of age (43%). The overall pooled clinical vaccine effectiveness was 27% (95% confidence interval -7 to 51%, P = 0.11) after adjustments. A statistically higher vaccine protectiveness of 55% (95% CI 20-75%, P = 0.01) was observed among asthmatics under 6 years of age compared with -5% in older children (95% CI -81 to 39%). The occurrence of acute respiratory disease among asthmatic children during influenza epidemics is very high, notably in the youngest. Influenza vaccination may reduce morbidity in asthmatic infants and pre-school children. However, larger, preferably experimental, studies are needed to establish the benefits of vaccination, notably in older asthmatic children.

Age Factors↗
PubMed2001

Quality of life in patients with diabetic foot ulcers.

PURPOSE: To compare Quality of Life (QoL) between diabetic patients with (former or present) and without foot ulcers. METHODS: Two patient groups of comparable age, sex distribution, type distribution and duration of diabetes were studied. Fourteen patients with former or present, but clinically stable diabetic foot ulcers (DFUs) were studied. The control group was 24 unknown patients with DFUs. None of the participants had other diabetic complications or conditions that would potentially affect QoL. A diabetic foot risk score and QoL were assessed. QoL was scored with the RAND-36, the Barthel Score (ADL) and the Walking and Walking Stairs Questionnaire (WSQ). RESULTS: Marked and significant differences were found in physical functioning (p < 0.001), social functioning (p < 0.05), physical role (p < 0.001) and health experience (p < 0.05) between the two groups with the RAND-36 and the four subscales of the WSQ (all p < 0.001). On all these scales, QoL was significantly poorer in the study group. A correlation was found between the risk scores and QoL (physical functioning and physical role Spearman's r: -0.66, -0.56 and WSQ -0.63, -0.64, -0.67 and 0.71, respectively). CONCLUSION: Presence or history of DFUs has a large impact on physical role, physical functioning and mobility. Physical impairments especially influenced QoL. Probably, QoL can be increased by providing attention that will enhance mobility and by giving advice about adaptations and special equipment.

Aged↗
PubMed1997

Over-the-counter availability of antimicrobial agents, self-medication and patterns of resistance in Karachi, Pakistan.

To determine whether the free availability of antimicrobial agents leads to misuse through self-medication, a house-to-house semi-structured interview was held in three different socio-economic areas of Karachi, Pakistan. Of the 2348 households visited, 1342 (57%) participated; this included 9209 individuals. Three hundred and twenty-two (3.5%) had used one or more antimicrobial in the previous 4 weeks, equivalent to 43 agents per 1000 persons per month. The most frequently used agents were amoxycillin (16.7%), co-trimoxazole (15.7%), erythromycin (10.9%), ampicillin/cloxacillin (Ampiclox, 9.1%) and metronidazole (4.5%). Of these, 91.4% were prescribed by a physician, 2.3% were advised by a chemist and 6.3% were used as self-medication. Self-medication increased with socio-economic status. High levels of resistance were found to ampicillin, co-trimoxazole, chloramphenicol and erythromycin. If these high resistance levels are related to the high frequency of antimicrobial use, over-the-counter availability cannot be held responsible. Education of the medical profession seems to be the single most important tool to control misuse of antimicrobial agents. Innovative approaches for continuous medical education are urgently needed.

Adolescent↗
PubMed1996

beta1-Integrins dominate cell traffic of leukemic cells in human bone-marrow stroma.

Migration patterns of leukemic cells in bone marrow are largely regulated by cell contacts between leukemic cells and stromal cells or extra-cellular matrix. The mechanism of this interaction with bone-marrow stromal cells was studied in a human in vitro model. Migration behavior of erythroleukemia cell line K562, derived from a patient with chronic myeloid leukemia, was compared with that of the erythroleukemia cell line HEL92.1.7 and the promyelocytic leukemia cell line HL60 from acute leukemias. Interaction varied between low binding affinity (K562) to intensive cell interaction (HEL92.1.7) followed by invasion into the stromal cell monolayer. Some of the HL60 cells adhered to stromal cells, while the remainder migrated into the stromal cell monolayer. The role of adhesion molecules in these cell interactions was determined. Distinct expression of beta1-integrins ICAM-1, CD44 and VCAM-1 was detected on the different cell lines. Inhibition studies pointed to a dominant role of VLA-4- and VLA-5-mediated interactions. K562 lacked VLA-4 and a low binding affinity of the VLA-5 on these cells resulted in an absence of binding to the bone-marrow stroma. These results indicate the VLA-5/fibronectin, VLA-4/fibronectin and the VLA-4/VCAM-1 interaction pathways between leukemic cells and bone-marrow stroma.

Bone Marrow↗
PubMed1994

[Beneficial effect of exercise therapy in urinary incontinence in family practice depends largely on therapy compliance and motivation].

OBJECTIVE: Determining the factors which influence the success of training therapy in women suffering from urinary incontinence. DESIGN: Descriptive. SETTING: Thirteen general practices in Nijmegen and environs, the Netherlands. METHOD: A total of 110 women between 20 and 65 years old, suffering from urinary incontinence were examined by their general practitioners. Age, personality, parity, psychological features and type, duration, severity, beginning of the disease, as well as the presence of cystocele or prolapse were recorded. Women were asked about their own experiences regarding factors that influenced success. The treatment consisted of training of pelvic muscles in stress incontinence and bladder training in urge incontinence. Outcomes and compliance were measured 3 and 12 months after start of treatment by means of a so-called incontinence diary. RESULTS: After 3 months the mean frequency of urine loss per week diminished from 21 to 8, and after 12 months to 6 times. Compliance was the most important contribution to success. Patients were more motivated to practise when the subjective burden of the urine loss was more severe. Other features did not influence success.

Adult↗
PubMed1992

The effects of treatment of urinary incontinence in general practice.

A total of 110 women who had reported urinary incontinence to their general practitioners were randomly assigned to a treatment or control group. Treatment consisted of pelvic floor exercises in the case of stress incontinence and bladder training in the case of urge incontinence. The results were measured after 3 and 12 months by a research assistant on the basis of a constructed severity scale, an incontinence diary, and a comparison by the patients themselves of their previous and current conditions. After 3 months the control group were given the same treatment. After a further 3 and 12 months, they were assessed in exactly the same way as the treatment group. After 3 months about 60% of the patients were either dry or only mildly incontinent; the mean number of wet episodes had gone down from 20 to 7, and 74% of the women felt improved or cured. These results were later corroborated by the control group. After 12 months this successful outcome was improved slightly further. It may be concluded that the majority of women with incontinence can be successfully treated by the general practitioner. The effect of this treatment continues after one year.

Adult↗
PubMed1992

Relationship between the working styles of general practitioners and the health status of their patients.

The aim of this study was to relate the working style of general practitioners to the health status of a sample of their patients. From a large regional sick fund forming part of the national health insurance system in the Netherlands a stratified sample was taken of general practitioners with at least 1000 patients on their list, taking into account the degree or urbanization of the area in which they practised and their annual referral rates to specialists. These 75 general practitioners were observed for two days in their surgeries by trained doctors and rated according to criteria defined beforehand. Taking into account these ratings and the annual figures from the sick fund for prescribing selected drugs and referrals to specialists, the general practitioners were classified into styles of practice - integrated, interventionist or minimal diagnostic. Twenty randomly selected women, aged 50-65 years, from each general practitioner's list, were interviewed and examined by independent doctors. The patients of general practitioners with the integrated practice style appeared to feel more healthy and to have more realistic expectations about the possibilities of professional help for common ailments. They tended to visit their doctor less frequently and to have fewer symptoms. The results showed an association between the quality of general practitioners and patients' health, and it may therefore be concluded that good general practitioners can further the health and well being of their patients.

Aged↗
PubMed1991

Medical versus behavioural skills: an observation study of 75 general practitioners.

This study deals with a replication of a previous research project on the correlation between medical and behavioural skills of general practitioners. The PREVARA observation schedule was used to assess these skills of 75 general practitioners. Fifteen surgery contacts were tape-recorded for each GP and were rated by trained observers. The study shows that fundamental dimension underlies the surgery behaviour of the GP: the various skills appear to be equally developed. More specifically, a positive correlation was found between performing obligatory physical examination and paying attention to psychosocial aspects. The results are discussed in the context of the evaluation of the vocational training and medical audit of GPs.

Clinical Competence↗
PubMed1991

Controlled trial of pelvic floor exercises in the treatment of urinary stress incontinence in general practice.

The aim of this study was to assess the usefulness of pelvic floor exercises in the treatment of urinary incontinence in women and to analyse the factors which determine a successful outcome. The study involved 66 women who had reported 'genuine stress incontinence' to their general practitioner. They were assigned at random to the treatment or control group. The treatment group received instructions in pelvic floor exercises from a general practitioner. The control group received no therapy. At the start of the trial the severity of the patients' incontinence was assessed objectively. This assessment was repeated after three months and patients were also asked for their own perception of whether their incontinence had improved. After the three months' evaluation the patients in the control group were also given instructions in pelvic floor exercises. After another three months they were assessed in the same way. About 60% of the patients in the treatment group were dry or mildly incontinent after three months compared with only one patient in the control group; the mean weekly frequency of incontinence episodes fell from 17 to five in the treatment group but remained virtually unchanged in the control group; and about 85% of the women in the treatment group felt that their incontinence had improved or was cured compared with no one in the control group. These results were later corroborated by those for the control group. The most important factor in the success of the treatment was the patients' motivation, as demonstrated by their adherence to the daily exercises.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Women with urinary incontinence: self-perceived worries and general practitioners' knowledge of problem.

In the context of a large scale survey of health problems in women aged 50 to 65 years, a study was undertaken on the effects of incontinence on daily life. For this purpose 1442 women randomly selected from the practice files of 75 general practitioners in the eastern part of the Netherlands were interviewed at home (response rate 60%). In cases of moderate or severe incontinence the general practitioner of the woman concerned was asked whether this problem had been diagnosed in general practice. Incontinence was reported in 22.5% of the women. Overall, 77.8% of the women did not feel worried about it and 75.4% did not feel restricted in their activities; even for women with severe incontinence (daily frequency and needing protective pads) only 15.6% experienced much worry and 15.7% much restriction. About a third of the women with incontinence (32.0%) had been identified by their general practitioner. The greater the worries and restrictions owing to incontinence, the greater the chance that the incontinence was known to the general practitioner concerned. Only a small minority of the women who felt severely restricted were not identified by their general practitioner. There was a positive relation between recognized incontinence and a history of hysterectomy. This study contradicts the image of the incontinent woman as isolated and helpless; most women in this study seemed able to cope.

Aged↗
PubMed1987

Humoral immunity in measles infection: a critical factor?

Cell-mediated immunity is generally regarded as the essential factor in recovery from measles infection. In other viral infections humoral immunity has been considered a critical factor when antibody titres were correlated with outcome or when serum therapy proved protective. A review of available studies of severe-to-fatal cases of measles infection having non-neurological symptoms indicate that the antibody response is depressed in virtually all cases. The current view of immune globulin being an ineffective therapeutic agent is based on treatment of measles encephalitis; in fact, the least effect should be expected among encephalitis cases since some already have antibodies from the onset of symptoms. Larger examinations of measles with other than neurological symptoms suggest that immune globulin has a beneficial impact on the clinical course of infection. There are indications that hyperimmune globulin increases the efficacy of this form of treatment. Since measles is still a major cause of hospitalization and mortality, further studies of the therapeutic effect of specific immune globulin are warranted. From our current knowledge, both the humoral and cell-mediated immunity seem to be critical factors in recovery from measles infection.

Antibody Formation↗
PubMed1987

Development of respiratory illness in childhood--a longitudinal study in general practice.

The prognosis of early childhood respiratory illness has been studied by analysis of historic cohorts using data recorded since 1967 in the continuous morbidity registration project of the University of Nijmegen. The characteristics of this project are discussed, including the stability of the practice (study) population, a factor which allows longitudinal analysis to be performed.The development of respiratory morbidity during the first eight years of life has been analysed and a group of 710 patients characterized on the basis of their respiratory morbidity in the first two years of life. In general the highest levels of respiratory morbidity are seen in the first years of life, with a gradual decline over the years studied. Upper respiratory tract infections are largely responsible for this morbidity. An elevated level of episodes of respiratory illness in patients aged two to seven years was observed when the following characteristics of early life respiratory morbidity were present: more than three episodes of respiratory illness, lower respiratory tract infections or catarrhal conditions. However, by the age of seven years the level of morbidity of the children with these characteristics was very similar to that of children without these characteristics. Respiratory morbidity in childhood is predominantly benign and self-limiting. Only children with atopic conditions in early childhood showed a higher prevalance of asthma and chronic bronchitis at the end of the study period.

Child↗
PubMed1986

Severe measles in Sunderland, 1885: a European-African comparison of causes of severe infection.

On the basis of research in Guinea-Bissau, this paper re-analyses a severe measles epidemic which occurred in 1885 in Sunderland (England). In both England and Guinea-Bissau, acute measles mortality was higher in households with multiple cases than in families with only a single case of measles. Secondary cases (infected in the house) had higher mortality and higher frequency of severe complications than index and single cases. In Sunderland, severe complications were associated with a history of previous respiratory infection and with greater number of siblings. Since cases with severe complications had significantly prolonged prodromal symptoms and shorter periods of incubation, it is suggested that high dose of infection may be an essential mechanism in the pathogenesis of severe disease. Overcrowding may be a major determinant of severe measles because it increases the risks of intensive exposure, intercurrent infections, and previous respiratory infection.

Adolescent↗
PubMed1985

Introduction of measles into a highly immunised West African community: the role of health care institutions.

In an urban area of Guinea-Bissau, where more than 80% of the children have been vaccinated, measles continues to be a major cause of child mortality. Compared with the period before the introduction of vaccination, more cases occur outside the community, while more cases within the district are now guests and newcomers. Half of the new introductions of measles into the community and 30% of the measles deaths can be traced back to the paediatric ward. Contact with health care institutions plays an important role in the transmission of measles, particularly among the youngest children. This consequence of health care may be avoidable, however, since several studies suggest that sick children can be vaccinated safely and effectively.

Adolescent↗
PubMed1984

Measles vaccination and reduction in child mortality: a community study from Guinea-Bissau.

Earlier studies have suggested that general measles vaccination programmes should not be made a priority in developing countries because the presumably malnourished children saved from measles are likely to die from something else. Recent community studies indicate, however, that malnutrition is not the cause of high measles mortality. In an urban community in Guinea-Bissau, child mortality has been registered for a period of 3 years; 1 year before and 2 years after the introduction of a general measles vaccination program. In the years following the introduction of measles vaccination, mortality for children aged 6 to 35 months has significantly diminished. Though this is not a controlled study of vaccinated and unvaccinated children, much of the reduced mortality can apparently be attributed to the protective effect of measles vaccination. Children with a history of earlier measles infection had a significantly higher mortality rate than children vaccinated against measles. Rather than being a mechanism of natural selection taking the weakest children, measles apparently aggravates the condition of many children, leading to delayed excess mortality. In areas where the case fatality rate is high, vaccination against measles should be made an indispensable part of primary health care.

Child↗